Global patterns and processes of organismal niche in the marine environment

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The WHY of the WHERE and WHEN species are distributed on Earth is a central question in ecology. While multiple factors such as available habitat and evolutionary origin are considered to drive species distributions in our oceans, environment is considered a primary force. Environment not only regulates the occurrence of animals in habitats/at latitudes, but it also drives species interactions that structure food webs from micro- to macro-scales. The interaction of a species with abiotic (environment = habitat) and biotic (prey = diet) factors is termed the niche. In an era of rapid climatic shift - the Anthropocene - understanding how environmental variation moulds the niche of species will help to predict its effects on the stability and resilience of global food webs. While spatial distribution patterns of species are well known, such as increasing species biodiversity from high to low latitudes (the Latitudinal Diversity Gradient; LDG), the underlying causes of these patterns have received little attention in our oceans. The Latitudinal Niche Breadth Hypothesis (LNB), a famous theory proposed to account for LDG, states that smaller niches and greater species diversity will occur at the equator as compared to the poles because of increased environmental stability. I will examine the influence of environmental context on species niche at the poles, equator and along the polar-equatorial latitudinal gradient through testing the LNB hypothesis in our oceans. I will do this through: i) Establishing the relationship between niche size of species from known feeding groups (Trophic Levels; TL) at latitudinal extremes (pole and equator); ii) Testing causal links between established patterns of niche size and environmental variation at the pole and equator; iii) Adopting a macroecological approach to examine niche size patterns and environmental causal links across a continuous polar-to-equator latitudinal gradient; and iv) Testing if the trends fit expectations of the LNB hypotheses in the marine environment. My aim is to advance understanding of the impact of ongoing climate shifts on global ecosystems for sustainable resource management.