RESUMENEste estudio documenta la utilización de hábitat por reptiles en selvas mediana y baja, con tres estados sucesionales: menor de 10 años, entre 10 y 25 años y selvas maduras (> 30 años). La investigación se llevó a cabo entre abril de 1997 y enero de 1998 en la Reserva de la Biosfera Calakmul, Campeche, México. Los muestreos se realizaron a lo largo de un año para incluir las tres estaciones climáticas predominantes en la región: nortes, secas y lluvias. Utilizamos métodos complementarios de muestreo: búsqueda directa en transectos y fuera de ellos, y muestreo con trampas, para evitar sesgos. La información recabada se analizó mediante técnicas multivariadas y de ordenación, para identificar tendencias o afinidades de las especies hacia cierto estado de la vegetación. Se encontraron 10 especies en mayor abundancia y representación en al menos 5 de los 6 tratamientos, que fueron utilizadas para comparar las diferencias entre los sitios conservados de los perturbados. ABSTRACTThis study documents patterns of habitat use by reptiles in low and medium height tropical forest in three successional stages: less than 10 years old, between 10 and 25 years old, and mature (>30 years old) forests. The investigation took place between April 1997 and January 1998 in the Calakmul Biosphere Reserve, Campeche, Mexico. Sampling took place throughout one year period to include the three predominant seasons in the region: dry, wet and nortes. To avoid sampling biases, we used complementary methods: direct search in transects and outside transects, and trapping. We used multivariate and ordination techniques to identify trends in habitat use. Once that patterns of habitat use were identified, we used analysis of variance to test differences in abundance. We identified 10 species with high abundance, inhabiting at least in five of the six treatments, which were used to compare differences between preserved and disturbed sites. 95Acta Zoológica Mexicana (n.s.) 24(1): 95-114 (2008)

Members of the Crotalus durissus species complex are widely distributed from Mexico to Argentina in areas with mainly seasonally dry tropical deciduous forest. Although four species (C. culminatus, C. durissus, C. simus and C. tzabcan) are currently recognized, species limits remain to be tested. Previous genetic studies suggest that C. durissus and C. simus may be paraphyletic and that at least one cryptic species may be present. We analyzed 2596 bp of DNA sequence data from three mitochondrial and one nuclear gene to infer phylogenetic relationships in the Neotropical rattlesnakes. We also examined museum and wild specimens as well as captive animals to analyze morphological characters. Our results suggest that the current taxonomy of the Crotalus durissus species complex does not reflect evolutionary history. We found strong support for five independent lineages within Crotalus simus (sensu lato), with genetic and morphological evidence for three previously recognized taxa and two new species, as well as three major lineages within C. durissus that each represent species hypothesis to be tested with additional evidence. We also found support to retain C. totonacus in the Crotalus molossus species complex. We suggest conservative taxonomic changes to the complex and related species, but more evidence is needed (e.g., morphology, ecology and venom composition) to clarify relationships among species.

1. Anthropogenic activities have resulted in declines in many marine turtle populations. Their complex life cycle (e.g. female philopatry, hatchling migration, adult movements between breeding and foraging areas) makes it difficult to fully understand some of the biological implications of human impacts on their populations, but genetic tools can play a major role in understanding population dynamics and thus improve conservation and management strategies. 2. Using the mitochondrial DNA control region, this study examines the composition, population structure, and connectivity between rookeries and foraging aggregations, in addition to their relationship with Atlantic rookeries and foraging areas of the hawksbill turtle in the Yucatan Peninsula. 3. Haplotype composition of rookeries showed EiA22, EiA39, and EiA41 as endemic haplotypes and revealed a segregation between the Gulf of Mexico and the Yucatan and Quintana Roo rookeries, defining two management units. Foraging aggregations present 15 haplotypes, some common for Atlantic and others for Mexican rookeries. Considering the Gulf of Mexico versus the Mexican Caribbean, significant population genetic structure was revealed, inferring a differential recruitment of hawksbill turtles. 4. Rookery-centric mixed-stock analysis reveals a high contribution of Mexican turtles to local foraging aggregations, principally in the Gulf of Mexico. Foraging-groundcentric mixed-stock analysis showed that the Gulf of Mexico foraging aggregation is predominantly composed of individuals from local rookeries, whereas Mexican Caribbean foraging groups have a mixed composition with individuals from Barbados, Brazil, and Puerto Rico rookeries. The connectivity between rookeries and foraging aggregations suggests that the ocean currents and swimming behaviour influence the distribution of hawksbill turtles. 5. Our results highlighted the importance in identifying management units in nesting and foraging areas to develop monitoring and management programmes at

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