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Martínez-Méndez N, Mejía O, Ortega J, Méndez-de la Cruz FR.2017. Climatic niche evolution in the viviparous Sceloporus torquatus group (Squamata: Phrynosomatidae).PeerJ Preprints5:e3493v1https://doi.org/10.7287/peerj.preprints.3493v1
The cold-climate hypothesis is the main and most supported explanation of the evolution of viviparity among reptiles. This hypothesis sustains that viviparity arose as a means to save eggs from an increased mortality in nests linked with low temperatures. In this sense, some authors have stated that viviparity could constitute an evolutionary constraint. However, the link between evolutionary constraints and the evolution of ecological niches has not been well studied. Here, we study the climatic niche evolution of a group of viviparous lizards from North America to test whether the diversification of the group is linked with Phylogenetic Niche Conservatism (PNC). We evaluated phylogenetic signals and trait evolution, besides a reconstruction of ancestral climate tolerances, and did not find PNC in the ecological niche of the species in the group. Surprisingly, we did not find conservatism in any bioclimatic variables associated with temperature; we only had evidence of conservatism in Precipitation Seasonality (Bio15) and Precipitation of Coldest Quarter (Bio19). Analysis of relative disparity through time (DTT) indicates high divergence around 4.0 MYA and 0.65 MYA that coincides with orogenic and glacial periods. There is no evidence that climatic niche differentiation was the main factor in the diversification of the studied group. Orogenic and glacial periods probably promote cycles of the availability of new territories and isolation, which could promote the rapid accumulation of ecological differences between the species of the group.
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Vouchers and GenBank accession numbers for the sequences used in phylogenetic reconstruction
Phylogenetic Principal Component Analysis (pPCA) with two global principal components (PC1/PC2) for the weighted means of PNOs of each bioclimatic variable
The arrows are the loadings that indicate the direction and strength of each environmental variable to the overall distribution. The percentages of variance explained by the first two PCs are in the axis labels. Species names consisting of the four letters of the species epithets, except for Sceloporus ornatus caeruleos (caeru).