Disturbance has benefits as well as costs for fragmented populations of a cryptic grassland reptile

Landscape Ecology - Conservation practitioners face complex decisions about the management of spatial and temporal disturbance regimes when disturbance plays a significant role in the dynamics of...     

Classical metapopulation theory as a useful paradigm for the conservation of an endangered amphibian

Classical metapopulation theory (CMT) has proven an attractive paradigm for ecologists concerned with the conservation of aquatic-breeding amphibians, given its apparent fit with the population dynamics of these animals, and the opportunities the concept provides to assess alternate management options. Nevertheless, several authors have cautioned against uncritical application of this paradigm. We assessed the application of CMT to the conservation of the endangered growling grass frog (Litoria raniformis) in the urbanising landscapes of Melbourne, Victoria, Australia. Support for five predictions developed from the basic tenets of CMT was assessed using a multi-year occupancy and mark–recapture data-set. There was congruence between all five predictions and data. Wetland occupancy was strongly influenced by the proximity of neighbouring populations (‘connectivity’), but the estimated rate of dispersal between wetlands was low. Wetland occupancy was also temporally dynamic, with only a weak effect of connectivity on the probability of extinction, but a strong positive influence of connectivity on the probability of colonisation. Our work confirms that CMT provides a useful model of the dynamics of L. raniformis in urbanising landscapes, and justifies the application of the paradigm to conservation planning for this species. We argue that CMT may prove relevant to numerous aquatic-breeding amphibians, and encourage assessment of the application of CMT to the conservation of these animals.     

The influence of uncertainty on conservation assessments: Australian frogs as a case study

We evaluated the influence of uncertainty, based on variation in expert opinion, on assessment of conservation status of Australian amphibians. We examined relationships between different biological variables and inferred relative extinction risk, the influence of uncertainty on resulting ranks, and regional patterns of extinction risk and uncertainty. Our results were in general agreement with the International Union for the Conservation of Nature and Natural Resources but also reveal apparent high extinction risks among some taxa that the IUCN did not classify in any threatened category. These differences were exaggerated when the most conservative status assessments were taken from variation in expert opinion. Our assessments of relative extinction risk were strongly dependent on basic demographic variables, particularly population size, geographic distribution of populations and age at first reproduction. We identified regional hotspots of high relative extinction risk and poor knowledge of amphibians, leading to high uncertainty about the conservation status of species from those areas. Regional clustering of species with high relative extinction risk and high uncertainty may indicate higher levels of relative extinction risk than previously assessed. Our results highlight the influence of uncertainty on interpretation of conservation assessments of organism groups with large knowledge gaps. Uncertainty should be further incorporated into conservation planning as it not only highlights taxa with potentially underestimated extinction risk, but also facilitates identification of knowledge gaps informative of conservation status. Knowledge of regional patterns of extinction risk and uncertainty assists conservation planning through identification of regions of high extinction risk and/or large knowledge gaps.     

Effects of temperature on the fast-start swimming performance of an Australian freshwater fish

Abstract –  The fast-start swimming performance of juveniles of an Australian freshwater (warm-water) fish, golden perch, was examined in the laboratory at six water temperatures ranging between 10 and 25 °C. Fast-start swimming performance of fish was considerably reduced at temperatures less than 15.5 °C. Temperatures of less than 15 °C are typical of the thermal regime downstream of large dams in south-eastern Australia, where conditions are more suited to introduced cold-water fish species. We conclude that the swimming performance of native warm-water fish such as golden perch is likely to be negatively affected by cold-water releases from deep outlets in thermally stratified dams.