Within the Mesoamerican biodiversity hotspot is Belize, home to high terrestrial and marine biodiversity. Increases in human population size and ecotourism have triggered land-use change, often to the detriment of natural coastlines and forests. Two crocodilian species are present within Belize, both which have suffered past population decline due to habitat degradation and overexploitation. Morelet’s crocodile (Crocodylus moreletii) is found primarily in freshwaters whilst American crocodile (Crocodylus acutus) is more prevalent in highly saline environments. Both are historically sympatric along the brackish coastline, but it is unclear if land-use change is driving contact between the two and affecting genetic integrity of one or both crocodilians. Hybridization between the species has been identified using both mtDNA and microsatellite evidence, however the full magnitude of the process is not fully understood. This project focused on investigating the extent of hybridization across Belize using genomic variants identified by double digest restriction-site associated DNA sequencing (ddRADseq). Skin clips from 80 individuals were taken, and in total 24 were identified as admixed. Five genetically pure populations of C. moreletii were identified, three at inland areas, including the protected Chiquibul National Park. One genetically pure population of C. acutus was identified on northern offshore islands, and another on the southern mainland. Hybrids appear restricted to the central to southern coastline and in close proximity to purebreds. Inland areas and offshore islands may provide refuge for genetically pure crocodilians but confinement to small areas, particularly for offshore C. acutus, exposes the species to the effects of inbreeding and lowered genetic diversity. This research warrants further investigation into pure populations of both C. moreletii and C. acutus in unsurveyed areas of Belize and has potential to inform designation of management units that encompass not only the species, but their habitats and the ecosystems in which they reside.
Assessing hybridization between Morelet’s crocodile (Crocodylus moreletii) and American crocodile (Crocodylus acutus) in Belize using genome wide markers
Wilkie, C. J. (Author). 21 Jun 2022
Student thesis: Master's Thesis › Master of Science by Research (MScR)