Population Extinction Risk Research Articles

Genetic load and extinction in peripheral populations: the roles of migration, drift and demographic stochasticity

We analyse how migration from a large mainland influences genetic load and population numbers on an island, in a scenario where fitness-affecting variants are unconditionally deleterious, and where numbers decline with increasing load. Our analysis shows that migration can have qualitatively different effects, depending on the total mutation target and fitness effects of deleterious variants. In particular, we find that populations exhibit a genetic Allee effect across a wide range of parameter combinations, when variants are partially recessive, cycling between low-load (large-population) and high-load (sink) states. Increased migration reduces load in the sink state (by increasing heterozygosity) but further inflates load in the large-population state (by hindering purging). We identify various critical parameter thresholds at which one or other stable state collapses, and discuss how these thresholds are influenced by the genetic versus demographic effects of migration. Our analysis is based on a ‘semi-deterministic’ analysis, which accounts for genetic drift but neglects demographic stochasticity. We also compare against simulations which account for both demographic stochasticity and drift. Our results clarify the importance of gene flow as a key determinant of extinction risk in peripheral populations, even in the absence of ecological gradients.This article is part of the theme issue ‘Species’ ranges in the face of changing environments (part I)’.

Impact of the strong Allee effect in a predator-prey model

<abstract><p>In this work, we propose and investigate a new predator-prey model with strong Allee effect in prey and Holling type Ⅱ functional response in predator. By performing a comprehensive dynamical analysis, we first derive the existence and stability of all the possible equilibria of the system and the system undergoes two transcritical bifurcations and one Hopf-bifurcation. Next, we have calculated the first Lyapunov coefficient and find the Hopf-bifurcation in this model is supercritical and a stable limit cycle is born. Then, by comparing the properties of the system with and without Allee effect, we show that the strong Allee effect is of great importance to the dynamics. It can drive the system to instability. Specifically, Allee effect can increase the extinction risk of populations and has the ability to switch the system's stability to limit cycle oscillation from stable node. Moreover, numerical simulations are presented to prove the validity of our findings.</p></abstract>

Increasing temperature weakens the positive effect of genetic diversity on population growth.

Genetic diversity and temperature increases associated with global climate change are known to independently influence population growth and extinction risk. Whether increasing temperature may influence the effect of genetic diversity on population growth, however, is not known. We address this issue in the model protist system Tetrahymena thermophila. We test the hypothesis that at temperatures closer to the species’ thermal optimum (i.e., the temperature at which population growth is maximal, or T opt), genetic diversity should have a weaker effect on population growth compared to temperatures away from the thermal optimum. To do so, we grew populations of T. thermophila with varying levels of genetic diversity at increasingly warmer temperatures and quantified their intrinsic population growth rate, r. We found that genetic diversity increases population growth at cooler temperatures, but that as temperature increases, this effect weakens. We also show that a combination of changes in the amount of expressed genetic diversity (G) in r, plastic changes in population growth across temperatures (E), and strong G × E interactions underlie this temperature effect. Our results uncover important but largely overlooked temperature effects that have implications for the management of small populations with depauperate genetic stocks in an increasingly warming world.

The hidden side of the Allee effect: correlated demographic traits and extinction risk in experimental populations

Because Allee effects have major impacts on the dynamics of small populations, they are routinely included in demographic models for the evaluation of extinction risks. However, the structure of most common models implies that other demographic parameters (like the maximum growth rate) are modified by the inclusion of an Allee effect, which also affects in return the extinction risk of the population. Whether such correlations between demographic traits occur in natural populations or merely reflect a practical constraint related to model formalism is of primary importance to understand better the dynamics of small populations. We investigated this question using 20 populations of Trichogramma wasps raised under similar conditions, of which 3 were subject to an Allee effect. We showed that these 3 populations were also characterized by lower maximum growth rate and lower carrying capacity, and that their extinction probability was higher than for non-Allee populations. These results provide the first empirical demonstration of a correlation between the presence of positive density-dependence and impaired demographic performance, which increases the extinction risk of population, especially during the establishment phase.

Life-history strategy and extinction risk in the warm desert perennial spring ephemeral Astragalus holmgreniorum (Fabaceae).

