Limb length and poison glands size as predictors of anti-predatory performance in South American true toads

Developmental Plasticity in Growth and Performance Blur Taxonomic Boundaries in South American True Toads (Rhinella)

Developmental plasticity can affect traits directly related to survival, and some changes may promote or impair population persistence in changing environments. At the same time, it can also originate new complex phenotypes, surpassing species-specific boundaries. Therefore, plastic responses have the potential to participate in processes of micro and macroevolution. In this study, we evaluate plastic responses to different thermal regimes during development in traits related to survival and also used for taxonomic classification of two true-toad species, Rhinella icterica and Rhinella ornata. We raised tadpoles representing distinct operational taxonomic units (OTUs) at different temperatures, and the resulting phenotypic patterns suggest canalization in R. icterica and complex variation revealed by plasticity among R. ornata OTUs. Plastic responses to thermal regimes produced differences among the OTUs in traits associated with specific survival strategies of Rhinella species. Some changes surpassed taxonomic boundaries and rescued lineage-specific phenotypic patterns, establishing unusual phenotypic combinations for these species. Our results illustrate the contribution of developmental plasticity for processes involving phenotypic differentiation among species in traits directly related to survival.

Morphological Correlates of Locomotion in the Aquatic and the Terrestrial Phases of Pleurodeles waltl Newts from Southwestern Iberia

Animals capable of moving in different environments might face conflicting selection on morphology, thus posing trade-offs on the relationships between morphology and locomotor performance in each of these environments. Moreover, given the distinct ecological roles of the sexes, these relationships can be sexually dimorphic. In this article, I studied the relationships between morphological traits and locomotor performance in male and female semiaquatic Pleurodeles waltl newts in their aquatic and their terrestrial stages. Morphology was sexually dimorphic: males have proportionally longer limbs and tails, as well as a better body condition (only in the aquatic phase), whereas females were larger and had greater body mass in both phases. Nonetheless, these morphological differences did not translate into sexual divergence in locomotor performance in either stage. This finding suggests other functions for the morphological traits measured, among which only SVL showed a positive relationship with locomotor performance in both stages, whereas the effect of SMI was negative only in the terrestrial stage, and that of tail length was positive only in the aquatic stage. In any case, the morphological correlates of terrestrial and aquatic locomotion did not conflict, which suggests no trade-off between both locomotory modes in the newts studied.