Microsatellite and mitochondrial DNA variation defines island genetic reservoirs for reintroductions of an endangered Australian marsupial, Perameles bougainville

Genetic mixing in conservation translocations increases diversity of a keystone threatened species, Bettongia lesueur

Translocation programmes are increasingly being informed by genetic data to monitor and enhance conservation outcomes for both natural and established populations. These data provide a window into contemporary patterns of genetic diversity, structure and relatedness that can guide managers in how to best source animals for their translocation programmes. The inclusion of historical samples, where possible, strengthens monitoring by allowing assessment of changes in genetic diversity over time and by providing a benchmark for future improvements in diversity via management practices. Here, we used reduced representation sequencing (ddRADseq) data to report on the current genetic health of three remnant and seven translocated boodie (Bettongia lesueur) populations, now extinct on the Australian mainland. In addition, we used exon capture data from seven historical mainland specimens and a subset of contemporary samples to compare pre-decline and current diversity. Both data sets showed the significant impact of population founder source (whether multiple or single) on the genetic diversity of translocated populations. Populations founded by animals from multiple sources showed significantly higher genetic diversity than the natural remnant and single-source translocation populations, and we show that by mixing the most divergent populations, exon capture heterozygosity was restored to levels close to that observed in pre-decline mainland samples. Relatedness estimates were surprisingly low across all contemporary populations and there was limited evidence of inbreeding. Our results show that a strategy of genetic mixing has led to successful conservation outcomes for the species in terms of increasing genetic diversity and provides strong rationale for mixing as a management strategy.

Genealogical relationship inference to identify areas of intensive poaching of the Orange-fronted Parakeet (Eupsittula canicularis)

Background

The Orange-fronted Parakeet (Eupsittula canicularis) is the Mexican psittacine that is most captured for the illegal pet trade. However, as for most wildlife exploited by illegal trade, the genetic diversity that is extracted from species and areas of intensive poaching is unknown. In this study, we analyzed the genetic diversity of 80 E. canicularis parakeets confiscated from the illegal trade and estimated the level of extraction of genetic diversity by poaching using the mitochondrial DNA sequences of cytochrome b (Cytb). In addition, we analyzed the genealogical and haplotypic relationships of the poached parakeets and sampled wild populations in Mexico, as a strategy for identifying the places of origin of poached parakeets.

Results

Poached parakeets showed high haplotype diversity (Hd = 0.842) and low nucleotide diversity (Pi = 0.00182). Among 22 haplotypes identified, 18 were found exclusively in 37 individuals, while four were detected in the remaining 43 individuals and shared with the wild populations. A rarefaction and extrapolation curve revealed that 240 poached individuals can include up to 47 haplotypes and suggested that the actual haplotype richness of poached parakeets is higher than our analyses indicate. The geographic locations of the four haplotypes shared between poached and wild parakeets ranged from Michoacan to Sinaloa, Mexico. However, the rare haplotypes detected in poached parakeets were derived from a recent genetic expansion of the species that has occurred between the northwest of Michoacan and the coastal region of Colima, Jalisco and southern Nayarit, Mexico.

Conclusions

Poached parakeets showed high genetic diversity, suggesting high extraction of the genetic pool of the species in central Mexico. Rarefaction and extrapolation analyses suggest that the actual haplotype richness in poached parakeets is higher than reflected by our analyses. The poached parakeets belong mainly to a very diverse genetic group of the species, and their most likely origin is between northern Michoacan and southern Nayarit, Mexico. We found no evidence that poachers included individuals from Central American international trafficking with individuals from Mexico in the sample.

