title: The scale of divergence: a phylogenetic appraisal of intercontinental allopatric speciation in a passively dispersed freshwater zooplankton genus.
abstract: Molecular studies have enlightened our understanding of freshwater zooplankton biogeography, yet questions remain regarding the scale and commonality of geographic speciation. Here, we present a mtDNA-based phylogenetic hypothesis for 92 Daphnia species from all seven continents, with a focus on North and South America, Europe, and Australia, and use it to explore the frequency, scale, and geographical orientation of allopatric divergence events. Allopatric speciation can conservatively account for at least 42% of cladogenetic events among the species included in our study; most of these involve intercontinental splits. Closely related species pairs are concentrated in the circumarctic region and between northern and southern continents, aligned with bird migration routes, suggesting recent dispersal. By contrast, deeper phylogenetic patterns are consistent with vicariance scenarios linked to continental fragmentation. The possible reasons for the puzzling persistence of these ancient patterns in light of the eroding force of dispersal are considered. Our results demonstrate the high frequency and complex pattern of allopatric speciation in this ancient, passively dispersed genus.
authors.affiliation: Department of Biology, University of Waterloo, 200 University Avenue West, Waterloo, Ont., Canada N2L 3G1. sadamowi@uoguelph.ca
authors.forename: Sarah J
authors.initials: SJ
authors.lastname: Adamowicz
authors.forename: Adam
authors.initials: A
authors.lastname: Petrusek
authors.forename: John K
authors.initials: JK
authors.lastname: Colbourne
authors.forename: Paul D N
authors.initials: PD
authors.lastname: Hebert
authors.forename: Jonathan D S
authors.initials: JD
authors.lastname: Witt
mesh_terms: D000818:Animals; D004272:DNA, Mitochondrial / Q000235:genetics; D003621:Daphnia / Q000145:classification / Q000235:genetics*; D019143:Evolution, Molecular; D005819:Genetic Markers; D049810:Genetic Speciation; D005843:Geography; D010802:Phylogeny; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA; D015048:Zooplankton / Q000145:classification / Q000235:genetics*
chemical_list: D004272:DNA, Mitochondrial; D005819:Genetic Markers