Rapid development of multiple nuclear loci for phylogenetic analysis using genomic resources: An example from squamate reptiles

Recently, as genome-scale data have become available for more organisms, the development of phylogenetic markers from nuclear protein-coding loci (NPCL) has become more tractable. However, new methods are needed to efficiently sort the large number of genes from genomic databases into more limited sets appropriate for particular phylogenetic questions, while avoiding introns and paralogs. Here we describe a general methodology for identifying candidate single-copy NPCL from genomic databases. Our method uses information from reference genomes to identify genes with relatively large continuous protein-coding regions (i.e., ≥700 bp). BLAST comparisons are used to help avoid genes with paralogous copies or close relatives (i.e., gene families) that might confound phylogenetic analyses. Exon boundary information is used to identify appropriately spaced potential priming sites. Using this method, we have developed over 25 novel NPCL, which span a variety of desirable evolutionary rates for phylogenetic analyses. Although targeted for higher-level phylogenetics of squamate reptiles, many of these loci appear to be useful across and within other vertebrate clades (e.g., amphibians), and some are relatively rapidly evolving and may be useful for closely-related species (e.g., within genera). This general method can be used whenever large-scale genomic data are available for an appropriate reference species (not necessarily within the focal clade). The method is also well suited for the development of intron regions for lower-level phylogenetic and phylogeographic studies. We provide an online database of alignments and suggested primers for approximately 85 NPCL that should be useful across vertebrates.