Genetic restoration in the eastern collared lizard under prescribed woodland burning

Eastern collared lizards of the Ozarks live in glades—open, rocky habitats embedded in a woodland matrix. Past fire suppression had made the woodlands a barrier to dispersal, leading to habitat destruction, fragmentation and local extinction. Reintroduced populations of lizards were subjected to 10 years of habitat fragmentation under continued fire suppression followed by twelve years of landscape restoration with prescribed burns. Prior to prescribed burning, genetic diversity decreased within glades and differentiation increased among glades. With woodland burning, genetic diversity within glades first decreased during an expanding colonization phase, but then increased as a dynamically stable metapopulation was established. Population differentiation among glades also stabilized in the metapopulation under weak isolation‐by‐distance. This study is one of the first to examine the genetic changes in a species of conservation concern throughout all the stages of decline and recovery and shows the importance of landscape‐level restoration for maintaining the genetic integrity of populations. This study also demonstrates how mark–recapture and genetic data together can yield detailed insight into metapopulation dynamics that would be impossible from just one type of data alone.     

Implications of Food Web Interactions for Restoration of Missouri Ozark Glade Habitats

Ozark glades are gaps in forested areas that are dominated by grasses and forbs growing in rocky, nutrient‐poor soil. Historically, these open, patchy habitats were maintained by natural and anthropogenic fire cycles that prohibited tree encroachment. However, because of decades of fire suppression, glades have become overgrown by fire‐intolerant species such as Eastern red cedar (Juniperus virginiana). Current restoration practices include cutting down invasive cedars and burning brush piles, which represent habitat for Northern fence lizards (Sceloporus undulatus). Because Sceloporus actively consumes herbivores, we hypothesized that the presence of these lizards in and around brush piles might result in a trophic cascade, whereby damage on native plants is reduced. Field surveys across six Missouri glades indicated that lizard activity was minimal beyond 1 m from habitat structures. This activity pattern reduced grasshopper abundance by 75% and plant damage by over 66% on Echinacea paradoxa and Rudbeckia missouriensis near structures with lizards. A field transplant experiment demonstrated similar reductions in grasshopper abundance and damage on two other glade endemic species, Aster oblongifolius and Schizachyrium scoparium. These results demonstrate that future glade restoration efforts might benefit from considering top‐down effects of predators in facilitating native plant establishment.     

The Effect of Fire Reintroduction on Endemic and Rare Plants of a Southeastern Glade Ecosystem

Open habitats dominated by herbaceous plants on thin, rocky soils occur within the forests of eastern North America. Although these habitats vary in origin, structure, geology, and species composition, all contribute greatly to regional biodiversity by harboring endemic and/or rare plants. Little is known about how disturbances affect plant populations in these ecosystems. Fire once was a frequent natural disturbance in the Ketona dolomite glades of Alabama, an ecosystem harboring eight endemic taxa and numerous other species of conservation concern. We designed an experiment to determine how the reintroduction of fire into the glades and surrounding longleaf pine forests affects populations of rare glade plant species. Experimental and control plots were established within the glades. Experimental plots were burned in April 2004, and all plots were surveyed during two subsequent growing seasons (2004 and 2005). Populations of three of 14 species of conservation concern declined significantly after the initial fire but recovered the next year. Among other herbaceous species, only five and two differed in population size in 2004 and 2005, respectively. In 2004, more species were more abundant in control than burned plots, but this difference was not detected in 2005. Multivariate community‐level analyses of species presence–absence suggested that the effects of fire were negligible by the 2005 survey. Populations of young trees that had invaded the glades declined dramatically as a result of treatment fires. These results suggest that the reintroduction of fire will not harm glade species and may help prevent encroachment of the surrounding forest.     

