Molecular evolution of sea turtles with special reference to the leatherback, Dermochelys coriacea
Loading...
Date
1995
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
Abstract
Nucleotide sequences from the ND4-tRNALeu (907 bp) and control (526 bp) regions of mitochondrial (mt) DNA were used to resolve areas of uncertainty in marine turtle (Chelonioidae) systematics. Parsimony analysis based only on the ND4-tRNALeu data could not resolve the position of the flatback, Natator depressus. A similar analysis based only on the control region sequence data failed to resolve the position of E. impricata and the loggerhead, Caretta caretta. The combination of both data sets with published cytochrome b data produced a phylogeny based on 1924 bp of sequence data which resolves the position of E. impricata relative to Caretta and Lepidochelys and joins N. depressus as sister to the Carettini. Atlantic and Pacific populations of Chelonia mydas were found to be paraphyletic with respect to the black turtle, C. agassizi, suggesting that the current taxonomic designations within the Pacific Chelonia are questionable. This analysis shows the utility of combining sequence data for different regions of mtDNA that by themselves are insufficient to obtain robust phylogenies. There was relatively little variation in the sequence of the mtDNA control region among 8 nesting populations of Dermochelys coriacea from the western Atlantic, Indian Pacific and eastern Pacific oceans. Lack of distinctive geographic structuring of haplotype distributions indicates dispersal among ocean basins, however there was evidence of restricted gene flow between two Caribbean island populations and the Caribbean mainland populations. Analysis of data from three polymorphic nuclear (microsatellite) loci shows these island populations are genetically similar to the mainland populations. The combined DNA results suggest that natal homing does occur to some degree in D. coriacea, but that populations are connected by male mediated gene flow. Genetic distances obtained from the microsatellite data produce different outcomes depending on the mutation model assumed by the analysis. The method based on distances calculated from the proportion of shared alleles produces a phylogeny that is congruent with the geographic relationships between the populations, suggesting that microsatellites show promise as genetic markers for stock identification. This is the first study to use molecular markers to study the population genetics of D. coriacea.
Description
Vita.
Keywords
Major zoology