Stephen Beatty

Urbanisation has a wide range of impacts on biological communities, which can affect individual animals' health and may lead to population declines if health effects cause decreases in lifespan or reproductive output. Here, health metrics of the southwestern snake‐necked turtle ( Chelodina oblonga ), a freshwater turtle endemic to and declining in southwestern Western Australia, were compared among populations from three wetlands in the Perth metropolitan area that differ in degree of urbanisation. In November 2023, 7–10 adult turtles were trapped in each of the three wetlands, scaled body condition was calculated, and a blood sample was collected from each individual to quantify blood glucose concentration and immune function, measured as bactericidal capacity, and baseline physiological stress level, measured as heterophil: lymphocyte ratio. There was no association between degree of urbanisation and any of the health metrics measured, suggesting that adult C. oblonga in populations from more natural habitats do not exhibit higher body condition, greater immune functioning or lower baseline physiological stress levels than adults from more disturbed habitats, and that impacts on individuals' health are likely not directly driving the apparent lack of recruitment observed in urban populations of this species. However, El Niño‐induced drought conditions during the sampling period may have placed additional environmental stress on all populations, not just those in more urbanised areas, potentially masking differences in health that may have been detectable in years more reflective of mean climatic conditions. An important next step is to quantify potential seasonal and interannual changes in health metrics across a wider range of populations and hydrological regimes to determine the magnitude to which drought conditions impact physiology in this species, the extent to which physiological plasticity may buffer individuals against negative health impacts, and whether physiological plasticity differs along a broader gradient of anthropogenic disturbance.

Adverse fire regimes threaten biodiversity, potentially leading to population declines and increased extinction risk. Understanding how varying fire regimes affect threatened species is essential for effective ecosystem management, including in Western Australia where diverse ecosystems are exposed to wildfires, Indigenous burning, and prescribed fire. We compiled and synthesised data on the threat of adverse fire regimes to threatened animal taxa in Western Australia. Using a threat classification scheme, we ranked adverse fire regimes as having either no, low, medium, high, or unknown impact on each taxon. A total of 212 taxa were reviewed, 153 (72%) of which are considered fire-threatened: 29 high, 67 medium, 43 low, and 14 unknown impact. This includes 100% of threatened amphibians (3 taxa), 91% of threatened mammals (29), 71% of threatened invertebrates (85), 67% of threatened fish (6), 63% of threatened reptiles (10) and 61% of threatened birds (20). Only some bird (6), mammal (5), and invertebrate (18) taxa received a ranking of ‘high’. Across all fire-threatened taxa, we synthesised 330 fire response cases from 169 studies. Most taxa (75%) are considered fire-threatened due to small ranges and limited dispersal (primarily invertebrates and island taxa), with much smaller numbers reliant on long-unburnt vegetation (>10–40 years; 7%) or habitat features that take decades to form (e.g. tree hollows; 7%). Many taxa should be considered putatively fire-threatened until further information on their fire responses and the nature of fire regimes within their ranges is collected. We identify key research priorities to inform fire management and threatened species conservation.

This data set contains size and/or sex data from 41,021 freshwater turtles from 38 species and 428 populations located in parts of Australia both with and without introduced foxes, as well as populations in the United States of America, which naturally have raccoons (Procyon lotor), foxes, and other nest predators. The goal was to examine population-level body size distributions to establish a baseline for “typical” turtle populations and test whether populations that are exposed to introduced foxes have proportionately fewer juveniles compared to both AU populations that lack introduced foxes and USA populations that are naturally exposed to nest predators. We additionally conducted analyses on the biases of trapping methods, effects of sample size, and effects of water body type. This data set was assembled by pooling the data from numerous researchers.

