Microscale population structure and kinship analyses suggest philopatry of both sexes in franciscanas (Pontoporia blainvillei)
Cunha HA, Dias CP, Alvarenga LC, Wells RS, Cremer MJ
International Whaling Commission
Franciscanas (Pontoporia blainvillei) are threatened by extensive by-catch and other human-related activities. Their conservation may be even more complicated for populations that are differentiated on a microscale, between geographically close locations. Infrequent dispersal ultimately means that populations are independent from each other, and therefore they must be managed as distinct Management Units. We used genetic data to investigate the microscale population structure of franciscanas in southern Brazil, and to analyse kinship patterns, searching for evidence of philopatry in the species. Besides significant microscale population structure, we provide evidence that favours the hypothesis of philopatry of both sexes in franciscanas: a) both maternally-inherited mitochondrial DNA and biparentally transmitted nuclear microsatellites showed population differentiation between franciscanas of Babitonga Bay and nearby coastal waters; and b) in Babitonga, most dyads were of related individuals, and kinship was high, irrespective of the sex, indicating that both females and males had relatives in the local population. Those results suggest that kinship not only shapes group organisation, but is also an important feature of local populations, and that franciscanas do not disperse frequently between populations. The relevance of such findings for the conservation of franciscanas is discussed.