Jason Matthiopoulos

University of Glasgow

Title: Defining, estimating and understanding the fundamental niches of complex animals in heterogeneous environments

Abstract: During the past century, the fundamental niche, the complete set of environments that allow an individual, population, or species to persist, has shaped ecological thinking. It is a crucial concept connecting population dynamics, spatial ecology and evolutionary theory, and a prerequisite for predictive ecological models at a time of rapid environmental change. Yet, its properties have eluded quantification, particularly for mobile, cognitively complex organisms. These difficulties are mainly a result of the separation between niche theory and field data, and the dichotomy between environmental and geographical spaces. Here, I combine recent mathematical and statistical results linking habitats to population growth, to achieve a quantitative and intuitive understanding of the fundamental niches of animals. I trace the development of niche ideas from the early steps of ecology to their use in modern statistical and conservation practice. I examine, in particular, how animal mobility and behaviour may blur the division between geographical and environmental space. I discuss how the fundamental models of population and spatial ecology lead to a concise mathematical equation for the fundamental niche of animals and demonstrate how fitness parameters can be understood and directly estimated by fitting this model simultaneously to field data on population growth and spatial distributions. I illustrate these concepts and methods using both simulation and real animals and, in this way, confirm ideas that had been anticipated in the historical niche literature. Specifically, within traditionally defined environmental spaces, habitat heterogeneity and behavioural plasticity make the fundamental niche more complex and malleable than was historically envisaged. However, once examined in higher-dimensional spaces, the niche is more predictable, than recently suspected. This re-evaluation quantifies how organisms might buffer themselves from change by bending the boundaries of viable environmental space, and offers a framework for designing optimal habitat interventions to protect biodiversity or obstruct invasive species. It therefore promotes the fundamental niche as a key theoretical tool for understanding animal responses to changing environments and a central tool for environmental management. To this end, ecological mechanism (dispersal, density dependence, community effects and individual variation), integrated inference, and ecosystem optimization are the key future areas of development.