This study of Astragalus holmgreniorum examines its adaptations to the warm desert environment and whether these adaptations will enable it to persist. Its spring ephemeral hemicryptophyte life‐history strategy is unusual in warm deserts. We used data from a 22‐year demographic study supplemented with reproductive output, seed bank, and germinant survival studies to examine the population dynamics of this species using discrete‐time stochastic matrix modeling. The model showed that A. holmgreniorum is likely to persist in the warm desert in spite of high dormant‐season mortality. It relies on a stochastically varying environment with high inter‐annual variation in precipitation for persistence, but without a long‐lived seed bank, environmental stochasticity confers no advantage. Episodic high reproductive output and frequent seedling recruitment along with a persistent seed bank are adaptations that facilitate its survival. These adaptations place its life‐history strategy further along the spectrum from “slower” to “faster” relative to other perennial spring ephemerals. The extinction risk for small populations is relatively high even though mean λ s > 1 because of the high variance in year quality. This risk is also strongly dependent on seed bank starting values, creating a moving window of extinction risk that varies with population size through time. Astragalus holmgreniorum life‐history strategy combines the perennial spring ephemeral life form with features more characteristic of desert annuals. These adaptations permit persistence in the warm desert environment. A promising conclusion is that new populations of this endangered species can likely be established through direct seeding.

A multiscale analysis of landscape resistance reveals genetic isolates in an endangered forest-specialist species the Barbary macaque (Macaca sylvanus)

In forest-specialist mammals, forest loss may induce resistance to animal movement and reduce gene flow between populations, and thereby increase genetic erosion and extinction risks for populations. Understanding how landscape features affect gene flow is of critical importance for conservation. Using landscape genetic tools at multiple spatial scales, we assessed the effects of landscape heterogeneity (in particular the presence of wide open or rural habitats) on gene flow in an endangered forest-specialist species – the Barbary macaque (Macaca sylvanus) –, in its major forest site in Morocco. We genotyped 248 individuals from 23 macaque groups using 11 microsatellite loci. We modelled different scenarios of isolation by landscape resistance. We further tested the relationships between genetic distance and isolation by resistance, after controlling for the effect of isolation by distance. Our results revealed a significant genetic structure and a disruption of gene flow even in geographic proximity. Whatever the spatial scale, remoteness from the forest edge beyond 1 km acted as a barrier to macaque movements. In addition, at a fine scale, human-dominated areas were also detected as a barrier. The detection of private alleles in each population suggests an ongoing process of isolation. The preservation of the Barbary macaque implies 1) strictly avoiding all silvicultural practices (in particular clear-cutting of holm oak forests) that could contribute to increase distances between forest patches, 2) restoring corridors between forests, 3) and preserving key small forest patches as potential stepping stones facilitating macaque dispersal.

Applying Population Viability Analysis to Inform Genetic Rescue That Preserves Locally Unique Genetic Variation in a Critically Endangered Mammal

Genetic rescue can reduce the extinction risk of inbred populations, but it has the poorly understood risk of ‘genetic swamping’—the replacement of the distinctive variation of the target population. We applied population viability analysis (PVA) to identify translocation rates into the inbred lowland population of Leadbeater’s possum from an outbred highland population that would alleviate inbreeding depression and rapidly reach a target population size (N) while maximising the retention of locally unique neutral genetic variation. Using genomic kinship coefficients to model inbreeding in Vortex, we simulated genetic rescue scenarios that included gene pool mixing with genetically diverse highland possums and increased the N from 35 to 110 within ten years. The PVA predicted that the last remaining population of lowland Leadbeater’s possum will be extinct within 23 years without genetic rescue, and that the carrying capacity at its current range is insufficient to enable recovery, even with genetic rescue. Supplementation rates that rapidly increased population size resulted in higher retention (as opposed to complete loss) of local alleles through alleviation of genetic drift but reduced the frequency of locally unique alleles. Ongoing gene flow and a higher N will facilitate natural selection. Accordingly, we recommend founding a new population of lowland possums in a high-quality habitat, where population growth and natural gene exchange with highland populations are possible. We also recommend ensuring gene flow into the population through natural dispersal and/or frequent translocations of highland individuals. Genetic rescue should be implemented within an adaptive management framework, with post-translocation monitoring data incorporated into the models to make updated predictions.

