Morphological evolutionary acquisitions in the specialized genus of lizards Phymaturus (Iguania: Liolaemidae). The origin of herbivory and saxicolous mode of life in liolaemid lizards

Resumen

With few exceptions, there are still not enough studies on the origin of herbivory and the saxicolous mode of life in lizards of the Liolaemidae family, nor on the possible morphological adaptations that may have favored these traits. In the present study, we recorded external measurements and collected data from skeletons representing all major clades of Liolaemus and Phymaturus, as well as Ctenoblepharys. To identify modifications that could explain the different body shapes and their possible relationship with modes of life, we studied seventeen body measurements, the lengths of the bony and inscriptional ribs, and the number of trunk vertebrae. ANOVA and principal component analysis were performed, and the evolution and origin of these characters were analyzed in a metatree of the family. We found that Phymaturus and herbivorous species of Liolaemus exhibit the largest abdominal volume and body size. Greater abdominal capacity, trunk height, and head height characterize the herbivorous saxicolous clades, which is reasonable for accommodating larger viscera and plant contents, as well as providing a flattened head shape important for using rock crevices as refuges. On average, Phymaturus species possess at
least two additional vertebrae, and their inscriptional ribs are elongated, contributing to their greater abdominal volume. We also observed pseudo-valvules in the small intestine, which may favor slower movement of plant material along the digestive tract. According to our analysis, herbivory and the saxicolous mode of life were acquired by Phymaturus independently within
the Liolaemidae family. Our phylogenetic statistics indicate that the body measurements studied have a strong phylogenetic imprint. Thus, in the phylogeny of Liolaemidae, the origin of herbivory and saxicoly can be traced to the ancestors of different lineages (at least eight and seven cases, respectively) and was later inherited by almost all descendants.