School of BioSciences - Theses
Permanent URI for this collection
Search Results
1 - 2 of 2
-
ItemTaxonomy, ecology and conservation genomics of North-Eastern Australian Earless Dragons (Agamidae: Tympanocryptis spp.)( 2018)Land clearing and modification of natural habitats is threatening biodiversity globally. In Australia, most native grassland habitats have been heavily modified for agriculture, including cropping and grazing. Grassland specialist species, including earless dragon lizards (Tympanocryptis spp.) in north-eastern Australia, are of conservation concern due to this continued habitat loss and fragmentation. However, the north-eastern Australian group of earless dragons (including the recently described T. condaminensis, T. wilsoni and T. pentalineata) are at significant risk, due to the presence of multiple undescribed cryptic Tympanocryptis lineages within this region. It is imperative that the taxonomy is resolved for these cryptic lineages of conservation concern, so conservation of these species may occur. One of the major challenges for taxonomists in recent times has been the species delimitation of morphologically cryptic taxa. The detection of distinct molecular lineages within cryptic genera has increased exponentially over the past decades with advances in genetic techniques. However, there are discrepancies in the rate and success of detection of cryptic taxa between studies using genetic methods and those using classic external morphology analyses. Therefore, novel integrative methods for species delimitation of cryptic taxa provide an avenue to incorporate multiple lines of evidence, including the application of osteological variation assessment where external morphological assessment fails to distinguish species. I develop a new pipeline integrating genomic data using single nucleotide polymorphisms (SNPs) and osteological geometric morphometric evidence from micro X-ray computed tomography (CT) imagery to assess variation between cryptic lineages for confident species delimitation. Here, I use this novel integrative pipeline to delimit cryptic lineages of earless dragons in north-eastern Australia. Prior to this study, there was evidence of three undescribed species of Tympanocryptis in this region. Using single mitochondrial and nuclear genes along with >8500 SNPs, I assess the evolutionary independence of the three target lineages and several closely related species. I then integrate these phylogenomic data with osteological cranial variation from CT imagery between lineages. I find that the very high levels of genomic differentiation between the three target lineages is also supported by significant osteological differences between lineages. By incorporating multiple lines of evidence for species delimitation, I provide strong support that the three cryptic lineages of Tympanocryptis in north-eastern Australia warrant taxonomic review. Earless dragons are found in most environments across the Australian continent, including a variety of ecological niches, from stony desert to tropical woodland or cracking clay savannah, although each species is often restricted to s certain habitat-type. I investigate the phylogenetic relationships among currently described earless dragons and newly delimited putative species with an assessment of broad biogeographic divisions, focussing on the north-eastern Australian Tympanocryptis group. I found significant structure across the north-eastern Australian lineages, with deep divergence between lineages occurring in the inland Great Artesian Basin region and more coastal Great Dividing Range. Regional diversification is estimated to have occurred in the late Miocene with subsequent Plio-Pleistocene speciations, and divergence and distributions of these species may therefore be reflective of the climate induced grassland-rainforest oscillations during this time. Based on these phylogenetic geographic relationships and the species delimitation from the integrative taxonomy approach, I describe three new species of Tympanocryptis from the cracking clay grasslands of the Darling Riverine Basin (T. darlingensis sp. nov.) and Queensland Central Highlands (T. hobsoni sp. nov.), and the stony open eucalypt woodlands on the Einasleigh Uplands (T. einasleighensis sp. nov.). The revision of these species provides further taxonomic clarity within the Tympanocryptis genus, and is an imperative step in the conservation of the north-eastern Australian earless dragons. These three putative Tympanocryptis species and the other three recently described earless dragons in north-eastern Australia inhabit restricted niches and areas with varying levels of habitat fragmentation and modification, and are therefore of significant conservation concern. However, little is known about these six north-eastern Australian earless dragon species. I utilise genomic methods to investigate population connectivity and genetic structure to determine management units. I then use species distribution modelling (SDM) to assess habitat suitability and fragmentation of each species. I integrate results of these analyses to form conclusions on the distribution and population structure of these earless dragons. I then discuss the major threatening processes and potential conservation strategies. This thesis uses several integrative approaches in resolving the taxonomy and forming conclusions on the conservation management of the north-eastern Australian Tympanocryptis species. This study successfully delimits cryptic lineages, explores the phylogenetic and geographic relationships between species, and provides baseline population genomics and ecological data to be used for conservation assessments and management decisions of earless dragons in north-eastern Australia.
-
ItemCost-effective methods in conservation( 2018)Conservation resources are scarce, whether it is time, money or effort. Therefore, wise spending is important and decisions need to be made on how to prioritise limited resources between different conservation actions. Effectively targeting declines in biodiversity requires monitoring and management, each of which contribute differently to improved conservation outcomes. Monitoring provides information about the system (whether it is about the state or the dynamics), while management aims to halt downward population trajectories. Often monitoring and management are competing for the same resources, creating trade-offs in how these resources should be spent. In this thesis, I examine trade-offs in conservation, by focusing on how alternative resource allocations within monitoring, and between monitoring and management, impact the ultimate conservation outcome. I illustrate this with two case studies: the endangered growling grass frog (Litoria raniformis) metapopulation around Melbourne, Australia, and the invasive yellow crazy ant (Anoplolepis gracilipes) on Christmas Island, Australia. The first chapter provides a general introduction to the role of monitoring and management in conservation and the trade-offs that exist within and between them. In the second chapter, I examine whether increasing the spatial coverage of a monitoring program for the growling grass frog can replace learning about metapopulation dynamics in terms of population persistence. The advantage of obtaining reliable estimates from spatial monitoring over temporal monitoring is that wasting invaluable time is avoided. In the third chapter, I explore management of the endangered growling grass frog metapopulation, and study how alternative resource allocations between monitoring and management affect the confidence about sufficient offsetting actions. Increasing urbanisation requires habitat offsetting to reduce further declines in the metapopulation. Investing in monitoring might result in more precise estimates of the metapopulation dynamics, and hence allow managers to be more confident about which management strategy might be best. More management, on the other hand, might reduce the extinction risk of the metapopulation directly, provided suitable actions are chosen. Determining the optimal allocation of resources between the two is important to ensure the metapopulation gains as much as possible from the implemented offsetting management. In the fourth chapter, I switch focus to an invasive species, the yellow crazy ant, and investigate how to optimally survey an island for high density super-colonies. I compare effectiveness of a survey strategy that explicitly accounts for the variation in survey cost across the island with alternative ones that ignore survey cost estimates. In the fifth chapter, I determine the amount of monitoring data that contains sufficient information to find the ant super-colonies. Using a habitat suitability model for the super-colonies, combined with survey cost estimates, I prioritise sites, and evaluate the impact of more monitoring data on the amount of super-colonies found. Monitoring a small part of the island is sufficient to find the maximum possible super-colonies for a particular budget, resulting in the effectiveness of the survey strategy levelling off. This suggests that the resources that are currently spent on monitoring the entire island, can be redirected towards management of the invasive species. Finally, in the last chapter, I summarise the main findings of this research and discuss some potential paths for future research.