Population genetic structure, gene flow and sex-biased dispersal in frillneck lizards (Chlamydosaurus kingii)

By using both mitochondrial and nuclear multiloci markers, we explored population genetic structure, gene flow and sex-specific dispersal of frillneck lizards ( Chlamydosaurus kingii ) sampled at three locations, separated by 10 to 50 km, in a homogenous savannah woodland in tropical Australia. Apart from a recombinant lizard, the mitochondrial analyses revealed two nonoverlapping haplotypes/populations, while the nuclear markers showed that the frillneck lizards represented three separate clusters/populations. Due to the small population size of the mtDNA, fixation may occur via founder effects and/or drift. We therefore suggest that either of these two processes, or a combination of the two, are the most likely causes of the discordant results obtained from the mitochondrial and the nuclear markers. In contrast to the nonoverlapping mitochondrial haplotypes, in 12 out of 74 lizards, mixed nuclear genotypes were observed, hence revealing a limited nuclear gene flow. Although gene flow should ultimately result in a blending of the populations, we propose that the distinct nuclear population structure is maintained by frequent fires resulting in local bottlenecks, and concomitant spatial separation of the frillneck lizard populations. Limited mark–recapture data and the difference in distribution of the mitochondrial and nuclear markers suggest that the mixed nuclear genotypes were caused by juvenile male-biased dispersal.     

The effects of fire on the frillneck lizard (Chlamydosaurus kingii) in northern Australia

Abstract A population of frillneck lizards, Chlamydosaurus kingii, was monitored by radio telemetry and mark-recapture techniques between April 1991 and April 1994, as part of a landscape-scale fire experiment, in Kakadu National Park, Northern Territory. The study aimed to investigate both the short- and longer-term effects of fire on a lizard species in a tropical savanna where fires are frequent and often annual. Frillneck lizards are able to survive fires that occur in the first few months of the dry season by remaining perched in trees. A high level of mortality (29%) occurred during late dry-season fires, along with changes in their behavioural response to fire: sheltering in either larger trees or hollow termite mounds. Food is more accessible after fires due to the removal of ground vegetation. This is reflected in greater volume and diversity of prey in stomach contents after fires. This increase is more pronounced after late dry-season fires, possibly due to increased accessibility of prey caused by more complete vegetation removal. Frillneck lizards show an overall preference for trees with a dense canopy cover located in an area with a low density of grass. Fire has an effect on this relationship. Frillneck lizards in habitat unburnt for a number of years tend to perch in trees with a smaller canopy, whereas lizards in annually burnt habitat perch in trees with a dense canopy. Volume and composition of lizard stomach contents was broadly similar among fire treatments over a 2 year period, although termites were more predominant in stomach contents of lizards in unburnt habitat. Wet-season body condition is lower in lizards from unburnt habitat, although the reason for this is unclear. These results demonstrate the importance of different fire intensities and regimes on the ecology of a lizard species in a tropical savanna.     

The influence of invasive fire ants on survival,space use,and patterns of natural selection in juvenile lizards

Invasive species have altered natural communities and exposed native species to new selective pressures. These pressures are particularly acute when invasive species are predators of natives. The invasive red imported fire ant has expanded its range significantly in the southeast United States and has become an important predator of native species that share similar habitat preferences, like the prairie lizard, Sceloporus consobrinus. Recent studies indicate that lizards that have coexisted for a long period of time with fire ants have responded both plastically and adaptively to this invasion. However, despite considerable work, few “controlled” experiments have been conducted to explore the influence of fire ants on vertebrates in natural populations. In this study we released hatchling lizards on two experimental islands that differed in fire ant density to investigate the influence of fire ants on lizard survival, habitat/space use, and patterns of phenotypic selection. We demonstrate that fire ant presence significantly explains patterns of lizard survival among populations and over small spatial scales within populations. As a consequence of survival patterns or avoidance behavior, lizard habitat use was significantly altered in the presence of fire ants in high density. Finally, we found strong signatures of natural selection on lizard body size and body condition, but the patterns of selection did not appear to be influenced by variation in fire ant density. This study highlights the direct influence of predatory fire ants on hatchling lizard mortality and habitat use. These effects can have important demographic and population-level consequences.     