Impacts of run‐of‐river hydropower on coho salmon (Oncorhynchus kisutch): the role of density‐dependent survival

AbstractPredicting whether anthropogenic sources of mortality have negative consequences at the level of population dynamics is challenged by mechanisms like density‐dependent survival that can amplify or offset the loss of individuals from anthropogenic disturbances. Run‐of‐river (RoR) hydropower is a growing industry that can cause frequent mortality of salmonid fry through rapid reductions in streamflow, leading to stranding on dewatered shores. However, whether individual‐level impacts reduce population growth rates or increase local extinction risk is difficult to predict. We used a stochastic stage‐structured matrix model to evaluate how the timing and magnitude of anthropogenic flow fluctuations impacted population abundance and extinction risk of coho salmon (Oncorhynchus kisutch), which spend up to 1.5 yr in many streams regulated by RoR hydropower. We additionally assessed how the timing (spring, winter) and strength (weak, moderate, high) of natural density‐dependent bottlenecks experienced by salmon in freshwaters tempers or amplifies the potential for RoR‐induced mortality to scale to emergent population dynamics. We compared population sizes and the 45‐yr probability of quasi‐extinction under 12 scenarios that varied the frequency (0–20 events per year) and magnitude (1–10% mortality per event) of RoR‐induced flow fluctuations, as well as the timing and strength of density‐dependent bottlenecks occurring during the first year in freshwater. We found that even mild flow fluctuations by RoR hydropower can impact coho salmon population dynamics, especially if density dependence is weak or occurs early in freshwater residency (spring). When density dependence was strong and during winter, the potential for population‐level impact was lessened, but populations still declined by 13–42% when RoR‐induced mortality was severe (5–10%) or frequent (10–20 events/yr). We conclude that strong density‐dependent survival bottlenecks could partially mitigate the loss of fry from anthropogenic flow fluctuations, especially if bottlenecks occur late in freshwater residency, but not for all intensities of flow fluctuations. Even with strong density dependence in winter, our models predict declining populations by up to 70% under strong and very frequent flow fluctuations, which should serve to caution those tasked with regulating flows in streams affected by RoR hydropower.

In-stream habitat availability for river dolphins in response to flow: Use of ecological integrity to manage river flows.

Population decline and extinction risk of river dolphins are primarily associated with flow alteration. Previous studies predominantly highlighted maintenance of adequate flow for low water seasons when habitats contract and the risk of local extinction escalates. Although river dolphins are sensitive to reduction in river flow, no studies quantify the relationships between flow and ecology of river dolphins to mitigate the potential adverse impacts of flow alteration. We quantify the relationships between flow and the ecology of river cetaceans concerning Ganges River dolphins (GRD; Platanista gangetica gangetica) usable area availability (AWS) for the low water season at wider flows (50-575 m3/s) at finer spatial and temporal scales. This study reveals that distribution of area usable to GRD is highly regulated by the adequate flow and river attributes (velocity and depth) interactions that likely offer energetically efficient modes of locomotion to GRD, suggesting the hydro-physical environment as a major determinant of river dolphin distribution and abundance. Flow and AWS relationships indicate that the flow during the dry season negatively contributed to AWS, whereas that of pre-monsoon maximized the AWS, suggesting that modifying flow regimes does alter in-stream habitats at varying spatial scales and may influence life-history strategies. Substantial fragmentation in suitable pool availability and loss of longitudinal connectivity exhibited by dry season flow suggested a higher risk of adverse biological effects during the dry season, which may reduce population viability by reducing survivorship and reproduction failure. Owing to river dolphins' dependence on the attribute of freshwater flow, they can be expected to be more affected by flow regulations as interactive effects. Considering the seasonal effects and changes in the availability of usable areas by flow alteration, adopting effective habitat retention plans by water-based development projects appears critical to avoid further ecological risks in aquatic species conservation. Identifying priority riverscapes for river cetaceans and prioritizing investment opportunities is an essential first step towards effective riverine cetacean conservation.

Classification of Urban Regeneration Activation Areas by the Levels of the Population Extinction Risk : A Case Study of Gyeongsangbuk-do

Classification of Urban Regeneration Activation Areas by the Levels of the Population Extinction Risk : A Case Study of Gyeongsangbuk-do

Is Evolution in Response to Extreme Events Good for Population Persistence?

