Fine-scale biogeography: tidal elevation strongly affects population genetic structure and demographic history in intertidal fishes

Abstract

Numerous studies have demonstrated population genetic structuring in marine species, yet few have investigated the effect of vertical zonation on gene flow and population structure. Here we use three sympatric, closely related clinid species, Clinus cottoides, C. superciliosus and Muraenoclinus dorsalis, to test whether zonation on South African intertidal rocky shores affects phylogeographic patterns. We show that the high-shore restricted species has reduced gene flow and considerably higher F ST values (F ST = 0.9) than the mid-and low-shore species (F ST < 0.14). Additionally, we provide evidence for remarkably different demographic and evolutionary histories, ranging from extreme population bottlenecks to population persistence, which are probably linked to effective population size and habitat specialisation. This study further highlights the need for a multispecies approach to unravel the biological and evolutionary processes that drive extant population genetic patterns in marine species, as even closely related species with similar life histories show highly variable results.

The Influence of Pleistocene Climatic Changes and Ocean Currents on the Phylogeography of the Southern African Barnacle, Tetraclita serrata (Thoracica; Cirripedia)

“…1). Such reduced gene flow was also shown for rocky shore fishes [22], [26] and an endemic sea urchin, Parechinus angulosus [24] strongly suggesting that gene flow is reduced for inshore coastal species in this region. Cape Point is also characterized as a region where a major biogeographic break occurs [19].…”

“…Such variance in patterns also applies to the study of demographic change; some marine species have been shown to maintain demographically stable populations throughout the LGM, without significant changes in population sizes, while others show population bottlenecks with post-LGM recolonization; both scenarios seem equally plausible [8] and can be found even in closely related species [26]. To better understand the evolutionary processes that drive changes in population sizes and distributions, it is important to carefully consider the timing of population expansions and contractions [27].…”

“…Further, no evidence for vicariance events, such as those shown along the south-western coast of Australia as a result of the land bridge across the Bassian Isthmus, [16], [17], [18], have been documented [19]. However, a number of southern African marine species show some degree of population genetic structuring along their geographic ranges, [20], [21], [22], [23], [24], yet barriers vary between species and there are few congruent patterns [19], [25], even in closely related species [26]. The variability in these patterns makes the explanation of the processes involved in generating the population genetic structuring particularly complex [26].…”

Phylogeographic patterning among two codistributed shrimp species (Crustacea: Decapoda: Palaemonidae) reveals high levels of connectivity across biogeographic regions along the South African coast

“…Similar Pleistocene population expansion estimates have been reported for other South African coastal organisms, including the Cape sea urchin Parechinus angulosus [32], the clinid species Clinus cottoides , C . superciliosus and Muraenoclinus dorsalis [37], and the southern African barnacle Tetraclita serrata [41]. …”

“…At least three marine biogeographic provinces are recognised; the cool-temperate Namaqua province on the western coastline (Lüderitz, Namibia to Cape Point, South Africa), the warm-temperate Agulhas province on the southern coastline (Cape Point to Algoa Bay, South Africa) and the sub-tropical East Coast Province on the eastern side (Algoa Bay to the northern borders of the Kwazulu Natal coastline) [36], see Fig 1. The exact spatial boundaries between these provinces are not strictly delineated, as barriers vary across taxa and there are few congruent patterns [2], [32], even with closely related species [37], which forms transition zones. For estuarine organisms an additional barrier to dispersal is presented by South Africa’s highly dynamic estuarine system, whereby approximately 70% of all estuaries are either permanently disconnected from the sea by the formation of sand bars at the mouth (closed estuaries) or are only temporarily open [38].…”