Corticosterone manipulation reveals differences in hierarchical organization of multidimensional reproductive trade‐offs in r‐strategist and K‐strategist females

Abstract

Life history trade‐offs are often hierarchical with decisions at one level affecting lower level trade‐offs. We investigated trade‐off structure in female side‐blotched lizards (Uta stansburiana), which exhibit two evolved strategies: yellow‐throated females are K‐strategists and orange‐throated are r‐strategists. Corticosterone treatment was predicted to differentially organize these females’ reproductive decisions. Corticosterone‐treated yellow females suppressed reproduction but survived well, and augmented egg mass without decreasing clutch size. Conversely, corticosterone enhanced mortality and reproductive rates in orange females, and increased egg mass only after lengthy exposure. Corticosterone did not affect post‐laying condition, suggesting that corticosterone increased egg mass through enhanced energy acquisition (income breeding). Corticosterone enhanced survival of lightweight females, but decreased survival of heavy females, introducing a foraging vs. predation trade‐off. We conclude that rather than being a direct, functional relationship, observed trade‐offs between offspring size and number represent evolved differences in hierarchical organization of multidimensional trade‐offs, particularly in response to stress.

Testing hypotheses about individual variation in plasma corticosterone in free-living salamanders

“…Our lack of support for the current-condition hypothesis is consistent with the literature, which has shown mixed support for the CORT-fitness hypothesis, which is conceptually similar to the current-condition hypothesis. In several studies, the correlation between CORT and fitness was highly context dependent (Bonier et al, 2007(Bonier et al, , 2009bDantzer et al, 2014;Lancaster et al, 2008;Magee et al, 2006). Other studies have found unpredicted positive correlations between CORT and indicators of fitness (Cyr and Romero, 2007;Silverin, 1998).…”

Hormonally mediated maternal effects, individual strategy and global change

“…In contrast, manipulation of FSH and follicle number in female side-blotched lizards illuminated the endocrine control of the trade-off between egg size and egg number [118]. FSH-manipulated females treated during vitellogenesis resulted in an increased clutch size with a concomitant decrease in egg mass [119].…”

Life history trade-offs, the intensity of competition, and coexistence in novel and evolving communities under climate change

“…Individuals solve this dilemma by investing in some traits, which are related to primary energy allocation and which are closely linked to fitness (such as growth rate, body size, stress response, timing of reproduction, offspring quantity and quality, longevity and dispersal), at the expense of other such traits. The nature of trade-off functions among these traits can be quite complex, involving multidimensional allocation decisions or higher order properties of trait values [32]. Despite these complexities, a simplistic 'Y' model is often a useful heuristic to depict the essence of individual allocation decisions, with the caveat that many trade-offs do not conform to this simple structure [13] (figure 1a).…”