Meeting Abstract

S10.9  Tuesday, Jan. 6  Evolution of neuroendocrine mechanisms that regulate reproduction in white-footed mice (Peromyscus leucopus) HEIDEMAN, Paul D.*; PITTMAN, Julian T.; College of William and Mary pdheid@wm.edu

An important question in evolutionary physiology is how phenotypic variation in reproduction and life history traits are caused by natural genetic variation in underlying neuroendocrine traits. Seasonal timing of breeding involves a large number of traits that are linked genetically and physiologically in complex ways, and most of these traits have more than one function. We predict that levels of genetic variation in seasonal timing of breeding should be positively related to (1) the complexity of the neuroendocrine regulatory systems involved, (2) the number of uncorrelated or weakly correlated selection pressures that act on elements of these systems, and (3) the heterogeneity of seasonal environmental variation in time and space. The amount of genetic variation in seasonal timing of breeding might be negatively correlated with (1) life expectancy and (2) the duration of pregnancy and lactation. Our research on a single population of white footed mice, Peromyscus leucopus, has found high intrapopulation genetic variation in seasonal timing of breeding that is related to substantial genetic variation in melatonin binding, number of immunolabeled GnRH neurons, pituitary gonadotrophin hormone levels, testis size, food intake, daily activity, and metabolic rate. In contrast, genetic variation in circadian rhythms and melatonin secretion patterns appear not to be related to genetic variation in seasonal timing of breeding. We have also found genetic variation in phenotypic plasticity of seasonal timing of breeding. We discuss the importance of identification of within-population genetic variation in seasonal reproduction and correlated life history traits, genome approaches, candidate gene approaches, the potential role of epigenetic change, and modeling of these systems.