Fig. 2

a Phylogenetic relationships in the genus Xiphophorus. Black (south) and yellow (north) dots on branches indicate the geographic location of species relative to the Trans-Mexican Volcanic Belt. Major clades are color-coded with platyfishes in blue, northern swordtails in purple, and southern swordtails in green. Species not included in niche modeling are indicated with asterisks. For a larger version of the phylogeny with estimated divergence times see Additional file 1. b List of the nine Worldclim and three hydrographic variables from Hydro1k used for niche modeling and phyloclimatic analyses. c Phylogenetic PCA for multivariate niche space. The x-axis plots the loadings for principal component 1 (PC1) and the y-axis for PC2. The arrows indicate the loadings of the individual environmental variables for each PC and arrows are labeled according to the Worldclim variable that they represent. Taxa are represented by the first three letters of the species name with the exception of X. montezumae (monte) and X. monticolus (monti). Hydrographic variables were excluded from the PCA (see methods)