Molecular phylogeny of the leiobunine harvestmen of eastern North America (Opiliones: Sclerosomatidae: Leiobuninae)

Abstract

Phylogenetic relationships among the leiobunine harvestmen or “daddy-longlegs” of eastern North America (Leiobunum, Hadrobunus, Eumesosoma) are poorly known, and systematic knowledge of the group has been limited largely to species descriptions and proposed species groups. Here we obtained mitochondrial (NADH1, 16S and 12S rDNA) and nuclear (28S rDNA, EF-1α introns and exons) DNA sequences from representatives of each genus, virtually all Leiobunum species from the USA and Canada, four western North American outgroup species and the distantly related Phalangium opilio. We applied Bayesian, maximum-likelihood and parsimony methods under various data-partition treatments to reconstruct phylogeny and to test taxonomy-based phylogenetic hypotheses. Results were largely congruent among methods and treatments and well supported by bootstrap and posterior probability values. We recovered Leiobunum as paraphyletic with respect to Eumesosoma and Hadrobunus. Most species were encompassed by five well-supported clades that broadly correspond to groups based on male reproductive morphology (Hadrobunus group, an early-season Leiobunum group, L. vittatum group, L. politum group and L. calcar group). Relationships within species groups were often ambiguous or inconsistent with morphology, suggesting the presence of gene introgression or deep coalescence and/or the need for taxonomic revision.