Abstract
The saltwater crocodile (Crocodylus porosus) is the largest and most broadly distributed crocodilian species, and thus is of special conservation and economic interest. Similar to other parts of its range throughout the Indo-Pacific, C. porosus distributed in the Republic of Palau have experienced a severe population decline over the past century primarily due to commercial hunting and eradication campaigns. In addition, several thousand crocodiles of undocumented species and origin were imported into Palau during the 1930’s for commercial farming purposes, potentially polluting the gene pool of the endemic saltwater crocodiles. Analysis of 39 individuals collected throughout the Republic of Palau revealed a single mitochondrial DNA control region haplotype shared by populations sampled in Sulawesi, Borneo and Australia. The mtDNA results, in combination with microsatellite genotypic data at six loci, detected no evidence for inter-specific hybridization between endemic Palauan C. porosus and potentially introduced Crocodylus species. There was no evidence for a genetic bottleneck in the Palauan population, however an excess of rare alleles was identified, indirectly suggesting a recent history of admixture potentially linked to introductions of non-native C. porosus. Following from these findings, Palauan C. porosus should be included in the single ESU previously established for all saltwater crocodiles given the recovery of a fixed, but geographically widespread haplotype. Although Palauan C. porosus exhibited significant genetic differentiation relative to all other sampled populations, it’s delineation as a distinct management unit is precluded at the present time by evidence that the genetic integrity of the population may have been compromised by the introduction of non-native saltwater crocodiles.
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Acknowledgments
A special thanks to the people of Palau for their hospitality and graciousness over the course of this study. We would like to particularly thank Mr. Joshua Eberdong, and the Bureau of Marine Resources, Republic of Palau, for their extensive field and logistical support and our Palauan field colleagues, Mr. Harvey Kloulechad and Mr. Theodore Ngiramelekei, who took great personal risks in securing the field-sampled materials. Nancy FitzSimmons kindly provided replicate samples for calibrating the genotypic datasets and offered insightful comments that greatly improved this work. Peter John Brazaitis and Julian Dendy assisted us in the field, and Chaz Hyseni and Greg Mulvey aided in the collection of molecular data for this study. We wish to acknowledge the Peabody Museum of Natural History, National Museum of Natural History, and Field Museum of Natural History for providing access to their collections. Additionally, the St. Augustine Alligator Farm, and the Gladys Porter Zoo supplied blood samples from their extensive animal collections. George Amato and Kent Vliet provided assistance in multiple capacities, and Sarah Klain, Bureau of Marine Resources, Koror, Palau graciously prepared the locality map in Figure 1. This work was supported by the U.S. Fish and Wildlife Service’s Pacific Islands Coastal Program Grant # 122005M020.
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Russello, M.A., Brazaitis, P., Gratten, J. et al. Molecular assessment of the genetic integrity, distinctiveness and phylogeographic context of the Saltwater crocodile (Crocodylus porosus) on Palau . Conserv Genet 8, 777–787 (2007). https://doi.org/10.1007/s10592-006-9225-7
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DOI: https://doi.org/10.1007/s10592-006-9225-7