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

Abstract

1. 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. 2. 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 (N e ) to assist with future monitoring and recovery. 3. Microsatellite analysis indicated panmixia throughout most of the Mary River catchment with the exception of one downstream tributary -Tinana Creek (pop. Specific F ST = 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 H S = 0.554) and not significantly different from that of a sample of captive turtles from the pet tradeindicating 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.4. Estimates of N e applicable to the entire species in the wild were~136 and~158 using two independent methods. A reasonable management objective should be retention of N e 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.

Genetic diversity, structure, and kinship analysis ofTrachemys venusta venustain Wildlife Management Units and wild populations in south Mexico. Implications for conservation and management

“…With the exception of some studies that present low genetic diversity (value of H e < 0.4; [68–69]), freshwater turtles exhibit high values of genetic diversity (generally H e > 0.6-0.7; see Table 4 in [69] for examples, and [70]) based on microsatellites. Our values could be considered lower ( H e < 0.6) than many other freshwater turtles or even threatened species (see Table 4 in [69] for examples, and [70–71]), and are in agreement with values for wild populations of Elusor macrurus Cann & Legler 1994 (Testudines, Chelidae) an endangered Australian freshwater turtle [72]. The sole genetic study that reports value of genetic diversity for Trachemys spp.…”

“…Values of genetic diversity for captive population were slightly higher than wild population as reported for Elusor macrurus [72] and for Dermatemys mawii Gray, 1847 (Testudines, Dermatemydidae) [74]. Because founder individuals of the UMAs (captive population) come from two distinct localities: Pomposu that is within the Grijalva River Sub-Basin and El Espino in the Usumacinta River Sub-Basin (see Fig 1), the genetic pool of those founders could be higher due to the mix of genetic sources.…”

“…In this respect, all studies showed very low values of genetic diversity ( H < 0.15; [64–66]). The relatively low value of genetic diversity observed for wild population of T. venusta venusta compared to other turtle species, suggests that this species deserves reinforced attention and probably higher level of protection considering the threshold of 0.54 proposed by Willoughby et al [73] as a value to consider a species as Critically Endangered [72].…”

Peer Review #2 of "Patterns of genetic structuring at the northern limits of the Australian smelt (Retropinna semoni) cryptic species complex (v0.1)"

“…Creek runs into the Mary River not far from the mouth, with both drainages having tidal estuarine reaches in the lower sections. The differentiation of the Tinana Creek population from the main stem of the Mary River is also observed in a number of other freshwater species including Mary River Cod, Maccullochella mariensis (Huey, Espinoza & Hughes, 2013), Mary River Turtle, Elusor macrurus (Schmidt et al 2018), freshwater crayfish Cherax dispar (Bentley, Schmidt & Hughes, 2010) and Australian lungfish Neoceratodus fosteri (Hughes et al, 2015).…”

Impacts of maternal characteristics and temperature on juvenile survival in the crocodile lizard: Implications for conservation

“…Few attempts have been made to breed reptiles for conservation purposes (Hua et al, 2017;Schmidt, Espinoza, Connell, & Hughes, 2018), especially compared with the efforts devoted to endangered mammals (Nuss & Warneke, 2010;Smucny et al, 2004;Zhang, Swaisgood, & Zhang, 2004). Nonetheless, unlike many larger-bodied vertebrate species, most reptiles are well-suited to captive breeding and reintroduction programs given their small body size, relatively high fecundity, and low maintenance requirements (Shine, 2005;Hua et al, 2017;Schmidt et al, 2018).…”