17 December 2010

Kokako successfully anchored in ‘safe’ forest

This blog post was written by postgraduate student Anna Reuleaux as part of the course, Research Methods in Ecology (Ecol608).

North Island kokako are an endangered New Zealand forest species known for their beautiful song. In the past conservationists have translocated these birds from mainland areas to managed islands and succeeded in establishing new populations. These safe kokako havens were predominantly literal islands surrounded by water but also used have been islands of suitable forest in a ‘sea’ of grassland or farmland. The advantage of these islands is the guarantee that the birds will stay in the area that has been prepared for them by predator control. But how do you get birds to stay in a managed area if it is situated in continuous forest without any boundaries to stop dispersal?

Laura Molles and her colleagues attempted such a translocation to a managed area surrounded by continuous forest: Ngapukeriki is located in the Bay of Plenty on the North Island of New Zealand. The conservationists decided to use social attraction in order to encourage the kokakos to stay in the target area after release. For the kokako the presence of resident individuals indicates that they are likely to find the right habitat conditions, food resources and potential mates in the vicinity.

But what if there are no resident kokako yet in the target area? One answer is to trick the birds, giving them the impression that there are plenty of other kokako around. In this case three social attractants were used simultaneously: 1. releasing many birds at the same time; 2. keeping a pair of kokako in an aviary at the release site and 3. using playback of kokako song as ‘acoustic anchor’.

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Acoustic anchoring is the most exciting one of these tactics as it had never before been used in translocations of terrestrial birds. Recordings for the playback were made in the source population so that the translocated birds could be exposed to the song of their former neighbours, singing and calling in their familiar ‘dialect’. Three kokako held in the aviary at the release site responded positively to a trial playback.

Eighteen kokako were released in July and August 2005. After the release the playback was broadcasted for one and a half hours every morning from speakers near the release site. Most of the released birds visited the area of the playback at least once, some of them repeatedly. On several occasions kokako approached and counter-sang with the playback speakers.

All this is good evidence that acoustic anchoring is likely to have contributed significantly to the success of this translocation. On the other hand this study was not designed to prove the effectiveness of acoustic anchoring on its own but to find out if the combination of the three social attractants would lead to a successful establishment of a population. The re-introduction of kokako to Ngapukeriki can definitely be regarded as a success as the first young already fledged in 2006. “And every year since, the kokako of Ngapukeriki have bred successfully and the population continues to grow” says Laura.

The researchers also pointed out that acoustic anchoring is also worth investigating for the translocation of other terrestrial species. Laura Molles and her team have already put that into practice in a translocation of Tui to Banks Peninsula in 2009. The acoustic anchoring technique has also been trialled on robins, whiteheads and in two further kokako translocation projects.

This article is based on:

Molles, L.E., Calcott, A., Peters, D., Delamare, G., Hudson, J.D., Innes, J., Flux, I., Waas, J. 2009. 'Acoustic anchoring' and the successful translocation of North Island kokako (Callaeas cinerea wilsoni) to a mainland management site within continuous forest. Notornis 55(2): 57–68.


Photos from kokakorecovery.org.nz with kind permission from Laura Molles.

10 December 2010

It's time to take a step forward

This blog post was written by postgraduate student Lauren Maciaszek as part of the course, Research Methods in Ecology (Ecol608).


Penguin road sign in Westland.
Photo by Mollivan Jon
Kaka, kotuku, kea, kakariki, kokako, kereru, and kiwi. What do all of these have in common? Apart from providing some interesting alliteration and perhaps a bit of a tongue twister, they are all native New Zealand birds which are considered nationally vulnerable, threatened, or endangered. The Department of Conservation’s (DOC) 2005 Threat Classification System showed that 153 bird species were considered at risk, chronically threatened, or acutely threatened. Another 50 bird species might be at risk or threatened, but there was not enough information known to be able to classify them.

Conservation is a necessity in New Zealand, unless we want our surviving bird species to follow the moa, Haast’s eagle, and huia to extinction. The biggest challenge for conservation, both in the past and looking into the future, begins right in the middle of our capital city at Parliament – it’s getting funding. DOC’s already strained budget is being tightened again, and every cent for conservation needs to be spent as wisely as possible.

This is where more studies like the one done by Jonah Busch and Lincoln University’s Ross Cullen would be useful. Busch and Cullen used a panel data set of yellow-eyed penguin nest counts to analyse different recovery treatments and their effectiveness and cost-effectiveness (the study was published in the journal Ecological Economics in 2009).

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Three recovery treatments were assessed. The first was trapping, in which traps were laid out to kill predators. The second treatment was revegetation, in which appropriate plants were planted to provide shelter for the penguin and provide better breeding conditions. The third treatment was intensive management, which involved an on-site manager who cared for sick or injured penguins and managed nest boxes. The site manager also used trapping and revegetation, so this method is essentially a combination and enhancement of the other two methods.

Using the data from the different sites, Busch and Cullen then used econometric techniques to analyse how effective the treatments were, by focussing on the population growth rate over time. They also allowed for other factors which might impact their results, such as time lag between the treatment being implemented and beginning to have an effect, and the presence of the Hooker’s sea lion.

The results of the econometric analysis showed that only one of the treatment methods, the intensive management, was responsible for a significant increase (about 9%) in yellow-eyed penguin nests over the period of time (13–15 years) that the data covered. This shows that both the trapping and revegetation treatments are not particularly effective on their own, and that money spent on these treatments alone could be money unwisely spent. The cost of each additional nest gained through intensive management was also calculated, with the final cost shown as about NZ$68,600. The study also concluded that the intensive management was the only cost-effective method, because it was the only method that was effective.

Ross Cullen stated that he “would warmly support similar studies being completed on other New Zealand threatened species”. These studies would better inform conservation managers in New Zealand about how to spend their budget, and provide them with an idea of the outcomes that are likely to be reached with the money spent. However, Cullen also points out that similar studies would require time series data collected from a number of sites, and that this might only be available for a few species.

Perhaps, then, it is time to start collecting more data. Information is power, and when monetary power is restricted by budgets and forced into trade-offs between conservation efforts, it seems to me that it’s best to have all the information we can get. The way I see it, the study runs an analysis on a set of already collected data – that means no extra cost, time, or disturbance to the animals, and the data is also being used by others (such as DOC). This could be the beginning of a large step forward in conservation management. After all, what have we got to lose?


Source:
Buscha, J., and Cullen, R. 2009. Effectiveness and cost-effectiveness of yellow-eyed penguin recovery. Ecological Economics, 68(3):762–776


15 November 2010

Not so different

This blog post was written by postgraduate student Rohith C. Yalamanchali as part of the course, Research Methods in Ecology (Ecol608).

Australia and New Zealand: different environments, similar weeds.
Sourced from Google Earth.

Invasion biologists use the term “naturalisation” to describe when introduced species form self-sustaining wild populations. A subset of naturalised species become so widespread and have such large impacts that they are regarded as pests and weeds. An important step in predicting new pests and weeds is predicting which introduced species will naturalise.

The success of naturalisation of the introduced species depends on factors such as the geological, climatic, and biological conditions of the habitats it is introduced into. The native species present in the habitat also play role in this success (competition for resources).