Genetic Consequences of Multiple Translocations of the Banded Hare-Wallaby in Western Australia

Many Australian mammal species now only occur on islands and fenced mainland havens free from invasive predators. The range of one species, the banded hare-wallaby (Lagostrophus fasciatus), had contracted to two offshore islands in Western Australia. To improve survival, four conservation translocations have been attempted with mixed success, and all occurred in the absence of genetic information. Here, we genotyped seven polymorphic microsatellite markers in two source (Bernier Island and Dorre Island), two historic captive, and two translocated L. fasciatus populations to determine the impact of multiple translocations on genetic diversity. Subsequently, we used population viability analysis (PVA) and gene retention modelling to determine scenarios that will maximise demographic resilience and genetic richness of two new populations that are currently being established. One translocated population (Wadderin) has undergone a genetic bottleneck and lost 8.1% of its source population’s allelic diversity, while the other (Faure Island) may be inbred. We show that founder number is a key parameter when establishing new L. fasciatus populations and 100 founders should lead to high survival probabilities. Our modelling predicts that during periodic droughts, the recovery of source populations will be slower post-harvest, while 75% more animals—about 60 individuals—are required to retain adequate allelic diversity in the translocated population. Our approach demonstrates how genetic data coupled with simulations of stochastic environmental events can address central questions in translocation programmes.

Genetic diversity, inbreeding and cancer

Genetic diversity is essential for adaptive capacities, providing organisms with the potential of successfully responding to intrinsic and extrinsic challenges. Although a clear reciprocal link between genetic diversity and resistance to parasites and pathogens has been established across taxa, the impact of loss of genetic diversity by inbreeding on the emergence and progression of non-communicable diseases, such as cancer, has been overlooked. Here we provide an overview of such associations and show that low genetic diversity and inbreeding associate with an increased risk of cancer in both humans and animals. Cancer being a multifaceted disease, loss of genetic diversity can directly (via accumulation of oncogenic homozygous mutations) and indirectly (via increased susceptibility to oncogenic pathogens) impact abnormal cell emergence and escape of immune surveillance. The observed link between reduced genetic diversity and cancer in wildlife may further imperil the long-term survival of numerous endangered species, highlighting the need to consider the impact of cancer in conservation biology. Finally, the somewhat incongruent data originating from human studies suggest that the association between genetic diversity and cancer development is multifactorial and may be tumour specific. Further studies are therefore crucial in order to elucidate the underpinnings of the interactions between genetic diversity, inbreeding and cancer.

Genetic analysis of three remnant populations of the rufous hare-wallaby (Lagorchestes hirsutus) in arid Australia

The rufous hare-wallaby (Lagorchestes hirsutus) is now extinct in the wild on mainland Australia, but survives in captivity. However, endemic populations persist on Bernier and Dorre Islands, Western Australia. This study aimed to compare the genetic diversity and differentiation amongst three remaining rufous hare-wallaby populations using mitochondrial DNA (mtDNA) (cytochrome b, control region) sequence data and nuclear (microsatellite) markers. Levels of microsatellite diversity were low in both island populations but high in the captive mainland population. Levels of mtDNA diversity were low in all three populations. The mainland and island populations of L. hirsutus were found to be significantly differentiated for both microsatellite and mtDNA data, but the two island populations were significantly differentiated only for the microsatellite data. This pattern of differentiation is not consistent with the recognition of two separate island subspecies, but we recommend that the mainland and island populations be regarded as separate subspecies. The low diversity of the island populations and differentiation between island and mainland populations presents both challenges and opportunities for future management.

Breaking down scats: degradation of DNA from greater bilby (Macrotis lagotis) faecal pellets

Isolating DNA from scats (faeces) of threatened species is a valuable, non-invasive method for identifying individuals. To establish whether genotyping of greater bilby (Macrotis lagotis) individuals from faecal pellets collected in the field can be useful for population monitoring, an understanding of the DNA degradation rates is necessary. To determine the relationship between time and degradation of bilby faecal DNA, and assess whether a two-step elution process during extraction results in better-quality DNA, faecal pellets were collected from captive individuals, maintained under seminatural conditions, then harvested at known periods. DNA was amplified from faecal pellets with a 99% success rate and error rates of less than 5% up to 14 days after deposition. The amplification rate decreases, and the rate of allelic dropout increases with time, but DNA can still be amplified at rates above 60% and error rates below 15% at 90–180 days. We found that a second elution step was unnecessary, with more DNA amplified over a longer period using the first eluate. Viable DNA exists on bilby faecal pellets for a long period after deposition, which is useful for obtaining genetic samples for population monitoring programs and studies on population genetics.

