19 December 2011

The rules of attraction


It's the end of the year and, as such, I get to combine two things that I like and dislike the most. It's cricket season with representative tournaments all over the place. I am fortunate to have three boys with good cricket ability and I have a real passion for coaching the game. One thing about cricket is that it needs a lot of gear. And it ain't cheap! It is also Christmas time and that means shopping. I do not have a real passion for this. However, my sons' and my interest in cricket does make it easier to think of presents... (And, no, they don't read this blog so they are not getting a hint before the big day). But where to go to get the gear? Actually, it's an easy decision for us as one shop with a good name in cricket gives a discount for players in my district. Why would they want to get paid less for their products by me? Well they want to attract me into their shop so that I buy stuff (and hopefully more than I intended). They reward my behaviour by giving me a bargin. As it turned out we did spend considerably more than we planned... So this store uses an 'attract and reward' system so that they will gain benefits of their own. Seems like a good idea for humans but also something that might be useful in nature. Afterall, there are many opportunities to attract species of some benefit to you.

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A group of researchers, including Steve Wratten and Sophie Orre-Gordon from the Bioprotection Centre at Lincoln University, looked at the role of 'attract and reward' systems in crops, such as wine-grapes, broccoli and sweetcorn. These researchers provided artificial attractants modelled on herbivore-induced plant volatiles (HIPV). When plants are damaged by herbivores they produce HIPVs to let natural enemies of the herbivores know that their next meal is available on that particular plant. It saves these predators from having to spend so much time searching. The researchers, who published in Journal of Applied Ecology, used artificial HIPVs to bring natural enemies into a crop (attract) and planted buckwheat as a food source (reward). Insect numbers were monitored using yellow sticky traps over several weeks. Were these attempts to get more predators into crops successful? Certainly,there were more beneficial insects found in the crops. The 'attract and reward' system seemed to work for this. Of course, this system is only useful to the plants if these beneficial predator and parasitoid insects species actually reduce pest herbivore numbers. Significantly fewer pest larvae were found in the crops which had higher number of beneficial insects and this translated to significantly less damage on the fruit. So this seems like a win-win-win situation where the plants, growers and beneficial insects are all working together and getting good results. Now I'd better head off and finish my gift buying, there's a loyalty card deal going on at the mall.

23 November 2011

Dirty needs non dirt heap


As I mow my relatively small lawn I am always faced with what I should do with the lawn clippings. I could put them in a green waste bin or put them back into my garden soils. I usually go for the latter - it's easier and I feel like it's a better option for my garden. Nutrients go back into the soil, carbon is contained in my property, I don't get a sore back from carrying the catcher to the bin. The same decision making probably happens all over the world in people's yards. Given the sheer area of urban soils around the world this is probably an instance of where lots of small decisions add up to a major impact on the world around us. Just how useful is putting greenwaste back into the soil?
Nick Dickinson moved to New Zealand last year to take up a position as the Head of the Department of Ecology at Lincoln University. In between earthquake aftershocks he has found time to publish on this issue of urban soils with Luke Beesley. In a study published in Soil Biology and Biochemistry, Nick looks at what happens to dissolved organic carbon and heavy metals under different soil treatments.

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Nick set up experimental containers of soil and added greenwaste to some, biochar (a coal-like product) and noncomposted woody material in others. He also looked at the affect of adding earthworms as they churn the soil. The experiments were left for two months before water was collected from each and analysed for dissolved organic carbon and heavy metals. Addition of the various materials all contributed to increased mobility of dissolved organic carbon and heavy metals (rather than staying 'locked' into the soil they were moving around in water). Greenwaste seemed to increase this mobility compared to the biochar and woody materials. Earthworms also contributed to this mobility.
What does this mean for urban soils? While these additions increase the health of the soil, often urban soils are high in heavy metals. Ideally we do not want these metals to move out of the soils where they could contaminate ground water. Urban soils are also a useful place to lock up carbon and, again, we don't want it to move out of the system. So Nick and Luke conclude that non-composted additions are probably better to add to soils. However, they are quick to point out that doing these experiments at larger scales (like a backyard) are important before we read too much into the results. So I'll go on adding the lawn clippings to my garden soil in the meantime while knowing that acting locally really may be affecting globally!

15 November 2011

Darwin down on the farm


To Darwin, agriculture was a vital source of evidence for evolution and for natural selection. One area where Wallace disagreed with Darwin was in how useful agriculture was in explaining evolution. Wallace thought that the comparison was not very close nor was it very effective whereas Darwin devoted much space to it in the Origin. In many ways Wallace was proven correct as evolution has been only a bit player in agriculture over the last 150 years. Until now. A new book, Pragmatic Evolution: Applications of Evolutionary Theory edited by Also Poiani, is due out in December and looks at where evolution is helping to understand the world around us in a practical sense. One of those areas in in agriculture. One of the chapters, Evolution in agriculture, is written by Steve Wratten (Lincoln University) with a former student Mark Gillespie and colleague Aldo Poiani. In this chapter they review how understanding evolution is transforming what we know in the area of agroecology. Steve points out that most agricultural activities attempt to halt evolutionary processes, trapping ecosystems in a state which produces consistent crops and so on. Much evolutionary conflict comes from this including resistence to insecticides, reducing diversity in communities,and removing natural predators and competitors. Taking an evolutionary approach allows us to build more natural and sustainable agricultural ecosystems. In the chapter Steve explains how an evolutonary approach is vital for agriculture to move forward. Hopefully this is the start of evolution regaining its natural place in this most human of endeavours and that Darwin is welcomed down on the farm.

14 November 2011

What they will be doing this summer

Every summer the Department of Ecology offers summer scholarships to undergraduates to get a taste of research (and to be paid for 10 weeks doing it). It's a great way to figure out if this research lark is for you, to make contacts and to meet staff and postgraduates. This year we welcome a number of students who will be calling the department home for the summer.

Gerrit Roux is working on Using morphological and molecular approaches to determine the diet of ground beetle candidates for translocation to Quail Island with Stephane Boyer and Mike Bowie.

Maree Henderson-Fitzgerald is working on the Styx Living Laboratory with Kelly Walker.


Also at the Styx is Chris McClure examining the Effectiveness of a predator-proof fence for conserving lizard fauna in the Styx Catchment with Kelly Walker.

Cathy Mountier will work on the establishment of a monitoring programme for the Punakaiki Coastal Ecological Restoration Project with Mike Bowie.

Ben Wiseman will work with Kelly Walker to enhance and update the Entomological teaching collection.

Marie MacDonald will balance on cliff edges with abundance, behaviour and distribution of the Mt Somers bluff weta – Life on a precipice working with Mike Bowie.

Denise Ford will test a range of rodent traps and baits for species selectivity, bycatch, and animal ethics with Mike Bowie.

Finally, Ceridwin Benn will examine microbrial species compistion in possum bites as a means of identifying individuals with James Ross, Adrian Paterson and Rob Cruickshank.

Good luck and happy researching to these students! We'll find out how it all went next March.