Australia and New Zealand are closely neighbouring countries separated by 1600 km of sea. The significant differences between two countries include Australia having 29 times more land area, 5 times greater population and very different types of wildlife than New Zealand. Also, the indigenous people of Australia are Melanesian in orgin while New Zealand Maori are Polynesian (see Yahoo! Answers for a wide ranging discussion about the many differences between New Zealand and Australia).

Along with these differences there are similarities which will aid the understanding of this article. Similarities, include the recent European colonisation history and the presence of temperate climate zones (although much of Australia is warmer and drier than any of New Zealand). Surprisingly, naturalisation of introduced plant species turns out to be another similarity between these two countries, despite their many environmental differences.

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Jeff Diez, Phil Hulme, Richard Duncan and Jon Sullivan from Lincoln University, and colleagues, have analysed the naturalisation patterns of introduced plants in New Zealand and Australia (Diez et al (2009)).

The results of the study showed that out of the 12927 species that were introduced in both countries the number of them naturalised in both countries are surprisingly similar (Australia 1713 species (13%) and New Zealand 1617 species (13%)). Similar patterns are seen in genera naturalised; out of 2663 genera introduced to both countries, 807 (30%) naturalised in Australia compared 746 (28%) in New Zealand. Of the 155 families introduced to both countries, 152 (98%) naturalised in Australia compared to 155 (100%) in New Zealand.

The analysis of the plant families successfully naturalised in both countries showed that the top four families are the same in both countries: Juncaceae (76% of introduced species in this family naturalised in NZ and 61% in Australia), Poaceae (46%-NZ and 30% Australia), Cyperaceae (42% NZ and 39% Australia), and Amaranthaceae (36% NZ and 43% Australia).

Note that ranking of these families within the top four differs between the countries. Juncaceae and Cyperaceae are the two families which hold the same positions (first and third respectively) in both countries. The other two families Poaceae (second in NZ, fourth in Australia) and Amaranthaceae (fourth in NZ, second in Australia) switch between second and fourth positions depending on the country they are in. A similar pattern is shown with the other families in two countries with some exceptions.

We can conclude that naturalisation patterns of introduced species in both the countries are not so different, most likely due to similarities in colonization history and overlapping temperate climate zones. The study by Diez and colleagues can be used as a guideline for future studies with regards to naturalisation patterns of introduced plant species in these two countries. It also suggests that environmental differences between invaded countries are less important for predicting new naturalisations than differences in the country’s cultures of plant introduction and cultivation.

Source:
Diez, J. M., Williams, P. A., Randall, R. P., Sullivan, J. J., Hulme, P. E., and Duncan, R. P. 2009. Learning from failures: testing broad taxonomic hypotheses about plant naturalization. Ecology Letters, 12:1174–1183.


08 November 2010

Urban Realities: the contribution of residential gardens to the conservation of urban forest remnants

This blog post was written by postgraduate student Elisabeth Christensen as part of the course, Research Methods in Ecology (Ecol608).

Urbanization has destroyed and fragmented natural areas, resulting in decreasing native biodiversity. Fragmented natural areas can only sustain small populations of plants and animals, and these are often vulnerable to extinction. Minor fluctuations in climate or resources, which would be unremarkable in large populations, can be catastrophic in small, isolated populations. Furthermore small populations have higher risks of inbreeding and a decrease in genetic diversity.


View Larger Map

In Christchurch City, the urban remnant Riccarton Bush is an example of such an isolated fragment of natural habitat. In Riccarton Bush, the number of native vascular plant species has declined by a third, from 106 to 67, over the last 125 years. In order to achieve sustainable wild plant populations, the management of urban remnants needs to find a way to expand the plant populations into the surrounding urban areas and thereby increasing their effective population size and genetic diversity. A recent study shows that residential gardens have the potential to play an important role in the conservation of native plant species.

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Brendan Doody, Jon Sullivan, Glenn Stewart, Harvey C. Perkins, all from Lincoln University, together with Colin Meurk from Landcare Research, recently published the first results from an ecological and sociological study in the journal Biodiversity and Conservation where they answered the three following questions:

  1. Are native woody species naturally dispersing from the urban forest remnant and establishing in surrounding urban residential gardens?

  2. How are garden management practices influencing the establishment of native woody species in urban residential gardens?

  3. What is the awareness of and support for the use of native plants among local residents?



Kahikatea tree
Photo by Alan Liefting
As an example of an urban remnant they specifically looked at Riccarton Bush, which is the only remnant in Christchurch dominated by the native tree species kahikatea (Dacrycarous dacrydioides, shown in picture and also known as white pine). Jon Sullivan says about the significance and rarity of Riccarton Bush: "It is the only old growth lowland forest in Christchurch to have survived the creation of the city. It is also one of only two lowland old-growth forest fragments left in mid-Canterbury that are not associated with the Southern Alps or Banks Peninsula." Nationwide, only 2% of pre-settlement kahikatea forest remain.

The study revealed that some of the native woody species, especially kahikatea, are dispersed by birds into the surrounding gardens, mostly within a radius of 250 meters. However it also showed that the juvenile trees never reach maturity as most gardeners tend to remove all non-planted woody species.

These results suggest that there exists a natural potential for regeneration but that it is insufficient without human intervention. This is where the last part of the study becomes interesting. What is the attitude towards native plants among garden-owners?
A carefully designed questionnaire was developed to answer this.

The results from their questionnaire revealed that attitudes towards New Zealand's native flora were overall positive. 84% agreed or strongly agreed that ‘species unique to New Zealand are important to our identity’ and 81% that ‘native plants are attractive’. When it came to having native plants in their own gardens the answers were a bit more reluctant yet still positive - 54% agreed or strongly agreed ‘they would be prepared to plant Riccarton Bush species in their garden’.


Kahikatea seedlings.
Photo by Mollivan Jon


The study also found that people in general lack knowledge of native species, for example only 2% were able to correctly identify a seedling of the kahikatea tree. This suggests that information and education is an important step towards engaging people in conserving native plants. Another important factor is for the garden-owners to have control over the location of plantings as many are concerned about too much shade in the garden.

If this article has encouraged you to get out there and help preserve New Zealand's native plants, you can get in contact with an organization such as Trees for Canterbury which does community projects and environmental education and has a native plant nursery. The majority of their trees in the nursery are grown from seed collected in the Canterbury Plains and Banks Peninsula in order to ensure genetic integrity of the native plant populations. This is an important fact to remember, as the genes of native plant populations in the urban remnants are adapted to make them fit for the local environment. However this may be threatened by gene flow from non-local or modified plants in the surrounding gardens.

Source:
Doody, B. J., Sullivan, J. J., Meurk, C. D., Stewart, G. H., and Perkins, H. C. 2010. Urban realities: the contribution of residential gardens to the conservation of urban forest remnants. Biodiversity and Conservation, 19:1385–1400.


