Spatial and temporal patterns of genetic variation in native and introduced populations of the Nile monitor (Varanus niloticus)

Stephanie Ann Dowell, Fordham University


Genetic analyses at both broad and fine geographic scales can provide useful information to aid in wildlife management. Here, I examine the genetic patterns within the Nile monitor (Varanus niloticus), throughout its native and non-native ranges. I used a multilocus approach, examining DNA sequence data at four mitochondrial and three nuclear loci (totaling 4,251 bp) in addition to 11 microsatellite markers. For my fine-scale analysis of exploited populations in Sahelian Africa, I found evidence of extensive genetic structure. The westernmost populations, under constant high levels of harvesting for the skin trade, were found to exhibit lower levels of genetic variation compared to the other populations in the region. Across their full distribution throughout sub-Saharan Africa, I found evidence for three separate genetic lineages within V. niloticus, occupying the western, northern, and southern regions of the continent. The level of sequence divergence exhibited by the western lineage was consistent with that of reptiles currently recognized as separate species. This analysis revealed no genetic difference between V. niloticus and individuals identified as the ornate monitor (V. ornatus). I am therefore urging for taxonomic revisions in this species group. By incorporating ecological niche modeling (ENM), I found evidence for climatic niche conservatism among all three V. niloticus lineages, suggesting these distinct genetic groups diverged in allopatry. Lastly, three breeding populations of V. niloticus currently inhabit Florida, found in Cape Coral, West Palm Beach, and Homestead. Using the patterns of genetic variation throughout their native range as a reference, I determined the source of all three introduced V. niloticus populations to be the southern coastal region of West Africa. An ENM built from the source population occurrence points revealed regions with high suitability for V. niloticus are restricted to peninsular Florida, even in future climate projections. By combining genetic and ecological data, I have provided a comprehensive analysis, revealing the patterns of genetic variation in V. niloticus at multiple scales, and the processes that likely generated these patterns. This empirical data can be used to inform conservation practices of V. niloticus as well as co-distributed African species.

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Recommended Citation

Dowell, Stephanie Ann, "Spatial and temporal patterns of genetic variation in native and introduced populations of the Nile monitor (Varanus niloticus)" (2015). ETD Collection for Fordham University. AAI3728437.