23 February 2015

The final post!

EcoLincNZ has shifted to http://ecolincnz.lincolnecology.org.nz/. There is/will be more content at the new site. All of the older posts have also been shifted there. So head on over!

13 February 2015

Their weevil ways: too specialised to survive on the Chathams?

Change has been much on my mind recently. With one son moving into Christchurch to continue with university, another moving to Dunedin to start university and only the third at home for a couple more years (he said hopefully), I have been asked repeatedly about what I will do in the medium term. Down size the house? Maybe look at positions elsewhere? Make a lifestyle change? I'm not sure what motivates these comments as I am happy in my nice, large, old house (it would be great to actually be able to use some of the rooms myself, finally). I enjoy living at Lincoln and working at the University. And I like being an evolutionary biologist. However, on Darwin Day 2015, let me consider my options. If I was to look for another evolutionary biologist position (especially one that focused on biogeography or coevolution) my options would be fairly limited. Within New Zealand there are about seven other similar positions at universities, maybe about the same again in Crown Research Institutes.
In the 20 years that I have been at Lincoln I can remember evolutionary biologist jobs coming up about three times. So it would be very difficult to move within New Zealand. Should I want to go overseas then there are definitely more jobs, but not a whole lot more (and there is a lot of competition!). So I am reasonably tied to Lincoln. Why? Because I am so specialised. To do my job I need a research environment, access to postgraduate students, funding, an organisation that values evolution research and so on. Specialisation, while allowing me to be successful in what I do, has effectively limited my dispersal ability (providing I want to stay being an active evolutionary biologist).

Similar thoughts abound in biology about specialisation. The idea is that specialisation allows a species to do really well as it efficiently utilises a niche but, come a crisis like climate change or a new predator, specialisation will hinder fast adaptation for change for the species and generalists will win out in these situations. So specialists are successful during stable periods but generalists do better in unstable periods, or so theory suggests. It is also thought that species can become so specialised that there is no way back to being a generalist. This has been summarised as Dollo's Law which states that evolution is not reversible. While we know of many examples where evolution does reverse (descendent species becoming more like distant ancestors rather than recent ancestors) specialisation does seem to make such reversals more difficult. For example, parasitism is often portrayed as a dead-end in evolution. Many parasites lose all sorts of traits, such as limbs, complex digestive systems, sense organs and so on, mostly because they live in their food. Once you have lost or substantially changed these traits then it is incredibly difficult to return to a nonparasitic way of life (but not impossible as Rob Cruickshank and I showed for mites a few years ago).
Two coxella weevils getting acquainted. 

For most species this issue, while interesting to evolutionary biologists, is not a real day-to-day concern. However, for threatened species this problem of specialisation can influence the likely fate of the species. If a species is too specialised then it may be too difficult to find a solution that will allow the species to be conserved. If you need to live in a certain type of habitat, say peat wetland, and this habitat is limited or disappearing, then you have a problem. If you need to eat a certain type of food, say a particular type of honey dew, and the insect that produces the dew is limited or disappearing, then you have a problem. Emily Fountain, with Jagoba Malumbres-Olarte, Rob Cruickshank and myself, have investigated this problem in a threatened weevil species, the coxella weevil (Hadramphus spinipennis). This weevil species is found in the Chatham Island group, an isolated archipelago 800km east of mainland New Zealand. The coxella weevil is now found on two small islands, Mangere and Rangatira, which are 15 kms apart. The weevil lives on, and eats, one plant species, Dieffenbach’s speargrass (Aciphylla dieffenbachii). The coxella weevil was once found over the whole Chatham archipelago but now persists on these two small islands in small clumps of speargrass. The speargrass is extremely patchy and this is not helped by the weevils who will graze out patches of a plant before moving to a new patch. Both islands were once over-run with livestock (which found the speargrass tasty) and since their removal there has been much planting of native forest trees and natural regeneration, which removes suitable habitat for the speargrass to grow in. So the coxella fate seems tied to the plant that they have specialised on which must make them susceptable to extinction.
Rangitira with Pitt Island in the distance