14 October 2010

The long invasion

New Zealand has worried about invasion for the last 200 years. Dotted around our major harbours are gun emplacements built to repel Russian and Japanese imperial designs in the late nineteenth and mid twentieth century’s, respectively. Of course neither of these invasions eventuated but there have actually been enormous numbers of successful invasions into our proud island nation. Thousands of plants, hundreds of insects and multitudes more have colonised New Zealand since Europeans themselves arrived. Species continue to arrive and New Zealand spends a lot of time and effort in preventing them from doing this or in trying to reduce the impact of these invasive species when they do get here. Much of the ecological research at Lincoln University and the Lincoln Crown Research Institutes is centred around these issues. One strand of this research is to understand the rules that describe the spread of non-native species through the landscape and over time. Many aspects complicate our understanding of these rules especially the fact that rules may differ at the level of local habitat, region or island. Also, factors that are important in the early phases of an invasion, like human modifications of habitat that suit the invading species, may be less so after several decades when the invading species becomes more widespread.

hawkweedA carpet of Hieracium pilosella hawkweed in the Canterbury high country. Photo by Mollivan Jon
In a new study published in Austral Ecology, Nicola Day and Hannah Buckley of Lincoln University have looked at the fate of three closely related invasive species over three decades. The plant species Hieracium (Hawkweed, Asteraceae) are native to Europe but are invasive in many parts of the world where they often degrade native and pastoral grasslands. In New Zealand, three species in particular, H. lepidulum, H. pilosella, and H. praealtum, were introduced accidentally in grass-seed mixtures and cause major problems in high country areas. Day and Buckley wanted to know which ecological and environmental traits explained the spread of these species, whether these traits were important at all scales and whether they were the same for all three species. To test these ideas they were able to make use of a fantastic long term study. In the mid 1980s, 124 study sites were set up in high altitude tussock grasslands in Otago and southern Canterbury. Information about the plant species found at these sites and characteristics of the site, like levels of calcium and phosphorus and climate data, were collected. The sites were resampled in the mid 90s and again between 2005 and 2007. So Day and Buckley had the luxury of looking at the changes that had occurred over three decades.

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Overall, all three species increased at all scales during the study. All three species had complex relationships with the various traits measured. However, it appeared that there were some predictable patterns to be detected. For example, all three species were better able to invade areas of short-tussock than tall-tussock. It also appeared that each species shared a similar invasion trajectory for their population spread but that they were at different phases in their invasions. H. praealtum is widespread but its increase is slowing and is probably towards the end of its invasive phase. H. pilosella is in an earlier stage of its invasion and continues to spread at a high rate. H. lepidulum is only a minor component in the grasslands and seems to be in the earliest lag phase of its invasion (H. lepidulum was the last of the three species to naturalise). This study shows the benefit of sampling over decades and over large distances. In some ways this is a little worrying for ecological research which typically does studies over small scales and one or two years. Day and Buckley show that to understand the small scale you sometimes have to think at the larger scale.


Darwin & the Sandwalk 3


Here is one that is just as topical as it was in the 90s. The Marsden Fund is the major fund for 'blue skies' (i.e. no immediately applied purpose) science in New Zealand. This year 91% of those that applied failed to get funding! I'm not sure that Charles would have recieved much funding in this environment! "Oh yes I'd like to breed a few pigions and see what happens".

01 October 2010

Life above our heads – the invertebrate fauna of West Coast rata canopy

This blog post was written by postgraduate student Andrea Honig as part of the course, Research Methods in Ecology (Ecol608).


Kathrin Affeld did not choose an ordinary topic for her PhD thesis at Lincoln University. She and her team of scientists carried out a research project on the invertebrate fauna high up in the canopy of northern rata trees on the West Coast of the South Island of New Zealand. Northern rata, or Metrosideros robusta, in the family Myrtaceae, are tall emergent trees in New Zealand's temperate rain forests and before Kathrin's work their canopies were unchartered territory for science. Her project would be a real pleasure for all the outdoor climbing fans among us.


To collect data, Kathrin climbed 15–25 m up each tree before she could set up her experiments. Photo by Mollivan Jon


As Kathrin stated in 2004, “I’m looking at invertebrate communities that live in epiphytes and their response to climate change.” The study gave a significant insight into the high level of invertebrate diversity present in the canopy of northern rata trees at the two sites studied and uncovered several species new to science including one genus of species

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Kathrin and her colleagues decided to sample epiphyte mats directly, because conventional methods, such as insecticide fogging, would not be appropriate for capturing all invertebrates, as any individuals in funnel shaped plants or thick humus layers would be missed. Each sample had to be detached from the bark and transported carefully in plastic bags to the lab. Invertebrates were extracted using Berlese funnels over several days.

Berlese funnels are a common method to extract invertebrates from soil or litter samples. Heat produced by a light bulb dries the sample. Invertebrates will move away from the light and heat and fall down the funnel through a mesh into a preservative fluid (for example, ethanol).

Berlese funnel.
Illustration by
Andrea Höing, Lincoln University.


To make sure all invertebrates were extracted the researchers washed all remaining organic material over three stacked sieves with their mesh size decreasing from 1.7 mm to 75 μm.


Berlese funnels in action extracting invertebrates from Kathrin Affeld's canopy samples. Photo by Mollivan Jon


Identification could be conducted by expert taxonomists for most species to family level, but it was a great challenge to go further and just 16.2% were assigned to species level. There were at least 10 new species found and one new genus, although there is likely to be many more species new to science amongst the many specimens that could not be identified to species. All of the species collected in this study can be viewed at the Entomology Museum at Lincoln University, Canterbury, New Zealand.

Data analysis showed that the study reflected only a portion of the real biodiversity in the podocarp-broadleaf forests canopy. This portion already indicated a highly diverse invertebrate fauna, both functionally and taxonomically (more than 242,000 invertebrates were collected). Results were presented in a 17 page long table giving important baseline information to each species, site where they were found, sampling time, feeding guild and their status, if they are endemic, introduced, cosmopolitan or native.

The most interesting discoveries included the following.
  • Several undescribed and new species in epiphyte mat habitats (>10 new species).

  • Extended geographical ranges for various species.

  • Large arboreal ant colonies; until this study they had been known as solely ground nesting species.

  • Relatively small numbers of exotic insect species (7 species, all in relatively small numbers); this information is very important for assessing invasion risk.


All this information is important in terms of national biodiversity inventories and global species estimates. Kathrin further recapitulated the importance of investigating invertebrates and epiphytes of New Zealand: “Understanding their distributions and interactions is fundamental for predicting and dealing with the threats posed by habitat loss and climate change. Data from my study could further be incorporated in climate change models and used to identify conservation priorities.”

This study was the first invertebrate inventory of New Zealand forest epiphyte habitats. It provides important baseline data for conservation of biodiversity in New Zealand's forests. However, it also highlights how much we have yet to learn about the amazing bio-diverse canopies above our heads. For detailed information on this study see Affeld et al. 2009.

Affeld, K., Worner, S., Didham, R.K., Sullivan, J. Henderson, R., Malumbres Olarte, J., Thorpe, S, Clunie, L, Early, J, Emberson, R., Johns, P., Dugdale, J., Mound, L., Smithers, C, Pollard, S., and Ward, J. 2009. The invertebrate fauna of epiphyte mats in the canopy of northern rata (Myrtaceae: Metrosideros robusta A. Cunn.) on the West Coast of the South Island, New Zealand. New Zealand Journal of Zoology 36,177–202.

27 September 2010

Darwin & the Sandwalk 2

Another SYSTANZ cartoon from the 90s.

