Invasive wild deer exhibit environmental niche shifts in Australia: Where to from here?

Invasive species have established populations around the world and, in the process, characteristics of their realized environmental niches have changed. Because of their popularity as a source of game, deer have been introduced to, and become invasive in, many different environments around the world. As such, deer should provide a good model system in which to test environmental niche shifts. Using the current distributions of the six deer species present in Australia, we quantified shifts in their environmental niches that occurred since introduction; we determined the differences in suitable habitat between their international (native and invaded) and their Australian ranges. Given knowledge of their Australian habitat use, we then modeled the present distribution of deer in Australia to assess habitat suitability, in an attempt to predict future deer distributions. We show that the Australian niches of hog (Axis porcinus), fallow (Dama dama), red (Cervus elaphus), rusa (C. timorensis), and sambar deer (C. unicolor), but not chital deer (A. axis), were different to their international ranges. When we quantified the potential range of these six species in Australia, chital, hog, and rusa deer had the largest areas of suitable habitat outside their presently occupied habitat. The other three species had already expanded outside the ranges that we predicted as suitable. Here, we demonstrate that deer have undergone significant environmental niche shifts following introduction into Australia, and these shifts are important for predicting the future spread of these invasive species. It is important to note that current Australian and international environmental niches did not necessarily predict range expansions, thus wildlife managers should treat these analyses as conservative estimates.

How to prioritize species recovery after a megafire.

Due to climate change, megafires are increasingly common and have sudden, extensive impacts on many species over vast areas, leaving decision makers uncertain about how best to prioritize recovery. We devised a decision-support framework to prioritize conservation actions to improve species outcomes immediately after a megafire. Complementary locations are selected to extend recovery actions across all fire-affected species' habitats. We applied our method to areas burned in the 2019-2020 Australian megafires and assessed its conservation advantages by comparing our results with outcomes of a site-richness approach (i.e., identifying areas that cost-effectively recover the most species in any one location). We found that 290 threatened species were likely severely affected and will require immediate conservation action to prevent population declines and possible extirpation. We identified 179 subregions, mostly in southeastern Australia, that are key locations to extend actions that benefit multiple species. Cost savings were over AU$300 million to reduce 95% of threats across all species. Our complementarity-based prioritization also spread postfire management actions across a wider proportion of the study area compared with the site-richness method (43% vs. 37% of the landscape managed, respectively) and put more of each species' range under management (average 90% vs. 79% of every species' habitat managed). In addition to wildfire response, our framework can be used to prioritize conservation actions that will best mitigate threats affecting species following other extreme environmental events (e.g., floods and drought).

Debido al cambio climático, los mega incendios son cada vez más comunes y tienen un impacto repentino y extenso sobre muchas especies en inmensas superficies, lo que deja a los tomadores de decisiones con incertidumbre sobre cuál es la mejor manera de priorizar la recuperación. Diseñamos un marco de apoyo a las decisiones para priorizar las acciones de conservación para mejorar los resultados para las especies inmediatamente después de un mega incendio. Para esto, se seleccionan localidades complementarias para extender las acciones de recuperación por todos los hábitats de las especies afectadas por el incendio. Aplicamos nuestro método a las áreas afectadas por los mega incendios de 2019-2020 en Australia y analizamos las ventajas de conservación del método mediante la comparación entre nuestros resultados y aquellos de un enfoque en la riqueza de especies (es decir, la identificación de las áreas que recuperan de manera rentable la mayor cantidad de especies en cualquier localidad única). Encontramos que 290 especies amenazadas estuvieron probablemente afectadas de manera severa y requerirán acciones inmediatas de conservación para prevenir la declinación poblacional y la posible eliminación. Identificamos 179 subregiones, la mayoría en el sureste de Australia, que son localidades clave para extender las acciones que benefician a muchas especies. El ahorro en los gastos fue de más de AU$300 millones para reducir el 95% de las amenazas para todas las especies. Nuestra priorización basada en la complementariedad también extendió las acciones de manejo posterior al incendio a una mayor proporción del área de estudio en comparación con el método de riqueza de especies (43% versus 37% del paisaje gestionado, respectivamente) y colocó más de la distribución de cada especie bajo manejo (en promedio 90% versus 79% del hábitat manejado de cada especie). Además de la respuesta a los incendios, nuestro marco puede usarse para priorizar las acciones de conservación que mitiguen de mejor manera las amenazas que afectan a las especies después de otros eventos ambientales extremos (p. ej., inundaciones y sequía).

Addressing the global snakebite crisis with geo-spatial analyses - Recent advances and future direction.

Venomous snakebite is a neglected tropical disease that annually leads to hundreds of thousands of deaths or long-term physical and mental ailments across the developing world. Insufficient data on spatial variation in snakebite risk, incidence, human vulnerability, and accessibility of medical treatment contribute substantially to ineffective on-ground management. There is an urgent need to collect data, fill knowledge gaps and address on-ground management problems. The use of novel, and transdisciplinary approaches that take advantage of recent advances in spatio-temporal models, 'big data', high performance computing, and fine-scale spatial information can add value to snakebite management by strategically improving our understanding and mitigation capacity of snakebite. We review the background and recent advances on the topic of snakebite related geospatial analyses and suggest avenues for priority research that will have practical on-ground applications for snakebite management and mitigation. These include streamlined, targeted data collection on snake distributions, snakebites, envenomings, venom composition, health infrastructure, and antivenom accessibility along with fine-scale models of spatio-temporal variation in snakebite risk and incidence, intraspecific venom variation, and environmental change modifying human exposure. These measures could improve and 'future-proof' antivenom production methods, antivenom distribution and stockpiling systems, and human-wildlife conflict management practices, while simultaneously feeding into research on venom evolution, snake taxonomy, ecology, biogeography, and conservation.

