Trait-based approaches to conservation physiology: forecasting environmental change risks from the bottom up

Abstract

Trait-based approaches have long been a feature of physiology and of ecology. While the latter fields drifted apart in the twentieth century, they are converging owing at least partly to growing similarities in their trait-based approaches, which have much to offer conservation biology. The convergence of spatially explicit approaches to understanding trait variation and its ecological implications, such as encapsulated in community assembly and macrophysiology, provides a significant illustration of the similarity of these areas. Both adopt trait-based informatics approaches which are not only providing fundamental biological insights, but are also delivering new information on how environmental change is affecting diversity and how such change may perhaps be mitigated. Such trait-based conservation physiology is illustrated here for each of the major environmental change drivers, specifically: the consequences of overexploitation for body size and physiological variation; the impacts of vegetation change on thermal safety margins; the consequences of changing net primary productivity and human use thereof for physiological variation and ecosystem functioning; the impacts of rising temperatures on water loss in ectotherms; how hemisphere-related variation in traits may affect responses to changing rainfall regimes and pollution; and how trait-based approaches may enable interactions between climate change and biological invasions to be elucidated.

Figure 1.

Various theoretical representations of the relationship between the environment, some form of trait or species source pool and the final set of traits or abundances. (a) The relationship between trait distributions and performance filters used by Webb et al. [14]. (b) The approach taken by Kearney & Porter [29] to illustrate the relationship between species distribution models (a statistical description of what goes on inside the black square), and mechanistic niche modelling, which is explicit about the internal processes. (c) The macrophysiological approach described by Chown et al. [30]. (d) The relationship between isolation and time and how this may influence community assembly and phylogenetic relationships among species. The different coloured dots represent different species, and the coloured island the filter to colonization of such an isolated area (adapted from Emerson & Gillespie [19]).

Figure 2.

(a) The trade in ivory through Durban harbour (South Africa) over time in the 1800s. Note how rapidly the supply from across the eastern parts of the sub-continent was diminished (redrawn from data in McCraken [48]). (b) The relationship between body mass and US dollar prices for various African mammal families (redrawn from Johnson et al. [49]).

Figure 3.

The removal of large-bodied individuals and large-bodied species (indicated by the red rectangles) will eventually lead to the removal of several forms of physiological function owing to the strong relationships between size and function. This may be the case even if relationships are significantly negative, but in the case of no relationship the effect may not be realized.

Figure 4.

(a) Global temperature changes and changes in ectotherm metabolic rates between 1980 and 2010. The panels indicate, in order, changes in temperature, mass-normalized metabolic rate and relative changes in mass-normalized metabolic rate, respectively. Adapted from Dillon et al. [91]. (b) Changes in cuticular (i) and respiratory (ii) water loss rates (WLRs) in the dung beetle Scarabaeus spretus at different temperatures and following different acclimation treatments. Redrawn from Terblanche et al. [104].