Emily and Jagoba surveyed the populations of coxella weevil and speargrass on Mangere and Rangitira. She collected a tarsus off the end of one leg from each weevil that she found and was able to extract DNA from these individuals. Emily, in a paper published in PeerJ, found that there was a small difference between the weevil populations on each island, what you might expect if they had been isolated for a relatively short amount of time (around 1000 years). Despite the differences, this indicates that even these specialised weevils can disperse over water, at least occasionally. There was a lack of genetic diversity which suggests that the weevil populations have been through a bottleneck. There was even some evidence that the coxella weevil is sometimes found on other plant species, although whether they are foraging or not could not be determined. On the upside, populations of weevils and speargrass have not declined as a result of the reforestation efforts at this point. So is specialisation a problem for the survival of the coxella weevil? It's fair to say that specialisation on speargrass will not help with conservation efforts, but so far it does not appear to have consigned this species to extinction just yet. After all, it's still easier for a coxella weevil to find a new speargrass plant than it is for an evolutionary biologist to find an evolutionary biology job!

03 February 2015

Weta workshop: The highs and lows of finding a new species

Morgan Shields was a third year undergraduate student when he found a new species of weta as part of his field ecology course. Morgan tells us how this came about.

A brand new weta species!
Finding a new species is a dream of most budding biologists. However, for many this never becomes a reality. I was lucky enough to live this dream during the 2014 ECOL310 Field Ecology course at Lincoln University, when I collected a highly divergent species of cave weta (Rhaphidophoridae) during my research project. A highly divergent species is one that is identified as likely new species but has not been confirmed. It was a pretty sweet feeling that, as an undergraduate student, I had found something that no else had likely ever documented before. My excitement was magnified when the find was celebrated by lecturers in the Ecology department who had taught me for the last three years.

Our intrepid student hard at work.
However, my buzz soon wore off as reality sunk in.  Although the specimens had been identified as a likely new species of the genus Pleioplectron by entomologists Peter Johns and Marie McDonald, who specialise in weta, this could not be confirmed without detailed phylogenetic and morphological studies. And these are only the first steps to formally recognising a new species; one must then study many specimens to determine the natural variation within the species and create a formal description with assigned voucher specimens to show how this weta differs from all others. This description then has to be published in a taxonomic journal, having gone through a rigorous peer-review process from experts in the field. Only then is the species named, which is a privilege for any entomologist. It is currently unclear who will undertake this journey but perhaps it could be a pet project of mine. Having realised the lengths required to formally describe new species, I have come to the conclusion that in many circumstances, such as my project, it is simpler to find an already known species.
A pitfall trap in the forest at Boyle River.
The cave weta were collected during my field ecology project at Boyle River, near the Lewis Pass in the Southern Alps of New Zealand, which examined how invertebrate community composition differs between native beech and kanuka habitats. This information could then contribute to invertebrate conservation. Pitfall traps, which are essentially plastic cups with a preservative inside, were used to catch the weta and other invertebrates which were identified to recognisable taxonomic units (RTUs). These RTUs are then looked at by experts and my highly divergent cave weta species was later determined as a likely new species. Reflecting on this adventure, the field ecology course provided this opportunity to find some of New Zealand’s hidden wonders and apply the skills that I had learnt in my degree on a real research project, in a spectacular part of the Southern Alps and supported by hands-on lecturers. This was one of the best courses I have taken and I would recommend it to anyone who wants to get out into the bush to do some real hands-on ecology.

