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Hill, Sarah
- PublicationResponse of the soil seed-bank of Cumberland Plain Woodland to heatingSoil was investigated in a Cumberland Plain Woodland community to determine the presence of a soil seed‐bank and whether species richness and abundance of plants germinating from it were affected by heating such as that experienced in a fire. Soil samples were taken from the Holsworthy Military Area, in the south-eastern region of the Sydney Basin, New South Wales, Australia, and one of four treatments was applied; soil was heated to 80°C, 40°C, unheated or unheated with litter not removed. Sixty‐eight species, representing 26 families including 11 exotic and 57 native species germinated from the soil. Herbs and grasses dominated and were in similar proportions to those surveyed in the above‐ground vegetation, suggesting that the soil seed‐bank reflected the current structure of the vegetation, although species composition differed. Species responded differently to heating. The seeds of some species germinated when heated at a higher temperature (80°C), particularly those from the family Fabaceae, whereas other species were more common in unheated or lightly heated samples (40°C). This suggests that fire is likely to change the species composition of the above‐ground vegetation and indicates that management must ensure that species that do not germinate when heated are maintained, as well as those species that germinate following heating. A large proportion of soil seed‐bank species showed low germination rates in the trials, and 112 above‐ground species did not germinate in the soil samples. We do not understand whether species of these two sets do not produce a soil‐stored seed‐bank or whether the seed‐bank has been depleted by past practices at Holsworthy. Further research is needed.
- PublicationUsing devitalised seeds in myrmecological researchField studies of myrmecochory (seed dispersal by ants) can benefit from the use of devitalised seeds, particularly where these studies may involve invasive plants or plants outside of their natural range. Here, we test three different methods of seed devitalisation - gamma irradiation (10.6 kGy over 9.1 h at 23.7-25.4 °C), heating (150 °C for 30 min) and freezing (submerged in liquid nitrogen for 10 min) - in three different Australian plants: Acacia longifolia, Acacia melanoxylon and Kennedia rubicunda. We further test their suitability post‐treatment as stimuli for use in field studies of myrmecochory. Gamma radiation and exposure to heat effectively inhibited germination, whereas freezing did not. The devitalisation treatments did not appear to affect the attractiveness of seeds to ants as there was no significant difference in daily collection rate of control seeds compared to devitalised seeds.
- PublicationAssessing insect responses to climate change: What are we testing for? Where should we be heading?(PeerJ, Ltd, 2013)
; ; ;Binns, Matthew ;Bahar, Md Habibullah ;Ridley, Emma V ;Jung, Myung-Pyo; ;Yates, MichelleKhusro, MohammadTo understand how researchers are tackling globally important issues, it is crucial to identify whether current research is comprehensive enough to make substantive predictions about general responses. We examined how research on climate change affecting insects is being assessed, what factors are being tested and the localities of studies, from 1703 papers published between 1985 and August 2012. Most published research (64%) is generated from Europe and North America and being dedicated to core data analysis, with 29% of the studies analysed dedicated to Lepidoptera and 22% Diptera: which are well above their contribution to the currently identified insect species richness (estimated at 13% and 17% respectively). Research publications on Coleoptera fall well short of their proportional contribution (19% of publications but 39% of insect species identified), and to a lesser extent so do Hemiptera, and Hymenoptera. Species specific responses to changes in temperature by assessing distribution/range shifts or changes in abundance were the most commonly used methods of assessing the impact of climate change on insects. Research on insects and climate change to date is dominated by manuscripts assessing butterflies in Europe, insects of economic and/or environmental concern in forestry, agriculture, and model organisms. The research on understanding how insects will respond to a rapidly changing climate is still in its infancy, but the current trends of publications give a good basis for how we are attempting to assess insect responses. In particular, there is a crucial need for broader studies of ecological, behavioural, physiological and life history responses to be addressed across a greater range of geographic locations, particularly Asia, Africa and Australasia, and in areas of high human population growth and habitat modification. It is still too early in our understanding of taxa responses to climate change to know if charismatic taxa, such as butterflies, or disease vectors, including Diptera, can be used as keystone taxa to generalise other insect responses to climate change. This is critical as the basic biology of most species is still poorly known, and dominant, well studied taxa may show variable responses to climate change across their distribution due to regional biotic and abiotic influences. Indeed identifying if insect responses to climate change can be generalised using phylogeny, functional traits, or functional groups, or will populations and species exhibit idiosyncratic responses, should be a key priority for future research. - PublicationPotential impacts of fire and grazing in an endangered ecological community: plant composition and shrub and eucalypt regeneration in Cumberland Plain WoodlandExclosure plots were used to determine the effect of fire and grazing on the structure of a grassy-woodland community. Eighteen months after fire and fence treatments were applied, the species richness, cover and composition of shrubs, trees, herbs and grasses were assessed and compared to pre-treatment censuses. Unburned plots had fewer shrub species and a lower abundance of shrubs, indicating the importance of fire in promoting regeneration of shrub species. Eucalypt species were more abundant and richer following the wildfire burn in summer, suggesting timing of fires is an important aspect in the establishment of the canopy species. Interactions between fire and grazing were found for the abundance of eucalypts (although weak) and resprouting eucalypts, suggesting a subtle interaction between fire and grazing shortly after fire. There was no effect of grazing and no interaction effect between fire and grazing on shrub species richness and abundance or tree species richness and seedling abundance.