Anthropogenic climate change is forecast to drive regional climate disruption and instability across the globe. These impacts are likely to be exacerbated within biodiversity hotspots, both due to the greater potential for species loss but also to the possibility that endemic lineages might not have experienced significant climatic variation in the past, limiting their evolutionary potential to respond to rapid climate change. We assessed the role of climatic stability on the accumulation and persistence of lineages in an obligate freshwater fish group endemic to the southwest Western Australia (SWWA) biodiversity hotspot. Using 19,426 genomic (ddRAD-seq) markers and species distribution modelling, we explored the phylogeographic history of western (Nannoperca vittata) and little (Nannoperca pygmaea) pygmy perches, assessing population divergence and phylogenetic relationships, delimiting species and estimating changes in species distributions from the Pliocene to 2100. We identified two deep phylogroups comprising three divergent clusters, which showed no historical connectivity since the Pliocene. We conservatively suggest these represent three isolated species with additional intraspecific structure within one widespread species. All lineages showed long-term patterns of isolation and persistence owing to climatic stability but with significant range contractions likely under future climate change. Our results highlighted the role of climatic stability in allowing the persistence of isolated lineages in the SWWA. This biodiversity hotspot is under compounding threat from ongoing climate change and habitat modification, which may further threaten previously undetected cryptic diversity across the region.

Context
Obtaining a source of genetic data is a key constraint in population genomic research.

Aims
In this study, single-nucleotide polymorphisms (SNPs) were generated from oblong turtle (Chelodina oblonga) cadavers, to ascertain whether decomposed tissue could be used as a source of genetic data and to investigate genetic variation.

Methods
Tissue was opportunistically collected from 47 cadavers following a mass mortality event during April 2024 at Bibra Lake, Western Australia. Genotyping was performed using a Chelodina DArTseq platform, with a high-density assay of 2.5 million sequence reads.

Key results
Genetic diversity and inbreeding were investigated for 39 individual C. oblonga, using 8053 SNPs retained from data filtering. Observed and expected heterozygosities (HO = 0.26, HE = 0.31) for C. oblonga were relatively low compared with other freshwater turtle species within Australia. A high inbreeding coefficient (FIS = 0.17) was also detected, suggesting that inbreeding may threaten C. oblonga population viability at Bibra Lake.

Conclusions
This study highlights the utility of decomposed turtle cadavers as a viable source of DNA.

Implications
Management plans should implement strategies to improve gene flow between Bibra Lake and adjacent populations, such as establishing wildlife corridors to encourage migration between populations.

Context
The south-western corner of Australia is a biodiversity hotspot that includes a freshwater fauna with a high proportion of endemic species. The temperate perches comprise nearly half of the obligate freshwater fishes of the region, representing important components of local ecosystems and are of significant conservation concern.

Aims
Provide a spatially comprehensive molecular genetic assessment of species boundaries and major substructure for all local members of the family to better understand the interplay of ecology and environment across a common landscape.

Methods
Nuclear markers (allozymes) and matrilineal (cytb) datasets were generated to infer genetic groupings and any instances of hybridisation or introgression in relation to the current taxonomy, regional geography and ecological understanding.

Key results
There were contrasting patterns of diversification across genera, with Nannoperca housing four likely species-level splits, Nannatherina having three distinct geographically and ecologically separated subpopulations, and Bostockia comprising several refugial subpopulations that appear partially introgressed. Repeated genetic patterns were identified across particular biogeographic features, most notably the Margaret River and Shannon River.

Conclusions
This study highlighted the value of comparative range-wide molecular studies to inform taxonomy, ecology and conservation planning.

Implications
These analyses pave the way for taxonomic revision, management of key habitat refuges, and other conservation actions.

Turtles are declining globally, and absences of juveniles during surveys are often interpreted as evidence of threats to early life stages. In Australia, for example, it is widely argued that a low number of juveniles is likely due to nest predation by introduced red foxes (Vulpes vulpes). However, small sample sizes within populations, low detectability of juveniles and turtles' long lifespans often confound the conclusion that a paucity of juveniles indicates a declining population. Because turtles have long reproductive lifespans, we might intuitively expect most turtle populations to be heavily weighted towards large individuals, but a ‘typical’ or ‘healthy’ size distribution for turtle populations has not been well established.

