Phylogenetic relationships and historical biogeography of spined leaches (Cobitidae, Cobitis and Sabanejewia) as indicated by variability of mitochondrial DNA

For sequence analysis of the 12S rRNA gene in spined leaches, specimens of the following taxa were used: Sabanejewia balcanica, Cobitis paludica, C. b ilineata, C. fahireae, C. elazigensis, C. elongata, two different subpopula tions of C. taenia and four different sub-populations of C. turcica. Phylog enetic relationships among taxa were estimated using parsimony, neighbor-jo ining, and maximum likelihood algorithms. The calculation of the transition -tranversion ratio indicated that the taxa analysed were rather distantly r elated. Our analyses using the genus Sabanajewia as an outgroup suggest tha t C. bilineata is separated from the subgenus Cobitis sensu stricto and pla ced together with C. clongata as basal to all other species of the genus Co bilis. Support for the placement of C. paludica as basal to both the subgen era Bicanestrinia and Cobitis s.s. (without C. bilineata) is given by outco mes from three independent methods of phylogenetic reconstruction. A sister -taxon relationship for the subgenera Bicanestrinia and Cobitis s.s. withou t C. bilineata was consistently found. C. elazigensis was closely related t o the population of C. turcica from Lake Beysehir in Turkey. Both formed a sister-group to the remaining populations of C. turcica, while C. fahireae was basal to C. taenia. A molecular clock was calculated based on sequence divergence values and palaeogeographical data. This suggests that different historical colonization routes must have been used by different clades of spined leaches. (C) 2001 The Linnean Society of London.