Samuel Banks

Newly discovered landscape traps produce regime shifts in wet forests

We describe the “landscape trap” concept, whereby entire landscapes are shifted into, and then maintained (trapped) in, a highly compromised structural and functional state as the result of multiple temporal and spatial feedbacks between human and natural disturbance regimes. The landscape trap concept builds on ideas like stable alternative states and other relevant concepts, but it substantively expands the conceptual thinking in a number of unique ways. In this paper, we (i) review the literature to develop the concept of landscape traps, including their general features; (ii) provide a case study as an example of a landscape trap from the mountain ash (Eucalyptus regnans) forests of southeastern Australia; (iii) suggest how landscape traps can be detected before they are irrevocably established; and (iv) present evidence of the generality of landscape traps in different ecosystems worldwide.

Genetic spatial autocorrelation can readily detect sex‐biased dispersal

Sex‐biased dispersal is expected to generate differences in the fine‐scale genetic structure of males and females. Therefore, spatial analyses of multilocus genotypes may offer a powerful approach for detecting sex‐biased dispersal in natural populations. However, the effects of sex‐biased dispersal on fine‐scale genetic structure have not been explored. We used simulations and multilocus spatial autocorrelation analysis to investigate how sex‐biased dispersal influences fine‐scale genetic structure. We evaluated three statistical tests for detecting sex‐biased dispersal: bootstrap confidence intervals about autocorrelation r values and recently developed heterogeneity tests at the distance class and whole correlogram levels. Even modest sex bias in dispersal resulted in significantly different fine‐scale spatial autocorrelation patterns between the sexes. This was particularly evident when dispersal was strongly restricted in the less‐dispersing sex (mean distance <200u2003m), when differences between the sexes were readily detected over short distances. All tests had high power to detect sex‐biased dispersal with large sample sizes (nu2003≥u2003250). However, there was variation in type I error rates among the tests, for which we offer specific recommendations. We found congruence between simulation predictions and empirical data from the agile antechinus, a species that exhibits male‐biased dispersal, confirming the power of individual‐based genetic analysis to provide insights into asymmetries in male and female dispersal. Our key recommendations for using multilocus spatial autocorrelation analyses to test for sex‐biased dispersal are: (i) maximize sample size, not locus number; (ii) concentrate sampling within the scale of positive structure; (iii) evaluate several distance class sizes; (iv) use appropriate methods when combining data from multiple populations; (v) compare the appropriate groups of individuals.

Cross‐sectional vs. longitudinal research: a case study of trees with hollows and marsupials in Australian forests

How different are insights based on cross-sectional studies from those of longitudinal investigations? We addressed this question using a detailed case study encompassing a rare suite of inter-connected cross-sectional and longitudinal investigations that have spanned the past two decades and included work on: (1) the decay and collapse of large-cavity forest trees (termed “trees with hollows”), (2) populations of a suite of species of arboreal marsupials that are reliant on trees with hollows as nesting and denning sites, and (3) relationships between the abundance, type, and condition of trees with hollows and the presence, abundance, and species richness of these animals. Our case study was from the montane ash eucalypt forests of the Central Highlands of Victoria, southeastern Australia. Our longitudinal studies led to new insights that either would not have been possible from a cross-sectional study, or which were unexpected because they did not conform, or only partially conformed, to postulated res...

Landscape genetics of an early successional specialist in a disturbance-prone environment

Species that specialize in disturbed habitats may have considerably different dispersal strategies than those adapted to more stable environments. However, little is known of the dispersal patterns and population structure of such species. This information is important for conservation because many postfire specialists are at risk from anthropogenic changes to natural disturbance regimes. We used microsatellite markers to assess the effect of landscape variation and recent disturbance history on dispersal by a small mammal species that occupies the early seral stage of vegetation regeneration in burnt environments. We predicted that a postfire specialist would be able to disperse over multiple habitat types (generalist) and not exhibit sex‐biased dispersal, as such strategies should enable effective colonization of spatially and temporally variable habitat. We found significant differentiation between sites that fitted an isolation‐by‐distance pattern and spatial autocorrelation of multilocus genotypes to a distance of 2–3 km. There was no consistent genetic evidence for sex‐biased dispersal. We tested the influence of different habitat‐ and fire‐specific landscape resistance scenarios on genetic distance between individuals and found a significant effect of fire. Our genetic data supported recently burned vegetation having greater conductance for gene flow than unburnt habitat, but variation in habitat quality between vegetation types and occupied patches had no effect on gene flow. Postfire specialists must evolve an effective dispersal ability to move over distances that would ensure access to early successional stage vegetation. Natural disturbance and natural heterogeneity may therefore not influence population genetic structure as negatively as expected.

