By wind, wings or water: body size, dispersal and range size in aquatic invertebrates

The past 15 years have seen a dramatic increase in the study of large-scale patterns and processes in ecology under the banner of macroecology (Brown & Maurer, 1989). Organismal body size is one of the key components of many of these studies, and the distribution of body size and its relationship with range size and abundance figure extensively in the macroecological literature (Gaston & Blackburn, 2000; Blackburn & Gaston, 2003; Gaston, 2003). Body size is also the central component of the ‘three-quarters scaling law’, which predicts that metabolism scales to body mass0.75 (e.g. Gillooly et al., 2001) and is seeing increasing use in ecological predictions, including those concerning trophic interactions (Woodward et al., 2005), population dynamics (Marquet et al., 2005), species diversity (Allen, Brown & Gillooly, 2002) and energy flow (Enquist et al., 2003); indeed, the scaling of metabolism with body mass has also recently been used in attempts to make macroecological predictions (e.g. Jetz et al., 2004).

Despite the recent surge of interest in large-scale ecological patterns, aquatic ecologists have been slow to take up the concept of macroecology. It could perhaps be argued that much of the aquatic ‘community ecology’ over the past couple of decades, relating assemblage composition in aquatic systems to environmental variables, was macroecology of sorts. However, this research has rarely progressed to examine over-arching patterns and their potential underlying mechanisms, and is therefore somewhat limited in how it can inform general ecological theory.