Diversification of the rainfrog Pristimantis ornatissimus in the lowlands and Andean foothills of Ecuador

Abstract

Geographic barriers and elevational gradients have long been recognized as important in species diversification. Here, we illustrate an example where both mechanisms have shaped the genetic structure of the Neotropical rainfrog, Pristimantis ornatissimus, which has also resulted in speciation. This species was thought to be a single evolutionary lineage distributed throughout the Ecuadorian Chocó and the adjacent foothills of the Andes. Based on recent sampling of P. ornatissimus sensu lato, we provide molecular and morphological evidence that support the validity of a new species, which we name Pristimantis ecuadorensis sp. nov. The sister species are elevational replacements of each other; the distribution of Pristimantis ornatissimus sensu stricto is limited to the Ecuadorian Chocó ecoregion (< 1100 m), whereas the new species has only been found at Andean localities between 1450–1480 m. Given the results of the Multiple Matrix Regression with Randomization analysis, the genetic difference between P. ecuadorensis and P. ornatissimus is not explained by geographic distance nor environment, although environmental variables at a finer scale need to be tested. Therefore this speciation event might be the byproduct of stochastic historic extinction of connected populations or biogeographic events caused by barriers to dispersal such as rivers. Within P. ornatissimus sensu stricto, morphological patterns and genetic structure seem to be related to geographic isolation (e.g., rivers). Finally, we provide an updated phylogeny for the genus, including the new species, as well as other Ecuadorian Pristimantis.

What drives genetic and phenotypic divergence in the Red‐crowned Ant tanager (Habia rubica, Aves: Cardinalidae), a polytypic species?

“…Isolation by adaptation (IBA; Rundle & Nosil, 2005) is defined as the effect of environmental gradients that results in divergent natural selection that can lead to adaptive phenotypic divergence between populations, resulting in a positive correlation between genetic divergence and adaptive phenotypic differentiation (Funk, 1998;Guayasamin et al, 2017). Isolation by environment (IBE, Wang & Bradburd, 2014) is defined as the occupation of two populations in different points on the ecological gradient.…”

A new cryptic species of Anolis lizard from northwestern South America (Iguanidae, Dactyloinae)

“…This finding suggests that other cryptic species of anoles from the Tropical Andes are yet to be discovered, as has been the case in other taxa (e.g. Guayasamin et al 2015; Arteaga et al 2016; Guayasamin et al 2017), and we highlight the importance of building modern specimen collections of supposedly known species (e.g., A.aequatorialis ), particularly from poorly explored areas. After extensive geographical sampling, we conclude that the new species described in this paper occurs only north of the Mira River Basin in northern Ecuador (Figure 13).…”

Origin of elevational replacements in a clade of nearly flightless birds – most diversity in tropical mountains accumulates via secondary contact following allopatric speciation

“…Because shallow divergence in putatively neutral loci and high rates of speciation may reflect rapid divergence mediated by adaptation in the face of gene flow, future studies should explicitly test predictions of ecological speciation (Smith et al, 2005) to determine whether elevational replacements on the eastern Andean slope may indeed be uniquely explained by parapatric divergence. The same is true for the western slope of the northern Andes, where phylogeographic patterns suggest parapatric speciation may have occurred in amphibians and reptiles (Arteaga et al, 2016;Guayasamin et al, 2017).…”