01 November 2011

Of questionable character


It is almost election time here in New Zealand. This year we have been spared much of the usual hoo hah because of the recent (and spectacularly successful) Rugby World Cup dominating the news as well as the Canterbury earthquakes before that. One of the tasks that we will have on Election Day is to find out what New Zealanders think of our voting system. We moved away from a winner takes all 'first past the post' system 15 years ago but there is a move to bring this back. The problem with 'first past the post' is that you can become the government despite winning less than half the overall vote, and once you are in you can act as if you won 100%. Other systems encourage representation in proportion to the amount of votes you won. What has this to do with ecology? Well it turns out that there are similar issues when it comes to analysing large molecular data sets. Such data sets can tell us about the evolutionary history of a group of species; who is related to who and when their last common ancestor lived. The problem is that most of the methods for finding these patterns tend towards the first past the post ideal. The evolutionary tree is built from the strongest signal and other signals are ignored.
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Rob Cruickshank has explored the issue of character conflict within molecular data sets in a recent issue of Zootaxa. Ideally, your data set would contain one signal, that of the evolutionary history of a group. Unfortunately there are a number of factors that can introduce other signals, such as convergence, parallel evolution, human error, high rates of change and so on. So within your data set there are usually competing signals, much as within society there are competing political parties. Most analyses simply find the signal with the most votes and this is proclaimed the winner. However, Rob points out that there are several ways to find smaller strength signals to further analyse, after all one of these might be the true answer of how species are related. For example, the fantastically named spectral analysis looks at each signal in the data and shows how much support there is (how many characters agree with this signal) and what conflict they have (how many characters disagree with this signal). Sometimes the signal with the greatest support has a lot of conflict whereas the next largest signal has none. Given that we might expect the correct phylogentic signal to have little conflict then this might encourage us to look further than the loudest signal. This would be like being given two votes: one for the person/party that you wanted to support and one for the person/party that you especially didn't want. If the leading candidate is also the one with the largest conflict then maybe they are not as good for consensus politics as the next candidate with a much lower conflict score. Certainly, in the world of species relationships determined by molecular characters, this might be something worth considering.

13 October 2011

Lantana: a fuel's paradise?


Given the sheer number of invasive species in New Zealand and the difficulties that we have with them it often feels like things couldn't get much worse for our native ecosystems. Of course things can always get worse and there are some prominent invasive pest species in other parts of the world that we don't have, thankfully, here in New Zealand. One of these is the weed shrub lantana (Lantana camara). Although this South and Central American species is a major problem in various parts of the world, all I knew about it was that it was good at invading bush edges and regularly disturbed environments, hard to get rid of and was the title of a very good movie featuring Geoffrey Rush. Thanks to our new plant ecology lecturer, Tim Curran, I now know a great deal more.

Tim recently moved to our Department of Ecology from a field station in northern Queensland where he was part of the School for Field Studies at the Centre for Rainforest Studies. Lantana is a problem species in this part of Australia and Tim and colleagues have just published a paper in Weed Research on a potentially insidious aspect of this species. Lantana often invades dry rainforest (yes a strange combination but an important habitat nevertheless!) where it dominates the understory. One of the suggested problems that this invasion causes is in changing the fire regime, such that these habitats become more prone to fire. This change could be the result of chemicals in lantana that make it more ignitable (and therefore fires are more likely to start) or, by changing the structure of the understory, more fuel may accumulate that would aid in the spread and duration of fires (making them more damaging).

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Tim and his undergraduate students went to field sites in Forty Mile Scrub National Park and measured fuel bed depths, leaf litter depths, % cover of fuels in areas with and without lantana. They also took lantana specimens back into the lab and measured how much dry matter the leaves and twigs had as well as burn durations.


The results were reasonably clear-cut. Lantana was not found to be particularly ignitable. In fact, lantana burnt faster than many native plants, which would usually decrease the damage from a fire moving through a forest. However, measurements of fuel loads in dry rainforest found that fuel cover was significantly greater in areas with lantana and fuel bed depth changed from 9 cm without lantana to 66 cm with lantana. So, lantana added significantly more fuel to burn in the habitat (so fires would burn longer and more intensely in an area) and also allowed greater access to the canopy layer of the forest (so that parts of the habitat not normally at risk were affected).

This research helps to show why lantana is such a successful weed species. It is a species that is very good at colonising disturbed habitats and this study shows that lantana can cause further disruption of the habitat, allowing itself to become even more competitive. This study suggests that removing lantana from forest edges near frequently burned savannas should be a high conservation process. All in all, this is certainly one species we can do without here in New Zealand!

03 October 2011

The web stays in the pitcher


Some of my earliest biology memories are as a 9 year old at Balclutha Primary School working through food web diagrams. The idea of the interconnectedness and interdependence of life was an extremely powerful idea and I recall the first afternoon we worked on food webs more vividly than most in my primary years (although the day Rolf Harris came, sang and painted a picture was pretty cool; and then there was the great pea-shooter battle one afternoon – but I digress).
Of course at the time it was comprehending that the big things eat the little things who eat the planty things that really sank in. Suddenly the natural world around me started to make sense in a cool and interesting way. From what I see from my own sons’ passages through primary school, the whole food web activity still seems to exist, hopefully influencing future biologists. Which is great, as there is still much to be done on understanding how food webs work. Hannah Buckley (Lincoln University) and colleagues from around the USA have worked on a very simple food web that can be found all around North America, the fluid filled pitcher plant, Sarracenia purpurea. The long-lived (> 50 years) carnivorous plant grows in bogs, sand plains and pine savannahs across much of North America Within this carnivorous plant lives a small community that typically contains 6 arthropod species, 9 protozoans and 17 bacterial species. The beauty of the pitcher system is that the food web is about as simple as you can find, the links between the different species is reasonably well understood and, more importantly, the system is replicated in thousands of sites at a continental scale. That makes for a great natural experiment which they investigated earlier by looking at the variation between populations. In the present study they wanted to see what effect temperature, rainfall, atmospheric nitrogen availability as well as the abundance of the keystone species (the pitcher plant mosquito, Wyeomyia smithii) had on food webs.

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The team collected data from all over North America. At the level of individual pitcher plants, food web complexity was proportional to the volume of liquid in the plant – the more liquid, the more complexity (meaning the pitchers act just like little islands). At the scale of sites over North America there was a less clear cut picture of the pitchers. The further north the site was (moving to higher latitudes) the less variation there was is the various traits of the pitcher food web but, overall, food web structure was not driven very much by climate variables like rainfall and temperature and it seemed that food webs at sites were often built simply by which species historically happen to have arrived in the site in which particular order. This finding is a bit unexpected as it suggests that random processes play an important role at the larger scales. So there’s plenty more work to do on this great little model system. There is something quite satisfying in finding that food webs are still as cool and interesting as that day long ago in South Otago.

12 September 2011

It's thieves, not killers, that you should worry about!

You know, just once I would love to see some ecological research that found a really simple answer that explained the phenomenon under study. Alas, we live in a complicated world where it is difficult to make robust predictions. I guess it keeps us ecologists in jobs. For example, possums are the biggest pest species in New Zealand wild areas, controlling their numbers must be a good idea. Introduced stoats are a devastating predator in most of our ecosystems, again controlling them must be the best thing to do? Turns out that (surprise, surprise) it's just not that simple. There is the cliche that 'nature abhors a vacuum' and that applies to ecosystems as well. Remove a species from a local area and suddenly a different species has a new opportunity. The remaining species might benefit because you have removed its main predator and so numbers will boom (called mesopredator release) or because you have removed a competitor for resources and so numbers will boom (mesocompetitor release).