Conservation of genetic uniqueness of populations may increase extinction likelihood of endangered species: the case of Australian mammals

BACKGROUND

As increasingly fragmented and isolated populations of threatened species become subjected to climate change, invasive species and other stressors, there is an urgent need to consider adaptive potential when making conservation decisions rather than focussing on past processes. In many cases, populations identified as unique and currently managed separately suffer increased risk of extinction through demographic and genetic processes. Other populations currently not at risk are likely to be on a trajectory where declines in population size and fitness soon appear inevitable.

RESULTS

Using datasets from natural Australian mammal populations, we show that drift processes are likely to be driving uniqueness in populations of many threatened species as a result of small population size and fragmentation. Conserving and managing such remnant populations separately will therefore often decrease their adaptive potential and increase species extinction risk.

CONCLUSIONS

These results highlight the need for a paradigm shift in conservation biology practise; strategies need to focus on the preservation of genetic diversity at the species level, rather than population, subspecies or evolutionary significant unit. The introduction of new genetic variants into populations through in situ translocation needs to be considered more broadly in conservation programs as a way of decreasing extinction risk by increasing neutral genetic diversity which may increase the adaptive potential of populations if adaptive variation is also increased.

The room temperature preservation of filtered environmental DNA samples and assimilation into a phenol-chloroform-isoamyl alcohol DNA extraction

Current research targeting filtered macrobial environmental DNA (eDNA) often relies upon cold ambient temperatures at various stages, including the transport of water samples from the field to the laboratory and the storage of water and/or filtered samples in the laboratory. This poses practical limitations for field collections in locations where refrigeration and frozen storage is difficult or where samples must be transported long distances for further processing and screening. This study demonstrates the successful preservation of eDNA at room temperature (20 °C) in two lysis buffers, CTAB and Longmire's, over a 2-week period of time. Moreover, the preserved eDNA samples were seamlessly integrated into a phenol-chloroform-isoamyl alcohol (PCI) DNA extraction protocol. The successful application of the eDNA extraction to multiple filter membrane types suggests the methods evaluated here may be broadly applied in future eDNA research. Our results also suggest that for many kinds of studies recently reported on macrobial eDNA, detection probabilities could have been increased, and at a lower cost, by utilizing the Longmire's preservation buffer with a PCI DNA extraction.

Genetic Analysis and Captive Breeding Program Design for the Eastern Massasauga Sistrurus catenatus catenatus

The eastern massasauga Sistrurus catenatus catenatus is a declining species for which a captive breeding program was established in 2006. To effectively manage wild and captive populations, an understanding of genetic diversity within the species is necessary. We analyzed mitochondrial DNA sequences of 186 individuals: 109 wild snakes from 34 U.S. and Canadian counties and districts, all 52 breeding program members (23 of known and 29 of unknown origin), 18 other captives of unknown origin, and 7 outgroup representatives of desert massasauga S. c. edwardsii, and western massasauga, S. c. tergeminus. Statistical parsimony, maximum likelihood, and maximum parsimony analyses all identified eastern massasaugas as divergent from western and desert massasaugas. We found 18 different haplotypes among eastern massasaugas, comprising three geographically and genetically differentiated NADH dehydrogenase II (ND2) subunits that potentially reflect post-Pleistocene range expansion from unglaciated into formerly glaciated regions. Snakes of unknown origin could all be assigned unambiguously to these ND2 subunits. To maintain natural genetic variation, preserve diversity in captive lineages, and allow future augmentation or reintroduction, the Association of Zoos and Aquariums is managing these three geographic ND2 subunits separately within the Eastern Massasauga Species Survival Plan breeding program.

Prevalence, emergence, and factors associated with a viral papillomatosis and carcinomatosis syndrome in wild, reintroduced, and captive western barred bandicoots (Perameles bougainville)

