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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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    Monitoring strategies for the giant land snail Powelliphanta traversi tararuaensis (Gastropoda: Pulmonata: Rhytididae) : an assessment and exploration of current and future techniques : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science in Conservation Biology at Massey University, Palmerston North, New Zealand
    (Massey University, 2011) Turner, Rachel Lynn
    The current monitoring strategy employed in the management of Powelliphanta traversi tararuaensis, a threatened species of giant carnivorous land snail from the Manawatu region of New Zealand, was used to assess the state of two remaining population strongholds – Shannon Forest and Ohau. Conservation targets were found to be amiss in the Shannon Forest population. Average abundance of live P. t. tararuaensis there measured well below the recovery goal set by the Powelliphanta Recovery Plan. A decline in recruitment was also noted for the Shannon population, with the average size of snails found increasing between the surveys, and a significant drop in numbers of smaller individuals. P. t. tararuaensis populations in Ohau were found to be healthier with respect to conservation goals, with two study areas within the site having live P. t. tararuaensis numbers well above the target for recovery. Questions were then asked about the current monitoring program for Powelliphanta, in particular concerning the apparent destructive nature of the methodology and the lack of collection of detailed data on life history parameters and population dynamics. I thus tested the effect of a monitoring event on the short-term behaviour of P. t. tararuaensis using a mark-recapture study design. The disturbance to the area associated with monitoring had an effect on the re-sighting probability of marked snails, with individuals less likely to be encountered in the days following the monitoring event. New techniques for monitoring Powelliphanta snails were then explored to address the short-fall in methods of gaining life history data in the current program. Attaching tags to the shells of P. t. tararuaensis for individual identification using certain adhesives was found to affect the foraging behaviour of wild rats. Loctite and Araldite glues should be used with caution in a field setting, as they may predispose marked snails to depredation by rats. An alternative method for individual snail recognition was then trialled, utilising natural marks on snail shells and a photographic database. It was discovered that individuals of P. t. tararuaensis could be recognised by naturally occurring shell variation, but the accuracy decreased over a six month time-frame as new marks were gained and old ones evolved. This thesis concludes that the current monitoring system for Powelliphanta could be improved, both in the type of data gained for assessing management and conservation goals, and in the lessening of impact on snail behaviour. Monitoring strategies for land snails would benefit from incorporation of a non-invasive mark-recapture approach, such as photographic identification. Such techniques would allow for more directed conservation action, without potentially negative impacts on Powelliphanta behaviour.