EVOLUTIONARY RELATIONSHIPS OF SIBLING TAPEWORM SPECIES (CESTODA) PARASITIZING TELEOST FISHES

DNA/DNA hybridization and sequencing of rDNA (partial 18S rDNA and ITS 1) were used to investigate phylogenetic relationships among seven hos t-specific Bothriocephalus parasites (Cestoda, Pseudophyllidae). The s mall nucleotide divergence between six of the seven bothriocephalids s uggests that isolation and differentiation of Bothriocephalus lineages in the different host species probably occurred recently and over a s hort time span. Comparison of the molecular phylogeny of the parasite species to the phylogeny of their hosts (teleostean fishes) revealed l ittle congruence between the branching patterns of hosts and parasites , suggesting that bothriocephalids have not cospeciated with their hos ts.