21 September 2010

Coast-to-coast, biodiversity style

This past weekend, staff and students of Lincoln University's Ecol202 course, Biological Diversity, ventured west for their annual three day field trip of field biology and weather. This year held a bit more weather than usual, on account of a large storm slamming into the western side of New Zealand. It was reportedly one of the largest storms on the planet at the time, about the size of Australia.

Still, West Coast weather is never predictable so off we went. Things worked out surprisingly well. Rather than the usual New Zealand weather of "four seasons in one day", we instead got "four seasons in one hour". Each hour. We got a snowed on, rained on, blown about, and, surprisingly often, shined on.

A nice place for a lecture
David Pontin discusses kelp ecology at Truman's Track. Photo by mollivan_jon

beech
Beech-licking good. Sampling Ultracoelostoma honeydew in Lord's Bush. Photo by mollivan_jon

Highlights of our trip this year were seeing a New Zealand falcon (at Kelly's Creek in Arthur's Pass), plenty of weka around Moana, glow-worms in Punakaiki Cavern, a northern rata mid-way through strangling a large matai tree along Truman's Track, Lord's Bush (one of the last forests of the Canterbury Plains), and, as always, the Westland petrels flying in from the ocean to their colony at dusk.

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Some ill-timed horizontal rain squalls curtailed our annual fish'n'chips evening on the beach. We usually have dinner on a beach just south of Punakaiki watching Westland petrels (Procellaria westlandica) approach land. The rain dampened our chips forcing us to retreat to our bus. The huge stormy seas also prevented us from seeing to the horizon over the breaking waves where the Westland petrels would have been gathering. Gathering they were, though.

After dinner in the bus, we headed down to the roadside beside Nikau Scenic Reserve and watched the dark petrels slip through the sky to their colony in the forested hillside behind us. Student Tim Gale and I counted 89 birds arriving in 25 minutes between 6:47 pm (when the first bird arrived) and 7:07 (when we had not seen another bird for several minutes). That is down from the 150 birds we counted on last year's trip but is still an impressive turn-out for such a weather-filled evening.

It is quite something to see Westland petrels as they represent a glimpse into what much of coastal mainland New Zealand would have been like before people and their mammals arrived. The species is also remarkable in that it only nests in this area of the West Coast of the South Island and yet the birds regularly range at sea as far as the Chatham Islands to the east and are thought to go as far east as South America.

For the first time, we also did plant plots along our coast-to-coast transect where we recorded the diversity of shrubs and trees and measured features of the leaves of each species. Our trip spans over a 1,000 m of elevation and 5,000 mm (yes, five metres!) of annual rainfall so we hope to see some strong signals in the leaf morphology of the vegetation along the way. If it works out, we will tell you all about it on this blog.

You can see photos of our trip on our Ecology@Lincoln Flickr group.

20 September 2010

Are two heads better than one? Kokakos and playback responses

This blog post was written by postgraduate student Jetzabel Gross as part of the course, Research Methods in Ecology (Ecol608).



A Kōkako (Callaeas cinereus). Taken at Mt Bruce
Wildlife Centre, New Zealand.
Photo by Doug Mak
The perception of reality is different for each animal species and communication can be a very helpful resource. Yet animal communication skills are a complex topic to understand, for example, what is the function of bird songs? How are they perceived? Do only birds of the same species react to songs or do others as well? And more importantly are song emitters perceived differently by single or paired receivers?

These are some of the questions specialists working on bird behavior ask themselves and the research by Lincoln University's Laura Molles and Waikato University's Joseph Waas , whose results were published in the journal Animal Behavior in 2006, try to answer. Moreover with this study they wanted to generate knowledge of the advantages of both birds singing the same song at different times, or only the male singing, or the pair singing.

Hence, two variables were tested: one where the song of a single bird was broadcasted from one speaker and another where the song was split up between two speakers, simulating a duet. The perception of threat to a territory was measured by how fast nearby birds approached the playback speakers and by how long male and female birds of a pair spend next to each other.

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Photo by Guy Vickers
(Used with permission of Laura Molles,
kokakorecovery.org.nz )
To test these predictions in 2003 they conducted research in specially selected and marked areas of the Pongakawa Ecological Reserve, North Island, New Zealand. In these playback arenas, 11 territorial pairs of endemic and endangered, New Zealand kokako birds (Callaeas cinereus wilsoni) were tested and two playback stimuli were performed and each repeated four times. Observations were recorded visually and by audio indicating location of each bird and distance between pairs. The treatment consisted of three phases: a lure phase to attract the bird until it reached a specific position; a main playback, which lasted around three minutes and was the focal period where behaviours for the main findings of this research were extracted; and a post-playback period where observers kept monitoring birds for 30 minutes.

The main findings are as follows.

  • Perceiving Danger: Pairs (female and male birds) feel more danger to their bond if the song is broadcasted by a pair rather than by a single bird. This was suggested after observing that speakers broadcasting this simulated duet were approached faster by the bird pair. Some possible explanations for this faster approach are: 1) that birds find it easier to locate the two speakers, 2) confusing source of sound, 3) two speakers perceived as a moving opponent, thus more danger and 4) two speakers were perceived as very close opponents.

  • Proximity: Bird pairs did not stay close together during playback periods. It appears that the perceived danger in both broadcast situations is to the territory rather than to the bond. A remarkable observation is that cooperation for territory defense may be argued since observations indicated that male and female birds approached the speakers together.

  • Answering playbacks: Birds did match and anticipate the playback song very quickly suggesting that the birds pairs are quick in recognizing and react accordingly to familiar external audio stimuli.


Vandercamp, Naugib and colleagues suggest that matching and anticipating are aggressive signals in kokako, which has been observed in a number of other species.

The relevance of this kind of study is to generate expanding knowledge of the different functions singing brings to birds, and how essential it is for the maintenance of the complex interactions between them. Finally, a solid understanding of the behaviour of any relevant species is essential for conservation efforts on them.

Source:

Molles, L & Waas, J. 2006. Are two heads better than one? Responses of the duetting kokako to one and two speaker playback. Animal Behaviour, 2006, 72: 131–138.


17 September 2010

Darwin and the Sandwalk


During the 1990s the Systematics Association of New Zealand was a very active science group with regular conferences and a membership of around 100. SYSTANZ was based around scientists who were interested in systematics (the science of working out evolutionary relationships. There is an old site for SYSTANZ which has a good definition of what systematics is. Earlier this decade, for various reasons, the association went into abeyance. During the 1990s I was lucky enough to be the secretary for the association and produced regular newsletters. One of the things that Cor Vink and I added to newsletters were a series of cartoons. One was themed around Darwin walking along the Sandwalk (the route he built at Down House to take some exercise and ponder). Many of them were based on finding reasons for Darwin's delay of many years in publishing the Origin. The other series was on a phylogenetic superhero called Unrootedtreeman. Rather than consign these to the bottom of filing cabinets throughout New Zealand forever, I will occasionally show them off here at EcoLincNZ. This is the first one that wonders what would have happened if pay for view TV was around in Victorian times....


10 September 2010

Shaken but not stirred


The ecology staff are back at work today. Offices have been tidied, labs set right and we will be open for lectures on Monday. Ecology at Lincoln seems to have gotten off lightly after the big quake and aftershocks. The Entomology Research Museum is largely intact with some damage to one of the rows of cabinets (but it did the job in protecting the specimens). The wet collection is also intact. John Marris, the curator, took the accompanying photo. His office was in much worse condition!