Effects of intense wildfires on the nesting ecology of oviparous montane lizards

In midsummer 2002–2003, intense wildfires raged through the Brindabella Range of south‐eastern Australia, including sites where we have studied the ecology of scincid lizards (especially Bassiana duperreyi) for decades. Data‐loggers measured the thermal regimes experienced by eggs during these fires (revealing lethally high temperatures in nests under logs in the forest but minimal effect in nests under rocks in clearings). Eggs from forest‐clearing nests hatched successfully. Reproductive output of lizards in one area was reduced in the years post‐fire (perhaps because of inadequate food [insect] abundance to fuel female reproduction) but soon recovered. The fires reduced vegetation density and thus increased the availability of sun‐exposed rocks that serve as potential nest sites. However, the magnitude and duration of these effects differed among sites. Five years after these intense fires, canopy openness (and thus, sunlight penetration to create thermally suitable nest sites) was indistinguishable from pre‐fire conditions. Our data reveal strong spatial heterogeneity both in the immediate effects of fire on lizard reproduction and in longer‐term post‐fire changes in habitat quality. Surprisingly, these intense wildfires had only transitory and local effects on nest‐site availability for the heliothermic lizards that we study, but impacts likely were more severe on sympatric taxa that depend upon moist cool microhabitats.     

POSTFIRE RESPONSE AND GENETIC DIVERSITY IN ERICA COCCINEA: CONNECTING POPULATION DYNAMICS AND DIVERSIFICATION IN A BIODIVERSITY HOTSPOT

Understanding the processes of biological diversification is a central topic in evolutionary biology. The South African Cape fynbos, one of the major plant biodiversity hotspots out of the tropics, has prompted several hypotheses about the causes of generation and maintenance of biodiversity. Fire has been traditionally invoked as a key element to explain high levels of biodiversity in highly speciose fynbos taxa, such as the genus Erica. In this study, we have implemented a microevolutionary approach to elucidate how plant‐response to fire may contribute to explain high levels of diversification in Erica. By using microsatellite markers, we investigated the genetic background of seeder (fire‐sensitive) and resprouter (fire‐resistant) populations of the fynbos species Erica coccinea. We found higher within‐population genetic diversity and higher among‐population differentiation in seeder populations and interpreted these higher levels of genetic diversification as a consequence of the comparatively shorter generation times and faster population turnover in the seeder form of this species. Considering that genetic divergence among populations may be seen as the initial step to speciation, the parallelism between these results and the pattern of biodiversity at the genus level offers stimulating insights into understanding causes of speciation of the genus Erica in the Cape fynbos.     

Transient population dynamics impede restoration and may promote ecosystem transformation after disturbance

The apparent failure of ecosystems to recover from increasingly widespread disturbance is a global concern. Despite growing focus on factors inhibiting resilience and restoration, we still know very little about how demographic and population processes influence recovery. Using inverse and forward demographic modelling of 531 post‐fire sagebrush populations across the western US, we show that demographic processes during recovery from seeds do not initially lead to population growth but rather to years of population decline, low density, and risk of extirpation after disturbance and restoration, even at sites with potential to support long‐term, stable populations. Changes in population structure, and resulting transient population dynamics, lead to a > 50% decline in population growth rate after disturbance and significant reductions in population density. Our results indicate that demographic processes influence the recovery of ecosystems from disturbance and that demographic analyses can be used by resource managers to anticipate ecological transformation risk.     

