Fine-scale genetic breaks driven by historical range dynamics and ongoing density-barrier effects in the estuarine seaweed Fucus ceranoides L.

摘要: Factors promoting the emergence of sharp phylogeographic breaks include restricted dispersal, habitat discontinuity, physical barriers, disruptive selection, mating incompatibility, genetic surfing and secondary contact. Disentangling role each in any particular system can be difficult, especially when species are evenly distributed across transition zones dispersal barriers not evident. The estuarine seaweed Fucus ceranoides provides a good example highly differentiated populations along its most persistent distributional range at present rear edge distribution, NW Iberia. Intrinsic restrictions obvious this species, but have prevented F. from vastly expanding northwards following last glaciation, implying that additional factors responsible for lack connectivity between neighbouring southern populations. In study we analyze 22 consecutive Iberia to investigate processes generating maintaining observed high levels regional divergence. Variation seven microsatellite loci mtDNA spacer sequences was concordant revealing Iberian is composed three divergent clusters displaying nearly disjunct geographical distributions. Structure AFC analyses detected two with an admixed nuclear background. Haplotypic diversity W sector very low N sector. Within cluster, population structure also pervasive, although shallower. deep divergence sectors coupled support oceanographic defining location suggested 1) parapatric result reassembly formerly vicariant sub-populations, 2) discontinuities contact (and elsewhere) maintained despite normal migration rates. We conclude colonization immigration, as sources gene-flow, different effects. Migration established effectively too prevent their differentiation by drift or smooth historical differences inherited process. ceranoides, possibly low-dispersal general, appear unified large extent historical, non-equilibrium extinction colonization, rather than contemporary patterns gene flow.