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Interestingly, ecology staff at Lincoln have done research over the last couple of decades on the impact of earthquakes on forests in New Zealand. Richard Duncan and Glenn Stewart have looked at the periodicity of when trees were knocked over by earthquakes to get a picture of when future big quakes were dues. As they have reminded us for a decade, we are well overdue for a large alpine fault quake. Unfortunately, the one earlier this week was from a fault on the Canterbury Plains and we still await the other!


09 September 2010

A whole lot of shaking going on


What a long time a week is since the last blog! A 7.1 earthquake hit the Canterbury region at 4.35am on Saturday morning. The epicenter was just over 20 km away from Lincoln University. Despite a lot of damage there was, incredibly, no loss of life. This was due to the time of day it hit, luck and the preparedness of NZ for such quakes. We're not known as the shaky isles for nothing. However, this was the biggest land centered quake since the 1930s. And what a ride it was. The quake went for over 40 seconds which was long enough to think about exactly how big it was. A terrifying experience. Since Saturday there have been over 300 aftershocks, many over 5.0. Lincoln University has sustained a reasonable amount of damage which has closed the university for at least this week. The Ecology Department is in reasonably good shape.


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A couple of staff went into the department a few hours after the initial quake to get generators onto incubators and -80 freezers as there was a loss of power for most of the day. Most labs were surprisingly well off, having tight regulations for earthquakes seems to have worked. Most offices were a mess, monitors down, books all over, windows broken, filing cabinets toppled. I'm pleased we weren't working on the 4th and 5th floors at the time. We were concerned about the Entomology Research Museum and the priceless collection of insects but the new cabinets (upgraded just over a year ago) did their job. There was some damage to some of the collection not yet put away. The biggest remaining worry is for the wet collection which wasn't checked. Still overall, ecology seems to have survived and we should be back to work by Monday.


02 September 2010

The spirit of wine shall be green

This blog post was written by postgraduate student Juan F. Dueñas Serrano as part of the course, Research Methods in Ecology (Ecol608).



I know the cost in pain, in sweat,
And in burning sunlight on the blazing hillside,
Of creating my life, of giving me a soul:
I shall not be ungrateful or malevolent


Charles Baudelaire (1821-1867), The Spirit of Wine.

Set aside your work for a moment. Look for your favourite spot at home and allow yourself a moment of pleasant rest. Take a bottle of your preferred New Zealand wine and enjoy a sip while you read the label on the bottle. Does the description match your expectations? Hopefully, it will be a brief summary of the characteristics that help to define this delightful drink. Sometimes, labels will describe a picturesque bucolic scenery or use the notion of profound human values to remark on the quality of the product. Virtues such as honesty, character and, why not, spirit, are all often associated with wine. So let's think about where all these images and language come from.


Leafroller moth's caterpillar (Epiphyas
postvittana
) on a grape leaf.
Photo by Jean Tompkins, Lincoln
University
(used with permission).
Winemaking starts at the vineyard. It requires many years of study, experience and sometimes intuition to yield a grapevine that will satisfy the demands of discriminating consumers. But more than that, it requires a gifted land. Remember that the wine industry is a multi-million dollar business, so grapes are to be carefully selected and cultivated yet they also have to come in great volume. Accordingly, vineyards generally tend to become extensive mono-cultures, and like any other intensive resource use, this practice radically changes the landscape and carries with it a series of associated problems, such as increased vulnerability to pests. In the case of New Zealand vineyards, the introduced Australian leafroller moth Epiphyas postvittana is the unwanted guest and it must be controlled.

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Up until now, the conventional approach has been to apply pesticides over the precious vineyards to get rid of the inopportune 'bug'. But this presumably affects the environment, increases the cost of the final product, and potentially, will have a negative impact on the very glass of wine you are enjoying. The solution might come from nature. Regulation of insect populations by predation occurs naturally in an ecosystem, thus, if handled carefully, this capacity might potentially provide the agricultural landscape with a service, an 'ecosystem service'. This concept provides the basis for an alternative approach that tries to encompass the demands of a complex industry and the need of a truly sustainable landscape. After all, land is where the spirit of wine begins its journey.

This alternative to pesticides involves the manipulation of the habitat to enhance biological control, and it offers a great potential. A recent study published in the Journal of Applied Ecology by Mahumuda Begum and colleagues, including Lincoln University's Steve Wratten of the Bio-Protection Research Centre, features a series of greenhouse and field experiments that test the ability of selected flower's nectar and pollen to enhance the function of the omnivorous parasitoid wasp Thichogramma carverae. This was is a natural enemy of the light brown apple moth. Flowers potentially supplement the wasp diet by providing important resources such as sugar from the nectar and protein from pollen.

The main idea behind this approach is to incorporate selected flowering plants into the agroecological scheme of vineyards, hence naturally increasing the density and longevity of the wasp. This approach benefits the vineyards in different ways. First, by avoiding the costs associated with breeding up and releasing large numbers of the parasitoid. Second, by reducing occurrence of weeds and cover crops that can potentially host different stages of the pest by planting instead the selected plants; and third, by reducing both the cost and the amount of pesticides that need to be applied to vineyards.


Allysum (Lobularia maritima) strips in an organic lettuce crop.
Photo from Lincoln University (used with permission).


But the process is not straightforward. Experiments were needed to determine the best plants to provide the required 'ecosystem service', in this case biological control. The selected plants should not interfere with the wasp's ability to parasitise the moth. Additionally, the plants have to be a below-vine, shallow-rooted crop to avoid resource competition with grapevines. After conducting greenhouse experiments with combinations of several plant candidates in the presence of the parasite wasp and the moth, a trial in the field was performed to test greenhouse findings in a realistic situation. From the five plants originally selected, Begum and colleagues concluded that sweet alyssum (Lobularia maritima), a common garden plant, is the most effective candidate for the purpose described above.

This study demonstrates how the careful and informed manipulation of natural resources can improve the provision of ecosystem services. By integrating research on the functions that ecosystems naturally provide with reasonable economic revenue, we are taking a step forward towards the sustainability of our land. These alternatives to conventional practices are promising and will enable us to work with nature instead of against it. We will be assuming our role in providing environmental stewardship, or kaitiakitanga as Maori people beautifully put it, while giving wine a rightful 'green spirit'.

31 August 2010

The big pitcher

Ecologists spend a lot of time thinking about how species in communities are linked together. While we have made progress in understanding this at small scales (like your backyard) we have seldom tried to understand this at large scales (like across continents). One of the reasons for this is that there are huge numbers of species in communities and the problem of dealing with them all is too difficult. However, some communities are not so complex. Hannah Buckley (Lincoln University) and her colleagues, Thomas Miller (Florida State), Aaron Ellison (Harvard) & Nicholas Gotelli (Vermont), realised that there are some communities that are easier to study. In a paper published in Global Ecology and Biogeography, the team looked at communities that live with pitcher plants over much of North America. Pitcher plants collect rainwater in their leaves and these pools are colonised by species of bacteria, insects and so on. The pitcher plants create a simple community that can be investigated at a several scales: different pitchers (or cups) within a plant, different plants within a local population, and across the plant’s entire distribution (continental scale).
The pitcher plant Sarracenia purpurea was the subject for their study and is a long-lived (> 50 years) carnivorous plant that grows in bogs, sand plains and pine savannahs across much of North America. The pitcher-shaped leaves are open to the sky and collect rain and snow as well as various species of animals and bacteria that happen to arrive in the cups. Many of the species, finding themselves trapped in the pitcher, drown and form the basis of a food chain on which other species feed who, in turn, provide food for predators. The plants are thought to absorb some nutrients, particularly nitrogen and phosphorus, from the decaying bodies.

