The evolution of tadpole shape: first insights into larval diversity of the Physalaemus deimaticus group with the description of two new forms (Anura, Leptodactylidae, Leiuperinae)

The Physalaemus deimaticus species group comprises four species distributed in high-altitude areas in southeastern Brazil. In this study we describe the tadpoles of two of these species, Physalaemus claptoni and P. deimaticus, and explore the body shape evolution in the group. Both species share external features with the other species of the group, but P. claptoni presents a larger and globular body, while P. deimaticus is quite similar to Physalaemus erythros, its sister species, sharing a P3 tooth row of the same length than P2, and submarginal papillae distributed in rows. The phylomorphospace analysis based on geometric morphometrics demonstrated that species of the P. deimaticus group exhibit a wide range of shapes, encompassing a great part of the variation found in the Physalaemus signifer clade. Thus, although ecomorphological correlations between shape and habitat type (i.e., lentic/lotic gradient) are evident at a narrower phylogenetic scale (i.e., within the P. deimaticus group), they become ambiguous when examined at a broader phylogenetic context (i.e., P. signifer group). Despite the general homoplasy scenario and the absence of important transformations in the evolution of body shape of the P. signifer group, the optimizations retrieved shape changes for the common ancestor of P. deimaticus and P. erythros, supporting their close relationship. Our results show that phylogenetic morphometric methods are effective for describing the evolution of tadpole shape, a set of traits not easily captured by discrete characters or linear measurements. Furthermore, the description of two tadpoles of Physalaemus increases knowledge of the larval diversity of the genus.