Assessment of Genetic Diversity in Largetooth Sawfish, Pristis pristis, Populations Over the 20th Century

The Critically Endangered Largetooth Sawfish, Pristis pristis, experienced global declines in range and abundance over the past century and Australia is now their last stronghold. This research aimed to understand whether these declines have been accompanied by a reduction in levels of genetic diversity. Using P. pristis tissue samples sourced from natural history specimens, three fragments (616-bp, 386-bp, 141-bp) in the mitochondrial DNA (mtDNA) control region were PCR-amplified. At each fragment, significant genetic structure was found in P. pristis overall (ΦST=0.946, N=9; 0.813, N=54; 0.771, N=99). The Indo-West Pacific and Atlantic/Eastern Pacific each harbor genetically distinct lineages of P. pristis. Historic (i.e. pre 2000) genetic diversity indices were estimated at each fragment for P. pristis on a global level (averaged at h=0.730±0.024; π=0.009±0.003) and within Australia (averaged at h=0.698±0.159; π=0.005±0.000). When compared to contemporary datasets (averaged at h=0.648±0.047; π=0.007±0.003) (Phillips et al., 2011; Feutry et al., 2015), these data indicate that P. pristis have experienced a global loss in genetic diversity over the past century. Within Australia, there may not have been a major loss in genetic diversity since the 1970s. The 2–4 historic haplotypes observed in Australia, at each fragment, were also sampled in contemporary datasets. Conservation efforts aimed at retaining genetic diversity in P. pristis should focus on remnant populations outside of the Indo-West Pacific (i.e. Brazil). The long-term persistence of P. pristis in Australia may be sustainable if the abundance of current populations is maintained