AbstractClimate change is predicted to increase the severity of environmental perturbations, including storms and droughts, which act as strong selective agents. These extreme events are often of finite duration (pulse disturbances). Hence, while evolution during an extreme event may be adaptive, the resulting phenotypic changes may become maladaptive when the event ends. Using individual-based models and analytic approximations that fuse quantitative genetics and demography, we explore how heritability and phenotypic variance affect population size and extinction risk in finite populations under an extreme event of fixed duration. Since more evolution leads to greater maladaptation and slower population recovery following an extreme event, greater heritability can increase extinction risk when the extreme event is short. Alternatively, when an extreme event is sufficiently long, heritability often helps a population persist. We also find that when events are severe, the buffering effect of phenotypic variance can outweigh the increased load it causes.

Very high extinction risk for Welwitschia mirabilis in the northern Namib Desert

One of the most recognizable icons of the Namib Desert is the endemic gymnosperm Welwitschia mirabilis. Recent studies indicated that climate change may seriously affect populations in the northern Namibia subrange (Kunene region), but their extinction risk has not yet been assessed. In this study, we apply IUCN criteria to define the extinction risk of welwitschia populations in northern Namibia and assign them to a red list category. We collected field data to estimate relevant parameters for this assessment. We observed 1330 plants clustered in 12 small and isolated stands. The extent of occurrence has a surface area of 214.2 km2 (i.e., <5000 km2) and the area of occupancy a surface area of 56.0 km2 (i.e. < 500 km2). The quality of habitat is expected to face a reduction of 69.47% (i.e., >50%) as a consequence of climate change predicted in the area. These data indicate a very high extinction risk for welwitschia in northern Kunene, hence, we classify these populations as endangered (EN) according to IUCN criteria. Similar assessments for other subranges are prevented by the lack of relevant data, an issue that deserves further research attention. Our results advocate the necessity of a management plan for the species, including measures for mitigating the impact of climate change on isolated populations across its fragmented range.

The inflated significance of neutral genetic diversity in conservation genetics.

The current rate of species extinction is rapidly approaching unprecedented highs, and life on Earth presently faces a sixth mass extinction event driven by anthropogenic activity, climate change, and ecological collapse. The field of conservation genetics aims at preserving species by using their levels of genetic diversity, usually measured as neutral genome-wide diversity, as a barometer for evaluating population health and extinction risk. A fundamental assumption is that higher levels of genetic diversity lead to an increase in fitness and long-term survival of a species. Here, we argue against the perceived importance of neutral genetic diversity for the conservation of wild populations and species. We demonstrate that no simple general relationship exists between neutral genetic diversity and the risk of species extinction. Instead, a better understanding of the properties of functional genetic diversity, demographic history, and ecological relationships is necessary for developing and implementing effective conservation genetic strategies.

Reducing the Extinction Risk of Populations Threatened by Infectious Diseases

Extinction risk is increasing for a range of species due to a variety of threats, including disease. Emerging infectious diseases can cause severe declines in wild animal populations, increasing population fragmentation and reducing gene flow. Small, isolated, host populations may lose adaptive potential and become more susceptible to extinction due to other threats. Management of the genetic consequences of disease-induced population decline is often necessary. Whilst disease threats need to be addressed, they can be difficult to mitigate. Actions implemented to conserve the Tasmanian devil (Sarcophilus harrisii), which has suffered decline to the deadly devil facial tumour disease (DFTD), exemplify how genetic management can be used to reduce extinction risk in populations threatened by disease. Supplementation is an emerging conservation technique that may benefit populations threatened by disease by enabling gene flow and conserving their adaptive potential through genetic restoration. Other candidate species may benefit from genetic management via supplementation but concerns regarding outbreeding depression may prevent widespread incorporation of this technique into wildlife disease management. However, existing knowledge can be used to identify populations that would benefit from supplementation where risk of outbreeding depression is low. For populations threatened by disease and, in situations where disease eradication is not an option, wildlife managers should consider genetic management to buffer the host species against inbreeding and loss of genetic diversity.