Wendy Ruscoe from Landcare Research and a host of authors, including Richard Duncan from Lincoln University have examined the issue of meso-release in New Zealand ecosystems where there is a complex interplay of introduced pest species that degrade the natural ecosystems. There work has just been published in Ecology Letters.

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The group worked in forests of the North Island of New Zealand where they looked at interactions between a top predator (the stoat), two mesopredators (rats and mice) and an omnivore (possum). These are all species that are often controlled to reduce population numbers. (Note that in New Zealand the word 'control' generally means 'kill'). The team set up areas of stoat removal, possum removal, possum and rat removal and a control with no removal. Populations in the areas were assessed before and after control operations. The results were convincing. The removal of stoats (a top predator) caused no response in the two mesopredators (mice and rats). The removal of the omnivore (possum) released rats and their populations grew. The removal of rats led to a growth in mice numbers. The net result for the ecosystems was that removing possums and rats (while useful in the short term) probably had little long term benefits as other competitive species filled the void and continued to cause problems for the native biota. The lack of an impact from the removal of the predator was of great interest and suggests that competition, not predation, is the important process that shapes communities. So wildlife managers need to think in terms of multi-species control if they want to effectively manage ecosystems in the long term. Which is a reasonably non-complex answer for a complex process!

02 September 2011

Buoyant moas and overweight explorers


The Third Combined meeting of the Australian and New Zealand Entomological Societies Conference has just concluded here at Lincoln University. Four days of good talks and plenaries. About 200 participants, of whom about a third were postgraduate students, made for much excellent discussion. I was involved in the opening symposium on New Zealand biogeography and whether we should consider Australia to be the mothership or sistership of our biota. I talked through a rough overview of the geological history of Zealandia and the implications for our biota. I strongly urged that we need to start thinking in terms of a Zealandia biota in addition to a Gondwanan biota. I also reiterated the geological evidence for the Oligocene drowning of Zealandia that saw almost all of New Zealand underwater about 23 million years ago (for previous blogs on these issues see here , here , here , here and here). I'm pleased to report that the concept of Zealandia and of a dramatic drowning seem to be gaining traction as measured by the content of other talks at the conference. There is one aspect, though, that I would like to address: the curious case of the buoyant moa.


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Pete Cranston delivered the opening keynote address to the conference just prior to our symposium. He spoke about austral chironomids (freshwater insects) and what they tell us about the ecological and biogeographical history of our part of the globe. All very interesting and delivered in his usual witty manner. At one point Pete thought to make a point about the likelihood of the Oligocene Drowning having occurred. One common response that I get to the idea is "yeah but what about the moa?". Moa were gigantic birds once common in New Zealand until driven to extinction by humans and are related to other large birds around the southern hemisphere. People find it hard to comprehend how big flightless birds could colonise an area across a big water gap. Pete illustrated this problem with the moa buoyancy hypothesis that was put forward by Rich Leschen in 2008 (you can find it here - scroll down to page 5). Although meant in a humorous sense, moa have natural floatation abilities to get across water gaps (and are spacious enough to bring other passengers), it is really saying "what a silly idea the drowning is to even contemplate that moa could colonise New Zealand". Of course I beg to differ.

I could come up with several comebacks. Kiwi, another ratite, clearly arrived well after the Zealandia broke away from Gondwanaland (as determined by molecular dates) and are more closely related to emu than to moa! So they got across the water OK. We now know that South American tinamou (small and flighted birds) are part of the ratite group and that the ancestors of each ratite regional group were able to fly and colonise these regions. Island species also often share a common evolution trajectory which results in gigantism and flightlessness in birds. So there is a method for moa to get across the water OK and one that explains why the are so large. Finally, we should not fall into the trap of assuming that modern traits were always the same. I think I'll call this the 'Fat explorer hypothesis'. New Zealand is fast catching the USA as the most obese country in the world. If I was looking at modern New Zealand and thinking about how humans arrived in our shaky islands, I might think that clearly, based on what we know about early waka and the sailing ships of Cook and the size of present day New Zealanders, that we would have been much too large to have fitted into these vessels and so there is no way we could have got here in that manner. Perhaps our ancestors lived in Gondwanaland and walked (waddled?) into Zealandia before it split apart? Of course this is a silly arguement, present morphology (large and round) is not a full-proof predictor about previous morphology (small and wiry). Clearly, our ancestors were much smaller and quite happily fitted their ships. In recent times, their descendants have have burgeoned until we see the size of our present populations. A good analogy for the moa perhaps. All good fun!



23 August 2011

Blue hotels: nestsite location in Little Penguins

Little Penguins (or Blue Penguins, Korora, Eudyptula minor or even, in Australia, Fairy Penguins) are the most common penguin to be found in New Zealand. They have numerous colonies ranging from a few nest to several thousands and they are found all around our shorelines.Despite being the most numerous penguin species in the New Zealand region there are concerns about population decline throughout the range. Some areas of New Zealand are of greater concern than others. Little penguins are restricted to colony sites that have easy access to the sea, where there is good soil to build burrows (or small caves) and where the right food is found in inshore waters.
One area of New Zealand that has been little studied for Little penguins is along the west coast of the South Island. Many colonies along this coastline are threatened with encroaching development by humans as well as a increasingly busy coastal highway. A recent study by Lincoln University researchers Jasmine Braidwood and Kerry-Jayne Wilson along with Janine Kunz (Georg-August University)examined which features of the habitat were important for burrow use and breeding success along the West Coast.

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Braidwood, as part of her Master of International Nature Conservation, collected data from 167 burrows and artificial nest boxes spread through five colonies in the Buller region as well as 110 burrows across three colonies in South Westland, over three years. Information on numbers of eggs, chicks and adults seen was recorded as well as distance from the high-tide line, track/road and edge of scrub, vegetation type, and terrain.

Over the two years, Little penguins were found in 1/3 to 1/4 of all burrows available, and breeding success increased over the period and was broadly similar to other parts of New Zealand. Most colonies were found in regenerating coastal forests and most burrows were with 25m of the sea. Of most interest was the lack of obvious impact of human activity on breeding success which gives some optimism for the future. The authors worked closely with the West Coast Blue Penguin Trust and hope that this study will provide information for improving the placement of nest boxes in Little penguin colonies in the future to best ensure good breeding success.



12 August 2011

Strewth! Australasian insect conference at Lincoln


The third combined Australian and New Zealand Entomological Societies conference will be held at Lincoln University from 28th August to 1st September. The theme of the conference is "The Status of Australasian Entomology: Where the bloody hell are we?". Currently, about 200 lovers of all things insecty (and honorary insects like spiders) are set to swarm on Lincoln. Participants will hear from keynote speakers Peter Cranston (What can insects, especially Chironomidae, tell us about austral ecological and biogeographical history?), Georgina Langdale (The economics of nature- findings from the TEEB study), Mark Burgman (Making the most of intelligence information and expert judgements for biosecurity), and Andy Suarez (The biogeography of ant invasions and its implications for biosecurity). Plenary speakers feature Steve Goldson, Steven Chown and Robert Hoare.


