Phylogenetic Distinctiveness of a Threatened Aquatic Turtle ( Sternotherus depressus )

نویسنده

  • JOHN C. AVISE
چکیده

The musk turtle ( Sternotherus minor ) is common throughout the southeastern United States. In 1955 a morphologically atypical form confined to the Black Warrior River System in Alabama was discovered and accorded full species status as S. depressus , the “flattened musk turtle.” Questions remain about the taxonomic status and evolutionary history of the flattened musk turtle because (1) the geographic distribution of S. depressus is nested within the range of S. minor ; (2) the flattened shell might be a recently evolved anti-predator adaptation; and (3) reports exist of intergrades between S. depressus and S. minor . We generated and employed sequence data from mitochondrial DNA to address the phylogenetic distinctiveness and phylogeographic position of S. depressus relative to all other musk and mud turtles (Kinosternidae) in North America. The flattened musk turtle forms a well-supported monophyletic group separate from S. minor . Genetic divergence observed between S. depressus and geographic populations of S. minor is no less than that distinguishing many kinosternid congeners from one another. These molecular genetic findings bolster rationale for the taxonomic recognition of S. depressus and, hence, for special efforts to protect this federally threatened species. Distintividad Filogenética de una Tortuga Acuática Amenazada ( Sternotherus depressus ) Resumen: Las tortugas acuáticas (“musk turtles”) de la especie Sternotherus minor (familia Kinosternidae) están ampliamente distribuidas en la región sudeste de los Estados Unidos de Norteamérica. En 1955, una variedad de musk turtle morfológicamente atípica, con el caparazón notoriamente comprimido y restringida a la cuenca del río Black Warrior en Alabama, fue descrita y asignada a una especie nueva, S. depressus (“flattened musk turtle”). Posteriormente, el origen evolutivo y el estatus taxonómico de esta nueva especie han sido cuestionados debido a: (1) su restringida distribución geográfica esta anidada dentro del rango de distribución de S. minor ; (2) El caparazón aplanado podría ser una adaptación anti-depredador recientemente evolucionada; y (3) existen reportes de morfologías intermedias entre S. depressus y S. minor . En el presente trabajo se emplean secuencias de ADN mitocondrial para evaluar la identidad genética, posición filogenética, y distribución filogeográfica de S. depressus en relación a las demás especies norteamericanas de la familia Kinosternidae. Los datos obtenidos confirman la identidad de S. depressus como una especie separada genéticamente de la poblaciones locales de S. minor , y de las otras especies de la familia Kinosternidae. Estos resultados sugieren el reconocimiento taxonómico de S. depressus y justifican los esfuerzos conservacionistas para proteger esta especie amenazada.

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تاریخ انتشار 1998