|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,
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.