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There are several themed sessions including:
Australia: Mothership or sistership th the New Zealand invertebrate fauna
Strategic trans-Tasman collaborations enhance arable and vegetable IPM in Australia and New Zealand
Biological control of athropods
Biodiversity and ecosystem services
Communication in a digital age
Climate change and insects
Community ecology
Conference organiser John Marris (Lincoln University Research Museum) promises an informative and fun time with lashings of 3 Boys beer and Wither Hills wine!


10 August 2011

A fine pine: Kakapo not picky about their diet

This article was prepared by postgraduate student Ana Baral as part of the ECOL 608 Research Methods in Ecology course. This marks the last of this year's cohort. Thanks to the class!

Kakapo are found only in New Zealand where these magnificent green parrots struggle for their survival. Only a few of these large birds survive in their natural habitats and are listed as a critically endangered species. Kakapo are unusual parrots in that they become active at night, cannot fly and forage on plants. These birds are ‘treasures’ of New Zealand.

Kakapo are vulnerable to introduced mammalian predators. By the mid 20th century, only a few Kakapo were fighting for existence in Fiordland and Stewart Island. Between 1970 and 1990, all known Kakapo were moved to predator free islands. One such island was Maud Island, in the Marlborough Sounds, because it was free from feral sheep and goats as well as mammalian predators of the Kakapo. The natural forest of Maud Island, now a scientific reserve of 309 ha, was highly modified to pasture and farmlands in the late 1800s. The island was brought back into the conservation estate in 1972 and restoration began. Nine birds were taken to Maud Island between 1974 and 1981.


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Fruiting species, including gooseberries, blackcurrants, guava and apple, were planted in 1975 to provide additional food for Kakapo. Since 1990, Kakapo have been provided with protein rich supplementary food , which includes apple, kumara (sweet potato), and the kernels of almonds, brazil nuts, sunflower seeds and walnuts, to induce breeding artificially.

In an effort to better understand Kakapo, Julie Walsh and Kerry-Jayne Wilson of Lincoln University and Graeme Elliott of Department of Conservation, New Zealand carried out research about home range size and habitat selection of Kakapo on Maud Island. At the time, there were 18 Kakapo on the island; four adult males, nine adult females and five juveniles.
All kakapo were fitted with small backpack radio-transmitters and the positions of birds were obtained at night for almost a year. They estimated seasonal home range size which varied from 1.8 to 145 ha. The home range was smallest in winter and the size varied individually in the use of habitats and plant species.
As a result of conservation initiatives, previously cleared and converted natural forest to pasture was changed to regenerating scrub of eight vegetation types. Nearly all Kakapo used the pine plantation in summer because they fed on pine needles, barks and young cones. Kakapo rarely roosted in the pines because pine has relatively open forest floor of the plantation, and the straight, often branchless, tree trunks. The Kakapo used the treeland scrub in the autumn because they were feeding on five-finger berries. The Kakapo avoided lowland scrub in all seasons and other vegetation types seasonally.

The researchers concluded that Kakapo were more that capable of surviving on highly modified Maud Island. However, despite supplementary feeding, the Kakapo have only bred on the island once. The lack of successful reproduction suggests that Maud Island’s vegetation does not provide sufficient high quality food to trigger or support breeding, though it is more than adequate to support non-breeding birds.



07 August 2011

Fly my pretties

This article was prepared by postgraduate student Nick MacDonald as part of the ECOL 608 Research Methods in Ecology course.
For those of you who have ever ventured beyond the boundaries of buildings and urban assemblages you would at some stage be greeted by one of Mother Nature’s miracles of aviation. I am referring to the New Zealand Hover fly (Melanostoma fasciatum) which can often be seen hovering, acrobating and nectaring at flowers around New Zealand’s natural environments. So what are these busy little creatures? What are they doing and where do they go?

Hoverflies are members of the insect family Syrphidae. They can vary in appearance depending on species and despite their black and yellow striped mimicry of wasps, are harmless and share a unique relationship with humans. Gardeners consider themselves lucky when they are blessed with the presence of hoverflies. This is because at a larval stage, they are predators and prey upon pest insects such as caterpillars, aphids and other small insects. When larvae get close to prey they strike grabbing hold of them with their mouths and suck them dry. Adult hoverflies are herbivorous feeding on the nectar from grass species and Dandelions. They are also expert fliers hovering, manoeuvring and in some cases walking from flower to flower collecting pollen. They are considered to be, along with bees, an important pollinator of New Zealand’s flowers.


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Field boundaries such as hedgerows and fence lines can impede hoverflies ability to pollinate. In a 2003 study, Field Boundaries as Barriers to Movement of Hover Flies(Diptra: Syphidae) in Cultivated Land by Wratten et al, the extent to which field barriers impeded hoverfly movements was analysed. The study used four types of field boundary with varying permeability in each replicate. The boundary types were: post and wire fences, poplars with gaps and dense poplars. Lacy Phacelia or Phacelia tanacetifolia, a plant with nectar rich flowers, was planted on one side of the four boundary types. Five yellow traps were placed on either side of the Phacelia, this provided a trap line on either side of each boundary. Hoverflies found in traps with Phacelia pollen in their guts were collected and counted. This enabled scientists to see if the permeability of a boundary would impede hoverfly flight movements between the Phacelia in each replicate.

Results showed that the type of boundary does have an effect. Less permeable boundaries, for example, the dense poplars had the lowest proportion of hoverflies in traps, post and fence boundaries had the highest proportion and poplars with gaps were in between. The ability of hoverflies to fly through boundaries and pollinate flower is directly influenced by the permeability of boundaries. Other studies such as: Interacting effects of landscape context and habitat quality on flower visiting insects in agricultural landscapes by David Kleijn and Frank van Langevelde, 2006, point to the importance of landscape context for hoverflies; the abundance and richness of hoverflies depends upon the quality of the habitat patches.
So, what does this mean for hoverflies and for us if we continue to erect impermeable boundaries? It would not be a stretch of the imagination to conclude, that there could be environmental implications for New Zealand. If we reduce hoverflies ability to gather food this could reduce their population numbers and lead to a decline in the pollination of New Zealand’s flowers. It could also, diminish larvae numbers and dilute their role as a bio-control mechanism. This could increase the need and use of pesticides and insecticides on our foods. Plants have evolved in conjunction with hoverflies and are dependent on this complex relationship. I suggest that we adopt a mindset that takes permeability of field boundaries into consideration. We could erect boundaries that work with hoverflies, not against them. After all they are here to help.

03 August 2011

Butterflies and wine: friends or foes?

This article was prepared by postgraduate student Hannah Lewis as part of the ECOL 608 Research Methods in Ecology course.
Most of us enjoy the sight of a butterfly flitting around our backyard, however many of us will not be aware of the importance of native butterflies in agricultural ecosystems and the plight that they are facing. Could you name even 3 types of native New Zealand butterflies? The monarch butterfly which is native to North America seems to be the most well known representative of butterfly species within New Zealand.

