Genetic divergence among morphotypes of Lake Tana (Ethiopia) barbs

Abstract

The genus Barbus is a paraphyletic assemblage that includes three different ploidy levels: diploid, tetraploid and hexaploid. 'B.' inhmdius, which inhabits Lake Tana (Ethiopia), is a hexaploid taxon that forms a 'species flock' consisting of at least 14 morphotypes. Thirtyone presumptive allozymic loci were analysed in a large sample of 'B.' intermedius. No diagnostic loci were observed between the morphotypes, but substantial differences in allele frequencies were found. One morphotype, Acute, differs significantly from the others. The presence of this genetic differentiation within the lake strongly suggests that the morphotypes are diverging lineages. Because of some parallel characteristics with cichlid species flocks, we put forward the hypothesis that the morphotypes of barbs in Lake Tana represent a species flock that originated via sympatric speciation with more rapid morphological than molecular differentiation. If the differentiation and the reproductive isolation are real, it is probable that the morphotypes already are or will soon reach the status of species. 0 1998 The Linnean Society of London ADDITIONAL KEY W0RDS:species flocksympatric speciationallozymes -Barbus.

Experimental evidence for the biological species status in Lake Tana's Labeobarbus flock (Cyprinidae)

“…Th e results strongly support the view that among the seven riverine spawning Labeobarbus species (including L. tsanensis , L. truttiformis , L. megastoma ) reproductive isolation is well established Palstra et al, 2004 ;de Graaf et al, 2005 ) and adds to the cumulative evidence from their ecology (Sibbing and Nagelkerke, 2001 ;de Graaf et al, 2008 ;), morphology (Nagelkerke et al, 1994 ;Nagelkerke and Sibbing, 2000 ) and genetics (Berrebi and Valiushok, 1998 ; Dixon et al, 1996 ;Kruiswijk et al, 2005 ) indicating that Lake Tana's labeobarbs are indeed 'good' biological species.…”

Preliminary insight into the age and origin of the Labeobarbus fish species flock from Lake Tana (Ethiopia) using the mtDNA cytochrome b gene

“…Cumulative evidence from their ecology (Sibbing and Nagelkerke, 2001;de Graaf et al, 2008), reproductive behavior (Nagelkerke and Palstra et al, 2004;de Graaf et al, 2005;Zworykin et al, 2006), morphology (Nagelkerke et al, 1994;Nagelkerke and Sibbing, 2000) and genetics (Berrebi and Valiushok, 1998;Dixon et al, 1996;Kruiswijk et al, 2005) has provided sufficient evidence that Lake Tana's labeobarbs are indeed 'good species'. Reproductive isolation is well maintained by macroand micro spatial differences in spawning areas, temporal differences in spawning period and assortative mating through size and chemoreception Palstra et al, 2004;de Graaf et al, 2003de Graaf et al, , 2005Zworykin et al, 2006).…”

Delimiting species by reproductive isolation: the genetic structure of epigean and hypogean Trichomycterus spp. (Teleostei, Siluriformes) in the restricted area of Torotoro (Upper Amazon, Bolivia)

“…This low degree of polymorphism contrasts with the marked morphological differences between the epigean and hypogean Trichomycterus, and among hypogean Trichomycterus (Pouilly and Miranda 2003). Morphological differences between epigean and hypogean fish could be the consequence of a phenotypic plasticity, as observed in certain forms of Astyanax (Herwig 1976) or of a much higher speed of morphological differentiation than genetic differentiation (Culver 1969;Berrebi and Valiushok 1998). Cases of low variability in the nuclear DNA of hypogean species or populations have been reported in many taxonomically distant families, either from RAPD (Balitoridae: Borowsky and Vidthayanon 2001) or isoenzymatic analyses (Characidae: Avise and Selander 1972;Amblyopsidae: Swofford, Branson and Sievert 1980;Trichomycteridae: Perez and Moodie 1993).…”