Corridors as a tool for linking habitats – Shortcomings and perspectives for plant conservation

Habitat fragmentation and isolation are considered important causes of biodiversity loss in cultural landscapes. To counter the negative effects of fragmentation such as reduced connectivity and increased risks of population extinction due to stochastic processes and genetic erosion, it has been proposed to establish linear ecological corridors to facilitate dispersal between isolated habitat patches. We summarise the current knowledge on the potential benefits and limitations of corridors for reducing the negative effects of habitat fragmentation on plant populations. We address the opportunities and problems that are associated with linear corridors and advocate the use of semi-open corridors as an alternative that might overcome some shortcomings of conventional corridors for plants. Observational and experimental studies have found that various types of linear corridors can increase plant dispersal. Other linear structures such as paths, roads, railways and streams may also function to a certain extent as corridors, although mostly for widespread species. Because plants are highly dependent on external agents such as animals or wind to reach new habitats, the effectivity of corridors is strongly influenced by their structural features and suitability for animal dispersers. However, many plant species can only use corridors for long-distance dispersal if they can also use them as stepping stone habitats where they can establish, grow, reproduce and then disperse further. This dispersal critically depends on suitable light conditions and disturbance regimes, and on a sufficient width of a corridor to reduce edge effects. Thus, hedgerows appear to be suitable corridors for some forest species but are too narrow for forest specialists from the interior of woodlands. Corridors do not only have positive effects but may also facilitate the spread of invasive species. Moreover, a potentially underestimated negative effect of linear corridors is that they may actually create new dispersal barriers when they intersect other habitats. For example, linear woodland corridors that intersect grasslands may successfully connect patches of woodland but simultaneously form strong barriers for grassland species and increase the fragmentation of their populations. As an alternative to linear corridors, we recommend “semi-open corridors” that simultaneously connect patches of both open habitats and woodlands and promote the dispersal of species of both types of habitat. This idea is based on the various types of semi-open landscapes in Europe that have been formed by grazing with livestock, resulting in a mosaic of open habitats, groups of trees or shrubs and small woodland patches, and are characterised by a high diversity of environmental conditions on a small scale. Wide corridors of such semi-open habitats may avoid the strong edge and barrier effects associated with linear corridors and provide suitable stepping stone habitats for species with different habitat requirements.

Morphometric Assessment of Golden Mahseer Populations in the Ganga River Basin, India

River fragmentation has adverse effects on fish populations due to restricted migratory pattern, resulting in risk of population extinction. It has been hypothesized that river fragmentation has led to changes in fish population structure. To test the hypothesis, 149 Golden Mahseer Tor putitora were collected from seven locations, including the Ganga River and upstream and downstream of two impounded headwater tributaries: the Bhagirathi and the Alaknanda rivers. Landmark–based “Truss” and “Geometric” morphometric differentiation was investigated to determine if variations in Golden Mahseer populations exist due to river impoundments. Truss network modeling yielded 90 size–corrected distance variables from 14 landmarks, following which analysis of variance (ANOVA), principal component analysis (PCA) and discriminant function analysis (DFA) were performed. Geometric morphometric modeling included relative warps, PCA, and canonical variate analysis (CVA). Both DFA and CVA plot illustrated overlapping, with DFA suggesting low percentage of classification between populations. Mahalanobis and Procrustes distances extracted from CVA were non‐significant (P &gt; 0.001) among populations. Results indicated the existence of single homogenous population of Golden Mahseer in the Ganga River. This study provides a basis for stock identification useful in developing a suitable plan towards conservation and restoration of Golden Mahseer populations in the fragmented Ganga River.

Bridging gaps in demographic analysis with phylogenetic imputation.

Phylogenetically informed imputation methods have rarely been applied to estimate missing values in demographic data but may be a powerful tool for reconstructing vital rates of survival, maturation, and fecundity for species of conservation concern. Imputed vital rates could be used to parameterize demographic models to explore how populations respond when vital rates are perturbed. We used standardized vital rate estimates for 50 bird species to assess the use of phylogenetic imputation to fill gaps in demographic data. We calculated imputation accuracy for vital rates of focal species excluded from the data set either singly or in combination and with and without phylogeny, body mass, and life-history trait data. We used imputed vital rates to calculate demographic metrics, including generation time, to validate the use of imputation in demographic analyses. Covariance among vital rates and other trait data provided a strong basis to guide imputation of missing vital rates in birds, even in the absence of phylogenetic information. Mean NRMSE for null and phylogenetic models differed by <0.01 except when no vital rates were available or for vital rates with high phylogenetic signal (Pagel's λ > 0.8). In these cases, including body mass and life-history trait data compensated for lack of phylogenetic information: mean normalized root mean square error (NRMSE) for null and phylogenetic models differed by <0.01 for adult survival and <0.04 for maturation rate. Estimates of demographic metrics were sensitive to the accuracy of imputed vital rates. For example, mean error in generation time doubled in response to inaccurate estimates of maturation time. Accurate demographic data and metrics, such as generation time, are needed to inform conservation planning processes, for example through International Union for Conservation of Nature Red List assessments and population viability analysis. Imputed vital rates could be useful in this context but, as for any estimated model parameters, awareness of the sensitivities of demographic model outputs to the imputed vital rates is essential.