The intensification of modern agriculture has resulted in an increase in food production to meet the requirements of a growing worldwide population. The amount of cereals (wheat, barley, oats etc) coming off an area of land has increased from 3800 kg/ha in 1968 to 8000 kg/ha 2008. A major issue with intensification has been the reduction of suitable habitat for butterflies and other insect species and the development of plant monocultures. Monoculture (photo 1) is the continuous planting of the same crop over a large area. Doing this greatly decreases the amount of places that are suitable for insects and butterflies to nest/lay eggs and live in. Insects are our main plant pollinators, without this essential function that they provide us for free, there would be no food to feed the world.


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Mark Gillespie of Lincoln University studied his PhD on the prevalence of butterflies in vineyards in the Waipara region, North Canterbury. The intensification of agriculture is one of the main drivers behind biodiversity loss. The introduction of agrochemicals and the creation of homogenous fields (monocultures) without hedgerows or shelter belts have modified natural habitats which have become unproductive for no other use than intensive agriculture and food production.

The analysis of six different vineyards partaking in the Greening Waipara project (see link 2 for more detail) showed that the endemic common copper (Lycaena salustius) (photo 2) and endemic southern blue (Zizina oxleyi) (photo 3) were the most prevalent native butterfly species. Mark measured butterfly density by doing The results show that it is important to maintain remnant vegetation sites for butterflies to inhabit near cropping areas as these are not influenced by farm machinery and agrochemicals.

Mark’s thesis results showed that the Greening Waipara plantings were of least importance to butterflies although this could be because they are so young. Having only been planted within the past 7 years, the plantings are also fairly isolated from other bigger patches of favourable living conditions. Basically, butterflies require a very diverse conservation area to sustain a population including differences in vegetation and the landscape.
To increase the population of butterflies in their vineyard, landowners need to see economic benefits to them being there. Aside from their general conservation value, native butterflies have aesthetic and economic effects on tourism and marketing. Making them good money earners for the landowner, particularly in wineries where tourists will stop and visit and spend some time outdoors. Currently, the vineyards in the Waipara Region are poor habitats for native New Zealand butterflies. Butterflies are commonly used as an indicator species of a particular environment, that is the presence or absence of butterflies native or otherwise can indicate the state of the environment that is being searched. Hence an increase in native butterflies can indicate a healthier environment which is better for the sustainability of monocultures in New Zealand.

27 July 2011

Names at light speed

A major staple of science fiction (especially tv and movies) is a device that can tell you what species of seaweed, stick insect, sun bird or slavering alien monster you are looking at. The tricorder of Star Trek is the most famous of these device. Just point and click and you get the identification of what the beastie is, lots of information about its ecology and the likelihood that it will suck your brain out. For the last decade ecologists have been working towards a machine with this ability but we may have been sidetracked by our DNA dependence. Much of the activity in this area has been around being able to diagnose species in the field by quickly analysing DNA samples. Which is fair enough because we have been spectacularly successful in using DNA to do all sorts of things (including quickly identifying species).
However, there may be a more elegant way of doing this: getting the answer, quite literally, at light speed (and what could be more scifi than that?). Rob Cruickshank (Lincoln University - pictured, appropriately in a red shirt) and Lars Munck (Copenhagen University) have summarised a new approach to identifying species that does not use DNA and gets us closer to 'point and click' technology. The most promising new method involves beaming near infra-red light onto the surface of the individual you wish to identify (say a beetle). You then calculate the amount of absorption/reflection of light coming off the surface. It turns out that different species of closely related species will absorb different amounts of light and have distinct 'fingerprints'. So without even collecting a sample you could identify individual species. At the moment this can only be done in a controlled lab environment and we are not sure if it will work on all sorts of different species with precision but the future is looking bright for the first 'real tricorder'! Make it so.

The Citizens of Mushroom City



Sky Blue Mushroom (Entoloma hochstetteri) – one of many fungi found within New Zealand

This article was prepared by postgraduate student Olga Petko as part of the ECOL 608 Research Methods in Ecology course.




When we hear the word “biodiversity” magnificent tigers and cute koalas, beautiful coral fish and bright parrots first come to mind. But biological diversity or, to be more precise, species richness, is not about appearance or popularity but is simply about numbers. And no other group can claim to be richer in species than the insects.




Insects can be found almost anywhere: running on sand in hot deserts or making tunnels inside icebergs, flying over tropical forest canopy or hiding behind curtains in your room. Any habitat is a home to countless six-legged dwellers, one just need to look. Little wonder that mushrooms are not an exception. To look at fungi of New Zealand to find out who exactly finds them irresistible is an adventure on its own for such a dedicated entomologist as John Marris from Lincoln University.

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The woodland insects associated with the fruiting bodies of macrofungi, i.e. mushrooms, include specialist fungi-eaters, generalist detritus feeders and all their associated predators and parasitoids. Marris and his colleagues used rotted commercial mushrooms (Agaricus spp) as a bait to collect insects from native beech forest (Nothofagus spp), native mixed forest, exotic conifers (Pinus radiate or Cupressus macrocarpa) and urban restoration areas. Overal 2 429 invertabrates were collected, which mainly consisted of beetles (Coleoptera), flies and midges (Diptera), also parasitic wasps (Hymenoptera). To name just a few interesting species: a parasitoid wasp of spider eggs Idris spp (Baeini), round fungus beetles Leiodidae, Saphobius spp (Scarabaidae) and moth flies Psychoda spp (Psyhodidae). Of course, as it always happens with these tiny creatures, among collected specimens were several newly-described genera and new species.




Moth fly




The list of insect species that are associated with mushrooms increases our knowledge of the nature of New Zealand. Worldwide habitat-specific insect assemblages are used as indicators of site quality and conservation value, as well as measurement of anthropogenic disturbance. The survey of Marris and his colleagues showed that two conspicuous native beetles Zeanecrophilus prolongatus and Saphobius can be used as good indicators of site quality. A handy method in assessing the remnant patches of New Zealand woodland. It also became clear that monoculture plantations of exotic conifers are not a wood equivalent of a desert and can compare favorably to native forests in terms of richness and diversity of insect faunas. What is most important these plantations can provide suitable habitat for indigenous insects too.

Round fungus beetleThere are many restoration projects in cities and around them. And here is the good news. The research brought new evidence that despite the fact that urban nature reserves are small in comparison to remaining native forest and low in total species richness, they still play a valuable role in conservation of invertebrates, providing a refuge at a local level.


This study was first of its kind in New Zealand. The “mushroom bait” method is not ideal, not all insects are attracted by the smell of commercial Agaricus. The researchers are sure that the use of any native New Zealand fungi as bait or alternative collection techniques will widen the species list of the citizens of Mushroom City.





<!--[if !supportLineBreakNewLine]-->Photo sources: mushroom, moth fly, round fungus beetle


22 July 2011

Tangled webs in braided rivers

Humans like to put things in boxes, name them, groups similar things together, impose order on chaos and generally make the world a tidier place. This is very much the case in biology where we seek to put names to species so that we can then make sense of a complex, living world. Unfortunately, the living world is not always so black and white. For example, there are times when groups look different to one another, and are called different species, but they still can successfully mate (or hybridise).
Such a situation may occur in the last stages of speciation, as it takes numerous generations for new species to fully diverge. Repeated crossing of hybrids with parent species is termed 'introgression' and this can often have negative impacts on the parent species, such as removing local adaptational traits. Because of these impacts, organisms usually have traits for avoiding mating with hybrids or members of closely related species. Luckily, introgression does leave its mark on an organism's DNA and can be readily detected. One group of organisms with a history of introgression is the spiders.

