Barbara J. Downes

1 Introduction Almost all levels of ecological organisation are influenced by the movement of individuals, including the structure and distribution of populations and communities; intra- and interspecific interactions and the flows of propagules, pathogens and nutrients within and among ecosystems.

1 INTRODUCTION The amount and spatial arrangement (configurational heterogeneity) of resources can influence species abundance and diversity and have functional consequences in ecosystems. Traditionally, ecologists have focused on the roles of resource quantity (resource concentration hypothesis) and diversity of resource types (compositional heterogeneity) in shaping biological communities (Hutchinson, 1957).

1 INTRODUCTION A central goal in ecology is to understand how and why numbers of organisms differ across time and space (Hixon et al., 2002; Sutherland et al., 2013). However, this understanding is often elusive for organisms with complex life cycles because limits to abundance can be set at any life stage (Marchant, 2021; Piana et al., 2019).