Once widespread across western and southern Australia, wild populations of the western barred bandicoot (WBB) are now only found on Bernier and Dorre Islands, Western Australia. Conservation efforts to prevent the extinction of the WBB are presently hampered by a papillomatosis and carcinomatosis syndrome identified in captive and wild bandicoots, associated with infection with the bandicoot papillomatosis carcinomatosis virus type 1 (BPCV1). This study examined the prevalence and distribution of BPCV1 and the associated syndrome in two island and four mainland (reintroduced and captive) WBB populations in Western Australia, and factors that may be associated with susceptibility to this syndrome. BPCV1 and the syndrome were found in the wild WBB population at Red Cliff on Bernier Island, and in mainland populations established from all or a proportion of founder WBBs from Red Cliff. BPCV1 and the syndrome were not found in the wild population on Dorre Island or in the mainland population founded by animals exclusively from Dorre Island. Findings suggested that BPCV1 and the syndrome were disseminated into mainland WBB populations through the introduction of affected WBBs from Red Cliff. No difference in susceptibility to the syndrome was found between Dorre Island, Bernier Island, and island-cross individuals. Severity of lesions and the number of affected animals observed in captivity was greater than that observed in wild populations. This study provided epidemiological evidence to support the pathological and molecular association between BPCV1 infection and the papillomatosis and carcinomatosis syndrome and revealed increasing age as an additional risk factor for this disease.

Role of genetic refuges in the restoration of native gene pools of brown trout

Captive-bred animals derived from native, alien, or hybrid stocks are often released in large numbers in natural settings with the intention of augmenting harvests. In brown trout (Salmo trutta), stocking with hatchery-reared non-native fish has been the main management strategy used to maintain or improve depleted wild brown trout populations in Iberian and other Mediterranean regions. This measure has become a serious threat to the conservation of native genetic diversity, mainly due to introgressive hybridization. Aware of this risk, the agency responsible for management of brown trout in the eastern Pyrenees (Spain) created "brown trout genetic refuges" to preserve the integrity of brown trout gene pools in this region. Within refuge areas, the prerefuge status with respect to fishing activities has been maintained, but hatchery releases have been banned completely. We evaluated this management strategy through a comparison of the stocking impact on native populations that accounted for stocking histories before and after refuge designations and fishing activities. In particular we examined the relevant scientific, cultural, and political challenges encountered. Despite agency willingness to change fishery policies to balance exploitation and conservation, acceptance of these new policies by anglers and genetic monitoring of refuge populations should also be considered. To improve management supported by genetic refuges, we suggest focusing on areas where the public is more receptive, considering the situation of local native diversity, and monitoring of adjacent introgressed populations. We recommend the use of directional supportive breeding only when a population really needs to be enhanced. In any case, management strategies should be developed to allow for protection within the context of human use.

Faecal DNA analysis enables genetic monitoring of the species recovery program for an arid-dwelling marsupial

The greater bilby, Macrotis lagotis, is a species of conservation significance in the arid and semiarid zones of Australia. A species recovery program has been underway since the mid-1990s but the incorporation of molecular genetic data within the program has been difficult due to the problems of obtaining regular, population-wide samples of this trap-shy and sparsely distributed species. In this study, we demonstrate that faecal pellets collected from around burrows in the dry, arid habitat of western Queensland provide a viable source for DNA extraction and analysis. Faecal DNA was used to generate population-level estimates of microsatellite and mtDNA diversity for comparison with previous estimates for the natural population derived from tissue samples. Data were used to assess both the reliability of faecal-derived genotypes and the extent of any diversity loss since the previous study. Microsatellite diversity recorded from eight polymorphic markers for the natural population (A = 4.31 ± 0.30, HE = 0.76 ± 0.03) was comparable with the previous study, indicating little change in genetic diversity for the natural population in the 10-year interim. Faecal genotypes generated for the recently reintroduced population matched the known number of founders as well as a known genotype, providing support for the reliability of the faecal DNA approach. The captive and reintroduced populations had significantly lower diversity levels than the natural population (A = 3.59 ± 0.28, HE = 0.68 ± 0.03; A = 3.57 ± 0.20, HE = 0.65 ± 0.03 respectively). Mitochondrial control region analysis, incorporating nested clade phylogeographic analysis (NCPA), agrees with earlier findings that populations of bilbies across the arid zone in Australia have only recently become fragmented, but the case for Queensland bilbies being strongly differentiated from other regions is diminished. Implications from this study include the need to further supplement the captive and reintroduced populations with additional out-bred individuals and that faecal DNA can be used effectively for ongoing monitoring and management of this species.