14 January 2015

Mossie-eating dragons, damsels causing distress

This year we are likely to develop a problem with leftovers at home. For the last few years leftovers have had a very short life in our fridge. You see we have had three teenage boys (and assorted teenage friends) around the house and it really is true about what they say about teens. They eat! So leftovers are usually consumed within a day or two as a snack between snacks. However, this year eldest son is moving out to flat in Christchurch while he continues with his engineering degree and second son is heading to university in Dunedin. That will leave mum, dad and youngest at home. So leftovers may well sit and increasingly take up space! Of course our food bill should go way down and the mean consumption per individual should go down as well. This does underline the variability that occurs when you measure foraging (finding and eating food) across life stages, seasons and so on. Another source of variation is in the social aspect of eating. Foraging behaviour can change in groups as well, whether from missing out through competition, such as when your teen uses the last of the milk so that you have none for your cereal, or trying food you wouldn't normally eat, such as last evening when we were at a Chinese restuarant and I tried some chilli jellyfish that a friend had ordered.
A New Zealand dragonfly Uropetala adult. What hungry teens they must have!

Complications in understanding foraging also apply to other organisms as well. While getting a good handle on foraging is always useful, it becomes very important in biocontrol situations. Often a biocontrol solution to dealing with a pest species is to introduce or enhance another species that will eat the pest. Perhaps the pest is an invasive species that has left its usual predators behind, or maybe it is a native species whose natural predators have declined to a point at which they are unable to control pest numbers. Understanding the foraging of predators on the target pest species becomes of prime importance.

One group of pests that are globally in need of control are the mosquitoes. Well over one million human deaths are recorded each year as a direct result of diseases carried by mosquitoes. Insecticides can only do so much and one important strategy is to encourage natural predators that can keep local mosquito populations in check. One type of predator that can make a difference are species from the order Odonata (the dragonflies and damselflies). These predators can munch their way through lots of mosquito larvae, or so previous research has suggested. However, these previous studies have looked at foraging rates in later naiad stages. This is like basing foraging rates in humans on observations of teens, and starving teens at that. Also, previous experiments were done with one Odonata species and one mosquito species. In nature, in addition to different life stages of the predator and prey in a local habitat, there are usually several different species of Odonata predators and mosquitoes.
Another Uropetala

In order to assess what foraging rates are like in more complex (and more realistic) conditions, Robbie Weterings, Chanin Umponstira and Hannah Buckley looked at dragonflies, damselflies and mosquito communities in Thailand. Odonata naiads were collected from canals around Mueang Kamphaeng Phet and sorted into dragonfly and damselfly groups (there were seven species in all). Mosquito larvae were collected from roof drains and water storage containers (there were two species). Containers were filled with water and a water plant was placed in them as well to provide some habitat complexity. One to five dragonflies or damselflies naiads of various ages from the various species were added to the container and finally 10 to 50 mosquito larvae from both species were introduced. Predation rates were then measured. In a paper in the Journal of Asia-Pacific Entomology the authors present the results of the experiment. Dragonflies consumed about 6 mosquito larvae per day and damselflies around 5. This was an order of magnitude lower that what had been recorded for earlier experiments (which had used the equivalent of starving teens). Rate of predation was related to how many prey were around (more prey more eating) and how many rival predators there were (more rivals, more competition). So measuring a cross section of your community in a complex habitat does make a difference when looking at how effective predators are. The good news is that even with these lower rates of predation for dragonflies and damselflies than previously found, if habitats have a healthy Odonata community then this should still keep mosquito numbers under reasonable control. Something to ponder as I gaze at a fridge-full of leftovers later in the year!

31 December 2014

Unrootedtreeman - paraphyletic

This is the last of the Unrootedtreeman cartoons that I found. Who knows, I may be able to find others (or convince Cor that we could do more...). Have a Happy New Year!

26 December 2014

Unrootedtreeman - short branches

SYSTANZ newsletters came out about twice a year back in the 90s and we would try to include a Sandwalk or Unrootedtreeman in each issue. Unfortunately, the association ceased as an entity in the early 2000s as systematics became an integral part of all ecological research.

25 December 2014

Unrootedtreeman - Xmas

Unrootedtreeman even had a Christmas message....