Meeting Abstract

P2.84  Monday, Jan. 5  Genetic variation of resource exploitation in the freshwater crustacean Daphnia BRANDON, C.S.*; DUDYCHA, J.L.; Northeastern Illinois University; University of South Carolina c-brandon@neiu.edu

Evolutionary divergence between two closely related populations requires genetic variation within those populations. When genetic variation is present, the different environments that populations encounter drive selection on traits that better adapt the populations to their habitats. An important trait in Daphnia, a small fresh water crustacean, is the ability to exploit different resource levels. We set out to investigate whether clones (individuals) of Daphnia genetically varied in their ability to exploit abundant versus scarce resources. In this study, we used four clones from different water bodies of each species (D. pulex, D. pulicaria). D. pulex inhabit small temporary ponds high in resources, whereas D. pulicaria inhabit deep, stratified lakes low in resources. For each clone, we fed them four different levels of the algae Ankistrodesmus falcatus. We measured the juvenile specific growth rate (ug/ug/day) for each clone at each resource level and calculated the slope between the poorest resource level and richest resource level defined for each species of Daphnia clones. This allowed us to determine resource sensitivity and minimum resource requirements. Daphnia that perform well in abundant resource conditions have more sensitive growth rates while those that perform well in scarce resource conditions have lower minimum resource requirements. We found that clones responded differently to different resource levels while some clones exhibited increasing growth rates with increasing food levels others exhibited stable growth rates across each resource level. By constructing rank order tables, we also found that more sensitive clones had higher minimum resource requirements, while the converse was true for less sensitive clones.