11 December 2009

Quail Island Biology Trip


Over the last decade the ecologists at Lincoln University have been very involved with the ongoing restoration work on Quail Island in Lyttelton Harbour. Mike Bowie, in particular, has been a major force in keeping the connection going. During this time there have been numerous trips out to the island with dfferent groups of postgraduate and undergraduate students. Over the last week Sue Unsworth. in her role as science outreach co-ordinator, has organised four days of activities on the island involving Year 12 biology high school pupils from the Christchurch and Timaru areas. The students helped in ongoing restoration and conservation projects on the island. They checked tracking tunnels (containing inkpads that leave behind footprints)that monitoring for predators like mice and rats (and luckily found none as there has been a major control operation this year). There were also gull and gull chick counts and lizard lodge (corrugated squares that lizards love to live under) checks for monitoring lizard numbers and species. Despite variable weather and long tiring days, fun was had by all.

05 November 2009

Town cats visit the wet rats


Cats are common pets all around the world. Nowhere is this so pronounced as in New Zealand where we have the highest rate of cats/households in the world. One of things that we like about cats is their independence but this comes with a downside - what does your cat do when it is not in the home? Cats are natural predators and we know that they will catch almost any sort of prey. Concerns have been raised that cats may have many negative impacts on local wildlife, especially where their homes are near wild areas. In a study recently published by researchers from Lincoln University (postgraduate students Shelley Morgan, Cara Hansen, and their supervisors James Ross, Shaun Ogilvie and Adrian Paterson) and University of Tennessee (Graham Hickling) in Wildlife Research, this issue was directly addressed. Travis Wetland is entirely surrounded by suburbs in north eastern Christchurch. It is about 120 ha and is the largest freshwater remnant of its type left in Canterbury. As such it has many important natural values and, conveniently, lots of cats live around the periphery. This study surveyed owners around the wetland to find out how many cats were present, what the cats ate, how many were kept indoors for part of the day, and what prey they brought back home. Twenty-one cats were given radio transmitters to examine just where the moggies were going to over a 12 month period. So what did we find out about the secret lives of felines?.

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First, there were a lot of cats - about 600 in the study area or 6.4/ha. Second, the cats didn't mind getting their fur wet. Most cats spent about 10% of their time inside the wetland, moving up to 200 m from the boundary. Of course, being cats, they spent nearly 2/3 of their time at home. Cats moved up to 270 m away from home but usually stayed within 100 m. Male cats had ranges three times larger than females. Almost 1000 prey items were collected during the study with 38% being rodents (mostly mice), 20% birds (almost all introduced birds, like sparrows), 18% reptiles and 22% insects (mainly moths). The bulk of hunting was done by cats from 1 to 6 years of age. Interestingly, cats with bells took more prey (probably because their owners correctly identified them as good hunters). So what does this all mean? Well it is clear that domestic cats do move into nearby 'wild' areas (even those that are quite wet). While there they do kill a great range of species. From a conservation point of view they certainly have an impact on species like native lizards. But of course nothing is that simple. The cats' main prey species are either direct predators (e.g. rodents) or competitors for food (e.g. sparrows) of native species found in the wetland. The question then becomes do the positive outcomes of having cats around, removing problems for native species, outweigh the negative outcomes, killing native species. At this point we can't answer that question. We are currently doing a similar study on cats living around a bush reserve on Banks Peninsula which may tell us more. So overall cats are not the villains they are made out be by some but neither are they as harmless as championed by others.

19 October 2009

A successful Banks Peninsula biodiversity workshop

The Banks Peninsula Biodiversity Workshop held at Akaroa on October 8th was a chance for local landowners to learn about the special biodiversity found on their Peninsula properties and what they can do to enhance the habitats for local native species. It was a long and successful day which was attended by over 170 people. Lincoln University and the Banks Peninsula Conservation Trust chose a range of experts to give quality talks on local native fish, invertebrates, birds, lizards, plants and integrating farming with conservation. All of the talks, questions and answers, workshop sessions are being compiled to create a proceedings of the event so that people who attended, and those who couldn’t make it, can read more on the subject. If you did not attend the workshop and would like an electronic copy of the proceedings, contact Mike Bowie.

The Lincoln University/Lincoln Envirotown biodiversity calendar was also launched at the workshop. The calendar suggests ways in which landowners can create or enhance habitats for native species and of course has a lot of spectacular pictures. The calendar is available for only $10. Contact Mike if you would like to buy a copy.



05 October 2009

Modelling the invasion


Although the Argentine ant (Linepithema humile) is not the fourth best novelty folk group in New Zealand it is impressively ranked in the top 6 most invasive ant species in the world. In a country like New Zealand this species poses a threat to the local biodiversity by removing native ant species and other prey species and thereby disrupting local ecosystems. Although the ant has established in New Zealand in the Auckland area there is a lot effort spent in trying to stop its spread. In the war against the invasion, knowledge of the future plans of the enemy is valuable in turning the tide. One way of obtaining this information is to create a model which can give us a good idea of where the ant is likely to spread to next so that we can stop this from happening.

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In research just published in Ecological Applications, researchers Joel Pitt and Sue Worner, members of the Lincoln University’s Bio-Protection Research Centre, and their colleague Andrew Suarez from University of Illinois, Urbana, have created models that allow greater accuracy in examining how Argentine ants spread around the landscape. The researchers were frustrated that most existing models only dealt with an abstract environment that was all of one type which helped with the mathematics of the model but was very unrealistic. The team decided to use a GIS approach to include realistic landscape information, such as land cover and local temperature, in their models. A simulation was run for each year from 1990-2005 to look at where the ants would move to and likely survive. What they found was that the simple model assuming a similar landscape was actually quite accurate for the first few years of the invasion. The more complicated model started to perform better after a few years and was reasonably accurate with its predictions when we look at actual spread in 2005 (predicting hotspots of activity in Auckland, Hamilton, Whangerei, Great Barrier Island and Tiri Matangi Island). The figure above shows the areas potentially able to be colonised by 2005 predicted by the simple model (circular lines), the complicated model (colours) and what actually happened (red dots - look closely, they are hard to spot away from Auckland!). The success of this approach will allow managers to better target their resources into monitoring areas that are most likely to be invaded.

17 September 2009

Banks Peninsula Biodiversity Workshop


On the 8th October from 9am till 7pm there will be a free workshop held in the Gaiety Theatre in Akaroa about enhancing biodiversity around the Banks Peninsula area. The Banks Peninsula Conservation Trust and Lincoln University have assembled a great line up of contributors for farmers and landowners who want to increase the native biodiversity on their properties. The programme features many speakers which much experience in various aspects of monitoring and enhancing biodiversity. Please contact Rachel Barker (rachel.barker@bpct.org.nz or 03 3296340) to register by the 2nd October.

