Showing papers by "Stephen E. Williams published in 2011"

Engineering a future for amphibians under climate change

Abstract: 1. Altered global climates in the 21st century pose serious threats for biological systems and practical actions are needed to mount a response for species at risk. 2. We identify management actions from across the world and from diverse disciplines that are applicable to minimizing loss of amphibian biodiversity under climate change. Actions were grouped under three thematic areas of intervention: (i) installation of microclimate and microhabitat refuges; (ii) enhancement and restoration of breeding sites; and (iii) manipulation of hydroperiod or water levels at breeding sites. 3. Synthesis and applications. There are currently few meaningful management actions that will tangibly impact the pervasive threat of climate change on amphibians. A host of potentially useful but poorly tested actions could be incorporated into local or regional management plans, programmes and activities for amphibians. Examples include: installation of irrigation sprayers to manipulate water potentials at breeding sites; retention or supplementation of natural and artificial shelters (e.g. logs, cover boards) to reduce desiccation and thermal stress; manipulation of canopy cover over ponds to reduce water temperature; and, creation of hydrologoically diverse wetland habitats capable of supporting larval development under variable rainfall regimes. We encourage researchers and managers to design, test and scale up new initiatives to respond to this emerging crisis. © 2011 The Authors. Journal of Applied Ecology

Targeted protection and restoration to conserve tropical biodiversity in a warming world

Abstract: Complex landscapes interact with meteorological processes to generate climatically suitable habitat (refuges) in otherwise hostile environments. Locating these refuges has practical importance in tropical montane regions where a high diversity of climatically specialized species is threatened by climate change. Here, we use a combination of weather data and spatial modeling to quantify thermally buffered environments in a regional tropical rainforest. We do this by constructing a spatial surface of maximum air temperature that takes into account important climate-mediating processes. We find a strong attenuating effect of elevation, distance from coast and foliage cover on maximum temperature. The core habitat of a disproportionately high number of endemic species (45%) is encompassed within just 25% of the coolest identified rainforest. We demonstrate how this data can be used to (i) identify important areas of cool habitat for protection and (ii) efficiently guide restoration in degraded landscapes to expand extant networks of critical cool habitat.

Persistence in Peripheral Refugia Promotes Phenotypic Divergence and Speciation in a Rainforest Frog

Abstract: It is well established from the fossil record and phylogeographic analyses that late Quaternary climate fluctuations led to substantial changes in species' distribution, but whether and how these fluctuations resulted in phenotypic divergence and speciation is less clear. This question can be addressed through detailed analysis of traits relevant to ecology and mating within and among intraspecific lineages that persisted in separate refugia. In a biogeographic system (the Australian Wet Tropics [AWT]) with a well-established history of refugial isolation during Pleistocene glacial periods, we tested whether climate-mediated changes in distribution drove genetic and phenotypic divergence in the rainforest frog Cophixalus ornatus. We combined paleomodeling and multilocus genetics to demonstrate long-term persistence within, and isolation among, one central and two peripheral refugia. In contrast to other AWT vertebrates, the three major lineages differ in ecologically relevant morphology and in mating call, reflecting divergent selection and/or genetic drift in the peripheral isolates. Divergence in mating call and contact zone analyses suggest that the lineages now represent distinct species. The results show that climate shifts can promote genetic and phenotypic divergence and, potentially, speciation and direct attention toward incorporating adaptive traits into phylogeographic studies to better resolve the mechanisms of speciation.

Rainforest litter quality and chemical controls on leaf decomposition with near-infrared spectrometry

Abstract: Plant-litter chemical quality is an important driver of many ecosystem processes, however, what actually constitutes high- or low-quality litter (chemical potential for fast and slow decomposition, respectively) is often interpreted by the indices available. Here, near-infrared spectroscopy (NIRS) was used to explore leaf-litter chemical quality and the controls on decomposition in the tropical rainforest region of north Queensland Australia. Leaf-litter samples from litterfall collections and litterbag studies were used. NIRS was used to calibrate the chemical compositions of the material (N, P, C, Mg, Ca, acid detergent fiber, acid detergent lignin, α-cellulose, and total phenolics) from a smaller sample set covering the spectral range in the full set of samples. Calibrations were compared for both separate (local) and combined models, for litterbags, and litterfall. Coefficients of determination (r2) in the local models ranged from 0.88 (litterbag Mg) to 0.99 (litterfall N), with residual prediction deviation ratios > 3 for all constituents except Mg (≈ 2.5). Mass loss in the litterbags was strongly related to the NIR spectra, with model r2's of 0.75 (in situ leaves) and 0.76 (common control leaf). In situ decomposability was determined from modeling the initial NIR spectra prior to decomposition with litterbag exponential-decay rates (model r2 of 0.81, n = 85 initial samples). A best subset model including litter-quality, climate, and soil variables predicted decay better than the NIR decomposability model (r2 = 0.87). For litter quality alone the NIR model predicted decay rate better than all of the best predictive litter–chemical quality indices. The decomposability model was used to predict in situ decomposability in the litterfall samples. The chemical variables explaining NIR decomposability for litterfall were initial P, C, and phenolics (linear model r2 = 0.80, n = 2471). NIRS is a holistic technique that is just as, if not more accurate, than litter–chemical quality indices, when predicting decomposition and decomposability, shown here in a regional field study.

Gap Analysis of Environmental Research Needs in the Australian Wet Tropics

Abstract: Environmental research involves "understanding how environmental systems function and interact, and the impact that humans are having on the environment". Strengthened linkages between terrestrial biodiversity researchers and end-users are desirable to reduce duplicative effort and achieve maximum return on public investment in applied research. To assist this process, our analysis provides a significant review and consultation process with the aim of identifying end‐user needs, research gaps and possible synergies, delivering a valuable resource for terrestrially focussed research providers and end-user groups. This report provides a resource for research providers by helping to locate relevant research information more efficiently, and by ensuring that proposed research is strategic and targeted at the needs of the end‐users. It provides a resource for end-users by delivering a repository of biodiversity research that is digested and easily accessible, and by identifying the areas of research where stakeholder interests overlap. Finally, the report can also be used by funding bodies to help guide the prioritisation of resources into future biodiversity research in the Wet Tropics bioregion.