Meeting Abstract

2.3  Thursday, Jan. 3  Intrapopulation Genetic Variation Facilitates Niche Expansion AGASHE, Deepa; University of Texas, Austin deeps@mail.utexas.edu

Evolutionary theory posits that adaptive potential is proportional to additive genetic variation in a population, implying that the rate and degree of adaptation to a novel environment increases with the amount of existing genetic variation for relevant traits. I present results of an experimental study to test this prediction, which has received very little empirical attention so far. As an example of adaptation, I chose to focus on resource niche expansion in a novel environment. I used laboratory populations of the red flour beetle Tribolium castaneum, usually reared on wheat flour, to test the degree and rate of adaptation to a novel resource (corn flour) as a function of genetic variation. I used four beetle strains differing in their acceptance of and performance on the novel resource to create populations with four levels of genetic variation. I measured their growth on the novel resource (corn flour) and in a habitat containing patches of both wheat and corn flour. To quantify adaptation, I periodically assayed fitness and development rate of individuals from each population. I quantified niche width expansion using stable carbon isotope ratios. As predicted by theory, I find that niche expansion increased as a function of genetic variation. On a mechanistic level, I find that the proportion of the population composed of a single strain (genotype) that performs well on corn is not sufficient to explain niche expansion. Rather, the presence of variation in multiple traits relevant to resource use and growth is necessary for niche expansion. These results thus provide empirical proof for a longstanding evolutionary theory and also increase our understanding of the mechanistic basis of adaptation via niche expansion.