All plots showed a change in species composition despite treatment, and 46 species (32% of total richness) were recorded only in the final survey. The high rainfall during the 18-month study is likely to be an important factor in facilitating the establishment of species following all disturbances. This may have ameliorated the impact of grazing as abundant food was available throughout the woodland. The interaction between fire and grazing may be more important in structuring these grassy communities during periods of lower rainfall. - PublicationImpacts of recent climate change on terrestrial flora and fauna: Some emerging Australian examples(Wiley-Blackwell Publishing Asia, 2019-02)
;Hoffmann, Ary A ;Rymer, Paul D ;Byrne, Margaret ;Ruthrof, Katinka X ;Whinam, Jennie ;McGeoch, Melodie ;Bergstrom, Dana M ;Guerin, Greg R ;Sparrow, Ben ;Joseph, Leo; ; ;Camac, James ;Bell, Nicholas ;Riegler, Markus ;Gardner, Janet LWilliams, Stephen EThe effects of anthropogenic climate change on biodiversity are well known for some high-profile Australian marine systems, including coral bleaching and kelp forest devastation. Less well-published are the impacts of climate change being observed in terrestrial ecosystems, although ecological models have predicted substantial changes are likely. Detecting and attributing terrestrial changes to anthropogenic factors is difficult due to the ecological importance of extreme conditions, the noisy nature of short-term data collected with limited resources, and complexities introduced by biotic interactions. Here, we provide a suite of case studies that have considered possible impacts of anthropogenic climate change on Australian terrestrial systems. Our intention is to provide a diverse collection of stories illustrating how Australian flora and fauna are likely responding to direct and indirect effects of anthropogenic climate change. We aim to raise awareness rather than be comprehensive. We include case studies covering canopy dieback in forests, compositional shifts in vegetation, positive feedbacks between climate, vegetation and disturbance regimes, local extinctions in plants, size changes in birds, phenological shifts in reproduction and shifting biotic interactions that threaten communities and endangered species. Some of these changes are direct and clear cut, others are indirect and less clearly connected to climate change; however, all are important in providing insights into the future state of terrestrial ecosystems. We also highlight some of the management issues relevant to conserving terrestrial communities and ecosystems in the face of anthropogenic climate change. - PublicationBeyond body size—new traits for new heights in trait-based modelling of predator-prey dynamics(Public Library Science, 2022)
;Wootton, Kate L; ;Jonsson, Tomas ;Banks, H T; ; Laubmeier, Amanda NFood webs map feeding interactions among species, providing a valuable tool for understanding and predicting community dynamics. Using species' body sizes is a promising avenue for parameterizing food-web models, but such approaches have not yet been able to fully recover observed community dynamics. Such discrepancies suggest that traits other than body size also play important roles. For example, differences in species' use of microhabitat or non-consumptive effects of intraguild predators may affect dynamics in ways not captured by body size. In Laubmeier et al. (2018), we developed a dynamic food-web model incorporating microhabitat and non-consumptive predator effects in addition to body size, and used simulations to suggest an optimal sampling design of a mesocosm experiment to test the model. Here, we perform the mesocosm experiment to generate empirical time-series of insect herbivore and predator abundance dynamics. We minimize least squares error between the model and time-series to determine parameter values of four alternative models, which differ in terms of including vs excluding microhabitat use and non-consumptive predator-predator effects. We use both statistical and expert-knowledge criteria to compare the models and find including both microhabitat use and non-consumptive predator-predator effects best explains observed aphid and predator population dynamics, followed by the model including microhabitat alone. This ranking suggests that microhabitat plays a larger role in driving population dynamics than non-consumptive predator-predator effects, although both are clearly important. Our results illustrate the importance of additional traits alongside body size in driving trophic interactions. They also point to the need to consider trophic interactions and population dynamics in a wider community context, where non-trophic impacts can dramatically modify the interplay between multiple predators and prey. Overall, we demonstrate the potential for utilizing traits beyond body size to improve trait-based models and the value of iterative cycling between theory, data and experiment to hone current insights into how traits affect food-web dynamics.