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Within New Zealand there are four species of Dolomedes, a genus of large spiders spread around the world. Dolomedes aquaticus is found among the stones of braided riverbeds and D. minor in grass and scrub areas as well as swamps and other wet areas. Although individuals from these two species often come into contact and have the potential for interbreeding to occur, a study by Vink and Duperre found that this did not happen throughout New Zealand. Everywhere, that is, except the southern end of the range that they sampled where there was the suggestion of introgression occurring. Following up this study was the task for honours student Vanessa Lattimore with here supervisors Adrian Paterson, Rob Cruickshank (both Department of Ecology, Lincoln University) and Cor Vink (LU Entomology Research Museum and AgResearch). Vanessa sampled from braided rivers throughout the southern South Island of New Zealand and obtained Dolomedes specimens from 13 locations. She then examined a nuclear gene (actin 5C) and a mitochondrial gene (COI) for evidence of introgression.
Evidence for introgression was found with three haplotypes (versions of a gene region) from D. aquaticus being present in D. minor and this was recently published in Invertebrate Systematics, where it made the front cover! (Although I didn't buy 5 copies for my mother) Interestingly, there was no evidence for movement of genes from D. minor to D. aquaticus.
Why is the introgression only occurring in one direction? Because of the way that mitochondrial DNA is inherited, the most likely reason is that males from D. minor are willing to mate with females of D. aquaticus whereas D.aquaticus males are either too big (they are much larger than D. minor males) or more picky than D. minor males. The geographical pattern of the three haplotypes are also different which suggests that these introgression events have happened at different places and probably at different times. A major question to arise out of this research is explaining why the introgressions occur in southern braided rivers and not elsewhere in New Zealand. The authors suggest that as braided rivers are prone to variable flows (from no flow to floods in short time periods) that D. aquaticus may be forced into the surrounding vegetation where D. minor are found from time to time.

21 July 2011

Archaea vs bacteria: who is doing most of the work?

This article was prepared by postgraduate student Aimee Robinson as part of the ECOL 608 Research Methods in Ecology course.

Nitrification is an important process in the nitrogen cycle and has the most obvious environmental implications. The end-product of nitrification is nitrate (NO3-) which can be leached into groundwater (see diagram below). High concentrations of nitrate can cause algal blooms and contamination of lakes and rivers. In drinking water, high concentrations can cause the potentially fatal blue baby syndrome in young children. This occurs when nitrate is converted to nitrite in the baby’s digestive system. This then reacts with the body’s oxygen carrying molecule, haemoglobin, forming a non-oxygen carrying molecule called methaemoglobin which decreases the infant’s ability to utilise oxygen. Nitrate from nitrification can also lead to the production of nitrous oxide (see diagram), a greenhouse gas, which has further implications for the environment through global warming and climate change. It is therefore important to understand the biological process of nitrification for the application of mitigation strategies to reduce these environmental hazards.


It has long been thought that ammonia oxidising archaea (AOA) (single celled micro-organisms which have no nucleus or any other bound organelles) only drive the nitrogen cycle in harsh environments. However, in a paper published in Nature, Linginer and colleagues discovered that AOA may be the most abundant ammonia oxidising organisms in soil ecosystems. This questions the traditional assumption that nitrification is dominantly the role of ammonia oxidizing bacteria (AOB) and begs to question what really is driving the nitrogen cycle in the soil?


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Although it has been shown that AOB dominate the nitrification process in some agricultural soils, it is interesting to see how AOA may react to nutrient changes in the soil and in the presence of an inhibitory substance.
In a recently published study in the Federation of European Microbiological Societies Microbiology from Hong Di and his team at the Centre for Soil and Environmental Research, Lincoln University, they investigated the role of AOA and AOB in differing layers of soil and determined the effects of animal urine and a nitrification inhibitor (DCD) application on the two organisms. Samples from Waikato, Canterbury and Southland were collected to gain a holistic view of New Zealand soils. They found that AOA was more abundant in the soil than AOB in both soil layers with the bacteria decreasing in the lower layer. With the addition of urine AOB greatly increased whereas AOA seemed to be inhibited. This demonstrates that AOA and AOB prefer different soil nutrient conditions with AOA favouring low-nutrient environments.

Adding nitrification inhibitor sufficiently reduced the AOB nitrification rates and hence lowered nitrate leaching and nitrous oxide production. The AOA were inhibited by the urine addition but this could have been due to the urine or DCD which were both present in the treatment. It would be useful to determine the AOA reaction to the DCD alone. However, because nitrification inhibitors work by preventing the enzyme produced from the organism rather than targeting the actual producer, Archaea would most likely react in a similar way to the bacteria and be inhibited.
This study demonstrates that AOB are the hardest workers in the soil nitrogen cycle, although AOA should not be underestimated. AOA’s abundance in the soil suggests their importance, but the processes they undertake are yet to be understood. Continued research from Lincoln University will continue to decipher the roles of AOA and their potential presence in agricultural soils as well as their value in lower nutrient environments.


19 July 2011

Newly discovered interaction has farmers buzzing

This article was prepared by postgraduate student Sam Read as part of the ECOL 608 Research Methods in Ecology course.
Nature is full of wonderful and surprising phenomena. Organisms can often be linked directly or indirectly in amazing and unpredictable ways. It came as somewhat of a surprise when honeybees were discovered to have an impact on caterpillars. Common sense would suggest honeybees (Apis mellifera) and caterpillars would have little to do with one another, as honeybees increase plant fitness by pollination and caterpillars decrease plant fitness by herbivory.
Other relatives of the bees are not so benign. Wasps (Vespula spp.) are generalist predators and are natural enemies of many caterpillar species worldwide. Rapid wing movement while flying creates vibrations in the air, heard as a buzz. Previous research indicated that these vibrations stimulate special sensory hairs on caterpillars and pre-warn them that predators are present. The caterpillar will then stop moving and damage to the plant will cease, until the predator has gone. Occasionally, the caterpillars may even drop off the plant, if the predator gets too close.
Wasps could therefore be effective biological control agents to reduce pests. However wasps themselves are considered pests by many. Wasps are one of the most invasive insect pests in the world. They cause problems to agriculture, horticulture, wildlife and are a nuisance in urban environments due to their nesting and aggressive behaviour. Instead, a similar alternative buzzing insect is required. As honeybees are of high economic value and also create a buzz, they were thought to be a potential candidate. A new study was published in Current Biology by Jürgen Tautz and Michael Rostas (Lincoln UNiversity), in which they carried out an experiment to test whether particular herbivores would show the same behavioural reaction with honeybees, as occurs with wasps.

