Small population size and extremely low levels of genetic diversity in island populations of the platypus, Ornithorhynchus anatinus

Abstract

Genetic diversity generally underpins population resilience and persistence. Reductions in population size and absence of gene flow can lead to reductions in genetic diversity, reproductive fitness, and a limited ability to adapt to environmental change increasing the risk of extinction. Island populations are typically small and isolated, and as a result, inbreeding and reduced genetic diversity elevate their extinction risk. Two island populations of the platypus, Ornithorhynchus anatinus, exist; a naturally occurring population on King Island in Bass Strait and a recently introduced population on Kangaroo Island off the coast of South Australia. Here we assessed the genetic diversity within these two island populations and contrasted these patterns with genetic diversity estimates in areas from which the populations are likely to have been founded. On Kangaroo Island, we also modeled live capture data to determine estimates of population size. Levels of genetic diversity in King Island platypuses are perilously low, with eight of 13 microsatellite loci fixed, likely reflecting their small population size and prolonged isolation. Estimates of heterozygosity detected by microsatellites (HE= 0.032) are among the lowest level of genetic diversity recorded by this method in a naturally outbreeding vertebrate population. In contrast, estimates of genetic diversity on Kangaroo Island are somewhat higher. However, estimates of small population size and the limited founders combined with genetic isolation are likely to lead to further losses of genetic diversity through time for the Kangaroo Island platypus population. Implications for the future of these and similarly isolated or genetically depauperate populations are discussed.

Mitochondrial Genome Analysis Reveals Historical Lineages in Yellowstone Bison

“…American bison survived multiple historic and recent population bottlenecks due to habitat reduction, commercial hunting, and diseases from imported domestic livestock [1]. Populations undergoing major reductions in size with constrained areas of distribution are vulnerable to the effects of inbreeding and the loss of genetic diversity through genetic drift [2,3]. …”

Development of polymorphic microsatellite loci in Odontobutis obscura using Illumina paired-end sequencing and the test of cross-species amplification

“…Considering that these 23 microsatellite loci were developed from O. obscura, it is particularly intriguing that O. interrupta and O. platycephala showed much greater genetic variation in the loci that were successfully amplified than did Korean O. obscura (Table 2), supporting the extremely monomorphic nature of the Korean population. Genetic diversity has been recognized as a critical factor affecting a population's fitness and potential persistence (Frankham, 2005;Bouzat, 2010;Furlan et al, 2012). The genetic data in this study have fundamental implications for the conservation status of Korean O. obscura, and urgent management strategies for this population are needed to alleviate the further loss of genetic variation and the negative effects of inbreeding and genetic drift (see also Furlan et al, 2012).…”

“…Genetic diversity has been recognized as a critical factor affecting a population's fitness and potential persistence (Frankham, 2005;Bouzat, 2010;Furlan et al, 2012). The genetic data in this study have fundamental implications for the conservation status of Korean O. obscura, and urgent management strategies for this population are needed to alleviate the further loss of genetic variation and the negative effects of inbreeding and genetic drift (see also Furlan et al, 2012). In the Japanese populations, our markers could be applied for the identification of lineages (geographic groups) or for tests of reproductive isolation.…”

An ecological role for assortative mating under infection?

“…Often species of greatest conservation concern exist in small, isolated and fragmented populations which are directly associated with a loss of genetic diversity (Furlan et al 2012). In turn this is known to reduce the evolutionary adaptive potential of a population, rendering it less capable of an evolutionary response to fluctuations in its environment (Willi et al 2006).…”