Extreme levels of intra-specific divergence among Cape Peninsula populations of the Cape galaxias, Galaxias zebratus Castelnau 1861, reveals a possible species complex

  • Marcus Wishart Freshwater Research Unit, Department of Zoology, University of Cape Town, Rondebosch 7700, South Africa; Current address: The World Bank, 1818 H Street NW, Washington DC 20433, USA
  • Jane Hughes Cooperative Research Centre for Freshwater Ecology, Australian School of Environmental Studies, Griffith University, Nathan 4111, Australia
  • Barbara Stewart Centre of Excellence in Natural Resource Management, University of Western Australia, 444 Albany Highway, Albany 6330, Western Australia
  • Dean Impson Western Cape Nature Conservation Board, Private Bag X5014, Stellenbosch 7599, South Africa

Abstract

The Cape galaxias, Galaxias zebratus, is part of the paleao-endemic fauna characteristic of the south-western Cape, South Africa, and is the only galaxiid found in continental Africa. A 284-bp fragment of the cytochrome b region of the mtDNA was sequenced from 48 individual galaxiids, representing 10 populations from the Cape Peninsula. Five sequences, for four additional populations sampled at the extremes of the species range, were obtained from the literature. Analysis of cytb mtDNA from these 14 populations of G. zebratus revealed five distinct and highly divergent lineages with low levels of intra-population mtDNA haplotype diversity. A new and distinct genetic lineage is described from the southern part of the Cape Peninsula. Estimates of genetic divergence between populations ranged from <1% to >17%. The observed level of sequence divergence represents the largest yet reported for any single fish species. The distribution of these lineages and their degree of sequence divergence refutes a model of isolation by distance. Results suggest that periods of low sea level may have been important in creating opportunities and alternative routes for dispersal and migration for Cape Peninsula populations.

Keywords: Cape Floristic Region, endemism, fish conservation genetics, fynbos, mtDNA, river

African Journal of Aquatic Science 2006, 31(1): 99–106
Published
2006-08-01
Section
Articles

Journal Identifiers


eISSN: 1727-9364
print ISSN: 1608-5914