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Click the picture for a detailed programme of events.

12 September 2009

Change under our toes


Grazed tussockland
Originally uploaded by pluckytree
Tussock dominated grasslands are an integral part of New Zealand’s native vegetation. Ecologically, they do not only harbor a large diversity of grasses, shrubs, small woody and herbaceous plants, but also give home to insects, reptiles and birds. Influenced by climatic conditions and land management practices, the spatial distribution of tussock grasslands has varied over time. It is assumed that in the early 1800’s, after Maori fires had cleared much of the forest and before European settlers arrived, they covered about one third of mainland. As of 2002, agricultural land conversion and spreading human settlement have left us with only about 3%.

Today, we are more concerned about “range restoration” and that the preservation of New Zealand’s native landscapes is implemented by adequate land management policies. However, not only has the spatial extent of tussock grasslands declined, but research over the past four decades has revealed ongoing changes in plant diversity and abundance of remaining tussock grasslands, towards an increased dominance of exotic weeds. The reasons for this have never been satisfactorily identified. The degradation has often been blamed on continuous pastoral use of grasslands, but research could never find unambiguous evidence for such a causal connection.

In order to find out more about what was happening in our native grasslands, Lincoln University researcher Richard Duncan and colleagues compared vegetation composition on fixed sample sites in Canterbury and Otago between the mid 1980's and 1990's (see the New Zealand Journal of Ecology, 25(2):35–47). They collected data on a variety of ecological and land management factors to test them for their influence on any observed vegetation changes. As expected, their results after the second measurement did fall in line with prior studies. Native plant species of all families had declined significantly, with the group of small herbs leading the sad trend. On average, one quarter of these plants had disappeared from all measured sites. One notable exception was native grasses of the genus Chionochloa, the snow tussocks, which had obviously benefited from a reduced impact of grazing. The only other significant increase, on the other hand, could be recorded for invasive weeds of the genus Hieracium.

So what had happened? Had the rise of invasive weeds and tall grasses driven out the native plants? Were people to blame, the old culprits, with their grazing livestock and fire management? Were site location and ecological conditions of any importance? To ruin all suspense and excitement right here and now: We don’t really know.

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All statistical analyses run throughout the study could not come up with a significant connection. Native plants did decline on sites with no Chionochloa and Hieracium at all, at the same rate as where these species dominated. Neither did moisture, aspect, increased vegetation cover nor human management play a significant role.

So what had happened? Had the rise of invasive weeds and tall grasses driven out the native plants? Were people to blame, the old culprits, with their grazing livestock and fire management? Were site location and ecological conditions of any importance? To ruin all suspense and excitement right here and now: We don’t really know.

I would like to leave you with a call for continued long-term research into the underlying patterns of our degrading tussock grasslands. Change could be going on independent of human management and so we might have to broaden our research scope and start looking into other factors. Also, the situation may have already changed by now. If towards the good or bad, we can only find out by continued monitoring.

Note that this was the motivation of a recent Lincoln University masters project by Nicola Day. Nicola led the re-surveying of the same plots. Her results will be published soon and we’ll be sure to blog about them here.

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

26 August 2009

Summer Scholarships


The Agriculture and Life Sciences Faculty at Lincoln University, including the Department of Ecology, is offering summer research scholarships over the summer vacation, valued at $5,000 each (tax free). The scholarship will last for 10 weeks. Scholarships will be awarded based on academic merit. So if you want to work on sandy beaches or follow tui around or search for weta in exotic places then have a look at the projects on offer.

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We have run summer scholarships for the last few years and many students have had a lot of fun getting involved with research (and getting paid!). Note that it may say that the due date is the 7th September when it is actually the 14th September.

18 August 2009

A really lousy day!


You won't usually see us evolutionary and ecological researchers driving around in a Ferrari, holidaying at tropical resorts or dining at the best establishments. But, hey, there are some perks! I am now the proud namesake of a bird louse species. Out there at this very moment crawling over the Gray-headed Tanager (Eucometis penicillata) somewhere in Central America are little feather lice called Myrsidea patersoni. The authors, Roger Price and Kevin Johnson, have named five new species of Myrsidea after people who have worked on lice, in the most recent issue of Zootaxa, including my colleague from down the corridor, Rob Cruickshank. Myrsidea is a reasonably common genus with over 120 species of lice that are found on passerine (song or perching) birds. Rob's louse, Myrsidea cruickshanki, is found on Carniol's Tanager (Chlorothraupis carmioli). Bird lice are little ectoparasites that live in the feathers of birds where they live their whole life-cycle feeding on debris and feather pulp. All birds have louse species and most birds around you will have some lice on them. I once picked 200+ off one Royal Albatross and that's not unusual for these big birds.

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The good thing about having a louse named after you, relative to most invertebrates, is that you do at least have a nice bird host species to show people ("OK, OK so the louse doesn't look like much but just look at what it lives on"). You're probably thinking about why so many people work on lice given that one or two would surely be enough. It turns out that lice are usually passed from parents to offspring in much the same way as genes. This means that the coevolve very closely with their host and allows the opportunity for evolutionary biologists to look at recurring patterns. That's where Rob and I have done our work, mainly with seabird lice (the picture is actually of a seabird louse from the Halipeurus genus found on shearwaters). Still, there's plenty of work to be done and there is a good chance that I might be able to reciprocate the honour for the authors with some songbird louse species of my own one day.

12 August 2009

On the beach: plant communities in dune systems


Sand dune habitats are found all around the world. Sandy coasts are ever-changing with the interactions between climate, geology and vegetation. Dune habitats have to contend with storm surges, wind and rain and human impacts. Considering how important these areas are to human activities it is surprising that so little is known about the biology of these systems. Dune systems are generally divided into three regions: foredune, interdune and backdune. Also, three different plant groups are found in dunes: dune builders (fast growing plants whose stems and roots stabilise the dunes), burial tolerant stabilisers (plants with rhizomes that can tolerate overwash and flooding and stabilise flat areas) and burial intolerant stabilisers (longer-lived species found in older dunes).

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A study by Hannah Buckley (Lincoln University) with Thomas Miller and Elise Gornish, colleagues from Florida State University, has been published in Plant Ecology. This study is the first to survey plant communities of dune systems over a relatively long period. The research took place on St George Island in Apalachicola Bay in north Florida. 249 plots were followed from 1999-2007 with measurements of the plants found growing in each plot being recorded each northern Autumn. The three dune regions had very different communities of plant species. Community structure was determined by elevation, soil moisture and soil richness. Hurricanes appeared to have a major role in reducing the diversity present. Diversity was low at the beginning of the study as Hurricane George had affected the area the year before (1998). Diversity then increased over the following years until Hurricanes Ivan (2004) and Denis (2005) reduced the diversity again. These results highlight the dynamic nature of plant communities in dune systems. It appears that there is a clear form of succession occurring in these habitats but that storm events tend to push the communities off their trajectories. Buckley is continuing to look at the processes that shape dune plant communities and has set up plots around New Zealand to do this work.

