Morphological heterogeneity in Coptodon zillii (Cichliformes, Cichlidae) from Nigeria: implications for population divergence

Abstract

The population divergence of three populations of Coptodon zillii (Gervais, 1848) from Aiba reservoir, Asejire reservoir, and Igbokoda river in Southwestern Nigeria was determined by characterising their morphometric measurements and meristic counts. Twenty-five morphometric measurements and six meristic counts were recorded on 50 individuals from each location. The morphometric data were size-corrected and analysed using the Kruskal-Wallis test and Principal Component Analysis (PCA), while the meristic data were analysed using Correspondence Analysis (CA). Results of the Kruskal-Wallis test revealed considerable morphological heterogeneity among the populations, with measurements of 13 morphometric traits significantly different at p ≤ 0.05. The PCA also indicated morphological divergence among populations, as the Asejire population formed a distinct cluster, while the Aiba and Igbokoda populations exhibited partial overlap. The PCA-based loading plot identified the pectoral spine length and lower jaw width as the most significant morphometric traits driving morphological divergence among the populations. Correspondence analysis revealed a large overlap of the meristic data, suggesting that the meristic traits could not eff ectively delineate the populations. The study therefore, concluded that the C. zillii populations from Aiba reservoir, Asejire reservoir, and Igbokoda river are morphologically divergent based on their morphometric characters only and should thus be managed accordingly.