Therefore, we collated data on 41,021 freshwater turtles from 38 species and 428 populations located in parts of Australia both with and without introduced foxes, as well as populations in the United States of America, which naturally have raccoons (Procyon lotor), foxes and other nest predators. We examined population-level body size distributions to establish a baseline for ‘typical’ turtle populations and test whether populations that are exposed to introduced foxes have proportionately fewer juveniles compared to both AU populations that lack introduced foxes and USA populations that are naturally exposed to nest predators.

We found that most turtle populations in AU and the United States were heavily skewed towards adults and had few juveniles, regardless of the presence of foxes or other nest predators. There were, however, clear differences among population survey methods: those that target shallow areas (e.g. crawfish traps) tended to capture proportionately more juveniles, and small sample sizes (∼<50) often produced inaccurate representations of size distributions. Additionally, we used a simulation to demonstrate that, given common turtle life history parameters, even stable populations should generally have low proportions of juveniles.

Based on our results, we encourage caution when interpreting turtle size distributions. A small number of juveniles does not inherently suggest that a population is declining due to high egg and/or juvenile mortality, and researchers should pay careful attention to the biases in their methods and strive to capture a minimum of 50–100 turtles before drawing inferences.

Freshwater turtles are crucial to aquatic ecosystems and among the most threatened vertebrates globally. As wetlands are increasingly affected by urbanisation and climate change, translocating turtles may become increasingly common to prevent population declines. Freshwater turtle responses to translocation remain poorly understood. This study examined the movement responses of the southwestern snake‐necked turtle, Chelodina oblonga , following relocation from a wetland slated for urban development. We radio‐tracked 40 of 268 turtles translocated to two wetlands, monitoring them for up to 228 days and analysing movement responses in relation to size, sex and release wetland using generalised linear models. Over half (54%) of the tracked turtles permanently left their release wetlands, and 38% homed back to their original wetland via a 3.2–7.0‐km estuarine river and a steep, ~15‐m high terrestrial bank. Movement out of the release wetlands was unrelated to turtle size or sex but significantly influenced by release wetland. Homing probability was not affected by size, sex or release wetland. Turtles were more likely to leave the release wetland closer to the source, possibly due to its smaller size or drying conditions. Release wetland significantly influenced the timing of both 'any' and 'homing' movements. Sex affected the timing of both movement types, while size influenced only 'any' movement timing. The study highlights that the characteristics of translocation sites are important in retaining translocated turtles. The study adds to the limited understanding of the movement responses of translocated freshwater turtles and has direct implications for the design of translocation programs.

Freshwater mussels are keystone species in freshwater streams, providing important ecosystem services, including biofiltration. While most research has focussed on Unionidae mussels in northern hemisphere perennial rivers, far less is known about the biofiltration capacities of Hyriidae mussels, which are prevalent in intermittent rivers in arid and semi-arid regions of the southern hemisphere. This study examined biofiltration of the imperilled Australian hyriid, Westralunio carteri . We estimated biofiltration capacity by measuring reduction in algal concentration across three temperatures (15, 20 and 25 ºC) under laboratory conditions. We then validated these laboratory results with field experiments using natural seston. Westralunio carteri exhibited a mean clearance rate of 177.5 (95% CI 125.4–229.7) mL/g dry tissue/hour in the laboratory and 210.9 (95% CI 171.6–250.2) mL/g dry tissue/hour in the field. Clearance rate increased with temperature, with maximum rates recorded at 25 ºC, and smaller mussels had higher mass-specific clearance rates. Clearance rate estimates aligned with rates in other hyriid mussels. Given its biofiltration capabilities, W. carteri may aid in maintaining water quality in intermittently flowing rivers of south-western Australia, where decreasing streamflow due to climate change is increasing the duration of drying in smaller, warmer and increasingly isolated refuge pools.