Post‐fragmentation population structure in a cooperative breeding Afrotropical cloud forest bird: emergence of a source‐sink population network

The impact of demographic parameters on the genetic population structure and viability of organisms is a long‐standing issue in the study of fragmented populations. Demographic and genetic tools are now readily available to estimate census and effective population sizes and migration and gene flow rates with increasing precision. Here we analysed the demography and genetic population structure over a recent 15‐year time span in five remnant populations of Cabanis's greenbul (Phyllastrephus cabanisi), a cooperative breeding bird in a severely fragmented cloud forest habitat. Contrary to our expectation, genetic admixture and effective population sizes slightly increased, rather than decreased between our two sampling periods. In spite of small effective population sizes in tiny forest remnants, none of the populations showed evidence of a recent population bottleneck. Approximate Bayesian modelling, however, suggested that differentiation of the populations coincided at least partially with an episode of habitat fragmentation. The ratio of meta‐N_e to meta‐N_c was relatively low for birds, which is expected for cooperative breeding species, while N_e/N_c ratios strongly varied among local populations. While the overall trend of increasing population sizes and genetic admixture may suggest that Cabanis's greenbuls increasingly cope with fragmentation, the time period over which these trends were documented is rather short relative to the average longevity of tropical species. Furthermore, the critically low N_c in the small forest remnants keep the species prone to demographic and environmental stochasticity, and it remains open if, and to what extent, its cooperative breeding behaviour helps to buffer such effects.     

Biogeographic anomaly or human introduction: a cryptogenic population of tree skink (Reptilia: Squamata) from the Cook Islands,Oceania

Archaeological and molecular data have revealed that the present day faunas of many island groups in Melanesia, Polynesia, and Micronesia are not representative of the biodiversity generated within this region on an evolutionary timescale. Erroneous inferences regarding the mechanisms of speciation and the significance of long distance dispersal in shaping the present diversity of these island systems have resulted from this incomplete diversity and distributional data. The lizard fauna east of Samoa has been suggested to derive entirely from human‐mediated introductions, a distribution congruent with biogeographic patterns for other Pacific species. Distinguishing between introduced populations and those that result from natural colonization events is difficult, although molecular data provide a useful means for elucidating population history and identifying the likely sources of introductions. We use molecular data (1726 bp of mitochondrial DNA and 286 bp of nuclear DNA) to evaluate a population of arboreal lizards from the Cook Islands and to determine whether this arboreal skink population is the sole endemic component of the lizard fauna east of Samoa or the result of human‐mediated introduction. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 100 , 318–328.     

Contrasting effects of landscape features on genetic structure in different geographic regions in the ornate dragon lizard,Ctenophorus ornatus

Habitat fragmentation can have profound effects on the distribution of genetic variation within and between populations. Previously, we showed that in the ornate dragon lizard, Ctenophorus ornatus, lizards residing on outcrops that are separated by cleared agricultural land are significantly more isolated and hold less genetic variation than lizards residing on neighbouring outcrops connected by undisturbed native vegetation. Here, we extend the fine‐scale study to examine the pattern of genetic variation and population structure across the species' range. Using a landscape genetics approach, we test whether land clearing for agricultural purposes has affected the population structure of the ornate dragon lizard. We found significant genetic differentiation between outcrop populations (F_ST = 0.12), as well as isolation by distance within each geographic region. In support of our previous study, land clearing was associated with higher genetic divergences between outcrops and lower genetic variation within outcrops, but only in the region that had been exposed to intense agriculture for the longest period of time. No other landscape features influenced population structure in any geographic region. These results show that the effects of landscape features can vary across species' ranges and suggest there may be a temporal lag in response to contemporary changes in land use. These findings therefore highlight the need for caution when assessing the impact of contemporary land use practices on genetic variation and population structure.     

Does relaxed predation drive phenotypic divergence among insular populations?

