World Status, Exploitation and Trade - WIDECAST

..INTRODUCTIONimpartially to represent differing points of view. We stress, however, thatall opinions expressed herein are those of the authors alone, and do notnecessarily reflect the views of those who have contributed material.MARINE TURTLE SYSTEMATICSSpecies, individually or as communities, are the typical target forconservation and management action, and the maintenance of maximum speciesdiversity is a fundamental, if often unspoken, goal (although many wouldemphasise genetic diversity, not necessarily at the species level).Although most taxonomists, and biologists in general, would probably definea species along traditional lines (a group of interbreeding naturalpopulations that are reproductively isolated from other such groups) ,ineveryday taxonomic practice the degree of reproductive isolation generallyis inferred from the degree of morphological difference between the samplesat hand. It has often been the case that very few morphological charactersare considered, frequently those most superficially obvious and mostsusceptible to enumeration.In the examples of reptile systematics investigated by Thorpe (1980, 198A),and by implication in reptile systematics generally, the view of populationdifferentiation derived by conventional procedures, by simple inspection ofa few superficial characters (of colour and lepidosis), compared veryunfavourably with that derived from multivariate analysis, employing a greatmany characters. Thorpe (1980) concluded "It is apparent that theconventional procedure of naming subspecies does not take into account theappropriate evolutionary facts and in practice does not refer to anyabstracted levels of divergence necessary for subspecific recognition.Consequently, a large number of meaningless subspecies are erected whichobscure the patterns of population differentiation..."Similar limitations are evident in sea turtle systematics, and in view ofthe intense conservation attention that has been paid to the group, it isunfortunate that their specific and infra-specific taxonomy remainsunsatisfactory in several respects. This is presumably attributable largelyto the paucity of taxonomic characters that have been employed, the lack ofsophisticated methods of analysis, and in part to the lack of information onbreeding systems and behaviour. These factors are exemplified by thesystematics of the Green Turtle Chelonia mydas ( sensu lato )For much of the past hundred years the genus Chelonia had been treated ascomprising the single species C. mydas . The north Australian formC. depressa (the Flatback) , although Initially described as a full speciesin 1880, was not widely recognised as distinct from mydas until its formalre-description, after thorough discussion. In the late 1960s (Williamset al. , 1967); the species has recently been moved from the genus Cheloniato the monotyplc genus Natator (Limpus et al . 1988).The remaining forms of Chelonia were generally regarded as comprising thesingle species C. mydas , often with two distinct subspecies recognised:C. m. aKassizii Bocourt, 1868 in the eastern Pacific (according to Carr,1975, from Baja California south to Peru and west to the Galapagos, Hawaiiand the Marshall Islands), and the nominate C. m. mydas (Linnaeus, 1758) inthe rest of the range. Carr (1975), however, recommended use ofC. m. iaponica (Thunberg, 1787) for Indian Ocean and western tropicalPacific forms, and suggested that Caribbean populations might eventually be