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    Spatial dynamics of anthropogenically altered dispersal patterns : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Ecology at Massey University, Albany, New Zealand
    (Massey University, 2017) Bütikofer, Luca
    The thesis put forward in this study is that anthropogenic disruption of natural dispersal is of central importance for the conservation of biodiversity. The main rationale being that dispersal, as a fundamental life history trait, is directly linked to, and affected by three of the main threats to biodiversity: Invasive species, habitat fragmentation and climate change. In terms of biological invasions, the introduction of exotic taxa into a foreign habitat is performed by people, and the spread of these species within the invasion range is often a result of human aided dispersal. Surprisingly though, not much emphasis is put on anthropogenic dispersal when modelling biological invasions. Habitat fragmentation is the direct consequence of habitat destruction. In a fragmented landscape, remnant natural patches host populations with varying degrees of inter-connectivity. Dispersal through degraded habitat is the key to maintaining viable meta-populations in a fragmented landscape. To facilitate dispersal in highly fragmented landscapes such as cities, a clear knowledge of the roles played by different land cover features (e.g. density of trees or traffic) is the starting point to make informed urban planning decisions. The main issue with climate change is not that climate conditions are disappearing, but that they are moving. As a consequence of this, organisms also need to move along with the climatic conditions they are adapted to. This process, named range shift, is being observed worldwide on several taxa. Researchers, however, put very little attention to the problems arising when “climate migrants” encounter dispersal barriers (e.g. anthropogenic land cover) on their path. The main body of work presented here consists in both the practical analysis of specific systems and the development of conceptual and methodological frameworks to address general issues. Among the former, I used population and landscape genetics approaches to analyse the case of Copper skinks (Oligosoma aeneum) in Auckland (New Zealand) as a recent and intensive habitat fragmentation scenario, with the goal of detecting the land cover types that allow the highest dispersal in urban settings. I also analysed the case of the Australian Litoria frogs (L. aurea, L. raniformis and L. ewingii) in New Zealand with the intent of quantifying the anthropogenic dispersal component of their invasion. As per the latter, I developed a novel method for estimating the anthropogenic component of biological invasions, infer their natural dispersal parameters, and forecast future developments of biological invasions. I also developed the novel concept of C-trap, whereby the shape and spatial orientation of the interface between natural and anthropogenic land cover types may originate traps for climate migrants, and used it to determine where, on a global scale, their high densities can further threaten endangered, endemic animal species. My results identified an early stage fragmentation scenario for urban Copper skinks in Auckland. Relatively high population genetic structure formed as a result of segregation by a motorway. However, the roles of other land cover types in controlling population connectivity could not be determined. Of all Litoria frog populations recorded in New Zealand, about 30% were found to be of anthropogenic origin. Even though the borders of the distribution range occupied so far are unlikely to expand, the density of populations within the range is expected to rise with new, suitable patches being found. Tests on virtual species with the novel methodology for the modelling of biological invasions showed good performance (accuracy in estimating natural dispersal kernel and anthropogenic contribution), also in the presence of challenging limitations in the input dataset. Finally, the global scale application of the C-traps concept to endangered, terrestrial species highlighted the high potential for conservation issues among climate migrants in Eastern Europe and Southern Asia. Although it is challenging to quantify the consequences for biodiversity conservation of anthropogenic alterations to natural dispersal, results from the applied studies confirm the initial thesis on their critical role as biodiversity threats; while the novel concepts and methodologies provide a valuable tool for better incorporating these aspects in ecological studies and conservation management.
