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Accueil du site → Doctorat → Mexique → Distribución, amenazas y estructura genética de la rana de patas rojas (Rana draytonii) en Baja California

Centro de Investigaciones Biológicas del Noroeste (CIBNOR) 2017

Distribución, amenazas y estructura genética de la rana de patas rojas (Rana draytonii) en Baja California

Peralta García, Anny

Titre : Distribución, amenazas y estructura genética de la rana de patas rojas (Rana draytonii) en Baja California.

Auteur : Peralta García, Anny

Etablissement de soutenance : Centro de Investigaciones Biológicas del Noroeste (CIBNOR)

Grade : Doctorado en Ciencias en el Uso, Manejo y Preservación de los Recursos Naturales 2017

The California Red-legged Frog (Rana draytonii) has experienced severe population declines in many parts of its range in western North America, particularly southern California. The United States federal government has formally listed the species as threatened under the Endangered Species Act of 1970, but lack of information about the current status of R. draytonii in Baja California has prevented any formal listing status in Mexico. To determine the current status of R. draytonii populations in Mexico, we surveyed for the presence of R. draytonii in Baja California and assessed the most likely threats to population persistence. Field work from 2013 to 2015 extended from the U.S.-Mexico border to the southern end of the species distribution in the Sierra San Pedro Mártir. Rana draytonii was found at six of 15 historical sites and four of 24 additional sites. All 10 occupied sites are confined to three watersheds within the Sierra San Pedro Mártir (two sites at Arroyo San Rafael, two sites at Arroyo San Telmo, and six sites at Arroyo Santo Domingo). These surveys showed that the current distribution represents approximately 15% of the historical distribution of the species in Baja California. Sites occupied by R. draytonii show significantly higher amounts of aquatic vegetation, shallow ponds and rocky substrate on the stream bank. Generalized linear models (GLM) that incorporated ecological variables showed that distance to urban areas, percentage of undisturbed natural area, and presence of livestock and exotic species are significant factors influencing R. draytonii occurrence. Non-lethal zoospore values of Batrachochytridum dendrobatidis (Bd), the pathogen causing the amphibian disease chytridiomycosis, were detected at all survey sites, and infection loads were positively correlated with altitude, season and year. Genetic information based on 11 microsatellites and single nucleotide polymorphisms (448 to 2,303 SNPs) derived from restriction site associated DNA sequences indicate that populations are genetically structured by drainage, with the arroyo Santo Domingo showing additional structure at the highest elevation site at La Grulla. Genetic diversity was low at all sites, especially at La Grulla, which may be at high risk of extirpation due to its isolation, habitat disturbance, and more extreme environment. Santo Domingo is the largest population with the highest genetic diversity, but individuals show evidence of significant inbreeding. Genetic diversity in Baja California populations is significantly lower compared to similar, extralimital populations in southern California and the northern Sierra Nevada. Creation of breeding habitat, assisted migration, monitoring exotic species and preventing their spread, and conducting studies to examine the effects of livestock grazing (particularly at La Grulla) is recommended to prevent the extinction of R. draytonii in Baja California.

Mots Clés : anfibio s ; genética ; exóticos ; quitridiomicosis


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Page publiée le 9 octobre 2017