title: Evolution in Hawaiian cave-adapted isopods (Oniscidea: Philosciidae): vicariant speciation or adaptive shifts?
abstract: We assessed evolutionary relationships among Hawaiian cave-adapted isopods using a maximum-likelihood criterion to analyze cytochrome oxidase I nucleotide sequences. Results support morphological data that two genera of philosciid isopods have invaded caves independently in the islands. In the genus Littorophiloscia, a sister relationship between a surface-dwelling species, L. hawaiiensis, and an undescribed cave species was corroborated. This evidence, along with the known parapatric distributions between species, supports a speciation event by an adaptive shift on the island of Hawaii from a marine littoral to a terrestrial subterranean habitat. The monophyletic genus Hawaiioscia contains four known obligate cave-dwelling species, each of which occurs on a separate island. However, despite present-day allopatric distributions between Hawaiioscia species, the geographic and phylogenetic patterns are not sufficient to support a vicariant mode of speciation. Instead, we believe that the known species of Hawaiioscia evolved from a widespread ancestral surface species or a group of closely related species through multiple, independent adaptive shifts on each of the islands of Kauai, Oahu, Molokai, and Maui. This is the first molecular investigation of evolutionary relationships between surface-dwelling and cavernicolous arthropods in Hawaii and it suggests that simple vicariance is insufficient to explain the evolution of troglobites in tropical zones.
authors.affiliation: Division of Insect Biology, Department of Environmental Science, Policy and Management, 201 Wellman Hall, University of California, Berkeley, CA 94720-3112, USA. mrivera@nature.berkeley.edu
authors.forename: Malia Ana J
authors.initials: MA
authors.lastname: Rivera
authors.forename: Francis G
authors.initials: FG
authors.lastname: Howarth
authors.forename: Stefano
authors.initials: S
authors.lastname: Taiti
authors.forename: George K
authors.initials: GK
authors.lastname: Roderick
mesh_terms: D000222:Adaptation, Physiological / Q000235:genetics; D000818:Animals; D003445:Crustacea / Q000145:classification / Q000235:genetics*; D004272:DNA, Mitochondrial / Q000737:chemistry / Q000235:genetics; D003576:Electron Transport Complex IV / Q000235:genetics; D019143:Evolution, Molecular; D008969:Molecular Sequence Data; D010802:Phylogeny; D013045:Species Specificity
chemical_list: D004272:DNA, Mitochondrial; D003576:Electron Transport Complex IV