A molecular framework for comparative analysis of the ant genus Polyrhachis
Ross H. Crozier1, Andy Beckenbach2, Simon KA Robson1, Rudy J. Kohout3, Michelle T. Guzik4, Michael T. Henshaw5, and Angela J. Shuetrim1. (1) School of Tropical Biology, James Cook University, Townsville 4811, Queensland, Australia, (2) Biological Sciences, Simon Fraser U, Burnaby, BC V5A 1S6, Canada, (3) Queensland Museum, South Brisbane, Australia, (4) School of Earth and Environmental Sciences, University of Adelaide, Adelaide, Australia, (5) Division of Science & Math, McKendree College, 701 College Rd, Lebanon, IL 62254
We used sequences from three mitochondrial and three nuclear genes to derive a molecular phylogenetic framework for the genus Polyrhachis. Not all sequences could be obtained for all species, so we used three files, with an increasing concentration on species with more sequence, of 42 (37 Polyrhachis species and 5 outgroups), 35 (32 Polyrhachis and 3 outgroups) and 16 species (15 Polyrhachis). We partitioned the genes using RY recoding for partitions with significant nonstationarity, and used 4x106 generation double runs with MrBayes 3.1.2, keeping 1000 trees from each run to determine posterior probabilities. We included species in all 12 subgenera; species of the the waste basket subgenus Myrmhopla proved polyphyletic and one species of Myrmatopa (P. lombokensis) associated with Myrmothrinax; two other Myrmatopa usually but not always associated with Myrmothrinax but otherwise subgeneric monophyly was not rejected (Aulacomyrma was represented by one species). Neglecting Myrmhopla, some groupings are strong: (Myrmothrinax, P. lombokensis), (Myrma, Polyrhachis), (Hedomyrma, Chariomyrma, Hagiomyrma) and (Campomyrma, Aulacomyrma). Associations between these groups are not consistently supported between the data sets, but an indicative arrangement is (Hemioptica, (Cyrtomyrma, (Myrmothrinax, P. lombokensis)), (Myrma, Polyrhachis), ((Hedomyrma, Chariomyrma, Hagiomyrma), (Campomyrma, Aulacomyrma))). Bayesian analysis of character evolution showed that the ancestral Polyrhachis was an arboreal weaver with cocoons, all states lost several times in subsequent evolution.