Population ecology and conservation status of Parodia carambeiensis (Cactaceae)

Abstract Parodia carambeiensis is a rupicolous, small-sized species, with globose cladode and showy flowers, and is the only endemic Cactaceae species in Paraná State (Brazil). Changes in natural landscapes and fragmentation isolate populations, increasing their vulnerability to local extinctions. Our aim was to verify the spatial distribution of P. carambeiensis, reviewing its conservation status and main threats in the distribution area. Expeditions were carried out in the Campos Gerais region to record the abundance, density and spatial distribution of P. carambeiensis populations. Local landscape and climatic variables as well as the joint effect of these with geographical distance, were analyzed. Our findings highlighted that population density differs among the studied sites and was driven by distinct levels of anthropic threats such as livestock, tourism, wildfires and their proximity to highways, along with the climatic variables evaluated (temperature range and precipitation). The models jointly explained 56% of the variation in the population density, which was mostly influence by climatic factors. Parodia carambeiensis is currently classified as (LC) least concern, however, our results provide strong evidence in favor of updating its status to (EN) endangered due to the elevated extinction risk of natural populations.

生境破碎对古尔班通古特沙漠南缘骆驼刺种群生物学特性的影响

在破碎化生境中，植物种群的生物学特性直接反映植物对环境的响应特征和适应对策，探讨不同破碎化程度生境中植株的大小、密度、结实率、种子大小、种子质量以及萌发特性等，对深入了解植物在不同生境中的生存和繁殖状况有重要的指导意义。对古尔班通古特沙漠南缘9个斑块化骆驼刺种群的形态特征和繁殖生物学参数进行了连续2年的调查研究，研究结果表明：随着生境破碎化程度的加剧，骆驼刺的株高、冠幅、密度、结实率、种子大小、种子质量以及萌发率等均显著下降（P < 0.05）。生境破碎不仅强烈抑制了骆驼刺植株的营养生长，使其生长矮小，个体分布稀疏，而且严重阻碍了骆驼刺的繁殖成功和种群更新，增加了种群衰退甚至灭绝的风险。;In the fragmented habitats, the biological characteristics of plant populations directly reflect the plant's response and adaptation to the environment. Researches on the size, density, seed setting rate, seed size, seed quality, and seed germination characteristics of plants in different fragmented habitats have important guiding significance for in-depth understanding of plants' survival and reproduction strategies. In this study, the morphological characteristics and reproductive parameters of Alhagi sparsifolia populations in nine patches at the southern margin of the Gurbantunggut Desert were investigated in 2018 and 2019. The results showed that with the increase of the degree of habitat fragmentation, the height, crown width, density, seed setting rate, seed size, seed quality, and seed germination rate of A. sparsifolia decreased significantly. The habitat fragmentation not only significantly inhibited the vegetative growth of A. sparsifolia, but also led to the sparsely distribution that seriously hindered its reproduction and population regeneration, increasing the risks of population depression and extinction.

Modelling the impact of canker disease and fire regimes on the population dynamics and extinction risk of the Critically Endangered and granite endemic shrub

Landscape-level processes such as fire regimes, increasing disease prevalence and a drying climate are emerging threats affecting plant groups such as the Proteaceae. Using field derived empirical data and a population simulation model we investigated population-level impacts of canker diseases and contemporary fire regimes on the threatened shrub and granite outcrop endemic Banksia verticillata R.Br. We found the persistence of B. verticillata on granite inselbergs is strongly influenced by fire frequency and extent, as well as the prevalence of canker disease. For populations where canker is present but having a relatively lower impact none of the fire scenarios resulted in extinction over the 100-year simulation, but all scenarios resulted in population decline with the magnitude of the effect increasing with fire frequency and extent (proportion of plants killed). In contrast, higher impact canker disease scenarios resulted in rapid population declines and potential extinction. Small increases in inter-fire adult survival reduced the rate of decline in populations with relatively low canker infestation. Research is urgently needed to understand the role that a warming and drying climate in the South-west Australian Floristic Region may have on the epidemiology of canker disease and the feasibility and effectiveness of treating individuals with appropriate fungicides.