Phylogeography of split kelp Hedophyllum nigripes: northern ice-age refugia and trans-Arctic dispersal

摘要

Pleistocene climate cycles greatly influenced the distributions of kelps in northern seas and gated trans-Arctic dispersals between the North (N) Pacific and N Atlantic oceans. Here, we used partial sequences of the mitochondrial DNA cytochrome oxidase I-5 ' (COI) and plastid ribulose-1,5-bisphosphate carboxylase/oxygenase large subunit-3 ' (rbcL) to resolve the phylogeography of the kelpHedophyllum nigripesin the Gulf of Alaska and globally. In the Gulf of Alaska, genetic diversity was moderate (COI:h = 0.493 +/- 0.076,n = 57;rbcL:h = 0.578 +/- 0.00047,n = 54), but nucleotide diversity was small (COI: theta(pi) = 0.00114 +/- 0.00100,n = 57;rbcL: theta(pi) = 0.0001 +/- 0.00089,n = 54). Concatenated sequences showed strong haplotype-frequency differences among populations (phi(ST) = 0.728). The addition of previously publishedCOIsequences from British Columbia showed a general absence of southern haplotypes in the Gulf of Alaska, supporting the conclusion of northern ice-age refugia.COIsequences in Canadian Arctic-Northwestern (NW) Atlantic populations differed by 1-2 mutation from Northeastern (NE) Pacific sequences, and unexpectedly, were marginally more closely related to populations in British Columbia than to geographically intermediate populations in the Gulf of Alaska.COIhaplotypes from the Svalbard Archipelago in the NE Atlantic showed no variability and differed by 1-2 mutations from haplotypes in the NW Atlantic. Time-calibrated genetic divergences indicated trans-Arctic dispersal(s) from the N Pacific into the N Atlantic in the mid-Pleistocene.