Refuge site selection by the eastern chestnut mouse in recently burnt heath

Context Temporal reduction in shelter is an indirect primary impact of fire. Removal of animal refugia has implications for shelter site selection and fidelity – factors that have been largely overlooked in studies of Australian rodent fauna. This information is critical for guiding species conservation and appropriate land management including prescribed burning practices. Aims We sought to determine which features of burnt heath were selected as shelter sites by the eastern chestnut mouse, whether there was sex and/or seasonal variation in shelter site selection and whether we could identify primary refugia. Methods We completed a radio-telemetry study to identify diurnal refuge sites and compare habitat attributes with those of a matched set of control sites. We then used habitat features and fidelity parameters to classify refuge site use. Key results We found the eastern chestnut mouse selected shelters with the presence of specific structures and had taller, denser vegetation than randomly selected control sites. There were no differences in habitat selection between the sexes. Shelter sites in the non-breeding season had greater vegetation density compared with those used in the breeding season. In the breeding season, the eastern chestnut mouse showed no evidence of increased fidelity to particular refuges. Vegetation density in winter was the best predictor of a primary refuge compared with whether or not an animal returned to a shelter site or the amount of time spent in a shelter site. Mice were ephemeral and non-gregarious in their refuge use. There was some evidence for inheritance of refuge sites from a parent, as well as inter-season shelter site fidelity. Conclusions The eastern chestnut mouse selected refugia that had habitat attributes offering maximum protection. Seasonality in refuge site selection is likely to reflect the reproductive and environmental trade-offs in critical resources during different seasons. The maintenance of multiple, rarely occupied shelters by the eastern chestnut mouse is consistent with data for other mammals. Implications Fire management should ensure retention of vegetation structure on the ground layer, dense habitat patches in burned areas, and be carefully planned during the winter season to maintain shelter and refuge sites to assist population persistence.

The use of topographic fire refuges by the greater glider (Petauroides volans) and the mountain brushtail possum (Trichosurus cunninghami) following a landscape-scale fire

We examined the abundance of arboreal marsupials in topographic fire refuges after a major fire in a stand-replacing crown-fire forest ecosystem. We surveyed the abundance of arboreal marsupials across 48 sites in rainforest gullies burnt to differing extents by the 2009 fires in the mountain ash (Eucalyptus regnans) forests of the Victorian Central Highlands, Australia. The greater glider (Petauroides volans) was less abundant within the extent of the 2009 fire. The mountain brushtail possum (Trichosurus cunninghami) was more abundant within the extent of the 2009 fire, particularly within unburnt peninsulas protruding into burnt areas from unburnt edges. Our results indicate that fire refuges may facilitate the persistence of some species within extensively burnt landscapes. Additional work should seek to clarify this finding and identify the demographic mechanisms underlying this response.

Fire severity alters spatio–temporal movements and habitat utilisation by an arboreal marsupial, the mountain brushtail possum (Trichosurus cunninghami)

Understanding how severe wildfires influence faunal movement is essential for predicting how changes in fire regimes will affect ecosystems. We examined the effects of fire severity distribution on spatial and temporal variation in movement of an Australian arboreal mammal, the mountain brushtail possum (Trichosurus cunninghami). We used GPS telemetry to characterise the movements of 18 possums in landscapes burnt to differing extents by a large wildfire. We identified a temporal change in movement patterns in response to fire. In unburnt landscapes, individuals moved greater distances early and late in the night and had less overlap in the areas used for foraging and denning, than in high-severity burnt landscapes. Habitat selection was dependent on the spatial context of fire in the surrounding landscape. Forest recently burnt at high severity may provide suitable habitat for species such as the mountain brushtail possum, if protected from subsequent disturbance, such as salvage logging. However, spatial and temporal patterns of habitat use and selection differ considerably between burnt and undisturbed landscapes. The spatial outcomes of ecological disturbances such as wildfires have the potential to alter the behaviour and functional roles of fauna across large areas.

Preventing the Extinction of an Iconic Globally Endangered Species -Leadbeater's Possum (Gymnobelideus leadbeateri)

Leadbeater’s Possum is an iconic but globally endangered species largely confined to the wet ash forests of Victoria, south-eastern Australia. The species is at risk of extinction as a result of widespread logging, recurrent wildfire, and the rapid decline of populations of large old hollow-bearing trees ’ the single most critical habitat element for Leadbeater’s Possum. We outline why recent strategies aimed at conserving Leadbeater’s Possum appear unlikely to be effective in preventing the species’ extinction. We outline what we believe to now be the only current viable approach to conserve this species. This is the rapid transition to a large protected forest reserve system where the primary process threatening the species ’ widespread industrial clear-felling ’ is removed.

The founder space race: a reply to Buckley et al.

We are delighted that Buckley and co-authors [1] share our interest in the long-term legacy of priority effects, and their reply to our article [2] raises several interesting discussion points. Our synthesis sought to highlight the broad conceptual links and similarities between diverse examples of density-dependent competitive exclusion of late arrivals by founders (‘founder takes all’) over a wide range of temporal and spatial scales. Naturally, with such a broad scope, the many various ecological factors that can influence the strength of such density-dependent processes could not be fully discussed, but we welcome an opportunity to extend our synthesis via this conversation.

Development of nine polymorphic microsatellite loci in the squirrel glider (Petaurus norfolcensis)

We designed nine polymorphic markers for the squirrel glider (Petaurus norfolcensis), an arboreal marsupial in eastern Australia. These markers will assist in the management of isolated populations and the evaluation of wildlife corridors.