title: The influence of Pleistocene climatic changes and ocean currents on the phylogeography of the southern African barnacle, Tetraclita serrata (Thoracica; Cirripedia).
abstract: The evolutionary effects of glacial periods are poorly understood for Southern Hemisphere marine intertidal species, particularly obligatory sessile organisms. We examined this by assessing the phylogeographic patterns of the southern African volcano barnacle, Tetraclita serrata, a dominant species on rocky intertidal shores. Restricted gene flow in some geographical areas was hypothesized based on oceanic circulation patterns and known biogeographic regions. Barnacle population genetic structure was investigated using the mitochondrial cytochrome oxidase subunit 1 (COI) region for 410 individuals sampled from 20 localities spanning the South African coast. The mtDNA data were augmented by generating nuclear internal transcribed spacer 1 (ITS1) sequences from a subset of samples. Phylogenetic and population genetic analyses of mitochondrial DNA data reveal two distinct clades with mostly sympatric distributions, whereas nuclear analyses reveal only a single lineage. Shallow, but significant structure (0.0041-0.0065, P<0.01) was detected for the mtDNA data set, with the south-west African region identified as harbouring the highest levels of genetic diversity. Gene flow analyses on the mtDNA data show that individuals sampled in south-western localities experience gene flow primarily in the direction of the Benguela Current, while south and eastern localities experience bi-directional gene flow, suggesting an influence of both the inshore currents and the offshore Agulhas Current in the larval distribution of T. serrata. The mtDNA haplotype network, Bayesian Skyline Plots, mismatch distributions and time since expansion indicate that T. serrata population numbers were not severely affected by the Last Glacial Maximum (LGM), unlike other southern African marine species. The processes resulting in the two morphologically cryptic mtDNA lineages may be the result of a recent historical allopatric event followed by secondary contact or could reflect selective pressures due to differing environmental conditions.
authors: Evolutionary Genomics Group, Department of Botany and Zoology, Stellenbosch University, Matieland, South Africa.
authors: Terry V
authors: TV
authors: Reynolds
authors: Evolutionary Genomics Group, Department of Botany and Zoology, Stellenbosch University, Matieland, South Africa.
authors: Conrad A
authors: CA
authors: Matthee
authors: Evolutionary Genomics Group, Department of Botany and Zoology, Stellenbosch University, Matieland, South Africa.
authors: Sophie
authors: S
authors: von der Heyden
mesh_terms: D000818:Animals; D001499:Bayes Theorem; D002467:Cell Nucleus / Q000235:genetics; D057231:Climate Change; D004272:DNA, Mitochondrial / Q000737:chemistry / Q000235:genetics*; D021903:DNA, Ribosomal Spacer / Q000235:genetics; D003576:Electron Transport Complex IV / Q000235:genetics; D019143:Evolution, Molecular; D014644:Genetic Variation; D005843:Geography; D006239:Haplotypes; D008969:Molecular Sequence Data; D009792:Oceans and Seas; D010802:Phylogeny; D011110:Polymorphism, Genetic; D017422:Sequence Analysis, DNA; D013019:South Africa; D001468:Thoracica / Q000145:classification / Q000235:genetics*; D014872:Water Movements
chemical_list: D004272:DNA, Mitochondrial; D021903:DNA, Ribosomal Spacer; D003576:Electron Transport Complex IV