19 July 2009

A tough decision for mum


NZ Fur seal
Photo by Kerry-Jayne Wilson, Lincoln University.


Pinnipeds are a widely distributed and highly diverse group of semi-aquatic marine mammals. These animals are unique in a sense that although they spend a lot of time in water, they have to come up on land to breed, moult and rest. Altogether, there are 3 families, the phocids, otariids and the odobenids. In New Zealand, we have 2 species from the Otariidae family, the New Zealand fur seal/ kekeno and the Hooker’s sea lion/ rapoko (Phocarctos hookeri).

New Zealand fur seals (Arctocephalus forsteri) were widely distributed before humans arrived. They could be found all throughout the coastlines of the North and South Island, as well as most offshore islands. However they were hunted for food by Maori, and Europeans further decimated their numbers for the pelt industry (as they did with pinnipeds throughout the world). Fortunately, due to full legal protection, their numbers are increasing and they are slowly re-colonising their former habitats.

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NZ fur seals live in a wide variety of coastal habitats, but breeding colonies (also called rookeries) occur usually on exposed, rocky, rugged shores. In 1976, M. C. Crawley and G. J. Wilson observed that nearly all rookeries have shelters from storms or big waves, and have broken and irregular terrain (see the journal Tuatara 22(1):1–28). There are also hauling grounds, where non-breeding adult males literally “hang out” in large numbers. These sites are similar to, and quite often near, established rookeries.

In 1993, Christine Ryan, Graham Hickling and Kerry-Jayne Wilson of Lincoln University investigated the breeding habitat preference of the NZ fur seals in Banks Peninsula (see Wildlife Research, 24(2): 225–235 (1997)). Their aim was to see if there were any significant differences between the breeding sites and non-breeding sites. They found out that NZ fur seals indeed chose steeper, rockier sites for breeding and suggested that these criterion be used for determining future breeding sites for conservation purposes.

Fur seals choose sites to assist in behavioural thermoregulation. This is because peak breeding season often occur during the hottest time of the year and the seals are reluctant to cool off in the sea—females have pups and males are defending territories. As fur seals are superbly adapted to the cold seas, they need crevices and rocky pools to help thermoregulate. This behavioural preference was also seen in other species of fur seals in other regions of the world.

In addition to thermoregulation, preference of steeper, rockier sites would favour pups and females in terms of safety and shelter, and also minimise harassments by humans and probably adult male fur seals.

It has been suggested that the present distribution of fur seals habitat in Banks Peninsula may also be a product from hunting in the bygone eras. Individuals that escaped sealers may have modified site preferences and, therefore, recolonisation patterns of subsequent generations. Furthermore, fur seals have natal site fidelity, which means that they return to the place where they were born to breed, and this could be a confounding factor in their preference of breeding sites.

Kerry-Jayne Wilson told me recently that there has been an increase in seal numbers and also breeding sites on Banks Peninsula since the survey was done. It would be interesting to find out if the habitat preferences observed previously are still significant for breeding animals when high densities are reached. Indeed, Christine Ryan and colleagues in their 1997 publication also pointed out that an increase in numbers may lead to breeding animals expanding into a broader range of habitat types, maybe even to those which they classified as “not suitable”.

The Department of Conservation website offers more general information about New Zealand fur seals and pinnipeds in New Zealand.

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

10 July 2009

Effluent bacteria lives and escapes..... sometimes

Dairy Cows have been getting a hard time in the media with catch phrases of ‘dirty dairying’ and ‘green streams’. But are scientists testing the impacts of land based effluent application on the natural New Zealand environment? It is, after all a natural product. What harm can it really do to natural ecosystems?


Cows: "Don’t blame us! Just because you call it effluent, doesn’t mean it’s any less natural than sewage!"
Thankfully Lincoln researchers are churning out papers on the properties, uses, and effects of dairy effluent. One of the latest by Shuang Jiang, Graeme Buchan, Mike Noonan and Neil Smith of Lincoln University and Liping Pang and Murray Close of the Institute of Environmental Science & Research studied the less widely examined property of bacteria in the form of faecal coliforms. The paper “Bacterial leaching from dairy shed effluent applied to a fine sandy loam under irrigated pasture” can be read in full in the Australian Journal of Soil Research, 46(7):552–564 (2008).

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Field trials considered the influence of seasonal variation (time) and soil water content (irrigation application). Trials involved the use of Lincoln University’s 6 soil lysimeters. Lysimeters are monitoring vessels containing large cores of soil. They are used for studying hydrological cycles within soil such as infiltration, runoff, and evapo-transpiration. Researchers got down and dirty collecting effluent and pouring it over the lysimeter soil. Typical soil treatment was mimicked by spray and flood irrigation, the two methods of water irrigation commonly used in the Canterbury region, and, of course, any rain that happened to fall. Researchers then watched and waited to see what, if anything, would make its way through the 700 mm depth of soil into the collection chambers for analysis.

700 mm of soil did not prove to be a barrier to leaching. Analysis discovered that bacterial leachate could readily penetrate 700 mm when facilitated by water in the mock water irrigation treatments. Alarmingly, summer trials had leachates with similar concentrations to the original dairy effluent.



Unfortunately those green streams aren’t just a figment of the media’s imagination


However, researchers were able to draw some recommendations for effluent disposal without submitting to the pessimistic catch phrases I referred to earlier. With an understanding of the disposal area’s soil properties and consideration of water irrigation treatment and seasonal variations, the amount of bacteria transportation can be greatly altered. Specifically, flood irrigation resulted in higher bacterial leaching and effluent irrigated in dry summer conditions posed a greater threat of shallow groundwater contamination.


Beautiful green pastures under dairy effluent irrigation outperform the neighbouring sheep farm.


So, it seems that with some careful consideration of the natural environment and ecosystem, dairy farming can prevent green streams whilst recycling nutrients. With the right conditions and management, soil acts as a natural filter of bacteria from the applied effluent before leaching to groundwater. However, this is also a warning to those that have considered only the nutrient losses from their poor practice as a pathogenic bacteria may be leaching unnoticed to your water supply right now!


An example of not so careful effluent application management.


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

03 July 2009

Kānuka vs. gorse, the battle is on!

There is a struggle going on in the New Zealand forest, and it’s a battle for ultimate (plant) domination. Kānuka (Kunzea ericoides) and mānuka (Leptospermum scoparium) were the original plant species that colonised forest sites cleared by natural disturbances in New Zealand. This has changed since the introduction of many “shrubby weed species” to a situation where many cleared sites are now colonised by gorse (Ulex europaeus), broom (Cytisus scoparius), tree lupin (Lupinus arboreus) and many other adventive plant species. The nearest kānuka and mānuka are often some distance away and don’t get a chance to establish.