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A field cage experiment was carried out using the beet armyworm caterpillars (Spodoptera exigua), as they are a generalist pest that feeds on at least 50 plant species. The caterpillars were applied to either bell pepper (Capsicum annuum), with or without fruit, or soybean (Glycine max). Honeybee hives were applied to half of the treatments, with the remaining half with no hives as controls.
When the honeybees were present, there was a significant reduction in leaf damage (60.6-69.3%). The caterpillars’ behavioural reaction to the honeybee buzz was similar to the reaction triggered by a wasp buzz. Honeybees created very similar air vibrations, at an almost identical frequency (Hz) to the wasps, which the caterpillars could not distinguish between.
These findings indicate that other caterpillar species with sensory hairs may also react to the presence of honeybees. Some smaller experiments were then carried out by Michael Rostás. The cabbage moth (Mamestra brassicae), a common European moth was then tested and did behave in a similar way in the presence of honeybees. The large white butterfly (Pieris brassicae) is another species which may potentially respond in a similar manner, as it responds to the air particle movement of hand clapping. Numerous other species worldwide could also be candidates, but future success may depend on honeybee densities in the area.
Honeybees can therefore not only perform pollination by transporting pollen from flower to flower, but also they may contribute to the reduction of plant damage by some herbivores. This unexpected interaction may prove to be a useful tool in the development of future integrated pest management programs.

07 July 2011

It’s about time – wildlife managers rejoice over new stoat toxin

This article was prepared by postgraduate student Tim Sjoberg as part of the ECOL 608 Research Methods in Ecology course.

New toxins that are effective, humane and sociably accepted are desperately needed in New Zealand for predator control. Wildlife managers have relied upon too few toxins for broad control of many predator species. The development of a safer, humane, and predator specific toxin is highly desirable and long overdue for New Zealand predator control.
New Zealand wildlife evolved in the absence of mammalian predators. Birds (such as Kiwi, Mohua and Kokako to name a few) have particularly been impacted by the introduction of non-native predators, and this is reflected by the extinction of over 40% (Eason et al. 2010) of the pre-human land bird species.
Stoats (Mustela erminea) were introduced into New Zealand in 1884 for the control of rabbits which were reducing pasture production. Stoats moved from farmlands and into the native forests where they have become the most significant factor in New Zealand’s historic fauna decline. Their large home ranges (up to 100 hectares), excellent swimming ability, and furious appetite for any animal that moves, has made the stoat, one of the Department of Conservation’s (DoC) main targeted animals.

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Control methods for stoats currently rely on labour intensive trapping and poisoning. However, the use of 1080 (sodium fluoroacetate) is becoming increasing unpopular in New Zealand, as public fears relating to the contamination of water supplies, possible sub-lethal effects on humans, welfare impacts on targeted species, and the potential of 1080 to kill native birds and other non-target species is still embroiled in controversy. At the present time there is no stoat specific toxin available.
Para-aminopropiophenone (PAPP) was investigated in the 1980’s as an alternative to 1080 for coyote (Canis latrans) control in North America. PAPP is a red blood cell toxin. This toxin works by reducing the oxygen supply to the brain, making animals lethargic, sleepy and unconscious prior to death, which is within 1 to 2 hours. This rapid time till death gives PAPP a high humane rating when compared with other toxins used worldwide.
PAPP was trialled by Connovation in conjunction with DoC at Lincoln University facilities, under the guidance of Professor Charlie Eason. Captured wild animals were given a PAPP paste within meat baits, which caused 95-100% mortality. There were no signs of discomfort, stress or vomiting associated with poisoning, and animals became unconscious quickly following ingesting the bait.
From this study , PAPP looks extremely useful for stoat control, with no toxins currently registered for use against stoats and few effective techniques are available to control them. PAPP has relative specificity for mammals, and is lethal to stoats at low doses. PAPP would therefore be a significant advance for wildlife protection in New Zealand. With stoats continuing to have significant impacts on a wide range of threatened birds, lizards and invertebrates, PAPP is a welcome relief for wildlife managers and long overdue.

Further reading:
Eason C., Wickstrom M.and Gregory. 1997. Product stewardship, animal welfare, and regulatory toxicology constraints on vertebrate pesticides. Proceedings of 50th New Zealand Plant Protection Conference. Pg 206-213
Gregory N., Milne L., Rhodes A., Littin K., Wickstrom M. And Eason C. 1998. Effect of potassium cyanide on behaviour and time to death in possums. New Zealand Veterinary Journal 46 pg 60-64
Littin K., O’Connor C., Gregory N., Mellor D and Eason C. 2002. Behaviour, coagulopathy and pathology of brushtail possums (Trichosurus vulpecula) poisoned with brodifacoum. Wildlife Research 29 pg 259-267
Littin K., Gregory N., O’Connor C., Eason C. and Mellor D. 2009. Behaviour and time to unconsciousness of brushtail possums ((Trichosurus vulpecula) after a lethal or sublethal dose of 1080 and implication for animal welfare. Wildlife Research 36 pg 709-720.


Mothbusters! The importance of forest fragments in nature conservation

This article was prepared by postgraduate student Elise Arnst as part of the ECOL 608 Research Methods in Ecology course.

New Zealand has vast areas of highly modified and fragmented, disconnected landscapes. It is important for the conservation of biodiversity to understand the ecology in these modified, human-dominated landscapes. Urbanised areas and farmland both tend to be on low-lying land that is high in nutrients and resources and previously supported biodiversity hotspots. Remnants of native forest are rare pockets of once widespread species and are important in conserving biodiversity. Both remnants and restored native vegetation are important in the conservation of other native species, such as invertebrates. To maintain and increase biodiversity we must build on such remnants by restoring native plant species in altered habitats.
Landscape-scale patterns in fragmented areas provide an important understanding of the ecological processes driving invertebrate distribution and abundance. In New Zealand there are many small patches of native trees, which are not joined to a larger patch of forest making it difficult for invertebrates to move between areas to find food or a new habitat. These patterns have been explained by Ruth Guthrie and two other Lincoln University scientists, Hannah Buckley and Jon Sullivan, in their study of cabbage tree (Cordyline australis) damage by the larvae of the endemic moth Epiphryne verriculata Feld (Lepidoptera: Geometridae) in Christchurch, New Zealand.



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Studying cabbage tree herbivory has helped to explain the abundance and distribution of E. verriculata. The larvae eat only cabbage tree leaves (i.e. they are monophagous), which means its ability to survive is dependent on the presence of the cabbage tree. This also means that the clearly identifiable damage on cabbage trees is a straight-forward way to determine the abundance of the moth larvae. Herbivory was measured by Guthrie et al. (2008) as the percentage of damaged leaves on a cabbage tree crown. Herbivory was seen on almost all trees across all sites, indicating a widespread presence of the moth in both natural and modified areas. Damage was higher in adult trees, this is likely to be because they provide a larger food source. Herbivory was also higher when few other cabbage trees were in close vicinity, which is a likely to be result of the moth larvae being monophagous – fewer cabbage trees means they will do more damage to less trees. The skirt of dead leaves on the cabbage tree was thought to be a refuge for adult moths but the presence or absence of a skirt appeared to have no impact on the level of damage. This may indicate that larval abundance is more dependent on the availability of food rather than suitable habitat for adults. The abundance and distribution of E. verriculata can help to explain more complex landscape-scale patterns.
There appears to be a pattern across the Canterbury Plains where endemic herbivorous invertebrates are present on their host plant regardless of landscape fragmentation. In the study by Guthrie et al. (2008) this was confirmed as larvae were found on cabbage trees in all landscape types. The widespread presence of larvae indicates that the availability of suitable host tress is the determining factor for the E. verriculata moth to be able to survive in an area. Native trees in both restored and urban areas provide potential habitat and food sources for invertebrates. This emphasises the significance of native flora in modified landscapes for maintaining invertebrate diversity, providing strong motivation to ensure we continue to promote native biodiversity through restoration in modified areas.
Guthrie, R.J., Sullivan, J.J. and Buckley, H.L. 2008. Patterns of host damage by the cabbage tree monophage Epiphryne verriculata Feld (Lepidoptera: Geometridae) across urban, rural and native forest habitats. New Zealand Entomologist 31: 77-87.


