Impacts of marine biogeographic boundaries on phylogeographic patterns of three South African estuarine crustaceans

Abstract

The South African coastline comprises 3 main biogeographic provinces: (1) the cooltemperate west coast, (2) the warm-temperate south coast, and (3) the subtropical east coast. The boundaries between these regions are defined by changes in species compositions and hydrological conditions. It is possible that these affect phylogeographic patterns of coastal organisms differently, depending on the species' ecologies and modes of dispersal. In the present study, genealogies of 3 estuarine crustaceans, each characterized by a different mode of passive dispersal and present in more than one biogeographic province, were reconstructed using mtDNA COI sequences, and the impacts of biogeographic boundaries on their phylogeographic patterns were compared. The species were (mode of dispersal in brackets): (1) the mudprawn Upogebia africana (planktonic larvae), (2) the isopod Exosphaeroma hylecoetes (adult rafting), and (3) the cumacean Iphinoe truncata (adult drifting). Two major mtDNA lineages with slightly overlapping distributions were identified in U. africana (the species with the highest dispersal potential). The other 2 species had 3 mtDNA lineages each, which were characterized by strict geographic segregation. Phylogeographic breaks in U. africana and E. hylecoetes coincided with biogeographic boundaries, whereas the phylogeographic patterns identified in I. truncata may reflect persistent palaeogeographic patterns. Ecological factors and modes of dispersal are likely to have played a role in both cladogenesis of the different lineages and in the establishment of their present-day distribution patterns.

Historical isolation and hydrodynamically constrained gene flow in declining populations of the South-African abalone, Haliotis midae

“…Similarly, the thermal front at Port Elizabeth could affect dispersal patterns along the east coast of South Africa although this barrier is not as strongly supported by the population structure analysis performed here for H. midae. The increasing evidence for association of intraspecific lineages with the three major marine biogeographic provinces of South Africa (Ridgway et al 1998;Teske et al 2006Teske et al , 2007Teske et al , 2008von der Heyden et al 2008), supports the idea that region-specific oceanographic processes play a significant role in the structuring of species along the coast. Species distributed along several coastal biogeographic provinces, are subjected to diverse physical and biological environments, leading to local adaptation and genetic divergence.…”

“…Oceanographic conditions and associated ecological factors determine three biogeographical regions along the South African coast: cool-temperate, warm-temperate and the sub-tropical (Emanuel et al 1992) Agulhas and Algoa Bay (Norton 2005;Teske et al 2006Teske et al , 2007von der Heyden et al 2008) and several studies indicate varying levels of permeability of these barriers for different species (Tolley et al 2005;Neethling et al 2008). In addition, it is expected that the extension of the biogeographic regions have been affected by Plio-Pleistocene climatic conditions such as habitat contraction, latitudinal shift of water temperatures, and variations in currents and coastal topography (Flores et al1999;Miller et al 2005;Bard and Rickaby 2009).…”

Dispersal barriers and stochastic reproductive success do not explain small-scale genetic structure in a broadcast spawning marine mussel

“…Oceanographic barriers that prevent extensive mixing of propagules from different regions are often invoked at larger geographic scales (several 100s to 1000s of kilometres) and may include upwelling cells (Waters & Roy 2004), long stretches of unsuitable habitat (Teske et al 2006, Ayre et al 2009) and areas where currents are deflected away from the coast and potentially displace propagules that become entrained in them (Teske et al 2011, Zardi et al 2011). The populations identified at these scales tend to exhibit evidence of genetic divergence that may be a function of long-term reductions in gene flow and/or divergent selection driven by environmental gradients (Teske et al 2011).…”

The Ecology and Food Web Dynamics of South African Intermittently Open Estuaries

“…Macrofaunal community composition within southern African IOCEs also demonstrates reduced diversity and is almost exclusively dominated by estuarine species [36,37]. The low diversity can in part be attributed to the poor representation of marine breeding species to the total macrofaunal community and reduced habitat availability (submerged macrophytes and [36,37].…”

“…The low diversity can in part be attributed to the poor representation of marine breeding species to the total macrofaunal community and reduced habitat availability (submerged macrophytes and [36,37]. In the virtual absence of any distinct horizontal gradients in salinity within these systems, sediment type, habitat availability, predation, and the activity of ecosystem engineers have been identified as important in determining the distribution of macrofauna within these systems [36,37].…”