Jon Sullivan (Lincoln University), Peter Williams (Landcare Research) and Susan Timmins (Department of Conservation), researched three different hypotheses that they obtained from the New Zealand literature on the relationship between the naturalised shrub gorse and the native shrub kānuka.

1. Kānuka stands have a different plant species composition and greater plant species richness than gorse stands at comparable successional stages.
2. Differences between gorse and kānuka stands do not lessen over time.
3. Several native plant taxa are absent from or less common in gorse than in kānuka stands.

The research was conducted in environmentally similar sites throughout the Nelson and Wellington regions. They selected a mix of young and old gorse and kānuka sites. At these sites they recorded the presence of all native and naturalised woody species, Department of Conservation weeds, ferns, orchids and a selection of herbaceous plants; they also recorded environmental variables. The results were published in a 2007 issue of the New Zealand Journal of Ecology.

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They showed that there are many differences in the final vegetation composition of a site that establishes under gorse dominated vegetation compared to a site that establishes under kānuka dominated vegetation. For example, gorse sites tend to be absent of, or have fewer beech trees (Nothofagus spp.), orchids (e.g. Pterostylis spp.), small leaved shrubs (e.g. Coprosma, Leptecophylla, Leucopogon) and the shrub daisy Olearia rani than kānuka sites. The gorse sites also displayed lower species richness (number of species) and a higher incidence of naturalised species than the kānuka sites. These factors tended to be persistent at the older sites, suggesting that these effects are long term and therefore inferring that gorse is not a substitute for kānuka when the desire is to return the site to a “natural state.”

There are many explanations for the differences between gorse and kānuka sites. Some of the differences may be explained by biological factors such as the nitrogen fixing ability of gorse and the effect this may have on below ground micro-organisms and soil invertebrates, or this could be due to different physical site characteristics like light penetration, soil temperature or soil moisture levels. Other factors may be different bird feeding preferences and subsequent seed dispersal between gorse and kānuka sites, or the documented increase in naturalised plants invading gorse sites

This study has shown that there is a difference in plant composition between gorse and kānuka sites and therefore, as good as any forest regeneration is, there needs to be more protection for areas of kānuka in landscapes where it is scarce. Also, in such landscapes, there will be benefits for biodiversity of planting kānuka back into areas dominated by gorse if the aim is to initiate native forest regeneration. There is also a need for further research into the main effects driving the differences found in this research paper. There is still much to learn about the ecology of gorse vs. kānuka.


Glossary

Adventive a plant or animal found in an environment where that it is not native to.

DoC weeds List of weed species actively managed on Department of Conservation reserves.

Succession the series of changes that create a fully-fledged plant community, e.g. from the colonization of bare rock to the establishment of a forest

Taxa A taxonomic group i.e. a plant species, genus or family.

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

02 July 2009

Geraniums: New New Zealand diversity

Geraniums are a common plant genus with more than 400 species worldwide. New Zealand has its own share of species with seven native species and nine introduced species. There is, however, a reasonable level of variation within some of the native species, including variants in the ultramafic Red Hills. Other species are found on the Chatham Islands (Geranium traversii) and through the Subantarctic (G. microphyllum). A DNA-based study was undertaken by Anthony Mitchell (University of Otago), Peter Heenan (Landcare Research) and Adrian Paterson (Lincoln University) of samples from all species and most variants in order to look at evolutionary relationships, time of divergence events and species status.

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In a paper published in the New Zealand Journal of Botany (47:21-31), the researchers conclude that there is low genetic variation within native New Zealand Geranium indicating that they are very closely related and the likely result of one colonising event to New Zealand. More sampling of Geranium species in South America and Australia would help to determine the likely source of these colonists. Morphological variation (like leaf shape and patterning) appeared to be a reasonable predictor of species status with plants that look different actually also being different at the molecular level. The level of differences between different populations also suggested that they may actually be at least five different species (although confirmation of this would require more detailed work). This work shows that even in reasonably well-studied groups that there are still many species to be found in New Zealand.

30 June 2009

Two bees or not two bees?


The short-haired bumblebee (Bombus subterraneus) is the rarest of four bumblebees introduced to New Zealand from the United Kingdom in the nineteenth century for pollinating clover and other important crops. Recently the same species has gone extinct in the UK, the last recording of it there being in 1988. Not surprisingly, the New Zealand population has been proposed as a source for re-introduction of this species to the UK. However, very little is known about the biology of this species and research is hampered by the difficulty of exact identification as it co-occurs with two morphologically similar species (B. hortorum and B. ruderatus).

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Dr Roddy Hale at Lincoln University and Dr Marie Hale at the University of Canterbury developed an undergraduate summer scholarship program to developed simple PCR-based molecular identification tools for these species. In a recently published paper in Conservation Genetics the student Lucy Stewart was able to rapidly, cheaply, and reliably identify not only B. subterraneus, but also the two other similar-looking species. We combined a species-specific internal primer with two non-specific external primers that amplify 426 bp of the Bombus Cytochrome b gene, to produce a presence/absence PCR test that is combined with a positive internal control. The result is a set of molecular tools that will allow us to separate three cryptic species and facilitate basic research on the biology of New Zealand’s rarest bumblebee.

28 June 2009

Sheltering the homeless spider

In the face of degradation of the environment and loss of species biodiversity, there is a call for innovative bio-indicators. New Zealand native spiders have answered it with their usefulness for measuring an ecosystem’s “health.” They can be used to monitor ecological restoration of natural and agricultural systems and monitor land and air pollution from industrial processes.

The tricky part is how to measure and monitor the biodiversity of spider species and their relative abundance at a given location. Several sampling methods are available for this kind of work but they will all give different results. Perhaps the easiest way of going about it is to use insecticide gas or ‘chemical fogging’ to cause any invertebrates in the area to drop dead to the ground and then be picked up for later examination. Another similar method is to use pitfall traps filled with a substance such as ethanol in which any invertebrate walking along can stumble into. These methods are very effective in the amount of spiders captured for examination but if you are investigating endangered species with conservation significance, it can prove counter-productive. The endangered species may not be spiders either as these sampling methods are non-discriminate to non-target species.

Non-lethal sampling techniques can be employed such as timed hand searches or basically shaking foliage until spiders fall off. These techniques have the advantage of being selective for which species, if any, are killed for further examination. A new non-lethal approach was described by Simon Hodge (Imperial College, London), Cor Vink (AgResearch, Lincoln), Jonathan Banks (Waikato University), and Mike Bowie (Lincoln University), published in a 2007 issue of the Journal of Arachnology.

