SREL Reprint #1923

 

 

 

 

MOLECULAR SYSTEMATICS OF MAP TURTLES (GRAPTEMYS): A COMPARISON OF MITOCHONDRIAL RESTRICTION SITE VERSUS SEQUENCE DATA

TRIP LAMB,1 CHARLES LYDEARD2 ROBERT B. WALKER,1 AND J. WHITFIELD GIBBONS2

1Department of Biology, East Carolina University, Greenville, North Carolina 27858, USA
2Savannah River Ecology Laboratory, P.O. Drawer E, Aiken, South Carolina 29802, USA

Abstract. -Analyses of mitochondrial DNA (mtDNA) restriction sites and sequences were used to estimate phylogenetic relationships in the emydid turtle genus Graptemys. We compared resolution and concordance among four mtDNA data sets: (1) restriction sites, (2) cytochrome b sequences (380 base positions [bp]), (3) control region sequences (344 bp), and (4) combined (cytochrome b and control region) sequences. Five of the 12 currently recognized species could not be distinguished on the basis of restriction sites. Cytochrome b sequences provided even less phylogenetic information, whereas control region sequences identified all taxa. Bootstrap consensus trees for the restriction site and control region sequence data resolved three monophyletic clades: a pulchra group, a pseudogeographica group, and the basal G. geographica. Of the four data sets, the control region offered the greatest resolution with respect to species identification and phylogenetic information. However, a character congruence approach, combining both sequence and restriction site characters, significantly bolstered bootstrap support for the major clades and enhanced phylogenetic resolution within them. Sequence divergence estimates (restriction sites: 0.0-3.2%; cytochrome b: 0.0-1.5%) for Graptemys are among the lowest values reported for a generic-level comparison involving-vertebrates. These findings are discussed in light of recent drainage isolation events along the Gulf of Mexico and a proposed slow rate of mtDNA evolution in turtles. [Mitochondrial DNA; restriction sites; DNA sequences; cytochrome b; control region; molecular systematics; Graptemys.]

SREL Reprint #1923

Lamb, T., C. Lydeard, R.B. Walker, and J.W. Gibbons. 1994. Molecular systematics of map turtles (Graptemys): a comparison of mitochondrial restriction site versus sequence data. Systematic Biology 43:543-559.

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