The evolution of striking phenotypes on islands is a well‐known phenomenon, and there has been a long‐standing debate on the patterns of body size evolution on islands. The ecological causes driving divergence in insular populations are, however, poorly understood. Reduced predator fauna is expected to lower escape propensity, increase body size and relax selection for crypsis in small‐bodied, insular prey species. Here, we investigated whether escape behaviour, body size and dorsal coloration have diverged as predicted under predation release in spatially replicated islet and mainland populations of the lizard species Podarcis gaigeae. We show that islet lizards escape approaching observers at shorter distances and are larger than mainland lizards. Additionally, we found evidence for larger between‐population variation in body size among the islet populations than mainland populations. Moreover, islet populations are significantly more divergent in dorsal coloration and match their respective habitats poorer than mainland lizards. These results strongly suggest that predation release on islets has driven population divergence in phenotypic and behavioural traits and that selective release has affected both trait means and variances. Relaxed predation pressure is therefore likely to be one of the major ecological factors driving body size divergence on these islands.     

Lizards in the suburbs: a single-garden study of a small endemic New Zealand skink (Oligosoma aeneum)

Detailed investigations of ecology and life history of lizards in New Zealand/Aotearoa are needed to inform their conservation and management. An early demographic study of copper skinks (Oligosoma aeneum) in a suburban garden was undertaken in Lower Hutt using mark–recapture methods, sampling weekly from March 1971 to December 1973. Oligosoma aeneum were seen on 1372 occasions, with 972 captures of 169 individuals. The maximum snout–vent length was 66 mm, 33% of skinks had complete tails, and colour differences suggested sexual signalling and warrant further study. Most captures occurred over November–March, with fewest over June–August. The estimated spring/summer population size in the garden (± SEM) was 83.6 (± 9.4) skinks, and the annual survival rate (± SEM) was 38.0% (± 16.0%). This is one of the few New Zealand lizard studies that have extended through all months of the year and it adds to limited information on lizard populations in suburban areas.     

DOES MATE LIMITATION IN SELF‐INCOMPATIBLE SPECIES PROMOTE THE EVOLUTION OF SELFING? THE CASE OF LEAVENWORTHIA ALABAMICA

Genetic diversity at the S‐locus controlling self‐incompatibility (SI) is often high because of negative frequency‐dependent selection. In species with highly patchy spatial distributions, genetic drift can overwhelm balancing selection and cause stochastic loss of S‐alleles. Natural selection may favor the breakdown of SI in populations with few S‐alleles because low S‐allele diversity constrains the seed production of self‐incompatible plants. We estimated S‐allele diversity, effective population sizes, and migration rates in Leavenworthia alabamica, a self‐incompatible mustard species restricted to discrete habitat patches in rocky glades. Patterns of polymorphism were investigated at the S‐locus and 15 neutral microsatellites in three large and three small populations with 100‐fold variation in glade size. Populations on larger glades maintained more S‐alleles, but all populations were estimated to harbor at least 20 S‐alleles, and mate availabilities typically exceeded 0.80, which is consistent with little mate limitation in nature. Estimates of the effective size (N_e) in each population ranged from 600 to 1600, and estimated rates of migration (m) ranged from 3 × 10⁻⁴ to nearly 1 × 10⁻³. According to theoretical models, there is limited opportunity for genetic drift to reduce S‐allele diversity in populations with these attributes. Although pollinators or resources limit seed production in small glades, limited S‐allele diversity does not appear to be a factor promoting the incipient breakdown of SI in populations of this species that were studied.     

Colonization, genetic diversity, and evolution in the Swedish sand lizard, Lacerta agilis (Reptilia, Squamata)

The Swedish sand lizard ( Lacerta agilis ) is a relict species from the post-glacial warmth period. From the geological history of this region, and more recent data on population fragmentation due to disturbance by man, it can be surmised that the Swedish sand lizards passed through at least one population bottleneck in relatively recent times. We tested this hypothesis by investigating the amount and structuring of genetic variability in six microsatellite loci in ten lizard populations from different parts of Sweden. We contrasted these data against those from a Hungarian population which we have reason to assume strongly resembles the founder population for Swedish sand lizards. The average number of alleles per locus in Sweden was 3.3, and these alleles were common in almost all populations, whereas the average number of alleles in the Hungarian population was 8.0. Likewise, the level of expected heterozygosity was lower in the Swedish populations (0.45) compared to the Hungarian population (0.70). The lower variability in Swedish populations is probably a consequence of a common population bottleneck during the immigration subsequent to the latest glacial period. The remaining variability is strongly subdivided between populations (F_ST=0.30) with the main genetic differences being between rather than within populations. Despite the marked isolation of the populations and the present small population sizes (N= 10–300 adults), the Swedish relict populations show a surprisingly high level of observed heterozygosity, indicating that small population size is probably a recent phenomenon.     

