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Understanding how community assembly processes drive biodiversity patterns is a central goal of community ecology. While it is generally accepted that ecological communities are assembled by both stochastic and deterministic processes, quantifying their relative importance remains challenging. Few studies have investigated how the relative importance of stochastic and deterministic community assembly processes vary among taxa and along gradients of habitat degradation. Using data on 1645 arthropod species across seven taxonomic groups in Malaysian Borneo, we quantified the importance of ecological stochasticity and of a suite of community assembly processes across a gradient of logging intensity. The relationship between logging and community assembly varied depending on the specific combination of taxa and stochasticity metric used, but, in general, the processes that govern invertebrate community assembly were remarkably robust to changes in land use intensity.

Full Text, Thesis (PhD Doctorate), Doctor of Philosophy (PhD), School of Environment and Sc, Science, Environment, Engineering and Technology, Climate change is predicted to increase the frequency, duration and severity of drought in many regions. Predicting how forest ecosystems will respond to increased drought is a key issue in forest planning and forest management. Invertebrates play a central role in forest health and diversity, yet our understanding of the impact of drought on invertebrate communities in forests is very poor. This PhD addresses the impacts of increased drought on herbivory-based insect communities in tropical rainforests. Most of our current knowledge on that topic consists of observations from around the world that outbreaks of leaf feeders and bark beetles are typically preceded with unusually warm, dry weather. While there have been many experimental drought studies on plants and insects living on them, most of them were small scale experiments limited to one or a few individual plants rather than a whole forest ecosystem, and often reported contradictory results. A framework linking drought severity, plant defence production, plant nutritional quality, and insect response among different insect feeding guilds could help understand why different insects seem to respond differently to drought. After reviewing the literature, I developed a framework that might predict how insects, and particularly herbivorous insects, may respond to prolonged drought. The framework incorporates the severity and longevity of drought and captures the plant physiological adjustments that follow moderate and severe drought and predicts the response of (i) different feeding guilds; (ii) flush feeders and senescence feeders; (iii) specialist and generalist insect herbivores; and (iv) temperate versus tropical forest communities. Intermittent and moderate drought may result in increases of carbon-based and nitrogenbased chemical defences, whereas long and severe drought events can result in decreases in plant secondary defence compounds. I predict that different herbivore feeding guilds will show different

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Full Text, Thesis (PhD Doctorate), Doctor of Philosophy (PhD), School of Environment and Sc, Conversion of forests to pasture has been extensive throughout the tropics and subtropics, and these forests continue to experience deforestation at high levels. Such clearing can alter plant-animal dynamics and thereby degrade ecosystem functioning. It is often assumed that re-establishment of vegetation will recover forest-like communities of animals such as invertebrates, together with the roles they play in important ecosystem processes. However, there has so far been little empirical evidence to support this. This thesis investigated the impact of deforestation on invertebrate-mediated ecosystem functioning, and its recovery during regeneration of rainforests on former pasture. Specifically, it focused on two key ecosystem processes which underly forest regeneration dynamics, while also comparing two different reforestation pathways. The two processes were leaf litter decomposition rates and insect seedling herbivory. For decomposition, functional associations with decomposer invertebrates as well as vegetation structure and floristics were also investigated. Both these ecosystem processes were examined across 25 sites representing different phases of rainforest deforestation and subsequent reforestation. The study area was the Numinbah Conservation Area and surrounds on the Gold Coast Hinterland, in the eastern Australian subtropics. Here the local council had begun restoration management on disused pasture approximately 10 years prior to the beginning of this thesis. Five study sites were placed in each of five vegetation types, consisting of two reference states of grazed pasture and old-growth rainforest (to represent the deforestation process and to indicate the target of restoration), together with three types of regenerating vegetation: unassisted woody regrowth aged 20-50 years on former pasture, and assisted regeneration aged 1-4 and 5-11 years after human interventions that aimed to accelerate natural regeneration within previously-unassisted regrowth

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