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They looked at the use of a new non-lethal sampling technique with artificial homes being placed out in the field for spiders to take shelter in. The inspiration for this idea came from previous researchers using the same technique to measure tree weta communities. Often these researchers would open up their weta shelters only to find native spiders hiding away instead. The shelters built for the spiders consisted of a block of wood with a central groove cut two thirds of the way down, a transparent plastic cover attached over the groove as a window and black polythene stapled over the window to block out light. All the researchers have to do is peal back the black cover to observe any spiders present.

Simon Hodge and colleagues found that within a year, 91% of their shelters placed in the field were occupied by spiders. Environmental factors such as soil moisture, light intensity on the shelter and ground slope were measured to see if they impacted occupancy frequencies but they proved inconclusive. The species of tree that the shelters were placed on and the height on the tree did not have an impact of occupancy rates either. The results of this research show the effectiveness of these shelters at harbouring spiders but as a surveying technique, the abundance and diversity of spiders measured is low compared to the current conventional sampling methods I mentioned earlier. The shelters also don’t cater for all species of spiders as only those that are tree dwelling are likely to adopt them as their new home.

Overall this sampling method can be employed not only as bio-indicator of the environment and biodiversity but as a tool for measuring spider communities within a habitat. To be effective in the field, this sampling technique would need to be accompanied by another sampling technique to bolster the amount of individuals and species of spiders found.

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

24 June 2009

Blue penguin population decline on the West Coast: is it caused by low breeding success?

Editor's note: this is an additional summary and commentary on the West Coast blue penguin story that was reported on last week by Wawrick Allen.


Photo by Kerry-Jane Wilson,
Lincoln University.
Even though blue penguins (Eudyptula minor) are still relatively common on New Zealand’s offshore islands, surveys by the West Coast Blue Penguin Trust indicate that there are only a few hundred left on the West Coast of the South Island mainland. But what is making one of the cutest and most beautiful birds of New Zealand decline in abundance? Is the blue penguin another victim of New Zealand’s numerous introduced predator species? Do possums (Trichosurus vulpecula) and stoats (Mustela erminea) account for this huge decline in the last 30 years by feeding on little blue penguin eggs and chicks? Or is the decline due to road kills caused by a bigger exotic species called Homo sapiens that runs them over with their speedy cars?

Apart from these reasons, the blue penguins might also have problems with the difficult tasks of finding a good nesting site, laying one or two eggs, keeping them warm until the chicks hatch, and rearing them until they are prepared for the big, wide world. Before the research described in this blog, not enough was known about the breeding biology of the West Coast's blue penguins to determine whether environmental or biological factors were the most important reasons contributing to the population decline.

Masters student Sol Heber, under the supervision of ornithologist Kerry-Jane Wilson and behavioural ecologist Laura Molles at Lincoln University, examined the breeding biology and breeding success of the West Coast penguin population. This work was published in a 2008 issue of the New Zealand Journal of Zoology.

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Blue penguin chicks.
Photo by Sol Herber,
Canterbury University.
Nine study sites distributed along the West Coast were observed during breeding season from August to December 2007. These study sites were checked several times a week for eggs, hatched or fledged chicks as well as potential predators. The hatching, fledging and breeding success rates were rather high: 78.9% of the eggs that were laid hatched, 83.9% of the hatched chicks fledged and the overall breeding success, meaning chicks that fledged out of the laid eggs, was 66.2%. These results are better than expected, showing that the blue penguins are doing well in breeding and that reasons other than low breeding success must be the main cause for the declining populations (unless 2007 was an exceptional year, which is unlikely). Some of these reasons have been described in this article and should be further investigated as soon as possible in order stop the alarming decline of blue penguin populations.


Penguin chick preyed on by a stoat.
Photo by Kerry-Jane Wilson,
Lincoln University.
In just the five month time period of this study, 15 road kills of little blue penguins were observed. This number doesn’t even include how many roadkills are not counted and how many happen at other study sites or over the duration of a whole year. As blue penguins are busy breeders and rear up to two chicks a year with both parents required to rear them, one adult road kill can account for the removal of up to three individuals from the population.

Even though only 10.7% of chicks were taken by predators, this hazard should also not be taken lightly. Other factors that may affect the West Coast blue penguin population are all human caused problems such as predation by dogs and habitat loss caused by erosion, subdivision and development of housing allotments. Furthermore, drowning in fish nets (by-catch) might constitute a sea mortality factor. More research is urgently needed to quantify adult mortality caused by all these factors, in particular road kill. Hazardous road crossing points regularly used by blue penguins should also be identified and modified.

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

The long subantarctic commute


Although New Zealand has a huge selection of seabirds, and is the centre of diversity for many groups, we are still in a very early stage in understanding the behaviour and ecology of these species (see the recent ecoLincNZ blog post by Jessica Parisi). Mostly this is understandable. Seabirds usually live on remote oceanic islands that are difficult to get to and even more difficult to stay on for any length of time. More importantly seabirds spend most of their time at, well, sea. What they get up to hundreds of kilometers from land is difficult to study. Luckily, technology is providing solutions. Tina Troup, as part of a Master of Science, was interested in the foraging of royal albatoss (Diomedea epomophora) during their breeding season. Where did the go? What did they do? Using satellite transmitters to track position, dry-wet recorders to identify when birds were on the water and heart-rate monitors to examine how much work the birds were doing, Tina trooped off to Campbell Island in the New Zealand sub-Antarctic zone.

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Ten southern royal albatross were tracked through incubation (January/February). In a recent paper published in New Zealand Natural Sciences (34: 19-28) Tina, along with Adrian Paterson and Craig Sixtus from Lincoln University, report on their findings. Royal albatross appear to have specific foraging grounds that are hundreds to thousands of kilometers from Campbell Island. This causes them fly in what we term a 'commute, forage, commute' foraging strategy. The birds would generally commute in a direct movement, covering up to 800km/day. Foraging was more haphazard and the birds covered less than 180km/day, making frequent changes in direction and landing often. Once birds were satisfied with an area they would then commute to the next area to forage.

Wind direction and strength were shown to be important in determining how quickly the albatrosses could move and in the directions that they tended to move in. Winds from head, tail and right angles made it difficult to return to the colony. Likewise, bird mass was also important with lighter birds under 9kg finding it difficult to land in winds over 40km/hr. Overall, there appeared to reasonable flexibility in starting each foraging trip with birds able to select different foraging sites depending on the direction and intensity of the winds around Campbell Island. Obviously, only being able to follow ten birds for a month limits what we can discover about the biology of the royal albatross. However, a small window has opened onto a part of their lives that we know little about.

