d03

Individualised niches in a variable environment – Consequences for environmental change responses and for species interactions

Meike Wittmann

In this project, we will explore the consequences of individual differences and the NC³-mechanisms when there is abiotic or biotic variation in the environments experienced by individuals. In two parts of the project, we will explore the consequences of individualised niches for a species’ response to environmental change and for interactions with other species. First, to model the effects on responses to environmental change, we will assume that an individual’s fitness depends on the match with its micro-environment, where the distribution of micro-environments changes over time. We will quantify average fitness across time and monitor population persistence or extinction, with or without heritable variation, niche choice, construction, and conformance. Our most important theoretical contribution will be to develop a two-dimensional theory of non-linear averaging (theory of population averages of non-linear functions of individual traits) that can accommodate the NC³-mechanisms. Building upon this theoretical framework, we will then explore how niche choice and niche conformance affect the response of fire salamander and fur seal populations to climatic variability (with A04 and A01, respectively). Second, we will develop a modelling framework to study the consequences of individualised niches and NC³ on species interactions. Here the relevant niche dimension for an individual is the trait of individuals of another species, with one or both species employing NC³-mechanisms to influence the match. Again, we will incorporate the NC³-mechanisms into a two-dimensional theory of non-linear averaging. As applications, we will explore the role of niche choice for the evolution of plant-herbivore interactions, in particular host-plant adaptation of phytophagous insects (with A06), and the effects of parasite niche construction and host niche conformance on host-parasite population dynamics (with C05). All in all, this project will serve to bring a more realistic and dynamic niche concept to studies of intraspecific trait variation and its consequences.