- PublicationImpacts of temperature on metabolic rates of Extatosoma tiaratum reared on different host plant speciesAccess to balanced nutrition enables optimum health and development, body repair, fat storage, increased fecundity and longevity. In the present study, we assessed the responses of a generalist leaf feeder (the phasmid Extatosoma tiaratum) reared continuously on one of three host plants, tree lucerne (Chamaecyisus palmensis), bramble (Rubus fruticosus) and Eucalyptus species, in a low fluctuating temperature environment until adulthood. Once all individuals reached adulthood, we exposed each individual to a ramping temperature event (starting at 25 °C and ramping the temperature at 0.25 °C min⁻¹) and assessed their metabolic rates (V̇꜀ₒ₂) responses at specific temperature 'bins' (25, 30, 35, 40 and 42 °C). Sex but not diet influenced respiration and metabolic rate. Male individuals, on average, had a higher V̇꜀ₒ₂ than females. Sex and diet were significant influences on V̇꜀ₒ₂ at different temperatures. Metabolic rates at lower temperatures were not affected by sex or diet type. At 35 °C, metabolic rates were influenced by sex and diet, with males reared on bramble and tree lucerne having a higher metabolic rate than females reared on the same foodplant, whereas Eucalypt reared animals showing an opposite trend. Lifetime egg production by females was 150% higher on bramble compared with the other host plants. Incorporating fluctuating temperature ranges into experiments will further help to understand the impact that thermal stress will have on the growth, development, performance and survival of insects in a more variable climatic and nutritional landscape.
- PublicationHigher predation risk for insect prey at low latitudes and elevations(American Association for the Advancement of Science (AAAS), 2017)
;Roslin, Tomas ;Hardwick, Bess ;Cameron, Erin K ;Dattilo, Wesley ;Donoso, David A ;Drozd, Pavel ;Gray, Claudia L ;Hik, David S; ;Hopkins, Tapani ;Huang, Shuyin ;Koane, Bonny ;Novotny, Vojtech ;Laird-Hopkins, Benita ;Laukkanen, Liisa ;Lewis, Owen T ;Milne, Sol ;Mwesige, Isaiah ;Nakamura, Akihiro ;Nell, Colleen S ;Nichols, Elizabeth ;Prokurat, Alena ;Sam, Katerina ;Petry, William K ;Schmidt, Niels M ;Slade, Alison ;Slade, Victor ;Suchankova, Alzbeta ;Teder, Tiit ;van Nouhuys, Saskya ;Vandvik, Vigdis ;Weissflog, Anita ;Zhukovich, Vital ;Slade, Eleanor M; ;Asmus, Ashley ;Barrio, Isabel C ;Basset, Yves ;Boesing, Andrea LarissaBonebrake, Timothy CBiotic interactions underlie ecosystem structure and function, but predicting interaction outcomes is difficult. We tested the hypothesis that biotic interaction strength increases toward the equator, using a global experiment with model caterpillars to measure predation risk. Across an 11,660-kilometer latitudinal gradient spanning six continents, we found increasing predation toward the equator, with a parallel pattern of increasing predation toward lower elevations. Patterns across both latitude and elevation were driven by arthropod predators,with no systematic trend in attack rates by birds or mammals. These matching gradients at global and regional scales suggest consistent drivers of biotic interaction strength, a finding that needs to be integrated into general theories of herbivory, community organization, and life-history evolution. - PublicationClassifying endangered vegetation communities: a case study of Cumberland Plain WoodlandsRemnants of an endangered community, Cumberland Plain Woodlands on shale, were studied in order to 1) investigate the conflict between the needs of legislation to define parameters of protected communities in a precise manner and the spatial variation in communities, and 2) to define floristic groupings in the Cumberland Plain Woodlands based on all plant species. Sites previously classified as Grey Box Woodland, Grey Box Ironbark Woodland and Spotted Gum Woodland map units were surveyed and compared to the same classification applied by one of the authors. Differences were evident, but both classifications showed statistically significant differences between map units, suggesting that although each classification is valid, the differences between these map units cannot be consistently applied. Canopy species were not useful descriptors of the community as they grouped differently to both the full species list and the understorey species. A significantly different community occurring at the transition between shale and sandstone in Holsworthy Military Area was identified, suggesting the importance of this area to the conservation of variability in communities in this area. The use of multivariate techniques to describe levels of variation in communities is discussed and a potential method for using a standard level of similarity to classify vegetation communities is introduced as a mechanism for defining communities using some consistent technique.
- PublicationEffect of Climate Change on Insect Pest ManagementInsect responses to environmental change are crucial for understanding how agro-ecosystems will respond to climate change. Many insect species are pests of crops, but they also play crucial roles as parasitoids and predators of key pest species. Changes in an insect population's physiology, biochemistry, biogeography and population dynamics may occur among populations across their distribution, among the growing seasons, and among crop types. An insect population's response to a rapidly changing climate may also be variable when insects interact with different competitors, predators and parasitoids and impose costs at different life stages. This also can influence the overall food production systems that can be at critical risk from the impacts of climate change (IPCC 2014).