19 June 2009

The World's Smallest (& Cutest) Penguin



Little blue penguins (Eudyptula minor) are the smallest penguins in the world and are found throughout New Zealand and southern Australia. They are exceptionally cute and cuddly and attract a vast amount of tourists to breeding colonies at Oamaru and Banks Peninsula, among many others. Unfortunately, since the arrival of humans in New Zealand, most little blue penguin populations on the mainland have been in a steady decline due to introduced predators, roadkill, human disturbance and fisheries by-catch. The decline of this charismatic penguin species must be halted in order to preserve not only the species but a significant amount of tourism revenue generated annually.

The numerous colonies of little blue penguins on the beautiful West Coast of New Zealand's South Island are some of those thought to be in decline. Sol Heber, from the Centre for Nature Conservation in Goettingen, Germany, along with Lincoln University ecologists Kerry-Jane Wilson and Laura Molles, studied the breeding biology and breeding success of little blue penguins on the West Coast as this was thought to be a possible factor contributing to the apparent decline.

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Blue penguin breeding burrows at nine study sites were checked at regular intervals from 23 August 2006 to 18 December 2006. Each time the boxes were checked, the number of adults, eggs and chicks present was recorded in order to determine breeding success, incubation time, guard period and nestling period. Vertebrate tracking tunnels and traps were also used to determine what potential predators may be present in each of the nine study sites.


Blue penguins
Photo by Jim Allen.
(Used with permission.)
Hatching, fledging and overall breeding success were found to be 78.9, 83.9 and 66.2% respectively. These breeding success values were quite high compared to breeding success data from five other colonies in New Zealand and Australia. Incubation, guard and nestling periods were also found to be in a similar range of times to the other sites. Rat (Rattus rattus) tracks were found in 60% of the tracking tunnels laid, the only potential predator which left tracks. Eight rats and four stoats (Mustela erminea) were the only predators which were caught in traps. This is a large potential hazard for the blue penguin population.

These results have a variety of implications when it comes to conservation of this species. It appears that the breeding success of the West Coast little blue penguins is not low enough to be contributing to the decline. The impact of predators on the population is also not as high as previously thought with only around 5.6% and 10.7% of eggs and chicks being taken by predators respectively. This then begs the question, "What is actually causing the decline of little blue penguins on the West Coast?"

Heber, Wilson and Molles concluded that the primary cause is probably adult birds being run over when crossing roads. If true, it is none other than humans who are having the biggest impact on the West Coast blue penguin colonies. When an adult bird is removed from the population during breeding season there is the potential that any eggs or chicks it is looking after will also die and there will also be a loss in breeding in subsequent years. Therefore, control of adult mortality of little blue penguins is the key to their survival on the West Coast.

The results of the study were published in the New Zealand Journal of Zoology, volume 35, pages 63–71, and can be found here. For more about breeding sites go here.

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

18 June 2009

I've been to Evolution 2009

Well the meeting is done. The talk is given. The t-shirt is purchased. I'm mooching about Moscow, Idaho ahead of my long flight back to New Zealand tomorrow. 1200 evolutionary biologists, mainly from the States, gathered here at the University of Idaho over the last week to discuss all things evolutionary. Moscow is a small town with a big university and the hospitality was, as they say, a credit to the region. New Zealanders had a large presence here this year. Dave Penny (Massey University) gave the past president's address for the Society of Systematic Biologists and encouraged us all to continually question ourselves and our science. There were numerous Kiwis either escaping winter or currently doing PhDs and postdocs overseas. In my session there were three of us speaking.

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The best thing about our session, entitled Phylogeography, apart from the awesome talks obviously, was that it was in a law school lecture room that had been built to resemble a court room. Evolution on trial indeed! After some of the cross examinations that I have been receiving lately about drowning New Zealand in the Oligocene I felt quite at home. Of course we all made the most of it with bad jokes. Thomas Buckley (Landcare Research) talked on the relationships of the stick insects, especially focussing on the very endangered tree lobsters of Lord Howe island. Martyn Kennedy (University of Otago) talked about the various paua snails in the North Island and how they have lost most of their shells over the last million or so years. I talked about the Chatham Islands, mainly focussing on the endemic flora and who they are related to and how long they have been there (New Zealand mainland and not long). Other New Zealanders talked on various NZ plant groups, population genetics, phylogenetic analysis methodologies, selection on fish genes and sexual selection.

There were lots of good talks and a major theme of the conference seemed to focus around rates of diversification of species. A great conference with lots of interesting discussions. Coupled with the summer sun and some excellent microbrewery beers, I feel revived and ready to plunge into some research.

15 June 2009

New Zealand Seeking: Seabird Enthusiasts


Pitt island shag
Photo by Kerry-Jayne Wilson,
Lincoln University.
There are over 80 breeding species of seabirds in the New Zealand region and one of them, the Pitt island shag (left), is also endangered. Nearly half are endemic, meaning they are found only in New Zealand. A special report on the current state of New Zealand’s seabirds was created in 2006 by seabird expert Kerry-Jayne Wilson (Lincoln University) for the Ornithological Society of New Zealand. The results are, unfortunately, quite grim. What’s even more disappointing is the lack of funding, support and research of these seabirds. I was quite astonished after reading this report as to how little is known of their status.

The main groups of birds the report refers to are as follows: albatrosses, petrels, penguins, shags, gannets and boobies, gulls, skuas and terns and Kermadec Island seabirds.

New Zealand, according to the report can be called the “home of the albatross, with 13 of 24 taxa of the world found there. Of that, 9 are endemic.” Quite impressive, I’d say. The petrels are a diverse taxa and share endemism with the albatrosses. Five of the six species of penguins that breed in New Zealand are in decline. Four are endemic. According to Kerry-Jayne Wilson, “Shags are a poorly studied group whose conservation needs are inadequately documented. For example, the biology of black and pied shags is moderately well known but little black shags have been little studied.”

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Among New Zealand’s seabirds in decline are many poorly-known New Zealand endemics. While an increasing population trend of the Australasian gannet proves hopeful, more information on the breeding biology and population trends of the masked booby is needed. Of the three species of gulls found in New Zealand, the black-billed gull is the one that is endemic, endangered and declining. Related to the gulls is the skua, also refered to by Kerry-Jayne as an aggressive predator, is now subject to intensive study by an Auckland University student. “Of the 5 species of breeding terns, 3 are endemic. The New Zealand fairy tern is the country’s most critically endangered seabird with only 10 breeding pairs in Northland.” Finally, the Kermadec Islands provide the only place in New Zealand where a number of tropical and sub-tropical seabirds breed.

Some key findings of this report were that “fisheries by-catch is a serious threat to albatrosses and some petrels and recreational set-net fishing poses an unquantifiable threat to penguins, shearwaters and shags.” Since this practice clearly affects many of New Zealand’s seabirds, it is my suggestion that alternative environmental and cost friendly fishing practices be proposed. As Kerry-Jayne Wilson says,“The conservation needs of most seabirds are not being met and unfortunately, much of the research on seabirds is driven by pressure from external agencies, rather than the needs of endangered species."

