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    Global warming responses within the New Zealand alpine radiation of acridid grasshoppers : a thesis submitted in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Ecology at Massey University, Manawatu, New Zealand
    (Massey University, 2024-07-20) Meza-Joya, Fabio Leonardo
    We are living in the Anthropocene, where humans are directly and indirectly altering climatic regimes, leading to warmer conditions with multifarious effects on the biosphere. Well-documented ecological responses to planetary heating include distributional, phenological, and/or phenotypical shifts. Anthropogenic global warming is predicted to significantly impact alpine ecosystems, yet our current understanding of alpine species responses to both ongoing and future global warming is limited. My thesis bridges this gap by investigating the influence of past and future climates on New Zealand’s endemic alpine short-horn grasshoppers (Orthoptera: Acrididae), as representatives of New Zealand’s alpine fauna. As one of the most ubiquitous herbivores in alpine areas worldwide, grasshoppers provide a marvellous lens to examine responses of native systems to increasing temperatures and explore the mechanisms behind such responses. For this, I used an integrative approach combining phylogeographic tools, demographic statistics, phenotypic data (size and shape), niche models and niche metrics, and genotype–phenotype–environment associations. My findings indicate that (1) distinct climatic, biological, and geophysical factors controlled population structuring of grasshopper species during the Pleistocene with a legacy of spatially separate intraspecific lineages; (2) departures from current climatic conditions are projected to vary with geography, and so species exposure and vulnerability to climate change will vary; (3) habitat loss predicted over the next 50 years of warming will lead to smaller and more-fragmented populations with reduced adaptive potential; (4) differences in niche features between diverging intraspecific lineages may lead to lineage-specific responses; (5) distinct climatic factors influence body size clines, and this might strongly influence potential phenotypic responses. An unexpected and important result is that closely related species are predicted to respond in different ways to climate change, suggesting such responses are more evolutionarily labile than conserved. Collectively, this body of research offers valuable insights into the eco-evolutionary responses of alpine organisms to global warming with broad implications for alpine biota everywhere in the world. The thermal environment is a powerful abiotic driver of evolution, and as we face unparalleled rates of warming, understanding how temperature hinder or foster evolution is critical for assisting management decisions that embrace evolutionary resilience.
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    Global flyway evolution in red knots Calidris canutus and genetic evidence for a Nearctic refugium
    (John Wiley and Sons, Ltd, 2022-04) Conklin JR; Verkuil YI; Battley PF; Hassell CJ; ten Horn J; Johnson JA; Tomkovich PS; Baker AJ; Piersma T; Fontaine MC; qu Y
    Present-day ecology and population structure are the legacies of past climate and habitat perturbations, and this is particularly true for species that are widely distributed at high latitudes. The red knot, Calidris canutus, is an arctic-breeding, long-distance migratory shorebird with six recognized subspecies defined by differences in morphology, migration behavior, and annual cycle phenology, in a global distribution thought to have arisen just since the last glacial maximum (LGM). We used nextRAD sequencing of 10,881 single-nucleotide polymorphisms (SNPs) to assess the neutral genetic structure and phylogeographic history of 172 red knots representing all known global breeding populations. Using population genetics approaches, including model-based scenario-testing in an approximate Bayesian computation (ABC) framework, we infer that red knots derive from two main lineages that diverged ca. 34,000 years ago, and thus most probably persisted at the LGM in both Palearctic and Nearctic refugia, followed by at least two instances of secondary contact and admixture. Within two Beringian subspecies (C. c. roselaari and rogersi), we detected previously unknown genetic structure among sub-populations sharing a migratory flyway, reflecting additional complexity in the phylogeographic history of the region. Conversely, we found very weak genetic differentiation between two Nearctic populations (rufa and islandica) with clearly divergent migratory phenotypes and little or no apparent contact throughout the annual cycle. Together, these results suggest that relative gene flow among migratory populations reflects a complex interplay of historical, geographical, and ecological factors.
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    Discontinuous distributions of iconic New Zealand plant taxa and their implications for southern hemisphere biogeography : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Plant Biology at Massey University, Palmerston North, New Zealand
    (Massey University, 2007) Knapp, Michael
    New Zealand has long been regarded as a key to understanding discontinuous distributions in the Southern Hemisphere. The archipelago is a fragment of the ancient super continent Gondwana. It has been isolated for 80 million years, has an excellent fossil record, and some of its most ancient biota such as the Southern Beeches (Nothofagus) and the Araucariaceae show disjunct distribution patterns with relatives on other fragments of Gondwana. Some of the most controversial problems of Southern Hemisphere biogeography with wide ranging implications involve New Zealand taxa. Three of them have been addressed in this thesis. The transoceanic relationships of the genus Nothofagus have long been regarded as an iconic example of a distribution pattern resulting from the break up of Gondwana. Phylogenetic analyses presented here show that, though most of the extant distribution of the genus is indeed shaped by tectonic events, Southern Beeches have crossed the Tasman Sea between Australia and New Zealand at least twice during the Tertiary period These results, together with findings of studies on other plant and animal taxa, emphasise the importance of dispersal but at the same time raise the question of whether any New Zealand taxa can be considered Gondwanan relicts. There is no geological evidence for the continuous existence of land throughout the Tertiary in the New Zealand area. However, molecular clock analyses presented in this thesis indicate that Agathis australis (New Zealand Kauri) diverged from its closest Australian relative prior to the Oligocene, or period of greatest submergence during the Tertiary. Thus these findings reject the hypothesis of the complete drowning of the New Zealand landmass during the Tertiary. They cannot reject the hypothesis of Stöckler et al. (2002) that the New Zealand Kauri lineage has persisted on the archipelago since its separation from Gondwana. Explanations for forest distribution patterns within the New Zealand islands themselves are diverse. New Zealand Nothofagus species show distribution gaps that are not explained by recent environmental factors alone. Early Miocene tectonic events and alternatively Pleistocene climates have been proposed as causes for this disjunct distribution pattern. Phylogeographic analyses reported in this thesis suggest that severe Pliocene and Pleistocene climates as well as Pliocene and Pleistocene tectonic events have shaped present day distribution and diversification of Nothofagus species in New Zealand.