The legacy of ice ages in mountain species: post‐glacial colonization of mountain tops rather than current range fragmentation determines mitochondrial genetic diversity in an endemic Pyrenean rock lizard

Aim The genetic impact of Quaternary climatic fluctuations on mountain endemic species has rarely been investigated. The Pyrenean rock lizard (Iberolacerta bonnali) is restricted to alpine habitats in the Pyrenees where it exhibits a highly fragmented distribution between massifs and between habitats within massifs. Using mitochondrial DNA markers, we set out: (1) to test whether several evolutionary units exist within the species; (2) to understand how the species persisted through the Last Glacial Maximum and whether the current range fragmentation originates from distribution shifts after the Last Glacial Maximum or from more ancient events; and (3) to investigate whether current mitochondrial diversity reflects past population history or current habitat fragmentation. Location The Pyrenees in south‐western France and northern Spain. Methods We used variation in the hypervariable left domain of the mitochondrial control region of 146 lizards collected in 15 localities, supplemented by cytochrome b sequences downloaded from GenBank to cover most of the species’ distribution range. Measures of population genetic diversity were contrasted with population isolation inferred from topography. Classical (F‐statistics) and coalescence‐based methods were used to assess the level of gene flow and estimate divergence time between populations. We used coalescence‐based simulations to test the congruence of our genetic data with a scenario of simultaneous divergence of current populations. Results Coalescence‐based analyses suggested that these peripheral populations diverged simultaneously at the end of the last glacial episode when their habitats became isolated on mountain summits. High mitochondrial diversity was found in peripheral, isolated populations, while the populations from the core of the species’ range were genetically impoverished. Where mitochondrial diversity has been retained, populations within the same massif exhibited high levels of genetic differentiation. Main conclusions As suggested for many other mountain species, the Pyrenean rock lizard survived glacial maxima through short‐distance range shifts instead of migration or contraction in distant southern refugia. Most of the main Pyrenean range has apparently been re‐colonized from a single or a few source populations, resulting in a loss of genetic diversity in re‐colonized areas. As a result, current levels of intra‐population mitochondrial diversity are better explained by post‐glacial population history than by current habitat fragmentation. Genetic population differentiation within massifs implies severe reduction in female‐mediated gene flow between patches of habitats.     

Disentangling the impact of demographic factors on population differentiation of an endangered freshwater crayfish (Austropotamobius pallipes) using population density and microsatellite data

1. Habitat fragmentation of stream ecosystems often results in decreased connectivity between populations and lower population sizes. Hence, understanding how habitat fragmentation affects genetic erosion is important for the preservation of freshwater biodiversity, in particular, as small populations suffer from loss of genetic diversity through genetic drift and loss of fitness because of inbreeding, increasing the risk of extinction. 2. Here, we assess the impact of demographic factors on population differentiation in the endangered freshwater crayfish Austropotamobius pallipes by analysing population genetic structure, estimating effective population sizes and comparing levels of polymorphism at five microsatellite loci with density estimates of 10 populations within a small French catchment that has become progressively confined to headwaters over the last six decades. 3. Levels of expected heterozygosity and allelic richness per population were relatively low (0.214–0.396 and 1.6–2.6, respectively). We found strong genetic differentiation between these geographically close populations (F_ST = 0.283), with weak statistical evidence for a pattern of isolation by distance. Estimates of effective population size were low (<150) in most populations, but potentially reached several thousands in three populations. 4. Population density and allelic richness were strongly positively correlated. A robust relationship between population density and heterozygosity values was also noted, but only after discarding two populations for which significant genetic signatures of a recent bottleneck were found; these two populations displayed high expected heterozygosity compared with a very low density. Populations with the highest densities of individuals had the highest effective population size estimates and vice versa. 5. Our results clearly show the importance of demographic factors and genetic drift on A. pallipes populations. Furthermore, analysis of genetic and population density data is a pragmatic and efficient approach to corroborate inferences from genetic data and can be particularly useful in the identification of populations experiencing a bottleneck and therefore in conservation genetics studies aiming at identifying priority populations for conservation.     

