- Title
- Employing SNP data to reveal population status and breeding secrets of two cryptic, endangered frog species
- Creator
- Stock, Sarah
- Relation
- University of Newcastle Research Higher Degree Thesis
- Resource Type
- thesis
- Date
- 2023
- Description
- Research Doctorate - Doctor of Philosphy (PhD)
- Description
- Amphibians are one of the most imperilled vertebrate groups in the world. However, the long-term trajectory for many amphibian populations is unclear due to the paucity of ecological knowledge because of a lack of monitoring and/or the cryptic nature of the species. Recent advancements in high-throughput DNA sequencing and genotyping technologies have led to a huge expansion in population genetics focused on threatened amphibians to overcome these issues. Two frog species requiring urgent conservation action are the heath frogs, Litoria watsoni and L. littlejohni that were only recently split taxonomically from each other. Little is known about the ecology of these species due to low detection rates and inconsistent behaviour. It is thought that both species have declined due to the chytrid fungus, Batrachochytrium dendrobatidis, however they are also threatened by habitat disturbance due to primary industry and fires. This thesis aims to guide the management of both heath frog species by outlining clear priority conservation actions and directing future research that will promote the long-term persistence of both frog species. This will be achieved by using high throughput sequencing to delineate populations, describe patterns of genetic diversity, estimate population sizes and explore mating systems. The first chapter of my thesis is a literature review exploring how genetic methods have been employed to study species facing ecological disturbances such as disease, drought and fire. My second chapter describes the pattern of gene flow, genetic diversity population size and inbreeding coefficients across all known populations of L. littlejohni. I detected five genetic clusters with moderate to strong genetic isolation. The two northern populations have elevated risk of extinction due to exceedingly small effective population size and reduced genetic diversity. In the third chapter, I employed molecular parental assignment methods to explore both the mating system and what traits influence male breeding success at a key study site to help fill this knowledge gap. This study provides the first evidence of inbreeding depression in Australian frog species, raising major concern for the future of this species. Males with both lower body condition and higher inbreeding coefficients were less likely to sire tadpoles. My fourth chapter found stream length, topographic position, soil and pond depth were all associated with genetic diversity in L. littlejohni. I also detected a barrier to gene flow in the Central Coast Range and described the extent of dispersal. This chapter highlights the need for additional habitat in the Central Coast Range and provides guidance for habitat modification or creation efforts. My last chapter focuses on L. watsoni, and I found five clear genetic clusters with strong genetic difference between the Victoria population and all other New South Wales populations. The significant genetic difference between New South Wales and Victorian populations indicates that assessment of the risk and potential outcomes of outbreeding depression are required. Collectively these studies provide the first detailed assessment of population genetics and mating systems for L. littlejohni and L. watsoni. The findings of this thesis will determine what conservation actions should be employed and the research directions for both species with the aim of reducing the potential extirpation of each population and ensure the persistence of both species. Additionally, these studies provide a benchmark for population size and genetic diversity that can be used for future monitoring of these two species. The study also highlights the power and usefulness of genetic methods for studies and conservation of rare and cryptic species.
- Subject
- genetics; amphibians; SNPs; conservation; litoria
- Identifier
- http://hdl.handle.net/1959.13/1504325
- Identifier
- uon:55495
- Rights
- Copyright 2023 Sarah Stock
- Language
- eng
- Full Text
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| Thumbnail | File | Description | Size | Format | |||
|---|---|---|---|---|---|---|---|
| View Details Download | ATTACHMENT01 | Thesis | 5 MB | Adobe Acrobat PDF | View Details Download | ||
| View Details Download | ATTACHMENT02 | Abstract | 745 KB | Adobe Acrobat PDF | View Details Download |