When taking into account the high endemism in New Zealand’s seabirds, one might expect there to be much enthusiasm regarding their conservation! Sadly, that’s not the case. Aside from the popular blue-penguin student projects taking place at various universities, interest in seabirds is, well, not so popular. What about the shags and petrels? Surely New Zealand's Department of Conservation has to have some interest. Well, no. DoC no longer has dedicated seabird specialists although there are a number of part-time staff working on seabird issues. According to Kerry-Jayne, the problem lies in the “lack of continuity and loss of expertise as skilled temporary staff move on at the end of their terms of employment.”

Overall, there are a number of organizations and volunteers concerned with the future of New Zealand’s seabirds looking to make a difference. With the appropriate funding, they would be able to. As for interested students, simply apply.

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

12 June 2009

Measuring the productivity of threatened-species programmes


Tuatara
Originally uploaded by beedieu
Out of the 7–20 million species believed to be on the planet, a loss ranging between 140,000– 5 million is projected over the next 25 years. Efforts to avert this situation are present but the challenge has been on how to evaluate the effectiveness of these programmes. As a result, a decision on whether to continue funding a programme or not is difficult. For example, it is not easy to justify why one programme should be given preference over the other if their outputs cannot easily be compared. Ross Cullen, Geoffrey Fairburn and Ken Hughey of Lincoln University have found a solution in their study “Measuring the productivity of threatened – species programmes,” published in a 2001 issue of the journal, Ecological Economics.


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In this study, an output measure, Conservation Output Protection Year (COPY), and Cost–Utility Analysis (CUA) method was used to evaluate New Zealand threatened species programmes. In New Zealand, there are 1000 threatened species out of which 31 have species recovery plans (DOC/MFE, 2000 and DOC, 1999). These recovery plans are normally directed toward controlling predators, especially the introduced ones such as possums (Trichosurus vulpecula) or competitor numbers. The species statuses are described by their position on a ranking system. An example of a widely known ranking system is the IUCN Red List criteria, which places species in one of the 11 categories including; Extinct, Critically Endangered, Endangered, Vulnerable, and Lower risk (IUCN, 1994).


Hector's dolphin
Originally uploaded by electropod

CUA was first developed to evaluate health–care programmes. It measures the output of a programme by way of utility or worth of a health status. The argument was, if the outcomes of health could be measured in units called ‘Quality Adjusted–Life-Years’ (QALY), it was possible to compare different medical interventions. Comparisons could be made if the direct costs of each type of intervention were divided by the QALY they gained (Drummond et al., 1997). Cullen et al. (1999) and Stephens and Lawless (1998) applied CUA to conservation and implicitly used the term ‘utility’ to refer to the change that occurs in an ecosystem. Cullen et al. (1999) developed the COPY as means for evaluating the output gained from various species conservation projects. COPY serves same functions as QALY does in health care evaluation because it allows effectiveness of unlike activities to be compared.

Twenty two threatened–species recovery programmes were sampled but from five, response was not obtained thus 17 were evaluated. A categorization system was developed which is closely related to the IUCN Red List although with seven categories. This was used to evaluate the conservation statuses of the species. Data for estimating COPY gained by each programme was provided by the conservation group leaders. They rated the species status with and without management for each year the recovery plan was in effect. Using two equations, the conservation pay–off and cost per copy for each programme were calculated.

Nine species recovery programmes produced zero COPY or no conservation output. One of the possible explanations to this is that threatened species take a long time to respond to conservation efforts. Eight species indicated improvement in their conservation status: Black stilt, Yellow–eyed penguin, short–tailed bat, Takahe, Hector’s dolphin, Campbell Island teal, Brothers Island tuatara and Cook Strait tuatara.

Estimating the cost of programmes and projects posed a challenge. Of interest were direct operational costs, organizational overhead component, staff salaries and the capital charge. However, the study indicated that the CUA can provide valuable information on the productivity of threatened-species recovery programmes.

References

Cullen et al., 1999. Copy: a new technique for evaluation of biodiversity protection projects. Pacific Conserv. Biol. 5 (1999), pp. 115–123.

Drummond et al., 1997. Methods for the Economic Evaluation of Health Care Programs (second ed.),, Oxford University Press, Oxford.

DOC, 1999 Department of Conservation Annual Report for the Year Ended 1999, Department of Conservation, Wellington.

DOC/MFE, 2000. New Zealand's Biodiversity Strategy, Wellington. Available at http://www.biodiv.govt.nz/.

Stephens and Lawless, 1998 Cost–Utility Evaluation of Natural Heritage Biodiversity Conservation Projects, Department of Conservation, Wellington.

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

08 June 2009

Flower power and its effects on the biocontrol activity of an omnivorous insect

Omnivorous insects are interesting and important beings, consuming both plant and animal matter. In agroecosystems they have been identified as potential biological control agents since they eat pest insects. Micromus tasmaniae, the brown lacewing, was the subject of a recent study, by Katherine Robinson and colleagues at Lincoln University (see the journal Basic and Applied Ecology, 9:172–181 (2008)). The brown lacewing is both a predator of many small insects and it feeds on nectar and pollen from flowers, making it omnivorous. Katherine and her colleagues attempted to understand the relationship between this predator and its prey and the effects of other food resources on the dynamics of this relationship within agroecosystems.

The authors report that it’s unclear how much predation actually affects plant- feeding pest species. However it has been reported that predators like the lacewing have been responsible for decreases in economic damage to crops by reducing herbivorous pest species.


Brown lacewing Micromus sp.
(Photo by bramblejungle).
Prey provides nutrients necessary for survival, development and reproduction. In biological control complementary resources are necessary for the predator to complete its lifecycle. Many omnivorous predatory species in agroecosystems rely on floral resources to provide nectar and pollen at the adult stage of their lifecycle.

Despite a number of studies, the omnivore’s potential role in biological control has included little research into how plant resources affect pest suppression. This includes attributes such as longevity and fecundity, which act over a longer term to affect predation at the population level. The main thrust of this study was to examine the presence of floral resources and how they influence the predatory role of the omnivorous insect, the adult lacewing.

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Katherine and her colleagues ran a number of experiments to determine whether floral resources affected omnivore predation dynamics. The first experiment established whether or not lacewings consumed plant matter as well as prey. This included the floral resource buckwheat Fagopyrum esculentum, which has a sucrose-rich nectar. The pea aphid Acyrthosiphon pisum was the prey subject. Lacewings were allocated to two treatments for 24 hours, those with flowers and those without, both containing aphids. The first treatment contained lacewings placed in an enclosure where one contained a water-filled vial containing buckwheat flowers, and the second treatment was an enclosure consisting of water only in the vial. After dissection, lacewings were examined using a reagent to determine the consumption of pollen or nectar.

