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    Spatial and environmental patterns of rare lotic macroinvertebrate diversity : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Ecology at Massey University, Manawatū, Palmerston North, New Zealand
    (Massey University, 2021) Rados, Dimitrios A.
    Stream macroinvertebrate communities comprise a few common taxa and many rare ones. Small populations of rare taxa can be more vulnerable to environmental change than those of common taxa. However, they are often discarded from community analyses on the grounds that they complicate data interpretation. The aim of this thesis was to evaluate the effect of rare taxa on assessing ecosystem health and on interpreting biodiversity patterns based on lotic macroinvertebrate communities. I assessed the effect of multiple types of rare taxa exclusion on biomonitoring, using macroinvertebrate data collected for the National River Water Quality Network of Aotearoa New Zealand. I compared the effect of different sampling methods on biodiversity patterns of rare taxa in pristine streams in the Tongariro National Park and determined the local environmental variables most strongly linked with common and rare taxa. Finally, I evaluated the effect dispersal processes and local environment have on structuring the common and rare components of lotic communities, considering the position within the stream network and the dispersal mode of the invertebrates. Exclusion of rare taxa led to significant misclassifications of ecological quality by biomonitoring tools that use presence-absence data, such as the Macroinvertebrate Community Index, and often masked their relationship with nutrient stressors. Different sampling methods collected clearly differentiated rare components of lotic assemblages, depending on the habitat sampled (riffles, non-riffles) and the life-stage of the invertebrates (benthic larvae, flying adults). A comprehensive species inventory can be compiled by combining methods, with benthic samples as the basis. Biodiversity metrics of the common and rare components of macroinvertebrate communities were related to similar environmental variables. While the structure of the two components was related to different variables, in combination they revealed a greater number of relationships with the environment. Rare taxa assemblages were not structured clearly by either local environment or dispersal processes, however their inclusion was necessary to demonstrate that the complete communities were determined by the local environment. Overall, I did not find any reason to exclude rare taxa from lotic macroinvertebrate studies, but rather found they can facilitate community analyses. Given the increasing threats on lotic macroinvertebrate biodiversity, it is also crucial to include them in such studies, hopefully so we can prevent their complete extinction.
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    The effects of hydrological and nutrient disturbance on stream invertebrate communities using a trait-based approach : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Aquatic Ecology at Massey University, Manawatu, New Zealand
    (Massey University, 2018) Dinh, Yen Thi Hai
    Anthropogenic altered flow regimes and nutrient enrichment can cause significant impacts on stream biota and may lead to species loss if characteristics of the local fauna are not compatible with the new environmental conditions. I used fourth corner models, Bayesian ordination, and regression analysis to assess those potential effects on trait and species composition of invertebrate communities in UK, New Zealand (NZ) and Vietnamese streams. NZ temperate mountain streams with greater substrate disturbance increased the abundance of plastron- respirers, but not those having two aquatic life stages or who were filter feeders. UK temperate rivers with predictable multiple high flows per year supported individuals having highly synchronized life history strategy; rivers with one prolonged rising climb and strong groundwater influence were better for those having a high reproduction strategy, and rivers with a steep peak flow supported both strategies. Nutrients affect functional feeding and life history traits via promoting algal overgrowth in NZ streams. Both periphyton biomass and nutrients increased the abundance of algae piercers, collectors and those having two aquatic life stages, being long-lived and having hermaphroditic ability; but decreased the abundance of shredders, scrapers, and those having univoltine life cycles. The post-flood recovery of invertebrate communities depended on the recovery of the food base of the food web that was, in turn, determined by the presence of a forest canopy cover and nutrient levels in a stream. Within the forest canopy stream, communities in the low nutrient site recovered by week 9 after a 1-in-50-year flood in Wellington, NZ. Without the forest canopy, the recovery of communities in nutrient impacted streams (by 25 weeks) was probably associated with a quicker regrowth of periphyton while communities in the low nutrient site had not recovered even after 40 weeks. Hydrological disturbances, nutrients, and their combination had strong effects on invertebrate communities in temperate streams. Taxa that survive in a site have trait characteristics that are highly compatible with both the hydrological and nutrient conditions at a site. In contrast to temperate invertebrate communities, Vietnamese tropical highland community structure was influenced more by elevation than disturbance. Further studies are required to clarify how flow disturbance may effect invertebrate communities in tropical streams.