Influence of drainage divides versus arid corridors on genetic structure and demography of a widespread freshwater turtle,Emydura macquarii krefftii,from Australia

The influence of Pleistocene climatic cycles on Southern Hemisphere biotas is not yet well understood. Australia's eastern coastal margin provides an ideal setting for examining the relative influence of landscape development, sea level fluctuation, and cyclic climatic aridity on the evolution of freshwater biodiversity. We examined the impact of climatic oscillations and physical biogeographic barriers on the evolutionary history of the wide‐ranging Krefft's river turtle (Emydura macquarii krefftii), using range‐wide sampling (649 individuals representing 18 locations across 11 drainages) and analysis of mitochondrial sequences (~1.3‐kb control region and ND4) and nuclear microsatellites (12 polymorphic loci). A range of phylogeographic (haplotype networks, molecular dating), demographic (neutrality tests, mismatch distributions), and population genetic analyses (pairwise F_ST, analysis of molecular variance, Bayesian clustering analysis) were implemented to differentiate between competing demographic (local persistence vs. range expansion) and biogeographic (arid corridor vs. drainage divide) scenarios. Genetic data reveal population genetic structure in Krefft's river turtles primarily reflects isolation across drainage divides. Striking north‐south regional divergence (2.2% ND4 p‐distance; c. 4.73 Ma, 95% higher posterior density (HPD) 2.08–8.16 Ma) was consistent with long‐term isolation across a major drainage divide, not an adjacent arid corridor. Ancient divergence among regional lineages implies persistence of northern Krefft's populations despite the recurrent phases of severe local aridity, but with very low contemporary genetic diversity. Stable demography and high levels of genetic diversity are inferred for southern populations, where aridity was less extreme. Range‐wide genetic structure in Krefft's river turtles reflects contemporary and historical drainage architecture, although regional differences in the extent of Plio–Pleistocene climatic aridity may be reflected in current levels of genetic diversity.     

Fire management to combat disease: turning interactions between threats into conservation management

As the number and intensity of threats to biodiversity increase, there is a critical need to investigate interactions between threats and manage populations accordingly. We ask whether it is possible to reduce the effects of one threat by mitigating another. We used long-term data for the long-lived resprouter, Xanthorrhoea resinosa Pers., to parameterise an individual-based population model. This plant is currently threatened by adverse fire regimes and the pathogen Phytophthora cinnamomi. We tested a range of fire and disease scenarios over various time horizons relevant to the population dynamics of the species and the practicalities of management. While fire does not kill the disease, it does trigger plant demographic responses that may promote population persistence when disease is present. Population decline is reduced with frequent fires because they promote the greatest number of germination events, but frequent fires reduce adult stages, which is detrimental in the long term. Fire suppression is the best action for the non-seedling stages but does not promote recruitment. With disease, frequent fire produced the highest total population sizes for shorter durations, but for longer durations fire suppression gave the highest population sizes. When seedlings were excluded, fire suppression was the best action. We conclude that fire management can play an important role in mitigating threats posed by this disease. The best approach to reducing declines may be to manage populations across a spatial mosaic in which the sequence of frequent fires and suppression are staggered across patches depending on the level of disease at the site.