Meeting Abstract
Variation in life history traits has been hypothesized to drive many macroevolutionary patterns of morphological variation. Anurans exhibit the highest life history diversity of all terrestrial vertebrates. The ancestral, and most widespread, reproductive condition is a complex biphasic life cycle in which there is aquatic oviposition with free-swimming tadpoles that undergo a dramatic metamorphosis. Direct development (DD; lacking the tadpole stage) has repeatedly evolved to presumably release species from water-dependent reproduction. Within the Andean radiation of marsupial frogs (genus Gastrotheca), species have transitioned between complex (biphasic) and simple (DD) life-cycles multiple times, but the factors that promoted these transitions and the morphological consequences of these events remain unknown. We hypothesized that biphasic Gastrotheca species have morphologically and functionally diverged from DD Gastrotheca due to disparate developmental mechanisms, differential selective pressures early in ontogeny (aquatic versus terrestrial), and dependence on aquatic habitats for reproduction. Alternatively, elevation may better predict morphology due to local adaptation, as this radiation occupies an extensive altitudinal range, inhabiting lowland rainforest to alpine tundra. Using phylogenetic comparative methods, we demonstrate that life history, body form, and locomotive strategies have been evolutionarily labile in Andean Gastrotheca. Montane species have morphologically diverged from lowland species multiple times, regardless of reproductive mode. Montane lineages have repeatedly evolved shortened hindlimbs, small toepads, and diminished locomotive abilities compared to lowland Gastrotheca species. These results suggest that the life history transitions in Gastrotheca are decoupled from shifts in morphology and habitat-use.
