A Molecular Phylogenetic Perspective on the Evolutionary History of Terraranan Frogs, a Vertebrate Mega-radiation
Open Access
- Author:
- Heinicke, Matthew Paul
- Graduate Program:
- Biology
- Degree:
- Doctor of Philosophy
- Document Type:
- Dissertation
- Date of Defense:
- September 11, 2009
- Committee Members:
- S Blair Hedges, Dissertation Advisor/Co-Advisor
Edward C Holmes, Committee Chair/Co-Chair
S Blair Hedges, Committee Member
Kateryna Dmytrivna Makova, Committee Member
David Michael Geiser, Committee Member - Keywords:
- Biogeography
Molecular Clock
Eleutherodactylus
Systematics
Oversea Dispersal
Amphibia - Abstract:
- Terraranans are one of the largest vertebrate radiations, with over 900 species (13% of all amphibians) distributed in the West Indies, Central America, and South America. Unlike most frogs, they lay eggs on land which hatch into froglets rather than tadpoles (direct development). In order to better understand the evolutionary pattern of this group, I have gathered DNA sequence data for over 300 terraranan species. Several main results have emerged. First, most terraranan species fall into four main groups (genera), each predominating in a different geographic region (Central America, the West Indies, northern and western South America, and southeast Brazil). Molecular clock analyses show that these genera are relatively young (between 20 and 50 million years old). Because land connections among Central America, the West Indies, and South America were broken by the beginning of the Cenozoic, these times of divergence suggest parallel origins by overwater dispersal for the West Indian and Central American clades. By using broad taxonomic sampling, and performing analyses with multiple nuclear and mitochondrial genes, a well-supported phylogeny was produced which is the basis of a new classification of terraranan frogs. An enigmatic undescribed frog was placed in a 17-gene molecular phylogeny. This phylogeny demonstrated that it represents the most basal species in Terrarana. Furthermore, this same analysis identified the marsupial frogs as the closest relatives of Terraranans. Together they form an enlarged clade of direct-developing species, suggesting this life-history trait evolved earlier than previously thought. Phylogenies and divergence time analyses of several non-terraranan vertebrate clades (West Indian Leptodactylus, lungfishes, and cartilaginous fishes) are also presented, which provide contrasts in diversification and biogeographic history to the terraranans.