04 July 2011

Bacteria, friend not foe in stream ecology

This article was prepared by postgraduate student Julia Bellemy as part of the ECOL 608 Research Methods in Ecology course.

Determining the ecology of freshwater streams is important because it contributes to our understanding of the effects of human activities on the stream and lets us monitor remediation strategies. The health of freshwater streams is typically determined by examining the diversity and abundance of fish and invertebrates. But there may be another way of determining the health of freshwater streams, in the form of tiny, microscopic bacteria. These bacteria may be useful as highly responsive indicators of changing environmental conditions.

Freshwater streams display both temporal (time) and spatial (space) differences. Time variation is a result of seasonal influences and space variation is due to flow regime, substrate type, water solutes, suspended materials and incident light exposure. It is believed that bacterial communities are good indicators due to their rapid life cycle. However, if we can’t see them, how do we know that they are present and observe changes? Bacteria can be detected using Automated Ribosomal Intergenic Spacer Analysis (ARISA) which creates ‘fingerprints’ of microbial communities. The ‘fingerprint’ produced is just like a human fingerprint, because it is unique to a bacteria species just like a fingerprint is unique to a person.

So how is ARISA used to construct a ‘fingerprint’? Unfortunately, it isn’t as easy as dipping bacteria into ink and pressing them against paper. First, the DNA has to be extracted from the cells and then DNA sequences are identified for each species. The length of the gene region varies between different species and this difference in length allows a unique ‘fingerprint’ to be constructed for each species.


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In the study “Spatial and temporal heterogeneity of the bacterial communities in stream epilithic biofilms” conducted by Gavin Lear from Lincoln University, the time variation in biofilm communities was analysed over a range of spatial scales. It was expected that the main study site, Cascade Stream, located within the Waitakere Ranges, west of Auckland, New Zealand, would have uniform water chemistry characteristics. Interstream variability was also assessed using samples from a second stream. It was hypothesised that there would be no significant bacterial variation on a spatial scale and that the temporal variation in the two streams would be similar.

The study found that the differences in bacterial communities were greater between streams than within the same stream. Significant spatial variation observed in the principle study site suggests that the hypothesis stating that there would be no significant bacterial variation on a spatial scale must be rejected. Greater variation was observed on the same rock than between sections of rocks and this indicates that reduced community similarity with increased physical distance was not observed.

So spatial variation was observed, but what about temporal variation? It was found that temporal variation was greater than spatial variation. The microbial communities not only changed over time, they never returned to their original composition over the duration of the study.

Now that we know that both spatial and temporal variation were observed we need to know why. The study concluded that water temperature and irradiance had the greatest influence on the bacterial communities. The most significant variation occurred when the warmest air and water temperatures were recorded.

In conclusion, ARISA was successfully used to determine spatial and temporal variation in bacterial communities in a freshwater stream with temporal variation having the most significant effect. Water temperature was identified as causing the greatest variation. Overall, the use of bacteria as indicators of freshwater ecology looks promising and should prove to be a sensitive technique of understanding the effects of human activities on freshwater systems and monitoring remediation strategies.

Further readings:
Lear, G., Anderson, M. J., Smith, J. P., Boxen, K. & Lewis, G. D. (2008). Spatial and temporal heterogeneity of the
bacterial communities in stream epilithic biofilms. FEMS Microbiology Ecology, 65. 463-473. Retrieved from
http://onlinelibrary.wiley.com/doi/10.1111/j. 1574-6941.2008.00548.x/pdf

Morgan, J. (2009). May the stream be with you. Retrieved May 22, 2011, from
http://www.jmorganmarketing.com/may-the-stream-be-with-you/

01 July 2011

Sharing knowledge with the community – the Styx Living Laboratory Trust

This article was prepared by postgraduate student Megan Oliver as part of the ECOL 608 Research Methods in Ecology course.

Communities around New Zealand are becoming more aware of the state of natural areas in their community and how they are becoming degraded from pollution. This awareness has resulted in restoration projects that begin with good intentions and enthusiasm but come to a halt because of a lack of understanding of ecological knowledge about the ecosystem that is being restored.

The Styx River originates in the suburb of Harewood, Christchurch. Springs feed the river as it moves north-eastwards through residential, horticultural, agricultural, and lifestyle developments as well as conservation reserves before it empties into the Brookland Lagon. The Styx River has two main tributaries, Smacks Creek and Kaputone Stream. The Styx Living Laboratory is a community restoration project that has a mixed board of scientists that help the community to keep going in their restoration project. Kelly Walker, senior tutor in biology at Lincoln University, is one of the scientists working on the Styx Living Laboratory Trust restoration project by contributing her knowledge of fresh water invertebrates to the community and is on the board of management.




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The aim of the trust is to restore the Styx river catchment in 40 years to an urban nature reserve by creating a living green corridor from the top of the Styx river catchment to where the river empties into the Brookland lagoon. Restoring the Styx river catchment includes both riparian plantings and in-stream restoration. A living green corridor is the area surrounding a focal feature, e.g. river, track etc; that is planted in native plant species which allows wildlife to either live in or pass through it.

The Styx River is a spring feed water system that is suffering from a sedimentation issue. The springs are drying up due to urban development which is increasing the amount of sedimentation in the river and then causes problems for fresh water invertebrate’s living in the river. There has been no indication that the recent earthquakes have caused the springs to dry up, as the springs had started drying up before the earthquakes occurred. There are six monthly samplings in the Styx River and its tributary waterways, collecting data on water quality, invertebrate species and spring status.

Kelly helps the community members when they survey the Styx River and its tributary waterways in identifying the invertebrates that have been collected. This work keeps the community involved in the restoration project by up-skilling the community group, which keeps them interested and makes them feel that their work is valuable to the restoration project. This enables there to be a closer relationship between the scientists and the community members which helps everyone keep the restoration project going.

Kelly also looks after the summer studies conducted by Lincoln University students on different topics in the catchment area. Previous studies have been on fresh water invertebrates, assessing the restoration of Radcliffe Drain which was a box drain, terrestrial arthropod abundance and diversity, lizard abundance and diversity of algae in the Styx River. These studies have produced interesting and useful results, including a new species of algae. The work done by the Styx Living Laboratory trust, community and the summer students has produced data that can be used as an indicator of how healthy the Styx River catchment is and shows how communities working with scientists can increase their knowledge and skills to take on a major urban restoration project.