Macroecological Patterns of Body Size in Mammals across Time and Space

Abstract

Macroecology is a way of thinking, exploring, and asking questions about complex ecological phenomena. By examining large-scale patterns across temporal, spatial, or taxonomic scales, consistent, common patterns emerge that suggest common underlying causes and processes. The fi eld is expanding rapidly, and macroecological approaches to biology have led to new insights into the operation of general mechanistic processes that govern the structure and dynamics of individuals, populations, and complex ecological systems (Smith et al. 2008). Here we are using a macroecological approach to examine patterns in mammalian body size distributions at multiple spatial and temporal scales. Body size is arguably one of the most fundamental attributes of an organism and has long been of interest to scientists. Many physiological and ecological traits scale with body size (Brown 1995). As a result, information about the body size of an organism can provide considerable information about its ecology and life history. There is enormous variation in the body size of extant organisms, encompassing approximately twenty-four orders of magnitude (Peters 1983; Calder 1984; Niklas 1994), and within mammals body size spans approximately ten orders of magnitude (Brown and Nicoletto 1991; Brown 1995; Alroy 1998; Marquet and Cofre 1999; Bakker and Kelt 2000; Lyons et al. 2004; Smith et al. 2004). Much effort has focused on the consequences of being a certain size and whether taxa exhibit an optimal size (e.g., Brown and Nicoletto 1991;