Contrasting population structures of three Pristis sawfishes with different patterns of habitat use

This research demonstrates how population structure differs in elasmobranchs with different patterns of habitat use. Population structure was assessed using data at microsatellite loci in three species of Pristis sawfishes in northern Australian waters. Statistically significant population structure was found in each of P. clavata (F-ST = 0.021, F'(ST) = 0.151, P < 0.001) and P. zijsron (F-ST = 0.026, F'(ST) = 0.130, P < 0.001), which spend their entire life in marine waters. In contrast, there was no evidence of significant population structure in P. pristis, which uses freshwater rivers as juveniles and marine waters as adults (F-ST = 0.004, F'(ST) = 0.029, P = 0.210). When combined with the results of mtDNA analyses from a previous study, the results suggested that dispersal in P. pristis is male-biased, whereas both male and female gene flow are restricted at large spatial scales in each of P. clavata and P. zijsron in Australian waters. The present study has provided the first evidence of sex-biased dispersal in a sawfish.