Their second experiment noted the effect of flowers on lacewing longevity in the absence of prey. Again subjects were allocated to two treatments, one without buckwheat and one with. Survival of lacewings was recorded until death.

Experiment three looked at effects of flowers on lacewing fecundity. Here the lacewings were allocated to six treatments, unpaired males with flowers, unpaired males without flowers, unpaired females with flowers, unpaired females without flowers, pairs with flowers and without flowers. Thirty aphids were added to the enclosures, surviving aphids were counted for 10 days from the unpaired treatments, and for 15 days from the paired lacewing treatments.

Their last experiment demonstrated the effect of flowers on lacewing survival and fecundity with or without prey. Lacewings were allocated to four treatments, flowers and aphids, with flowers and without aphids, without flowers, with aphids, without flowers or aphids. Survival and number of lacewing eggs were counted for 20 days.

The results of this study highlighted that the presence of buckwheat flowers actually reduced consumption of aphids. However without prey availability, longevity for lacewings was greater when supplemented with flowers. Where there was an abundant supply of aphids, lacewing fecundity was not affected by flowers. When there were fewer aphids, the provision of buckwheat flowers meant that lacewings laid eggs earlier and more eggs were laid each day.

This study has demonstrated that floral resources may play a role in mediation in omnivore and prey relationships, and with regard to biological control, flowers may have both positive and negative effects.

Check out these video clips of the lacewing doing what she does best, balancing her diet with meat and flowers. It's not surprising that this species common name is the ant lion! (Used by permission, Advanced Video Productions, Christchurch, New Zealand.)


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

05 June 2009

Is Rangatira Island’s status as a wildlife sanctuary threatened by burrowing seabirds?

Rangatira Island, part of the Chatham Islands group situated off the east coast of New Zealand, is a conservation priority in New Zealand due to its importance as a seabird breeding colony and a haven for threatened species. This includes birds endemic to the Chatham Islands and most importantly, the largest of two populations in the world of the critically endangered black robin (Petroica traversii). Black robins are especially vulnerable due to their tiny population size of only around 200 individuals.

The endangered black robin
(Petroica traversii).
(Photo: C. M. Roberts).















View Larger Map

Vegetation is vitally important for Rangatira Island to maintain its status as a wildlife sanctuary. It provides protection against the bitter and frequent winds blowing northwards from the Antarctic, locally known as the ‘roaring forties’. The island has a population of around 3 million burrowing seabirds, which equates to 14,000 birds per hectare. At this density, birds have the potential to greatly affect the terrestrial ecosystem through sea to land nutrient transfer in the form of bird poo. Vegetation regeneration is also disrupted by bird trampling and mechanical disturbance from the digging of nesting burrows.

Rangatira Island forest understorey (Photo: C. M. Roberts).


















A similar situation has occurred on Grassholm Island, off the coast of Wales. Grassholm Island supported half a million puffins (Fratercula arctica) in 1890, but trampling and burrowing by birds led to almost complete vegetation loss and extensive erosion. Eventually the island could no longer support a large seabird population. The paper 'Burrowing seabirds affect forest regeneration, Rangatira Island, Chatham Islands, New Zealand' by Cynthia Roberts, Richard Duncan and Kerry-Jayne Wilson aims to understand the relationship between burrowing seabirds and vegetation so that Rangatira may avoid the fate suffered by Grassholm Island. It was published in a 2007 issue of the New Zealand Journal of Ecology.

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Clearing of vegetation for sheep and cattle farming started in the early 1940's and anthropogenic affects on the Island's vegetation continued until the removal of the remaining stock in 1959. The clearing of vegetation and undergrowth on the southern side of the island has resulted in the death of forest margins from salt and wind exposure. This barren and exposed area is called ‘the clears’ and is void of bird habitat and forest cannot recolonise the salty eroded soil.

‘The Clears’ as seen from the summit of Rangatira in January 2003 (Photo: B.Bell).





Despite the potential for seabirds to cause a problem, prior to this study little was known about forest dynamics on Rangatira Island and the effect of burrowing seabirds. The observational field study carried out by Roberts, Duncan and Wilson investigated the dynamics of the relationship between burrowing seabirds and vegetation on Rangatira Island.

The forest was found to be dominated by Chatham Island ribbonwood (Plagianthus chathamicus) and has mostly regenerated since the removal of stock. With increasing burrow density, soil phosphorous increases and pH and seedling density decrease. There are also more burrows found in areas with lower altitude and lower tree density. Seabird exclosure plots under the canopy showed increased seedling density compared to when seabirds were not excluded. Plots comparing regeneration between canopy and canopy gaps showed that canopy gaps are characterised by significantly higher seedling densities and fewer burrows. It is clear from these results that both treefall gaps and seabirds strongly influence the regeneration of forest on Rangatira.

Forest on Rangatira clearly showing the dominance of the deciduous ribbonwood. (Photo: C. M. Roberts).







The study found that the main source of forest gaps seems to be the death of a species of tree daisy called the Chatham Island akeake (Olearia traversii). This species is slowly disappearing from the island, possibly reducing the ability of the forest to regenerate. There is a possibility that ribbonwood could progressively die and collapse, producing small canopy gaps resulting in a forest with a healthy age structure. Conversely, the young, even regrowth of ribbonwood could simultaneously succumb to the effects of extensive seabird burrowing resulting in catastrophic forest collapse. This would create an uninhabitable ecosystem similar to Grassholm Island and ‘the clears’ with catastrophic consequences for the fauna supported by the refuge that is Rangatira Island.

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

04 June 2009

Moscow bound!

Yes I am off to Moscow. Idaho! The annual Evolution conference is being held there this year. The conference is always a great event for members of the societies that produce the journals Systematic Biology, Evolution and American Naturalist. Usually there is a great New Zealand turn-out (indeed NZ was 'rewarded' in 2006 by hosting this conference in Christchurch). Indeed, in the biogeography session I am speaking alongside Marty Kennedy (University of Otago) and Thomas Buckley (Landcare Research). And what am I speaking on? Drowning Zealandia, colonizing the Chathams: The role of overwater dispersal in the biogeography of New Zealand.

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The talk will look at our recent research on the flora and fauna of the Chatham Islands archipelago. In particular, I will report on the patterns that we have found by looking at about 40 endemic plant taxa and their closest relatives outside of the Chathams. The majority of endemics do not seem to differ from their mainland relatives and those that do seem relatively recent arrivals, well within the last 2-3 million years that geology tells us is when the Chathams emerged from the ocean. Another chunk of research on dune insects finds similar results. Both data sets also imply that the South Island is a major source for Chatham lineages. The Chatham's biota ends up being a fascinating data set on over-water dispersal and colonisation. There is plenty more to tell, but that can wait for a future blog.