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Buckley collected the contents of pitchers from 39 sites across North America. When examined, across all sites, the researchers found 13 arthropod & rotifer species, 48 protozoan species and 29 bacterial morphotypes. Pitcher plants typically hosted 6 arthropod species, 9 protozoans and 17 bacterial species. Nearly half of the species found were only from one site, whereas 4 species that specialise in living in pitchers (three fly and one mite species), were found at almost all sites. Overall, and very surprisingly, pitchers at the same site were less similar to each other in species make-up than comparing pitchers at different sites across North America! That is food webs, and therefore communities, were more variable at the smallest scale that at the larger scale. This is probably not as surprising as you would first think. For example, the streets in your home town can be highly variable as to the businesses that you might find there but if you compare between towns they will generally all have a pharmacy, a supermarket, a fish’n’chip shop, hairdressers, a joinery and so on. It’s all about the scale you ask your questions at. And that is the key finding of this study.
This study emphasises the benefits of examining how communities change at a variety of scales and should serve as a model for others. Buckley and her co-authors intend to use this idea of simple natural communities in future studies to examine the effects of local and continental scales on how biotic and abiotic challenges affect species richness and community membership.


26 August 2010

Not-so incy wincy spider

Cor Vink, adjunct curator of spiders at the Entomology Research Museum, Lincoln University and research scientist at AgResearch, has recently published a taxonomic revision of the New Zealand Pisauridae (nurseryweb spiders) with his colleague Nadine Dupérré (American Museum of Natural History) – Vink CJ, Dupérré N (2010) Pisauridae (Arachnida: Araneae). Fauna of New Zealand 64: 1-60. A taxonomic revision takes a good look at what we know about species in a particular group as well as any new species that have been discovered since the last major look. The Fauna of New Zealand series will eventually aim to cover all of the species found there. Cor is New Zealand's leading arachnologist and has discovered many new species of spider. Nadine is a talented drawer of spiders and you can see some of her work in the latest Angelina Jolie movie Salt (one of the characters is an arachnologist).

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Nurseryweb spiders are easily recognised in New Zealand by the nurseryweb that the female builds around the eggsac, which serves to protect the newly emerged spiderlings. New Zealand nurseryweb spiders do not build a web for prey capture and are sit-and-wait predators. Four closely related species of nurseryweb spiders are found in New Zealand; three on the mainland and one on the Chatham Islands. All species are endemic to New Zealand and are likely to be related to Australian species. The most common species is Dolomedes minor, which is found throughout New Zealand in scrubland, grassland, swamps, and marshes. Dolomedes aquaticus is found in open riverbeds and stony lakeshores throughout the South Island and in the southern half of the North Island. Another species, Dolomedes dondalei is found in shaded riverbeds throughout mainland New Zealand. The Chatham Islands species, Dolomedes schauinslandi, is known from only three islands (South East, Mangere, and Houruakopara Islands) and is nationally endangered due to its restricted range. Molecular evidence of interbreeding between two common mainland species, D. minor and D. aquaticus, was also discovered and this is being investigated further by B.Sc. honours student Vanessa Lattimore.


23 August 2010

Success for Nina Valley Restoration Group

Hurunui College established the "Nina Valley Restoration Group" at the start of 2009. Nina Valley is located near Lewis Pass and is a region of beech forest. The valley has a good level of accessibility with tracks running from the road to the head. A major goal of the group is to establish a breeding kiwi population. The group has successfully gained funding from BNZ Save the Kiwi and the Air New Zealand Environmental Trust.

The funding has been used to purchase 150 DOC200 and 40 Henry (resetting) traps to control mustelids, particularly stoats. Stoats have a large impact on bird breeding paopulations. In November 2009 about 20 volunteers - students, parents, and a couple of NZ Deerstalkers Association members - spread these out over 15 km of river valley in the Nina valley. The traps were checked and reset fortnightly by groups of 5-6 students and parents over the summer season.


The 2010 Youth Leadership for Sustainability Awards are a joint initiative between Environment Canterbury and Ngai Tahu recognising awareness of environmental and social issues among Canterbury’s youth. The individual award was open to students in Years 12-13 and recognised their work in sustainability, either through their own initiative or by supporting or leading a wider project. The group award celebrates the contributions of a youth organisation, marae or school. Nina Valley Restoration were placed as group category prize-winners, along with Lincoln Enviro Organisation and Youth River Action, in recognition of their excellent work.


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The "Restoration Group" consists of around 20 students, ranging from 12-15 years old. It was set up at the beginning of 2009 by Hurunui College science teacher, Tim Kelly, and DOC ranger, Malcolm Wylie. Since then, the group has done kiwi-listening, and trapping and tracking-tunnel training. They have had hands-on opportunities to view kiwi eggs and chicks raised through the BNZ Operation Nest Egg at Willowbank.

Since the Group was formed staff and students from the Department of Ecology at Lincoln University has helped with installing and monitoring tracking tunnel (purpose built wooden tunnels containing inkpads and paper that record when stoats move through them). Also, the department has hosted a group of Hurunui student while they investigated stomach contents of stoats caught in traps at Nina Valley.

Tim Kelly has recently applied to the Royal Society of New Zealand for a 6-month teaching fellowship. If successful he will be hosted at Lincoln University while working with Drs James Ross and Adrian Paterson and his study will investigate new self-setting traps for stoats and possums.

How to have a lousy time in Durham

Durham, England, famous for its grand old city and cathedral, where bus loads of senior citizens spend their day dragging their Zimmer frames over the cobbled streets to admire ye olde England. More recently and probably more famous in New Zealand, Durham's castle and cathedral might be better known as Hogwarts School of Witchcraft and Wizardry, as seen in the Harry Potter films. So, what have Lincoln University and Harry Potter got in common? Not a lot, but it sets the scene for where my current fieldwork is based.

I am in northern England to sample birds for feather lice. As you sit and scratch, feeling small legs walking through your hair, you might ask why I would travel half way around the world to do this. The source of almost all of New Zealand's introduced song birds is the UK. Sparrows, blackbirds, skylarks and finches, amongst others, were brought to New Zealand by settlers to help create a sense of home. Along with the birds came their feather parasites, although not all of the species. It is the pattern of what made it and what didn't that is of interest to us and will allow us to better think about invasive species (see this previous blog). We know how the lice are distributed around New Zealand but have only minimal knowledge about their ancestral home, especially the northern areas of England where many settler-ships left from. To model UK distributions of chewing-lice, I have been catching selected bird species and processing them for chewing lice.

