Spatial and genetic analyses of Africa's sacred crocodile: Crocodylus suchus

Seth William Cunningham, Fordham University


Chapter 1: Conservation and management of widespread species can be improved with proper understanding of patterns of genetic differentiation within the species of concern. Through the identification of appropriate units of management, effective conservation measures can be created to preserve the genetic diversity of a species into the foreseeable future. Here, we use a combination of mtDNA barcoding and nuclear genetic markers to assess levels of population sub-structuring in the newly rediscovered, cryptic species, Crocodylus suchus. Bayesian cluster analyses of 9 microsatellites suggest that marked levels of differentiation are present within the species. In keeping with patterns found on other African crocodiles, observed patterns of divergence are a generally associated with major aquatic landscape features. Regional clustering results suggest patterns of differentiation between West and Central African C. suchus populations comparable to those described in other African crocodilians. Further research, including additional sampling in the Congo basin, would clarify putative management units in this species. Chapter 2: The niche of an organism is defined by fundamental attributes of the species' natural history including its behavioral, physiological, and reproductive ecologies. These characteristics arise in response to both phylogenetic inertia and contemporary selective forces. Among closely related taxa, it is predicted that niche conservatism should result in poorly differentiated niche space. However, among more distantly related species, the converse should be true. We tested the idea that despite broad historic sympatry, the newly re-discovered crocodile (Crocodylus suchus), exists in a divergent niche space than the congeneric Nile crocodile (C. niloticus ) that is more closely related to non- African members of Crocodylus. Our environmental niche models for both species indicate that significantly different bioclimatic factors influence each species' model and that the niche of C. suchus is much more constrained than that of C. niloticus. The niche divergence observed among these taxa and their previously unrecognized phylogenetic distance support theories of niche evolution. In addition, published field observations of both species support our model's predictions and suggest that C. suchus is much more vulnerable to local extirpation than C. niloticus . We argue that niche differences between the two species provide additional support and urgency for the recognition of C. suchus as proposed by Hekkala & Shirley et al. (2011).

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Recommended Citation

Cunningham, Seth William, "Spatial and genetic analyses of Africa's sacred crocodile: Crocodylus suchus" (2015). ETD Collection for Fordham University. AAI1584730.