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    The effects of restoration on the structure and function of litter invertebrate communities in New Zealand native forest remnants : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Ecology at Massey University, Palmerston North, New Zealand
    (Massey University, 2012) Costall, Jessica Anne
    Much of New Zealand‘s remaining lowland forest exists as small, often degraded and heavily disturbed remnants on private farmland. Disturbances, such as livestock grazing and browsing by mammalian pests, are known to have a detrimental effect on native vegetation of these remnants. However, it is unclear what impact these disturbances have on the structure and function of forest floor invertebrate communities. Existing studies of forest fragmentation have predominantly focused on the effects of remnant area and shape, rather than remnant condition. This study examines how litter invertebrate habitat, community structure, and leaf litter decomposition, vary between grazed and ungrazed (fenced) remnants of differing size, and nearby forest reserves. Secondly, I examine how invertebrate community structure and function recover with time since livestock exclusion, with and without additional mammalian pest control. I found that grazed remnants provide dramatically altered habitat for litter invertebrates, compared to fenced remnants and large forest reserves. Grazed remnants are typified by having higher soil compaction, minimal understorey vegetation, and reduced litter cover. Consequently, grazed remnants have depauperate, yet highly variable invertebrate communities, compared to fenced remnants and forest reserves. Even very small forest remnants can support litter invertebrate communities very similar to that of larger forest reserves, provided they are protected from livestock grazing. Furthermore, invertebrate communities show strong recovery over time since livestock exclusion, particularly when livestock exclusion is combined with mammalian pest control measures. I found that litter decomposition rates did not differ between management treatments in my first observational study. However, in the second observational study, leaf decomposition rates at the edge of remnants increased with time since livestock exclusion, suggesting that restoration actions can lead to changes in ecological functioning. Small native forest remnants have high ecological value and substantial restoration gains can be made through the relatively simple action of fencing to exclude livestock.
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    The ecosystem effects of the biocontrol of heather (Calluna vulgaris) with the heather beetle (Lochmaea suturalis) : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science in Zoology at Massey University, Palmerston North, New Zealand
    (Massey University, 2012) Blayney, Andrew
    The biological control of invasive plants has the ability to affect sustainable and targeted control over large areas. Such biological control programs are an important tool in the control of invasive plants in conservation areas. The ultimate aim for these programs is to provide a net ecosystem benefit via the reduction of invasive plant densities. However, whether this aim is fulfilled is rarely evaluated. Invasive plant control results in large scale disturbance to ecosystems by removing the novel but often utilised habitat and resources provided by the invasive plant. Biological control is also complicated by having a novel organism introduced into the ecosystem with potential flow on effects for species and trophic level interactions. This research evaluated the ecosystem impact of the heather (Calluna vulgaris) biological control program using the heather beetle (Lochmaea suturalis) on the native tussock grassland in the central North Island of New Zealand. This was achieved by comparing invertebrate communities in a small scale experiment and over three large heather beetle outbreak sites. This work provides an extension to Keesing’s (1995) research on the effects of heather invasion on communities. Heather provides a novel and unsuitable food source to many native phytophagous insects, may disrupt host finding behaviours of these insects, and alter habitat structure and complexity affecting Araneae abundance. Changes in invertebrate community composition following control were related to the removal of these effects. This outcome was consistent with predictions from Keesing (1995) and in both small and large scale studies. Heather beetle presence was found to have a positive effect on Araneae and Collembola abundance. Heather control also had a positive for the common skink (Oligosoma nigriplantare polychroma) Overall the biological control of heather caused invertebrate communities to revert back to a composition resembling more closely those found in non-invaded habitats. This suggests that the biological control of heather provides a net positive conservation benefit to native tussock grasslands.