While you suffer winter in NZ, I am enjoying the UK summer. I arrived in the UK in early July and quickly made arrangements to join British Trust for Ornithology (BTO) bird ringers in the field. Bird ringing (or banding) is heavily regulated in the UK and takes at least two years to gain a licence to ring birds without supervision. Naturally, this is well beyond the scope of a Masters project. This means that I am at the mercy of suitably qualified people to complete my research. All of the ringers that I work with volunteer their time and they also pay for the rings and all other costs associated with ringing birds.


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Apart from their natural love of birds, there are other reasons why these people ring birds: the BTO run various ringing programmes, such as The Constant Effort Sites Scheme (CES) and Retrapping Adults for Survival (RAS) that rely on data collected by these volunteers. The CES sampling protocol dictates that each site is visited once every 10 days during the breeding season (this means 11 visits). The effort at each site remains constant, i.e., the same number of nets in the same positions for the same amount of time. For example, at the Foxglove Covert CES they erect 30, 18 metre mist-nets, begin ringing at sunrise (4am in mid-summer) and remain ringing for 10 hours; whereas, at the Rainton Meadows CES they erect 8 mist-nets (a mixture of 12 and 18 metre nets) and catch birds between 7am and 1pm.

The benefit of CES for my fieldwork is that I can plan on mist-netting at least once every 10 days, weather permitting. Birds loose body heat rapidly when they get wet, so to avoid bird mortality, nets must be collapsed when it rains. Wind also affects sample effort; birds are less active in high wind and the nets become highly visible flapping about. More importantly, birds can also be injured in a moving net (e.g., broken wings and strangulation). CES sites are usually visited in the weekend, so I must decide on which to visit. Lately, I have gone where I catch the greatest number of birds, but soon, to increase the number of records for more rare species, I will have to concentrate on locations where specific bird species are caught.

This is a convenient segueway to the RAS (Retrapping Adults for Survival) scheme. Sites are selected where many individuals of targeted species will be caught for monitoring species survival rates. So far, as part of my study I have processed birds at yellowhammer, house sparrow and blackbird RAS sites. There are some species that I have few records for, so I need to find redpoll, songthrush and starling RAS sites to sample at. Which should fill the last five weeks that I am here.

While I am not delousing birds in the field, I process my samples in the lab (thanks to Biological sciences at Durham University). This entails sifting through my field samples under a dissection microscope. I have become quite tuned into finding lice floating about in a mixture of ethanol and flea powder, but it still takes about one day to process 10 samples. I have processed 135 birds (about 10% of all the birds caught at these sites) and blackbirds are by far the most lousy bird, both for prevalence and intensity.
Ok, gloves on and back to work....


11 August 2010

Banks Peninsula Biodiversity Workshop: Proceedings

The Biodiversity Workshop that was held at Akaroa in October 2009 is now available as a proceedings. The proceedings compile information from the various presentations given on the day and were put together by Mike Bowie, Rachel Barker and Tina Troup.

Over the course of a very successful day, scientists, conservation organisations and landowners came together to talk about conserving Banks Peninsula’s special plants, birds, lizards, fish and invertebrates. The proceedings run to 49 pages and are packed with information on on trapping various predators threatening the native species, how to conserve and/or restore habitats of native species present on Banks Peninsula as well as updates on the management of various endangered species, such as tui or little penguins.

You can read the proceedings here.

19 July 2010

Vegetarian zombie weevils rise from down under


A Canterbury Knobbled Weevil on Aciphylla.
Photo by Mike Bowie, Lincoln University
(used with permission).


In 2004, in an unsuspecting sleepy town in South Canterbury, zombies rose from the dead. Headlines were dedicated to spreading the news, zoologists world-wide were excited, all due to the rediscovery of a species thought to be extinct for 82 years! Wow, like the takahe? Well, maybe: a weevil. It may be smaller than the charismatic species we are used to hearing about, but no less important.

Despite the fact that specimens are located in history museums around the world, the endemic Canterbury knobbled weevil (Hadramphus tuberculatus) had not been seen alive for 82 years. To everyone’s great surprise, it was rediscovered in Burkes Pass in 2004 by Laura Young while she was studying for her Masters degree. It is currently one of New Zealand’s most endangered invertebrate species. The news at that time exclaimed how four specimens were found (and consequently pinned and archived). But what happened after that? Were there any survivors? Lincoln University researchers and students were quickly hot on the trail of this elusive large, flightless knobbled critter to find out.

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Following the rediscovery, conservation efforts to save this species have been impressive, especially when we know so little about the species. Sampling measures have mainly included the use of pitfall traps and visual searches of the speargrass species that the weevil is known to primarily feed on (speargrass, or Spaniards, are species of Aciphylla, a famously spiky New Zealand plant in the carrot family). These efforts located more weevils within a second site on farmland across the road from the location of the initial rediscovery. However, until this last summer, all past efforts found very few additional weevils in either area. The summer of 2007–2008 recorded just six specimens; five located on Aciphylla, one in a pitfall, and the 2008–2009 summer returned no weevils at all. Thankfully, the past season (summer 2009–2010) found 49 weevils, the majority of which were recorded in the original area and all bar one were caught in pitfall traps.

Emily Fountain, a Lincoln PhD student currently studying the weevil, has hypothesised that the reasoning for these vast differences in weevil numbers between years is due to the ecology of the speargrass. Many threatened New Zealand birds put much more effort into breeding during the years their food plants flower heavily (“mast-seeding”). In contrast, Emily thinks that knobbled weevils are easiest to catch in years of poor flowering. Last summer very few plants flowered. Emily proposes that this caused a weevil mass movement, interplant dispersal, to locate more food resources that resulted in a very successful pitfall trap count. The previous two summers were good flowering years so the weevils are thought to not have needed to move around so much. This may be why the few specimens that were found were mainly located on the speargrass plants rather than between them.

Environment Canterbury and Department of Conservation staff in Twizel have both been frantically trying to protect the weevil and its habitat with the use of rat, stoat and hedgehog predator control since its rediscovery in 2004. Lupin spraying and the decapitation of wilding pine seedlings has also been a priority to stop competition with speargrass. The future conservation efforts for this species may include translocations, but this will only be once Emily’s research into the genetic health of the current population is completed. This research will allow us to see if the species is genetically stable enough to survive in additional populations. Until this time, a booklet has been released by Mike Bowie (Lincoln University) to inform farmers, and the general public, on what they can do to help locate more weevils and how they can aid in the species conservation. If you find a large knobbled weevil on a speargrass in Canterbury or Otago, please contact Mike.

Although the Canterbury knobbled weevil is, well, a weevil, its rediscovery was a significant event in New Zealand’s history. It reignited the awareness in the general public about the importance of the lesser known species. It also provides hope for other ‘extinct’ species that may be out there somewhere, still managing to survive under the radar of human detection, waiting for their chance to walk, or crawl, among the living again.


More information:
Bowie, M. 2009. The Canterbury Knobbled Weevil, Hadramphus tuberculatus, Conservation Guide. Lincoln University. (1.7 MB PDF)

Young, L. M., Marris, J. W. M., and Pawson, S. M. 2008. Back from extinction: rediscovery of the Canterbury knobbled weevil Hadramphus tuberculatus (Pascoe 1877) (Coleoptera: Curculionidae), with a review of its historical distribution. New Zealand Journal of Zoology, 35:323–330.


This blog post was written by postgraduate student Vanessa Lattimore as part of the course, Research Methods in Ecology (Ecol608).

