Project Title: Gene-tagging the dugongs of southern Queensland to determine population dynamics, relatedness and movements
Chief Investigators: Dr Janet Lanyon and Ms Jennifer Ovenden
This project gene-tagged dugongs in Moreton, Hervey and Shoalwater Bays to obtain information that will be used to determine structure, dynamics, connectedness and stock size of these urban dugong populations in southern Queensland.
Small skin samples were collected from dugongs in Moreton, Hervey and Shoalwater Bays using a skin scraper on a pole deployed from a boat. These samples were then screened against a panel of 26 dugong-specific polymorphic microsatellite DNA loci that we have developed. Since this panel is suitable for individual identification of dugongs, we were able to identify new dugongs first sampled in 2007, and also match dugongs sampled in previous years. By the end of 2007 we had genetags (individual identities) for more than 500 different dugongs in Moreton Bay (over 7 seasons), 110 dugongs in Hervey Bay (2 seasons) and 29 dugongs in Shoalwater Bay (one season). We also developed sex-specific molecular primers to determine gender of dugongs. These primers detect the male-specific SRY gene and also differentiate the male-specific ZFY gene from its gametologue ZFX in DNA from the skin sample. This assay accurately assigns gender in dugongs, and also in the related Florida manatee. The combination panel of DNA and sex-specific primers allowed us to determine identity and sex for each dugong from which a skin sample was obtained.
The microsatellite dataset used to genetically-identify individual dugongs is also suited to determine the level of population genetic subdivision between the three regions. We found slight but significant population genetic structuring overall among the three sampling locations with most of the genetic variation found within populations (95%) rather than among (5%). Genetic distance and geographic distance appeared to be positively correlated with dugongs from nearby locations (e.g. Moreton and Hervey Bays) being more genetically similar than those more distant (e.g. Moreton and Shoalwater Bays).
In addition to the microsatellite dataset, we also used control region mitochondrial DNA sequence data to examine population structure. To generate this sequence data set it was necessary to design novel primers to amplify a fragment of control region mitochondrial DNA of ~ 800 base pair length. We sequenced 184 dugongs and found 12 different haplotypes: two haplotypes were shared between Moreton and Hervey Bays one haplotype was shared between Hervey and Shoalwater Bays, three haplotypes were shared between Moreton and Shoalwater Bays and six haplotypes occurred in Shoalwater Bay only. These haplotypes clustered into two clades that differed by an average of 14 nucleotide changes; haplotypes within each clade differed by 1-6 nucleotide changes. Despite sharing some haplotypes at high frequency we detected significant population genetic structuring among the three regions with an apparent isolation by distance model occurring.
In summary, preliminary analysis has detected significant population genetic structuring between Moreton, Hervey and Shoalwater Bays for both nuclear (microsatellite) and mitochondrial (sequence) markers, suggesting that the level of gene flow between these regions is low. This work will be continued to define regional management units for dugongs in southern Queensland, identify migration between these major populations and determine stock size(s) and composition.
