Phylogeny and biogeography of the genus Heterocope Sars 1863 (Copepoda: Calanoida): A molecular genetic, morphological, and distributional analysis

Phylogenetic and biogeographic relationships among the six species of genus Heterocope (Copepoda: Calanoida) were investigated using morphological, molecular genetic and spatial data at a global scale.;Analysis of 12 morphological characters provided an estimate of the phylogeny of the genus. Two equally parsimonious trees resulted, differing only in the placement of Heterocope soldatovi. Remaining nodes were relatively well-supported. Heterocope caspia is most plesiomorphic, H. borealis and H. septentrionalis are derived sister taxa.;A 300 bp portion of the 16S rRNA gene was sequenced using primers designed from copepod mtDNA sequences. Sequence data were not obtained from two species (H. soldatovi and caspia) due to sample age and sample preservation method. Cladistic analysis of unambiguously aligned sequences resulted in a single, most parsimonious tree, well-supported by the data. This relationship proved robust with respect to weighting strategies and outgroup choices. The mtDNA-based phylogeny did not conflict with morphology, but with failure of two species to amplify, mtDNA sequence data were not helpful in resolving the morphology-based ambiguity in placement of Heterocope soldatovi. Genetic distance values compared with similar values in a study of King Crab evolution, provided estimated divergence times for Heterocope species. The genus appears quite ancient.;Distribution of species of Heterocope was characterized based on 482 reports of occurrence. These data, from 145 published papers and 42 unpublished collections, were analyzed using geographic information systems (GIS) applications. Geographic range for each species was determined, and compared with previous descriptions. United Nations digital datasets were used to characterize distribution of Heterocope species. Vegetation datasets were unsuccessful in explaining the distribution of the species. Temperature and elevation were combined to explain distribution of two species. The relationship between regional distribution of the North American species and temperature may be related to intensity of fish predation. Glacial boundaries delimit the European distribution of Heterocope appendiculata.;Two Heterocope sister-species are characterized by distribution along similar temperature isotherms. Their phylogeny and distribution suggest a speciation event linked to a Beringian vicariant event, potentially a Pleistocene marine incursion. Genetic data are not currently adequate to date this divergence with confidence.