Conservation genetics of Franciscana dolphins
By Martin Mendez, PhD Candidate, Columbia University and Fundacion Aquamarina

      This project seeks to evaluate Franciscana dolphin population structure patterns and stock identity along the species’ distribution range, with a focus on its southernmost portion located off the coast of northern Argentina. Furthermore, we are addressing some of the environmental and ecological processes responsible for the observed genetic patterns in Franciscanas. The ultimate goal is to identify oceanographic drivers of population structure. This analysis uses cutting-edge genetic tools applied to a combination of nuclear and mitochondrial DNA, which allow an unparalleled level of accuracy in population identification and gene flow estimation. We developed a multidisciplinary framework combining genetic data with spatially explicit oceanographic information collected via remote sensing and in situ.

     Our data combining mtDNA sequence and microsatellite information support the previous proposition of two Franciscana populations in Brazil, one along the Uruguayan coast, and suggest the existence of at least three previously unidentified populations in Argentina, to the south of the La Plata River estuary in Argentina. Individuals from the San Clemente and San Blas areas showed the highest levels of genetic isolation, which is in line with the suggested residency patterns by Bordino and colleagues’ data from satellite-linked tagging. Contrary to what is common for many cetacean species, Franciscana population structure does not show a pattern of isolation by distance, in which populations that are further apart are genetically more differentiated. Rather, our data shows a pattern of isolation by environmental distance, suggesting that ecological and environmental phenomena are responsible for the observed genetic patterns.

     These genetic efforts are important elements of the current management strategies for Franciscanas, as they provide a reliable tool for the identification of demographically independent populations and population areas. Our multidisciplinary framework combining genetic and environmental data is providing a greater understanding of the ecology of this species and could potentially illuminate related issues in other coastal species.

     This work would not be possible without the invaluable support of the entire AquaMarina staff and volunteers or without the collaboration of the local wildlife authorities. Funding for this project comes from Wildlife Trust, the Sackler Institute for Comparative Genomics at the AMNH, and the Ocean Giants Program at Wildlife Conservation Society.