Evidence for panmixia despite barriers to gene flow in the southern African endemic, Caffrogobius caffer (Teleostei: Gobiidae)

Abstract

BackgroundOceanography and life-history characteristics are known to influence the genetic structure of marine species, however the relative role that these factors play in shaping phylogeographic patterns remains unresolved. The population genetic structure of the endemic, rocky shore dwelling Caffrogobius caffer was investigated across a known major oceanographic barrier, Cape Agulhas, which has previously been shown to strongly influence genetic structuring of South African rocky shore and intertidal marine organisms. Given the variable and dynamic oceanographical features of the region, we further sought to test how the pattern of gene flow between C. caffer populations is affected by the dominant Agulhas and Benguela current systems of the southern oceans.ResultsThe variable 5' region of the mtDNA control region was amplified for 242 individuals from ten localities spanning the distributional range of C. caffer. Fifty-five haplotypes were recovered and in stark contrast to previous phylogeographic studies of South African marine species, C. caffer showed no significant population genetic structuring along 1300 km of coastline. The parsimony haplotype network, AMOVA and SAMOVA analyses revealed panmixia. Coalescent analyses reveal that gene flow in C. caffer is strongly asymmetrical and predominantly affected by the Agulhas Current. Notably, there was no gene flow between the east coast and all other populations, although all other analyses detect no significant population structure, suggesting a recent divergence. The mismatch distribution suggests that C. caffer underwent a population expansion at least 14 500 years ago.ConclusionWe propose several possible life-history adaptations that could have enabled C. caffer to maintain gene flow across its distributional range, including a long pelagic larval stage. We have shown that life-history characteristics can be an important contributing factor to the phylogeography of marine species and that the effects of oceanography do not necessarily suppress its influence on effective dispersal.

Oceanic circulation, local upwelling and palaeoclimatic changes linked to the phylogeography of the Cape sea urchin Parechinus angulosus

“…Interestingly, Parechinus angulosus does not seem to be affected by the genetic break identified at Cape Agulhas, which is pronounced in other South African marine species (e.g. Evans et al 2004, Teske et al 2006, as geneflow appears to occur readily across this region (Neethling et al 2008).…”

“…It has, however, been previously hypothesized that, apart from oceanic circulation patterns, phylogeographic structure in the marine environment can also be the result of local upwelling, larval behaviour, recruitment stochasticity, freshwater plumes from rivers and habitat availability (e.g. Greenwood 1980, Lessios et al 2003, Banks et al 2007, Neethling et al 2008, Ross et al 2009, Hodgson 2010. The strong differentiation among populations occurring in the rocky Namaqua Province seems to support the notion that large stretches of presumably suitable habitat do not necessarily improve geneflow among sampling sites.…”

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

“…Population expansion postdating the Last Glacial Maxima (*20,000 ybp) has also been documented for other South African marine fauna such as spiny lobster Palinurus gilchristi (Tolley et al 2005), Palinurus delagoae (Gopal et al 2006), Cape hake Merluccius merluccius (von der Heyden et al 2007), Caffrogobius caffer (Neethling et al 2008) and Cape fur seal Arctocephalus pusillus pusillus . It demonstrates the profound influence that glaciations had on population structure and gene flow even on Southern Hemisphere species.…”

“…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).…”

Intraspecific variation in carapace morphology among fiddler crabs (Genus Uca) from the Atlantic coast of Brazil

“…In fiddler crabs, gene flow is promoted by larval transport on oceanic currents and tides (Epifanio et al 1988, Neethling et al 2008, Weersing & Toonen 2009, López-Duarte et al 2011, and larvae of long planktonic duration are expected to disperse over greater distances (Grantham et al 2003, Lester et al 2007, Shanks 2009). This should promote extensive communication among populations, maintaining uniformity in morphology and genotype across the species' range.…”