The Cerrado is a wide Neotropical savanna with tremendously high endemic diversity. Yet, it is not clear what the prevalent processes leading to such diversification are. We used the Cerrado-endemic lizard Norops meridionalis to investigate the main abiotic factors that promoted genetic divergence, the timings of these divergence events, and how these relate to cryptic diversity in the group. We sequenced mitochondrial and nuclear genes from 21 sites of N. meridionalis to generate species tree, divergence time estimations, and estimate species limits. We also performed population-level analysis and estimated distribution models to test the roles of niche conservatism and divergence in the group diversification. We found that N. meridionalis is composed by at least five cryptic species. Divergence time estimations suggest that the deepest branches split back into the early-mid Miocene, when most of the geophysical activity of the Cerrado took place. The deep divergences found in N. meridionalis suggest that beta anoles invaded South America much earlier than previously thought. Recent published evidence supports this view, indicating that the Panama gap closed as early as 15 mya, allowing for an early invasion of Norops into South America. The spatial pattern of diversification within N. meridionalis follows a northwest-southeast direction, which is consistent across several species of vertebrates endemic to the Cerrado. Also, we found evidence for non-stationary isolation by distance, which occurs when genetic differentiation depends on space. Our preliminary data in two out of five lineages suggest that niche conservatism is an important mechanism that promoted geographic fragmentation in the group.

Colombia hosts the second highest amphibian species diversity on Earth, yet its fauna remains poorly studied, especially using molecular genetic techniques. We present the results of the first wide-scale DNA barcoding survey of anurans of Colombia, focusing on a transect across the Eastern Cordillera. We surveyed 10 sites between the Magdalena Valley to the west and the eastern foothills of the Eastern Cordillera, sequencing portions of the mitochondrial 16S ribosomal RNA and cytochrome oxidase subunit 1 (CO1) genes for 235 individuals from 52 nominal species. We applied two barcode algorithms, Automatic Barcode Gap Discovery and Refined Single Linkage Analysis, to estimate the number of clusters or “unconfirmed candidate species” supported by DNA barcode data. Our survey included ~7% of the anuran species known from Colombia. While barcoding algorithms differed slightly in the number of clusters identified, between three and ten nominal species may be obscuring candidate species (in some cases, more than one cryptic species per nominal species). Our data suggest that the high elevations of the Eastern Cordillera and the low elevations of the Chicamocha canyon acted as geographic barriers in at least seven nominal species, promoting strong genetic divergences between populations associated with the Eastern Cordillera.

Aim The frog genus Rheobates (Anura: Aromobatidae) is endemic to mid-elevations in the Colombian Andes. Our aim was to evaluate the role of the northern Andean high peaks and the low Magdalena Valley in creating barriers to dispersal and promoting vicariance within Rheobates.Location Three disjunct mid-elevation flanks of the northern Colombian Andes: the eastern and western flanks of the Eastern Cordillera, separated by high mountain peaks, and the eastern flank of the Central Cordillera, separated from the Eastern Cordillera by the arid Magdalena Valley.Methods We analysed mitochondrial and nuclear DNA sequences from 37 individuals of Rheobates to infer their phylogenetic relationships, divergence times and ancestral areas. We used species distribution models to test the role of climatic variables in determining the present geographical boundaries of the species. ResultsThe phylogeny of Rheobates is largely predicted by geography, with one population from the eastern flank of the Eastern Cordillera sharing a most recent common ancestor with all other Rheobates 21 million years ago (Ma; 95% credible interval 31-10 Ma). Populations in the Central Cordillera were monophyletic, isolated across the Magdalena Valley with a divergence time estimated at 13 Ma . We also detected one recent crossing of the Eastern Cordillera, along with unanticipated latitudinal phylogeographical structure within the western flank of the Eastern Cordillera. Environmental niche tests indicated that the Magdalena Valley and the high peaks of the Eastern Cordillera are significant environmental barriers for Rheobates populations.Main conclusions Diversification in Rheobates coincided with the early Miocene uplift of Colombia's Eastern Cordillera and the hypothesized onset of aridity in the Magdalena Valley during the middle Miocene. Our study offers broad support for the classic mountain orogeny model of vicariant divergence, but suggests that lowland habitat heterogeneity also played a long-term role in promoting vicariance, despite a long history of palaeoclimatic fluctuations.

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