Conservation genetics of the Mary River turtle (Elusor macrurus) in natural and captive populations

Abstract

Abstract Many thousands of Mary River turtle eggs were harvested for the pet trade in the 1960s and 1970s before it was recognized as a new species in a unique genus. Pet turtles and their descendants still survive in captive collections. Elusor macrurus is now an endangered species after suffering dramatic population declines along the single Australian river that constitutes its entire range. A conservation genetic assessment was conducted to evaluate population subdivision within the remaining wild population of the Mary River turtle; to compare diversity of the wild population with a captive sample derived from the pet trade; and to establish a baseline estimate of effective population size (Ne) to assist with future monitoring and recovery. Microsatellite analysis indicated panmixia throughout most of the Mary River catchment with the exception of one downstream tributary –Tinana Creek (pop. Specific FST = 0.154). Subdivision between Tinana Creek and Mary River is a feature common to multiple co‐distributed freshwater taxa including the threatened Australian lungfish and Mary River cod. Microsatellite diversity of the wild adult population was low (average HS = 0.554) and not significantly different from that of a sample of captive turtles from the pet trade – indicating genetic diversity may be well represented in captive stocks. Mitochondrial DNA diversity was extremely limited, with only two haplotypes found in the wild and a single shared haplotype in captive turtles. Estimates of Ne applicable to the entire species in the wild were ~136 and ~158 using two independent methods. A reasonable management objective should be retention of Ne levels >100 during recovery of the species. Additional recommendations include that Mary River turtles be listed as Critically Endangered, and that a recovery plan be developed that considers ‘headstarting’ – using captive bred stocks to supplement the wild population.