Abstract
The Australian lungfish is a unique living representative of an ancient dipnoan lineage, listed as ‘vulnerable’ to extinction under Australia’s Environment Protection and Biodiversity Conservation Act 1999. Historical accounts indicate this species occurred naturally in two adjacent river systems in Australia, the Burnett and Mary. Current day populations in other rivers are thought to have arisen by translocation from these source populations. Early genetic work detected very little variation and so had limited power to answer questions relevant for management including how genetic variation is partitioned within and among sub-populations. In this study, we use newly developed microsatellite markers to examine samples from the Burnett and Mary Rivers, as well as from two populations thought to be of translocated origin, Brisbane and North Pine. We test whether there is significant genetic structure among and within river drainages; assign putatively translocated populations to potential source populations; and estimate effective population sizes. Eleven polymorphic microsatellite loci genotyped in 218 individuals gave an average within-population heterozygosity of 0.39 which is low relative to other threatened taxa and for freshwater fishes in general. Based on F ST values (average over loci = 0.11) and STRUCTURE analyses, we identify three distinct populations in the natural range, one in the Burnett and two distinct populations in the Mary. These analyses also support the hypothesis that the Mary River is the likely source of translocated populations in the Brisbane and North Pine rivers, which agrees with historical published records of a translocation event giving rise to these populations. We were unable to obtain bounded estimates of effective population size, as we have too few genotype combinations, although point estimates were low, ranging from 29 - 129. We recommend that, in order to preserve any local adaptation in the three distinct populations that they be managed separately.
Highlights
For species of conservation concern, increasing or maintaining effective population size (Ne) and maintaining levels of genetic diversity has been considered critically important [1]
Expected heterozygosity of the 11 polymorphic loci averaged 0.39 across the seven sample sites and allelic richness per site averaged just over 2 when sample sizes were standardized across populations at 16 individuals (Table 1)
The estimates of NE were mostly quite small, but confidence levels were broad, indicating that the magnitude of sampling error was comparable to the signal of among locus genetic linkage in the data
Summary
For species of conservation concern (i.e. endangered or vulnerable), increasing or maintaining effective population size (Ne) and maintaining levels of genetic diversity has been considered critically important [1]. This is important because species with low levels of genetic diversity may be less resilient to environmental stressors such as pathogens [2] and climate change [3]. There is the possibility of reduced fitness if the introduced individuals are genetically differentiated from the resident population [4]. Management of threatened species requires information on both the genetic diversity within populations and levels of genetic divergence between populations
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