Phylogenetic Relationships and Species Delimitation of the Nile Monitor (Varanus niloticus) Complex in Nigeria Using Multilocus Molecular Markers

This study investigates the phylogenetic relationships and species boundaries within the Varanus niloticus complex in Nigeria using a multilocus molecular approach, addressing the unresolved taxonomic status of Nigerian monitor lizard populations that has implications for conservation policy and CITES implementation. Recent molecular studies have suggested that Varanus niloticus as currently defined may comprise two or more species, but Nigerian populations have not been included in any phylogeographic study. Tissue samples were collected from 112 individuals from 18 localities spanning four ecological zones in the South West, South South, North Central, and North East zones. Mitochondrial (cytochrome b and ND4) and nuclear (RAG1 and c-mos) markers were sequenced. Phylogenetic analyses used maximum likelihood, Bayesian inference, and species tree methods. Species delimitation analyses were conducted using GMYC, BPP, and ABGD approaches. Molecular results strongly supported two reciprocally monophyletic mitochondrial clades corresponding to forest zone and savanna populations, with divergence estimated at 4.2 million years. Nuclear markers showed incomplete lineage sorting but were concordant with mitochondrial structure. Species delimitation analyses consistently recognised two species, a forest clade corresponding to V. niloticus niloticus and a savanna clade corresponding to V. niloticus ornatus under current taxonomy but supported as distinct species under the phylogenetic species concept. The study provides the first molecular phylogeographic framework for Nigerian monitor lizards and calls for reassessment of CITES trade quotas to account for potentially distinct conservation status between taxa. Keywords: Varanus niloticus, phylogenetics, species delimitation, molecular markers, Nigeria.