Evolution and Extinction of West Indian Skinks (Scincidae)

Open Access
Author:
Conn, Caitlin Elizabeth
Area of Honors:
Biology
Degree:
Bachelor of Science
Document Type:
Thesis
Thesis Supervisors:
  • Dr S Blair Hedges, Thesis Supervisor
  • S Blair Hedges, Thesis Supervisor
  • Daniel J Cosgrove, Honors Advisor
Keywords:
  • evolution
  • systematics
  • extinction
Abstract:
Lizards of the family Scincidae (skinks) belonging to the genus Mabuya are distributed throughout the New World. All are smooth-scaled and have an eyelid window, and most are darkly colored with pale stripes. Researchers have had difficulty finding diagnostic characters to distinguish species, leading to taxonomic confusion for nearly two centuries. Five species are currently recognized on islands in the West Indies (Caribbean), and more are found throughout Central and South America. Analyses of their evolutionary history have been limited both morphologically and phylogenetically in the past. The current research project was conducted to develop a better understanding of the systematics of Caribbean island Mabuya. Morphological analyses were performed on over 700 museum specimens of Mabuya from Caribbean islands and Central and South America. Both conventional and unconventional characters were scored and included body proportions, scalation, and pattern. Molecular data were collected from three mitochondrial genes (12S ribosomal RNA, 16S ribosomal RNA, and cytochrome b) and one nuclear gene (myosin heavy chain), and maximum likelihood analyses were performed. Based on morphological and molecular phylogenetic results, 33 species were identified throughout the Caribbean islands, 26 of which are found—or were found—in the West Indies (the West Indies include most Caribbean islands, except those off of Central and South America, such as Trinidad and Tobago). In many cases, the species identified are endemic to single islands. Unfortunately, skinks in this area have decreased drastically in numbers in recent years. Because so many species were unrecognized for centuries, conservation efforts for Mabuya have been minimal. These lizards, including entire species, are now completely absent—extinct—from some islands due to both human activity and predation. Further research should focus on the protection of remaining Mabuya species throughout the Caribbean islands. Additionally, as evidence for the presence of unrecognized species in Central and South America was observed, morphological and phylogenetic studies should be conducted to resolve their systematics.