Moving beyond body size in trait-based ecological prediction
Body size scales with key processes across all stages of environmental filtering (e.g. desiccation tolerance, metabolism, prey consumption rates, movement; Brown et al. 2004), so it is not surprising that measures of organism size are applied so frequently in trait-based ecology. While the inclusion of body size, particularly in descriptions of food webs, has been of great benefit to describing ecological structure and function (Woodward et al. 2005; Brose et al. 2006; Jacob et al. 2011), this single trait explains a limited amount of variation in terms of trait-driven biological and ecological processes. Moreover, other morphological and physiological traits are also key mediators of the influence of size, such as body shape and metabolic approach to temperature regulation, respectively. Within size classes, variation in key behavioural and life history traits can influence establishment and persistence within ecological communities; for example, reproductive behaviours are often incorporated into trait-based analyses that model species’ and populations’ dispersal capabilities in changing and novel ecosystems (Estrada et al. 2018). The inclusion of traits other than body size can increase our understanding of current ecological community structure/function (Gravel et al. 2016), but perhaps more importantly, our ability to provide important insights for prediction of future ecological states arising from ongoing global change. However, the role of many behavioural, life history, physiological, and morphological traits (other than size) identified in this review—ranging from fecundity, to jaw strength, to flight initiation distance—are mediated by organism size, illustrating the all importance of incorporating a range of correlated traits into predictive analyses.