The comparative evolution of developmental plasticity across Anolis lizards

Abstract

Developmental plasticity describes the sensitivity of phenotypes to early-life environmental conditions, and occurs widely across organisms and traits. Depending on the spatial and temporal environmental context, developmental plasticity can produce adaptive, maladaptive, or neutral fitness outcomes. Therefore, an understanding of how developmental plasticity evolves is critical for understanding evolution. Yet, the evolutionary mechanisms behind the evolution of developmental plasticity remain largely unknown. I use comparative studies of developmental plasticity among anole lizards (Anolis) from different climatic origins to evaluate how climate and evolutionary history drive the evolution of developmental plasticity. I use experiments to quantify patterns of developmental plasticity and quantify maternal reproductive traits to bridge the gap between life stages and how offspring plasticity evolves alongside potential parental effects. In chapter 1, I find that differences in developmental plasticity among seven species of anole lizards are almost entirely explained by common ancestry, not by current or historical environmental heterogeneity, contradicting predictions about how plasticity should evolve in response to macroclimate. In chapter 2, I find little evidence of developmental plasticity of thermal physiology traits across the southeast latitudinal range of the green anole (Anolis carolinensis), suggesting that canalization is favored over plasticity for these traits. In chapter 3, I find strong evidence of geographic variation in maternal life history traits and only weak geographic variation in plasticity of offspring life history traits, suggesting that selection on adult reproductive traits may alter selection pressure for local adaptation of offspring traits. Lastly, in chapter 4, I show that both adults and offspring of lowland tropical rainforest anoles respond to ambient changes in moisture, but offspring do not exhibit thermal developmental plasticity. These results follow macroclimatic predictions of plasticity evolution, as the predictable environmental heterogeneity in the tropics comes from seasonal moisture and not seasonal temperature. Collectively, my dissertation work demonstrates that developmental plasticity evolves on a highly trait-specific and environment-specific basis within the confines of phylogenetic constraints. My work also shows that reaction norms did not follow predictions of adaptive plasticity evolution often, and canalization may be more common in response to omnipresent environmental factors.