Phylogenetic hypothesis

Phylogeny based on Barker et al. (2004) with additional phylogenetic information from three other sources (Ohlson et al. 2008; Murray et al. 1994; Jonsson & Fjeldsa 2006). Because several sources were used to construct this phylogeny, we used Grafen’s (1989) method of setting branch lengths such that the distance from nodes to tips is equal to the number of taxa in the clade minus one. We initially based species pairs on the work of Bonier et al. (2007), which provided species pairs that differed in their elevation and latitudinal ranges, indicative of differences in tolerances to environmental features. Additional species were added based on these same criteria, but using pairs previously identified by Hu and Cardoso (2009). See the electronic supplementary material of the paper describing these data for full reference details.