Hydroregulation in a tropical dry-skinned ectotherm.

While temperature effects on species' vulnerability to climate change are well studied, desiccation effects receive comparatively little attention. In addition, we poorly understand the capacity of ectotherms, and especially reptiles, to control water loss rates behaviourally by selecting suitable microhabitats. This study examined water loss rates and behavioural hydroregulation in the tropical rainforest skink Carlia rubrigularis to assess whether this dry-skinned ectotherm actively avoids desiccation and whether trade-offs occur between desiccation avoidance and selection of optimal temperatures, as previously shown in amphibians. Higher temperatures elicited humid refuge choice despite placing individuals in suboptimal thermal conditions, as indicated by preferred substrate temperatures. This finding emphasizes the importance of water loss even for taxa traditionally assumed to be highly desiccation resistant, and highlights this factor's potential influence on vulnerability to climate change by limiting activity times or by restricting individuals to thermally suboptimal microhabitats.

Extensive Acclimation in Ectotherms Conceals Interspecific Variation in Thermal Tolerance Limits.

Species' tolerance limits determine their capacity to tolerate climatic extremes and limit their potential distributions. Interspecific variation in thermal tolerances is often proposed to indicate climatic vulnerability and is, therefore, the subject of many recent meta-studies on differential capacities of species from climatically different habitats to deal with climate change. Most studies on thermal tolerances do not acclimate animals or use inconsistent, and insufficient, acclimation times, limiting our knowledge of the shape, duration and extent of acclimation responses. Consequently patterns in thermal tolerances observed in meta-analyses, based on data from the literature are based on inconsistent, partial acclimation and true trends may be obscured. In this study we describe time-course of complete acclimation of critical thermal minima in the tropical ectotherm Carlia longipes and compare it to the average acclimation response of other reptiles, estimated from published data, to assess how much acclimation time may contribute to observed differences in thermal limits. Carlia longipes decreased their lower critical thermal limits by 2.4°C and completed 95% of acclimation in 17 weeks. Wild populations did not mirror this acclimation process over the winter. Other reptiles appear to decrease cold tolerance more quickly (95% in 7 weeks) and to a greater extent, with an estimated average acclimation response of 6.1°C. However, without data on tolerances after longer acclimation times available, our capacity to estimate final acclimation state is very limited. Based on the subset of data available for meta-analysis, much of the variation in cold tolerance observed in the literature can be attributed to acclimation time. Our results indicate that (i) acclimation responses can be slow and substantial, even in tropical species, and (ii) interspecific differences in acclimation speed and extent may obscure trends assessed in some meta-studies. Cold tolerances of wild animals are representative of cumulative responses to recent environments, while lengthy acclimation is necessary for controlled comparisons of physiological tolerances. Measures of inconsistent, intermediate acclimation states, as reported by many studies, represent neither the realised nor the potential tolerance in that population, are very likely underestimates of species' physiological capacities and may consequently be of limited value.

Venom physiology and composition in a litter of Common Death Adders (Acanthophis antarcticus) and their parents.

Metabolic expenditure has been shown to increase abruptly in several snake species directly after venom expenditure, while the later stages of venom replenishment seem to involve minor costs. This study examines the dependence of increases in metabolic rate following venom expenditure on the stage of venom replenishment that the venom producing tissue is in at the time of venom extraction in the Common Death Adder, Acanthophis antarcticus. Potential changes in venom composition during venom replenishment are also explored to elucidate whether replenishment is achieved via low rates of synthesis of all venom components or by non-parallel protein production, i.e. initial production of some venom components and subsequent synthesis of others. The results of this study indicate that venom expenditure is followed by a sudden increase in metabolic rate when snakes have previously not expended venom for at least two days, suggesting that repetitive venom expenditure does not further increase the activity of venom gland tissue in this initial time period but that a second upregulation occurs when the tissue is past the initial activation stage. In addition, venom composition appears to remain constant during replenishment within an individual, while substantial variations can be observed even between siblings.

Costs of venom production in the common death adder (Acanthophis antarcticus).

The utilization of venom in predatory and defensive contexts is associated with benefits regarding minimization of energetic expenditure on hunting, maximization of success in prey acquisition and avoidance of injury from dangerous prey and aggressors. Multiple characteristics suggest that venom is quite expensive to produce, thereby creating a tradeoff between advantages and disadvantages associated with its possession. The metabolic costs of venom production have rarely been studied and no information on the detailed metabolic processes during venom replenishment exists. Where costs of venom production have been studied they are often not in context with other components of the energy budget of the study organism. Using flow-through respirometry, we examined changes in metabolic rate in the Australian elapid Acanthophis antarcticus after venom expenditure and feeding as well as during preparation for shedding to establish a comparison of the magnitude of energetic expenditure during venom replenishment and other common physiological processes. We also defined the temporal pattern of metabolic processes during venom replenishment at a higher resolution than has previously been attempted in snakes. Our results suggest that total costs of venom replenishment are relatively small when compared to costs of digestion and shedding. We conclude that, in spite of the manifold factors suggesting a high cost of venom in snakes, its production is less energetically costly than often assumed. Until further research can clarify the reasons for this more caution should therefore be applied when assuming that costs of venom production exert strong selection pressures on the ecology, behavior and evolution of venomous taxa.