Abstract

Nonnative cichlids (Coptodon zillii) have established populations in the Köyceğiz and Koca Lakes, located on the west coasts of Mediterranean Turkey. Conflicting species names in these lakes have been reported for many years. We studied samples from current populations of Coptodon in these lakes and the Pecenek canal concerning existing GenBank data. We estimated the possible ancestral population using sequence data in the mitochondrial D-loop segment. Inter and intra-population morphological variations of Coptodon were examined using 25 morphological and six meristic characters. Haplotype analysis revealed three unique haplotypes in three populations of Coptodon, indicating poor genetic diversity. Both maximum likelihood and Bayesian trees showed that these three haplotypes constitute a distinct subclade within the Coptodon zillii clade. This phylogenetic pattern indicates that populations of both lakes were founded by a single invasion of C. zillii and belong to a single species. Consistent with phylogenetic data, the populations of both lakes do not exhibit significant phenotypic divergence, though the Pecenek population is slightly divergent. Intra-population morphological variability may be due to phenotypic plasticity in response to habitat heterogeneity within the lakes.