I am Israel Leinbach, student in the Environmental Life Sciences program. My main interest is the ecology of arthropod food webs. In nature (including urban environments) food webs can be very complicated –Who consumes who? How abiotic factors influence these biotic interactions? Sometimes, a predatory arthropod (e.g. a scorpion) will kill and consume another predator (e.g. a wolf spider), and both predators may share additional prey (e.g. crickets). This small system (predator / predator / prey) is known as an IGP (intraguild predation) module and its dynamics may influence the overall food web stability. I am particularly interested in how water availability/abundance affects the dynamics of IGP and other food-web modules, and of food webs as a whole.
I have worked extensively on the San Pedro River, in a project was funded by the Department of Defense. With the help of trusty colleagues we erected several dozen large cages (2m3x 2m3). The blocked (quad) design included treatments with and without water, and different (both male and female) combinations of Large wolf spiders (Hogna sp.), Small spiders (Pardosa sp.) and crickets (Gryllus sp.). The idea is that crickets have high water content and differing carbohydrate/ protein profiles depending on whether the cricket is gravid or not. In addition, small spiders have a protein signature more homologous than larger spiders. We hypothesized that large spiders would prefer higher quality and quantity protein/carbohydrate sources when water is abundant.
The trials ran for several months and each treatment occurred over 3-5 days, after which all species were recaptured (using U.V. reactant marking techniques) to estimate consumption/selection. In addition to the physical design, the large spiders were injected (femoral) with double-labeled water (a blend of deuterium/18O stable isotopes) to estimate water turnover rates. This process involves drawing all the water from the captured spider with a cryogenic distillation method and sampling the water through an infer-red isotope analyzer. In addition, a group of spiders were processed through a flow-through respirometry configuration to estimate gas exchange and evaluate the resting metabolic rates. Samples of spiders from each treatment were evaluated (metabolism) to validate variation between and within treatments. Although the data is still being processed, the hypothesis seems to be supported so far.
Currently I am tackling the scorpion issue in the greater urban Phoenix. The CAP LTER has funded a three-part study to better understand the increasing scorpion abundance in residential neighborhoods. The project began with extensive sampling and identification of the various species of scorpions found in the cities. A sample of these scorpions will also be evaluated (metabolic rate comparison/ water turnover rates) and compared to specimens from rural deserts. The main experiment involves combining scorpions with prey and other predators in differing combinations. Small block home simulations (54 in total) have been created in a greenhouse to estimate consumption rates, cannibalism, intra-guild predation and interaction when water is abundant or limited. The community structure of these interactions has expressed some very interesting strategies. Scorpions appear to use cannibalism of young as a survival mechanism during prey limited (pesticide removed prey) bouts. This exciting study is currently in progress.
I love the natural world- especially pristine places. If you happen to be in the forest or desert, encounter a longhaired guy; with guitar and a collection vial, it may be me.
A couple of interesting factoids:
- I have collected and studied scorpions from many countries, including Peru, Paraguay, Mexico, Sri Lanka, India and Australia.
- I received the Explorer Grant to study the scorpion related cause of frequent stings with fatalities along a stretch of the Peruvian Amazon.
- I have so many hobbies that there is no time to wash the dishes.
- I have a special relationship with a trained desert hairy scorpion.