Systematics and population genetics of the South African freshwater crab fauna (Decapoda: Potamonautidae: Potamonautes)

[摘要] ENGLISH ABSTRACT:In the present study, the systematic status, aspects of the evolutionary biology and phylogeneticrelationships among species of the African freshwater crab genus Potamonautes in South Africaare examined. Systematic research between allopatric populations of P. brincki, using allozymeand morphometric data has revealed the existence of a new undescribed freshwater crab speciesoccurring in mountain streams of the Cape Peninsula. This species is described in the presentstudy. In addition, the diagnostic value of carapace dentition patterns in the taxonomy offreshwater crabs is explored among two toothed river crab species from South Africa. Thelatter study utilized P. warreni and P. unispinus where considerable variation in the dentitionpattern of the former species has been recorded. Fixed differences in allozyme locidemonstrated that these two taxa should indeed be considered separate, yet closely relatedspecies, while the morphometric data failed to reveal this taxonomic separation. The holotypeof P. warreni is re-described. The relationship of hybrid taxa between P. depressus and P.clarus populations are investigated. Evident from this study is that populations that occurequidistant from the two parental taxa have undergone extensive introgressive hybridization.Considering the pronounced sequence divergence and the occurrence of fixed allozyme locibetween populations, it is postulated that the hybrid populations should be considered to be on aunique evolutionary trajectory worthy of conservation. The population genetic structure of P.calcaratus is examined as this species is unique in its occupation of water holes. Resultsdemonstrate that the genetic population structure is the result of recent colonization andmoderate gene flow among populations. Phylogenetic relationships between the southernAfrican freshwater crab fauna is investigated with the use of sequence data from twomitochondial genes (12 S rRNA and 16 S rRNA), allozymes and morphology in an attempt tofirstly, test the usefulness of freshwater crabs as biogeographic indicators, secondly to explorethe relationship among hybrid taxa, and thirdly to examine Bott's (1955) subgeneric divisions.Results demonstrated that freshwater crabs can be used as biogeographic indicators, that hybridtaxa are phylogenetic ally closely related and that Bott's subgeneric divisions have no systematicbasis. Among the three data sets, the sequence data provided the best resolution, while thephylogenetic inferences derived from the allozyme data and the morphology was limited.

[发布机构] Stellenbosch University