Molecular phylogenetic relationships and phenotypic diversity in miniaturized toadlets, genus Brachycephalus (Amphibia: Anura: Brachycephalidae)

Abstract

Toadlets of the genus Brachycephalus are endemic to the Atlantic rainforests of southeastern and southern Brazil. The 14 species currently described have snout-vent lengths less than 18 mm and are thought to have evolved through miniaturization: an evolutionary process leading to an extremely small adult body size. Here, we present the first comprehensive phylogenetic analysis for Brachycephalus, using a multilocus approach based on two nuclear (Rag-1 and Tyr) and three mitochondrial (Cyt b, 12S, and 16S rRNA) gene regions. Phylogenetic relationships were inferred using a partitioned Bayesian analysis of concatenated sequences and the hierarchical Bayesian method (BEST) that estimates species trees based on the multispecies coalescent model. Individual gene trees showed conflict and also varied in resolution. With the exception of the mitochondrial gene tree, no gene tree was completely resolved. The concatenated gene tree was completely resolved and is identical in topology and degree of statistical support to the individual mtDNA gene tree. On the other hand, the BEST species tree showed reduced significant node support relative to the concatenate tree and recovered a basal trichotomy, although some bipartitions were significantly supported at the tips of the species tree. Comparison of the log likelihoods for the concatenated and BEST trees suggests that the method implemented in BEST explains the multilocus data for Brachycephalus better than the Bayesian analysis of concatenated data. Landmark-based geometric morphometrics revealed marked variation in cranial shape between the species of Brachycephalus. In addition, a statistically significant association was demonstrated between variation in cranial shape and genetic distances estimated from the mtDNA and nuclear loci. Notably, B. ephippium and B. garbeana that are predicted to be sister-species in the individual and concatenated gene trees and the BEST species tree share an evolutionary novelty, the hyperossified dorsal plate.

Distribution and predictors of wing shape and size variability in three sister species of solitary bees

“…More generally, there is a lack of information about the relationship between morphological and genetic variability at the intra-specific level. Indeed, due to the very low number of studies investigating the relationship between wing morphology and genetic variability at the intra-specific level for insects, the establishment of a general pattern seems hardly possible [62–64]. Among them, [63] have found that higher genetic variability implies higher wing shape variability in populations of butterfly but on the other hand, [64] do not find any concordance.…”

Cryptic Genetic Diversity Is Paramount in Small-Bodied Amphibians of the Genus Euparkerella (Anura: Craugastoridae) Endemic to the Brazilian Atlantic Forest

“…Phylogenetic relationships within Euparkerella are better supported in the tree inferred using the multilocus concatenated dataset when compared either to the mtDNA tree or the multilocus species tree, as observed in several other case studies [30,64–67]. This is likely explained by differences in the sensitivity of distinct methods to gene tree incongruences.…”

“…The six genetic units uncovered within Euparkerella from Rio de Janeiro State correspond to populations that are between 15 and 100 km away from the closest congeneric populations. Diversification in relatively small geographic scales seems relatively common in small-bodied, and particularly in miniaturized vertebrates [25,27,30,75,76]. Organismal body size has several functional, ecological, and evolutionary implications, in particular reducing physiological tolerance (e.g., higher sensitivity to dehydration) and dispersal in the case of extremely small-bodied species [27,77].…”

“…In the last decades several new genera and species of amphibians were recognized and described for the Neotropics as a result of increased sampling effort and taxonomic reevaluations using molecular data [5,28–30], but knowledge remains very poor on within genus species genetic diversification and evolutionary history. We here contribute to reduce this knowledge gap by examining patterns and levels of genetic diversity and inferring the phylogenetic relationships within the genus Euparkerella .…”

Ecological aspects of the pumpkin toadlet,Brachycephalus garbeanusMiranda-Ribeiro, 1920 (Anura: Neobatrachia: Brachycephalidae), in a highland forest of southeastern Brazil

“…Most species in the genus are aposematically coloured, predominantly in bright yellow or orange hues (Clemente-Carvalho et al 2011). Currently, the genus Brachycephalus encompasses 18 species, all endemic to the Atlantic Rainforest of southern and southeastern Brazil (Pombal and Izecksohn 2011).…”