Corroboree frog

Abstract: Background Conservation Breeding Programs (CBP's) are playing an important role in the protection of critically endangered anuran amphibians, but for many species recruitment is not successful enough to maintain captive populations, or provide individuals for release. In response, there has been an increasing focus on the use of Assisted Reproductive Technologies (ART), including the administration of reproductive hormones to induce gamete release followed by in vitro fertilisation. The objective of this study was to test the efficacy of two exogenous hormones to induce gamete release, for the purpose of conducting in vitro fertilisation (IVF), in one of Australia's most critically endangered frog species, Pseudophryne corroboree.

Abstract: Hundreds of amphibian species have declined worldwide after the emergence of the amphibian fungal pathogen Batrachochytrium dendrobatidis (Bd). Despite captive breeding efforts, it is unlikely that wild populations for many species will be reestablished unless Bd resistance increases. We performed a Bd‐challenge study in the functionally extinct southern corroboree frog Pseudophryne corroboree to investigate differences in Bd susceptibility among individuals and populations, identify genetic [major histocompatibility complex (MHC) class I] and genome‐wide variants associated with Bd resistance, and measure genetic diversity and population genetic structure. We found three MHC variants and one MHC supertype associated with Bd infection load and survival along with a suggestively associated single nucleotide polymorphism. We also showed that genome‐wide heterozygosity is associated with increased survival. Additionally, we found evidence of significant population structure among the four P. corroboree populations studied and high MHC genetic diversity. Our results indicate that there are immunogenetic differences among captive southern corroboree frogs; such differences could be manipulated to increase disease resistance and mitigate the significant threat of chytridiomycosis. These results demonstrate a potential long‐term solution to chytridiomycosis that could include breeding more resistant individuals and returning them to the wild.

Abstract: Summary The Southern Corroboree Frog (Pseudophryne corroboree) is one of Australia's most critically endangered frog species. The species occurs entirely within Kosciuszko National Park, which has a history of cattle grazing (up to the 1970s). A consequence of cattle grazing has been a significant reduction in the extent of montane and sub-alpine peat-bog systems that the species uses as breeding habitat. Furthermore, climate change and associated increased wildfire frequency is expected to further reduce the extent and quality of peat bogs throughout the Australian Alps. In this study, we investigated habitat selection for breeding pools and nest sites within peat-bog systems in order to inform the conservation management of the species and guide other management practices being undertaken in peat bogs where this species occurs. Occupancy of breeding males at bog pools was found to be positively associated with increasing pool area, water depth and mid-day temperature, and negatively associated with extent of bare substrate. The majority of breeding pools identified were ephemeral. Nest sites within vegetation where males call and where females deposit their eggs were located at mid-elevations in a range of vegetation types, with the majority of nests being within moss and sedge dominated by Sphagnum cristatum and Empodisma minor. We also found that male nest sites were not randomly distributed within the edges of pools, but were more often located in areas of loose vegetation. These results highlight the potential sensitivity of the Southern Corroboree Frog to predicted changes in peat-bog systems resulting from climate change such as earlier drying and a possible reduction in the size of bog pools. A monitoring programme focused on key features of the breeding habitat should be undertaken to provide a basis for developing and assessing management actions implemented in peat bogs occupied by this species.

Abstract: Southern corroboree frogs (Pseudophryne corroboree) have declined to near extinction in the wild after the emergence of the amphibian chytrid fungus Batrachochytrium dendrobatidis in southeastern Australia in the 1980s. A major captive breeding and reintroduction program is underway to preserve this iconic species, but improving resistance to B. dendrobatidis would help the wild population to be self-sustaining. Using 3' and 5' rapid amplification of complementary DNA ends (RACE), we characterized the major histocompatibility complex (MHC) class IA locus in this species. We then used sequences generated from RACE to design primers to amplify the peptide-binding region (PBR) of this functional genetic marker. Finally, we analysed the diversity, phylogeny, and selection patterns of PBR sequences from four P. corroboree populations and compared this with other amphibian species. We found moderately high MHC class IA genetic diversity in this species and evidence of strong positive and purifying selection at sites that are associated with putative PBR pockets in other species, indicating that this gene region may be under selection for resistance to Bd. Future studies should focus on identifying alleles associated with Bd resistance in P. corroboree by performing a Bd laboratory challenge study to confirm the functional importance of our genetic findings and explore their use in artificial selection or genetic engineering to increase resistance to chytridiomycosis.