Oral Session # 57: Evolutionary Ecology II: Animal.
Presiding: S Juliano
Wednesday, August 6. 1:30 PM to 5:00 PM, SITCC Meeting Room 201.

Local adaptation and plasticity of offspring size in guppies.

Bashey, Farrah*,1, 2, 1 Department of Biology, Riverside, CA2 Department of Biology, Bloomington, IN

ABSTRACT- Offspring number is closely tied to evolutionary fitness, yet many organisms produce relatively few offspring. Making fewer offspring can be adaptive if, by making fewer offspring, each offspring receives greater investment from the parent resulting in increased offspring fitness. In the guppy, Poecilia reticulata, offspring size varies genetically across populations and plastically in response to maternal condition. Across populations, variation in the competitive environment faced by newborn guppies is potentially an important source of selection on offspring size. Additionally, resource limited guppies produce larger offspring. I evaluate whether these effects of the maternal environment increase offspring fitness in low resource environments. Furthermore, these plastic differences in offspring size are of the same magnitude as the genetic differences between populations. I examine the genetic basis of plasticity in two populations of guppies and evaluate potential costs and limitations of plasticity that might favor local adaptation over plasticity in this system. Current evidence suggests that the direct benefits to offspring fitness of increasing offspring size may be compromised by links between plasticity and reproductive effort.

Key words: resource competition, phenotypic plasticity, life-history evolution, maternal effects