Life-history traits are interesting because in an evolutionary framework, they are closely tied to fitness; while from an ecological perspective they are fundamental in determining population dynamics. Moreover, these traits tend to be highly plastic and provide a good system for evaluating how traits evolve as reaction norms. My dissertation research examines the evolution of offspring size in the Trinidadian guppy Poecilia reticulata. Offspring size is one of the most intriguing life-history traits because it is influenced by selection in two generations. In guppies, offspring size differs genetically across populations and shifts plastically in response to maternal conditions. Optimality models predict that offspring size should increase as conditions for offspring growth or future reproduction decline. In guppies, an increase in offspring size is thought to be due to (1) selection in more competitive environments and (2) size-specific predation. However, variation in offspring size could be a correlated response and not the direct result of selection. I use lab and field experiments, coupled with dynamic optimization modeling, to distinguish between these hypotheses.
In a second project, I am examining the effect of resource availability on reproductive effort in the bluegill sunfish (Lepomis macrochirus). In contrast to mammals and birds which stop growing near sexual maturity, most fish, reptiles, and plants are indeterminate growers. Indeterminate growers face the ongoing decision of whether to allocate energy to reproduction or to growth. While increasing reproduction has an immediate fitness gain, allocating energy to growth can lead to even larger fecundity in the future. In this study, I am characterizing the energy allocation patterns of seven bluegill populations which vary in resource availability and test whether these patterns fit predictions of optimality theory.
PUBLICATIONS:
Bashey, F. and A. E. Dunham. 1997. Elevational variation in the thermal constraints and microhabitat preferences of the greater earless lizard Cophosaurus texanus. Copeia 1997: 725-737.
Leips, J., C. T. Baril, F.H. Rodd, D.N. Reznick, F. Bashey, G.J. Visser, and J. Travis. 2001. The Suitability of Calcein to Mark Poeciliid Fish and a New Method of Detection. Transactions of the American Fisheries Society 130:501-507.
Reznick, D. N., M.J. Bryant and F. Bashey r- and K-Selection Revisited: The Role of Population Density, Resource Availability, and Environmental Fluctuations in Life-History Evolution. Ecology (in Press).