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    Functional significance of highly variable colouration in the shore skink (Oligosoma smithi) : a thesis presented in partial fulfilment of the requirements for the degree of Doctor in Philosophy in Ecology at Massey University, Albany, New Zealand
    (Massey University, 2017) Baling, Marleen
    Variation in animal colouration is attributed to several biological functions, a key one being camouflage. Background-matching is a camouflage strategy where prey conceal themselves from predators by resembling their immediate backgrounds. Achieving optimal background-matching can be challenging, particularly in 1) visual backgrounds that form a mosaic caused by spatial variations in habitat characteristics, and 2) varying predator abundance or behaviour. Additionally, crypsis can be affected by alternative and potentially antagonistic functions, such as intraspecific signalling and thermoregulation. This thesis aimed to investigate the selective processes that affect prey colouration for background-matching in a heterogeneous environment. Specifically, I focused on the influence of habitat gradients, predator behaviour, and the potential conflict between camouflage requirements and thermoregulation or intraspecific signalling. Firstly, I conducted a detailed survey on the colour and colour patterns of a wild shore skink population (Oligosoma smithi) within a continuous heterogeneous habitat at Tāwharanui Regional Park. This population’s body colouration showed a significant association with a vegetation gradient, consistent with selection for background-matching. However, field experiments also revealed that predation risk for the more common colour pattern variants was double that of the rarer variant’s regardless of background type, consistent with predictions for apostatic selection (negative frequency-dependent selection). Secondly, I demonstrated that population colouration can respond to a change of habitat. One year after a translocation of shore skinks to an island habitat with a disjunct two-patch background, the population’s colours matched the simple substrate type (bare rocky stones) more than the complex substrate (high vegetation cover on sand). Skinks were darker, less intense in colour, and had lower colour pattern diversity compared to the founder and source populations at Tāwharanui. This study highlighted the potential significance of considering camouflage requirements of a species in human-induced translocations. Thirdly, in an analysis of seasonal effects to camouflage, I found no evidence that background-matching in the Tāwharanui population was compromised by differences in body colours between breeding and non-breeding seasons. This is likely because colours associated with intraspecific signalling (i.e. that exhibited age-dependence and sexual dichromatism) were located in the ventral body regions of skinks that would typically be hidden from predators. Finally, across 17 populations, shore skink colouration showed patterns of spatial variation consistent with thermal melanism (thermoregulation) and island syndrome. Despite the strong correlation of maximum monthly temperature on colours and latitude on colour patterns, I suggest that the significantly darker island populations were caused by a combination of local adaptation (i.e. crypsis) and non-selective forces (e.g., genetic drift). Overall, my thesis provides new insight on how different selection processes maintain dramatic colouration within a species, and marks the first quantitative research on colouration in New Zealand reptiles.
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    The future of indigenous fauna on private land : a case study of the habitat use of the small-scaled skink (Oligosoma microlepis) : a thesis in partial fulfilment for the degree of Master of Science in Conservation Biology at Massey University
    (Massey University, 2006) Teal, Rowena
    The small-scaled skink (Oligosoma microlepis) is a small (≤67 mm SVL) endemic New Zealand lizard that is currently listed as vulnerable by the IUCN (1994). The species is diurnal and heliothermic, inhabiting rock outcrops and piles scattered throughout the central North Island. All of the ca. 17 populations are small, isolated and confined to private land. The Oligosoma spp. Recovery Plan (2002) outlines the need to obtain basic biological data on the species, determine threats and to conduct advocacy with landowners. The first part of my study was to obtain an understanding of the factors affecting O. microlepis' habitat use. This was achieved by using the programme PRESENCE to model site occupancy of the species as a function of site covariates, as well as detection probability as a function of sampling covariates. A total of 45 sites were used, spanning 25 k, on three stations in the Inland Patea district. Presence-absence data and sampling and site covariates were recorded using an active search method for lizards at each site. Results showed that detection probability of small-scaled skink was most affected by rock temperature, the time of day and month surveying was carried out. Site occupancy was correlated with three site covariates. The first important site covariate was distance to the nearest stock route. Probability of site occupancy decreased as the distance to the nearest stock route increased, suggesting that grazing may maintain lizard habitat by keeping rocks clear of vegetation. The second important site covariate was the presence of a tree on the site. No O. microlepis were found when a tree was present on the site, probably due to shade and predation by birds. Lastly, rock piles had a significantly higher occupancy than rock outcrops. This difference could be due to a number of factors, including competitive exclusion by common gecko (Hoplodactylus maculatus), which were abundant on rock outcrops as well as the biophysical nature of outcrops inhibiting thermoregulation. The second part of my study was to conduct more extensive habitat analysis using ordination plots and a classification tree, and this analysis expanded on these site covariates affecting occupancy. Sites were more likely to be occupied if the herbaceous plant Gingidia montana was absent, if the site was not in a gully, if the site had a north-northwest aspect, and the site was close to a public road. This information can potentially increase the efficiency in surveying new sites for O. microlepis. The third part of my study was to conduct environmental education with the farming community to create awareness of O. microlepis and conservation issues in the district. I did this by the sharing of knowledge, the application of skills and subsequent steps towards conservation management on their land. This study demonstrates how environmental education at a local community level is a worthwhile activity in any research on private land. Future research is still needed on current threats to O. microlepis (e.g., introduced predators), the long-term impact of farming, metapopulation dynamics, and effectiveness of management techniques for conserving the species.