Introduction

There are seven (or eight) species of sea turtles: loggerhead ( Caretta caretta), green (Chelonia mydas), hawksbill ( Eretmochelys imbricata), Kemp's ridley (Lepidochelys kempii), olive ridley (Lepidochelys olivaceaf), flatback (Natator depressus), and leatherback (Dermochelys coriacea). All are listed either as threatened or endangered under the U.S. Endangered Species Act (http://www.fws.gov/northflorida/SeaTurtles/turtle-facts-index.htm, http://www.cccturtle.org/sea-turtle-information.php?page=flatback).¹ Breeding populations of the green sea turtle in Florida and on the Pacific Coast of Mexico are listed as endangered. All other populations are listed as threatened. Some taxonomists recognize pacific populations of the green sea turtle aa a distinct species, the black sea turtle, Chelonia agassizii. Black sea turtles are putatively distinguished from green sea turtles by several features [2]: marked melanism, smaller size, and slight dorso-ventral expansion.

Karl and Bowen [2] cite conflicting evidence about the reliability of these distinctions. They present new data derived from 1337 nucleotide positions in three single-copy segments of nuclear DNA (CM-12, CM-14, and CM-45).² Using these data they performed a phylogenetic analysis and produced the cladogram in Figure 1. Noting that the black sea turtle does not form a clade in their analysis, Karl and Bowen [2] argue that the black sea turtle may not be an eevolutionarily significant unit. They go on to argue that the black sea turtle is a ``geopolitical species,'' i.e., that it is a ``[group] of individuals confined to geographically or geopolitically defined areas [that] are accorded species status independent of morphological, genetic, and reproductive criteria.''

Figure 1: Majority-rule consensus tree of haplotypes in sea turtles. Numbers above each node are the percentage of 71 equally parsimonious trees containing the clade. Numbers below the node are the percentage of bootstrap replicates containing the node [2]

Pritchard [3] argues that folk taxonomy supports continued recognition of the black sea turtle as a distinct species, and provides a series of qualitative arguments to suggest that the phylogenetic analyses are misleading. Grady and Quattro [1] argue that problems arise because of the lack of concordance between molecular and morphological data sets. Shrader-Frechette and McCoy [4] apply a ``two-stage'' ethical analysis to the problem in an attempt to balance two ethical values: the value of unbiased research and the value of human and environmental welfare.³