07 July 2010

The origin of the Chatham Islands’ flora

The Chatham Island archipelago lies over 800 km to the east of mainland New Zealand. There are two major islands, Chatham and Pitt, and several smaller islands. Humans have lived on the islands for a few hundred years. There is a good level of diversity of species in the archipelago. For example, there are about 410 plant species, subspecies and varieties present although the vast majority are the same as mainland New Zealand species. There are 36 endemic plant species (species only found on the Chathams), including 17 trees and shrubs and 11 herb species. A recent study led by Peter Heenan (Landcare Research), with Anthony Mitchell (University of Otago), Peter de Lange (Department of Conservation), Jeanette Keeling (University of Auckland) and Adrian Paterson (Lincoln University) has used molecular methods to look at the evolutionary history of these endemic plant groups. Their work has now been published in the NZ Journal of Botany. In this study the group analysed 35 endemic species and their separate closest relatives using information from several gene regions to estimate evolutionary relationships and time since last common ancestor for each group.

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Not surprisingly, the vast majority of species had their closest relatives on the New Zealand mainland. It had been argued that most species colonising the Chathams would have originally come from northern New Zealand but this was not supported. Rather, closely related species were often those that were widespread around the mainland, perhaps indicating their ability to colonise successfully. Most of the speciation of Chatham species has occurred as allopatric speciation where the colonising population has since become isolated from mainland populations. Only six species pairs appear to have arisen within the Chathams themselves (from the genera Aciphylla, Coprosma, Hebe, and Olearia) and this speciation may be driven by niche differentiation into wet and dry habitats. These results are all consistent with the isolation of the Chatham Islands and the predominant winds and currents moving from the west (New Zealand) to east (Chathams) making it easy to colonise the Chathams but difficult to get back to the mainland.

The age of the endemic Chatham flora was investigated using molecular clocks. First, 14 species showed virtually no DNA divergence when compared to their mainland closest relative. This suggests that these Chatham species are recent arrivals. Second, 19 species showed low levels of divergence (less that 1%) which indicated a relatively recent colonisation of the Chathams over the last 3 million years. Finally, four species had much higher levels of divergence that implied 4-7 million years since the last common ancestor.

These results fit well with what we know about the geology of the Chatham Islands. The Chathams have a long history. They were part of Gondwanaland and then Zealandia (as seen by terrestrial dinosaur bones found on the islands). However, most of the last 60 million years have been spent underwater with short periods of volcanic island building. In recent times, the Mangere volcano produced land about 6 million years ago which had largely sunk again by 4 mya. The Rangitihi volcanics raised land about 2-3 mya and land has persisted since then. The plant evidence certainly supports this idea of most plant species arriving in a newly emergent land over the last two million years. Coupled with the fact that about 350 plant taxa are identical to mainland species, these findings support the idea of a young flora and the hint at the tremendous power of long distance dispersal and colonisation to establish diverse biotas on isolated oceanic islands.


13 May 2010

How many? Where-abouts?

In order to estimate the total population of a species you need to know the mean size of local populations and where the populations are. Numbers and amount of sites where species are present are usually linked and this is referred to as the abundance-occupancy relationship. However, there are many exceptions to this rule and it appears that many organism traits may affect either local numbers or distribution. Much of the research in this area, both showing the link between abundance and occupancy and where life history traits impact on this link, has been done on birds and insects. Plants, major drivers in ecosystems, have seldom been examined. Until now. Hannah Buckley (Lincoln University) and Robert Freckleton (University of Sheffield) have used data from sites that have been monitored for 25 years. The 52 high country tussock grassland sites are scattered throughout Otago and southern Canterbury of the South Island of New Zealand. The number of species and the number of individuals at each site were measured in the mid 1980s, mid 1990s and 2005-2007. The length of time that the plant populations have been monitored make for an unique opportunity to examine long term changes in species abundance and distribution. A paper in the Journal of Ecology has just been published on what they found.More...Occupancy and abundance of species at each site was highly correlated through all sample periods. Within each site, there was movement of species with 76% of species colonising and about 20% of species being lost from the sample transects. Traits that might impact on relationship between species abundance and distribution were measured. If a plant was ‘weedy’ (fast growing in most habitats) enabled the species to be more widely distributed than expected. If a plant was clonal (not sexually reproducing) this enabled the species to be more abundant at a site than expected. Surprisingly, dispersal ability and size did not affect a plant species’ distribution and abundance. Overall, this study is a positive step forward. It confirms that plants respond in similar ways to other organisms and increases our understanding on how plants species persist and move around the landscape.

23 March 2010

Parasites lost

One aspect that is often overlooked when thinking about biological invasions is that in addition to the invading species, be it a bird, beetle or banana, there are usually associated parasite species that come along for the ride. More intriguingly, sometimes one of the reasons why invasive species are so successful is because the parasite species that come with them cause greater problems for native species allowing the newcomer to out-compete the locals. At other times invasive species succeed because they left a nasty parasite at home and escaped their influence. Studying the absence of parasite species is a challenging task! There are several reasons why a parasite species might be missing from the host species new home. And here things get a little nautical...
In the late 90s Adrian Paterson, studying feather lice on birds in New Zealand, speculated that many parasite species of introduce birds species would not be present because they had 'missed the boat'. When birds, like sparrows and blackbirds, had been collected in Great Britain to be brought out with colonists to release in New Zealand, there was always a chance that a particular louse species might not be present on the individual birds collected and therefore never even had a chance to establish. Paterson had some limited data to support this idea.

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A new study by Paterson and Richard Duncan (both Lincoln University) and Catriona MacLeod and Dan Tompkins (Landcare Research) has examined this idea in a more sophisticated manner and is just published in Ecology Letters. The team realised that New Zealand is in a unique situation to test this idea. Bird species introduced into New Zealand were reasonably well recorded. We know roughly how many individuals were brought to New Zealand, how often attempts were made to establish populations and how successful they were. We also know a great deal about the louse species present in the UK and NZ. Using newly collected data where birds were collected in the UK and their lice recorded, as well as similar records from early in the 20th century, MacLeod and colleagues were able to work out the louse population distribution over a number of bird species. They then asked the question 'if, say, 33, individual greenfinches were used to establish a successful colony in NZ, how likely is it that these 33 individuals would have all or some of the louse species present in the UK for this particular sample?'. Complicated statistical methods ensued
The results were interesting. About 38% of UK louse species actually have colonised New Zealand successfully. Of those that failed, only 5% are predicted to have missed the boat. That is, it is likely, given the numbers of individual birds brought to NZ, that almost all louse species should have at least got onto the ships. Another third failed to establish because their host species also did not establish (which we term 'sinking with the boat'). Finally, 27% are 'lost overboard' where their hosts are successful but for some reason the louse species did not survive the colonisation event (perhaps because of low numbers). This is a rather surprising result as it tells us that a successful host colonisation is simply not enough to ensure a successive parasite invasion. This is promising in our efforts to stop the spread of pest species.
There are lots of ways in which this research may progress. For example, we currently have a postgraduate looking at louse distributions in populations in more detail. In particular, he is focussing on sampling error, that is that there may be stowaway species that are in low numbers and have avoided detection thus far. And there are many more nautical terms left to explore...