Genetic structure among populations of Potamonautes perlatus (Decapoda: Potamonautidae) from the Olifants River system in the Western Cape, South Africa

Abstract

Populations of Potamonautes perlatus were sampled at various points along the Olifants Rivers (220 km), in the Western Cape to examine the degree of genetic variation. Allozyme electrophoresis revealed a near ®xed allelic difference at one locus and extensive differentiation at another locus between populations from the upper and lower reaches of the Olifants River system. Limited hybridization in the region of population sympatry was observed. The narrow hybrid zone and the low occurrence of hybrids suggest selection against hybrids. These results provide evidence for two genetically distinct freshwater crab populations. We concluded that the genetic divergence between the two population groups represents a species boundary between the two populatios.

Carapace dentition patterns, morphometrics and allozyme differentiation amongst two toothed freshwater crab species (Potamonautes warreni and P. unispinus) (Decapoda: Brachyura: Potamonautidae) from river systems in South Africa

“…Similar results have also been reported in marine decapod crustaceans (Nelson & Hedgecock, 1980;Seeb, Seeb, & Polovina, 1990) and seem to be a common occurrence amongst decapod crustaceans. The low mean heterozygosity observed in the present study compares favourably with those reported in other freshwater crabs (Aotsuka et al, 1995;Daniels et al, 1998aDaniels et al, , 1999aGouws, 1999), yet these results were generally considerably lower than the mean value of 0.048 obtained for decapod crustaceans (Hedgecock et al, 1982) and studies on marine decapods (Stevens, 1990;Passamonti et al, 1997;Felder & Staton, 1994;Staton & Felder, 1995;Creasy et al, 1997;Maltagiati et al, 1998). However, low heterozygosity appears to be a common feature amongst freshwater crabs.…”

“…Although this genetic I value is high, it is comparable with some I values obtained for other interspeci®c comparison of river crab populations. For example, P. sidneyi and an undescribed species from KwaZulu-Natal, South Africa separated at a I value of 0.82 (Gouws, 1999), while an I value of 0.88 was reported between P. perlatus and P. granularis (Daniels, Stewart & Gibbons, 1999a), and P. perlatus and P. sidneyi separated at an I value of 0.83 (Gouws, 1999). Generally, however, genetic I values for interspeci®c potamonautid crab populations are considerably lower and include an I value of 0.66 between P. brincki and P. perlatus, (Stewart, 1997a), 0.68 between P. parvispina and P. perlatus, (Stewart, 1997b) and an I value of 0.66 between P. sidneyi and P. unispinus (Stewart & Cook, 1998).…”

Phylogeography of Potamon ibericum (Brachyura: Potamidae) identifies Quaternary glacial refugia within the Caucasus biodiversity hot spot

“…Freshwater crabs have limited dispersal abilities, are unable to surmount terrestrial, marine and mountainous barriers, and are highly philopatric and restricted to a freshwater system even for their lifetime (Daniels, Gouws, & Crandall, 2006;Poettinger and Schubart, 2014;Shih et al, 2011;Yeo et al, 2008). However, populations from nearby drainages can disperse over short land bridges during periods of heavy rainfall which will result in an invariant population genetic structure within a drainage system, as it was previously reported for freshwater crabs of the family Potamonautidae (Daniels, Stewart, & Cook, 2002;Daniels, Stewart, & Gibbons, 1998,1999, Pseudothelphusidae (Schubart, Rivera, Crandall, & Santl, 2011) and Potamidae (Keikhosravi et al, 2015). Some studies have also suggested that freshwater crabs can potentially disperse over short terrestrial barriers under high humidity conditions (Gherardi, Tarducci, & Vannini, 1988;Phiri & Daniels, 2014).…”