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....

24 December 2014

Unrootedtreeman - ravaging homoplasy!

For a while we had Unrootedtreeman merchandise (well a teeshirt)! I wore one at an evolution conference, maybe at Chico, California, and was surprised at the number of Americans who knew about the cartoon. The SYSTANZ newsletter only went to our members (mostly in NZ).

23 December 2014

Unrootedtreeman - Looks like a job

Unrootedtreeman was fun to create. Back in the 1990s, phylogenetics felt like doing research on the frontier. I suppose it still is, but back then almost everyone new the same methods and so on. So you could put a joke in about Hennig86 and most people would get it . (Hennig86 was a DOS-based program with cryptic commands - instead of 'exit' or 'end' you wrote 'yama' to close program. Yama is the hindu god of death and rebirth...) No wonder we needed Unrootedtreeman!

22 December 2014


In addition to our Sandwalk cartoons, Cor Vink and I also ran a series of cartoons on a phylogenetic superhero Unrootedtreeman in our SYSTANZ newsletters of the late 1990s. I recently found a bunch of those as well. This was back in the day when PAUP was king, parsimony and cladistics ruled, Mac Quadras were state of the art, maximum likelihood was in its infancy, when models of nucleotide substitution were developing. Heady times! One slow day during an analysis I was looking at a four taxon unrooted tree and realised that by adding a circle for a head that we had a stick figure. I showed my PhD student Cor and Unrootedtreeman was born. So, with a nostalgic fanfare....