ORCID Profile
0000-0002-8397-6695
Current Organisation
Edith Cowan University
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Publisher: Wiley
Date: 04-12-2019
DOI: 10.1111/ETH.12826
Publisher: Springer Science and Business Media LLC
Date: 14-08-2023
DOI: 10.1007/S11273-023-09943-2
Abstract: Invasive plants are a threat to natural ecosystems worldwide, with urban wetlands being some of the most susceptible and highly modified environments of all. The tiger snake ( Notechis scutatus ) is a top predator that persists in urban wetlands of south-western Australia, many of which have been degraded by introduced kikuyu grass ( Cenchrus clandestinus ). To evaluate the potential impact of kikuyu grass on habitat quality for tiger snakes we quantified the structural features of habitats within wetlands degraded by kikuyu grass and compared them to wetlands with native vegetation. We also examined tiger snake prey availability, assessed predation risk for juvenile snakes using clay models, and measured the thermal quality of the vegetation. Proliferation of kikuyu grass has reduced habitat structural heterogeneity by reducing available bare ground and increasing vegetation density. This homogenisation of habitat structure had little effect on the predation risk for juveniles or the thermal properties of tiger snake shelter sites however, one key prey species, the motorbike frog, had significantly lower abundance in the most impacted habitat. Habitat types with more structural complexity also offered tiger snakes more stable thermal regimes and lower predation risk. These findings indicate that the current extent of kikuyu grass invasion offers overall similar habitat quality for tiger snakes to native vegetation and may contribute to their persistence in urban wetlands however, both tiger snakes and their anuran prey may benefit from increased habitat structural complexity.
Publisher: Cold Spring Harbor Laboratory
Date: 06-03-2023
DOI: 10.1101/2023.03.06.531246
Abstract: Wetlands are particularly vulnerable to degradation in urban environments, partially due to the introduction of non-native plants. Invasive weeds in wetlands can replace native plants leading to alterations in habitat composition and vegetation, in turn, animal movements and ultimately population dynamics might be affected. Here we investigate how home range size and movements of western tiger snakes ( Notechis scutatus occidentalis ) differ in wetlands dominated by invasive kikuyu grass ( Cenchrus clandestinus ) compared to wetlands dominated by native vegetation to understand if and how the movement ecology of this top-order predator is altered by vegetation homogenization. To do so, we used Autocorrelated Kernel Density Estimators (AKDE) to estimate home range size, dynamic Brownian Bridge Movement Models to document movement trajectory confidence areas, and compared movement distances using a Bayesian regression model. Home range sizes by tiger snakes were 14.59 ± 9.35 ha smaller in areas dominated by invasive versus native vegetation. Moreover, within-day movement distances tended to be smaller in areas dominated by invasive versus native vegetation (mean ± SD: 9 ± 3 m versus 18 ± 6 m), but there was considerable overlap between the 95% credible intervals between these two groups. Smaller home ranges by tiger snakes in areas dominated by invasive kikuyu grass were likely driven by thermoregulation, with snakes moving vertically between basking locations on top of kikuyu and shelter sites at the base, rather than travelling horizontally along the ground to open basking areas in sites dominated by native vegetation. Additionally, fragmentation of sites dominated by invasive vegetation might have contributed to the comparatively smaller home ranges of snakes there. These findings add to our understanding how changes in habitat composition driven by invasive vegetation can affect animal space use and emphasise the need for further studies to understand how these changes affect population dynamics.
Publisher: Cold Spring Harbor Laboratory
Date: 12-12-2022
DOI: 10.1101/2022.12.07.519536
Abstract: Invasive plants are a threat to natural ecosystems worldwide with urban wetlands being some of the most susceptible and highly modified environments of all. The tiger snake ( Notechis scutatus ) is a top predator that persists in urban wetlands in south-western Australia, many of which have been degraded by introduced kikuyu grass ( Cenchrus clandestinus ). To evaluate the potential impact of kikuyu grass on habitat quality for western tiger snakes we quantified the structural features of habitats within wetlands degraded by kikuyu grass and compared them to wetlands with native vegetation, examined tiger snake prey availability, assessed predation risk for juvenile snakes using clay models, and measured the thermal quality of the vegetation. Proliferation of kikuyu grass reduced habitat structural heterogeneity by reducing available bare ground and increasing vegetation density. This homogenisation of habitat structure had little effect on the predation risk for juveniles or the thermal properties of tiger snake shelter sites however, one key snake prey species, the motorbike frog, had significantly lower abundance in the most impacted habitat. Habitat types with more structural complexity also offered tiger snakes more stable thermal regimes and lower predation risk. These findings indicate that the current extent of kikuyu grass invasion offers overall similar habitat quality for tiger snakes and may contribute to their persistence in urban wetlands, but they, along with their anuran prey, may befit from some increased habitat structural complexity in open areas.
Publisher: Public Library of Science (PLoS)
Date: 29-10-2021
DOI: 10.1371/JOURNAL.PONE.0259124
Abstract: Urbanisation alters landscapes, introduces wildlife to novel stressors, and fragments habitats into remnant ‘islands’. Within these islands, isolated wildlife populations can experience genetic drift and subsequently suffer from inbreeding depression and reduced adaptive potential. The Western tiger snake ( Notechis scutatus occidentalis ) is a predator of wetlands in the Swan Coastal Plain, a unique bioregion that has suffered substantial degradation through the development of the city of Perth, Western Australia. Within the urban matrix, tiger snakes now only persist in a handful of wetlands where they are known to bioaccumulate a suite of contaminants, and have recently been suggested as a relevant bioindicator of ecosystem health. Here, we used genome-wide single nucleotide polymorphism (SNP) data to explore the contemporary population genomics of seven tiger snake populations across the urban matrix. Specifically, we used population genomic structure and ersity, effective population sizes (N e ), and heterozygosity-fitness correlations to assess fitness of each population with respect to urbanisation. We found that population genomic structure was strongest across the northern and southern sides of a major river system, with the northern cluster of populations exhibiting lower heterozygosities than the southern cluster, likely due to a lack of historical gene flow. We also observed an increasing signal of inbreeding and genetic drift with increasing geographic isolation due to urbanisation. Effective population sizes ( N e ) at most sites were small ( 100), with N e appearing to reflect the area of available habitat rather than the degree of adjacent urbanisation. This suggests that ecosystem management and restoration may be the best method to buffer the further loss of genetic ersity in urban wetlands. If tiger snake populations continue to decline in urban areas, our results provide a baseline measure of genomic ersity, as well as highlighting which ‘islands’ of habitat are most in need of management and protection.
Publisher: Cambridge University Press (CUP)
Date: 09-2023
DOI: 10.1017/AEE.2023.24
No related grants have been discovered for Renae Isaacs-Guthridge.