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    Freshwater invertebrate responses to fine sediment stress: A multi-continent perspective
    (John Wiley and Sons Ltd, 2024-01) McKenzie M; Brooks A; Callisto M; Collins AL; Durkota JM; Death RG; Jones JI; Linares MS; Matthaei CD; Monk WA; Murphy JF; Wagenhoff A; Wilkes M; Wood PJ; Mathers KL
    Excessive fine sediment (particles <2 mm) deposition in freshwater systems is a pervasive stressor worldwide. However, understanding of ecological response to excess fine sediment in river systems at the global scale is limited. Here, we aim to address whether there is a consistent response to increasing levels of deposited fine sediment by freshwater invertebrates across multiple geographic regions (Australia, Brazil, New Zealand and the UK). Results indicate ecological responses are not globally consistent and are instead dependent on both the region and the facet of invertebrate diversity considered, that is, taxonomic or functional trait structure. Invertebrate communities of Australia were most sensitive to deposited fine sediment, with the greatest rate of change in communities occurring when fine sediment cover was low (below 25% of the reach). Communities in the UK displayed a greater tolerance with most compositional change occurring between 30% and 60% cover. In both New Zealand and Brazil, which included the most heavily sedimented sampled streams, the communities were more tolerant or demonstrated ambiguous responses, likely due to historic environmental filtering of invertebrate communities. We conclude that ecological responses to fine sediment are not generalisable globally and are dependent on landscape filters with regional context and historic land management playing important roles.
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    Terrestrial invertebrate communities : the effects of successional age, habitat structure and seasonality : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science in ecology at Massey University
    (Massey University, 1995) Munro, Vanessa M. W
    Ground dwelling invertebrate communities at five sites of successional vegetation of increasing age, were sampled with pitfall traps between December 1992 and January 1994. Species richness peaked in mid successional manuka and late successional broadleaf/podocarp habitats. Individual abundance was highest in early and mid sere sites. Increased habitat heterogeneity and complexity in mid succession may have elevated species richness above that of early sere sites. Furthermore, as manuka is a native plant with a wide geographical range, this may also have contributed to the higher species richness at the Manuka and Broadleaf/Podocarp forest sites. In contrast, the number of guilds per site was highest in the climax forest, and again probably relates to high habitat heterogeneity, complexity and plant diversity at these sites. Invertebrate faunae associated with wooden block refuges placed in the five successional habitats were collected in late November 1993 after nine months. The invertebrate assemblages associated with these blocks yielded similar patterns to those collected with pitfall sampling, with highest diversity and abundance in mid succession. Availability and spacing of alternative natural refuges again seems most likely to have influenced these patterns. Predator abundance was highest in the Pasture and declined as habitat age increased. However, predator diversity peaked in mid and late succession, declining again in the climax Podocarp forest. Competitive exclusion in the climax forest and an inability for native species to colonise exotic pasture, seem most likely to have limited predator species richness at these sites. In contrast, predation pressure, as assessed with caterpillar (Galleria mellonella) baits, increased along the successional gradient. Peak predation intensity in late succession is attributed to the larger size and greater effectiveness of predators occurring in these habitats. In summary, invertebrate community structure clearly changed along the successional gradient; species richness peaked in habitats of intermediate age, the number of guilds increased to peak in late succession, while the number of invertebrates declined. Predation intensity also increased with successional age, however, there was no clear relationship between predation levels, predator abundance or predator diversity.
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    Native and adventive detritivores in forests of Manawatu-Whanganui : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science in Ecology at Massey University, Manawatu, New Zealand
    (Massey University, 2013) Parker, Amie
    Little is known about many New Zealand invertebrates, including detritivores which have a key role in the functioning of ecosystems and are threatened by habitat modification and the addition of adventive species. Detritivores are an abundant group, and, like many other New Zealand taxa, they contain a high level of endemism that needs conserving. Detritivores are so scarcely studied, that it remains unknown how their forest communities are influenced by changes to New Zealand’s forest habitats. This study aimed to increase knowledge on the identity, abundance, and distribution of detritivores in forests of Manawatu-Whanganui. Four main questions were addressed: (1) are adventive detritivores capable of invading native forests?, (2) can pine forests provide an alternative forest habitat for native detritivores?, (3) does proximity to forest edge affect native and adventive detritivores?, (4) are native and adventive detritivores co-occurring in the same habitats? Three detritivore groups (Diplopoda, Isopoda, and Amphipoda) were collected from edge and centre plots in six pine forests and ten native forests (including those that are small and close to urban areas) in Manawatu-Whanganui region of New Zealand. The results show that a number of adventive taxa have spread throughout native forests in Manawatu-Whanganui, which does not support the hypothesis that native forests are resistant to adventive detritivores. Adventive Diplopoda were actually more abundant in native forests, and abundance of adventive Amphipoda and adventive Isopoda was high in both native and pine forests. Some native taxa were less dominant or absent in pine forests, and forest type influenced the community structure of Diplopoda and possibly Isopoda. The likelihood that a randomly collected detritivore would be an adventive was also influenced by forest type in all three detritivore groups. Human disturbance may have facilitated the invasion and establishment of adventive species, because small, urban, and highly modified native remnants appeared to have higher abundance and diversity of adventive species. Edge proximity had little influence on abundance of detritivores, but did affect the predicted likelihood of encountering an adventive individual in all three groups. Adventive and native detritivores co-occurred in all forest habitats and it is possible that adventive detritivores will be influencing native species. Native Amphipoda appear to be under the most immediate threat in Manawatu-Whanganui, with adventive Amphipoda having higher abundance and higher probability of being found throughout all investigated forest habitats; there is evidence that adventive Arcitalitrus is displacing native species. The presence of adventive species could alter the functioning of native forest ecosystems and further research into the effect of adventive species in native forest is recommended. The data also revealed that for all three investigated taxa pine forests can support as many native detritivores as native forests, suggesting that pine forests contribute to preserving native biodiversity. Pine forests may be used as a tool to conserve native detritivores, but the conditions which promote the establishment of native species need further investigation.
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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.