S5-1.2 Friday, Jan. 4 Corticosterone as a maternal effect: variability within- and between-species and speculations on links to fitness LOVE, Oliver/P*; WILLIAMS, Tony/D; Simon Fraser University; Simon Fraser University email@example.com
Maternal effects are assumed to provide the plasticity necessary for parents to individually optimize reproductive decisions with regard to offspring phenotype and to maximize inclusive fitness. Maternally-derived yolk hormones are often perceived to provide almost endless flexibility to mothers in this regard, but our understanding of the functional significance of variation underlying this potential flexibility remains very rudimentary. We start by discussing variability in maternal and yolk corticosterone at two levels: 1) intra-clutch and inter-individual variation within species which we suggest indicates that relative rather than absolute hormone levels might be important for individual fitness, and 2) we then use a priori hypotheses derived from life histories to examine data on inter-specific variation to determine why species should differ in deposition patterns. Yolk hormones (androgens and corticosterone) have been hypothesized to have “profound” effects on a mother’s fitness by altering the competitive environment within the nest. However, we argue that it is important to consider the extent to which hormonally-mediated maternal effects contribute to overall inclusive fitness in the context of other maternal life-history (e.g. timing of laying, clutch size) or behavioral strategies. When and to what extent would females be expected to utilize hormonally-mediated maternal effects - both within- and between-species? In some species (but not others) the most significant role of maternally-derived hormones may be providing an ‘insurance’ buffer against worst-case scenarios, rather than routinely and “profoundly” contributing to fitness. Throughout, we hope to convey the importance of interpreting yolk hormone patterns in individual mothers within the framework of life-history theory.