Is taxonomic homogenization linked to functional homogenization in temperate forests?

Abstract

Aim Biotic homogenization – the tendency for communities to converge in species composition – has occurred in many ecosystems, creating management challenges. The extent to which this convergence in species composition is related to convergence in trait composition (‘functional homogenization’), however, remains unresolved. Location North America, Wisconsin. Methods Using extensive plant community survey data from the 1950s and 2000s, and values for 11 traits measured on 169 species, we examined changes in functional beta diversity across 151 upland forest stands distributed across southern and northern Wisconsin. To estimate functional beta diversity, we used two recently developed pairwise functional dissimilarity metrics, plus an additive partitioning of functional diversity approach. Results Using pairwise functional dissimilarity metrics, we found no significant changes in functional beta diversity through time in either southern or northern upland forests. Under additive partitioning, species alpha diversity was lower than species beta diversity; whereas functional alpha diversity was much higher than functional beta diversity in both time periods and across all forest types. This suggests a high turnover of species but a low turnover of traits among communities. Main conclusions Although upland forests in Wisconsin have experienced taxonomic homogenization, they have not undergone functional homogenization, which may reflect a high functional redundancy among Wisconsin forest plants. As species decline further or disappear in response to habitat fragmentation and other global changes, functional redundancy may decline in a way that could diminish the functional diversity of Wisconsin's forests at both local and regional scales.

Does functional homogenization accompany taxonomic homogenization of British birds and how do biotic factors and climate affect these processes?

“…We applied a moving window algorithm so that each square within the dataset was included as the focal square in the calculations of turnover for both atlases. Two additional measures of functional turnover, nearest functional neighbor and mean functional dissimilarity (Sonnier et al., 2014; Swenson et al., 2012) between neighboring hectads were also calculated to test whether the occurrence of functional homogenization differs with the measure of functional turnover used. These measures use functional distances between species, similar to β rao , to calculate functional dissimilarity between communities; however, their construction and interpretation are less similar to β sim .…”

“…Understanding the turnover of traits in space and time, therefore, has been recognized as an essential area of investigation to determine whether changes in taxonomic turnover are accompanied by changes in functional turnover, or whether functional redundancy may ensure ecosystem functioning is maintained despite losses in taxonomic diversity (Villéger, Grenouillet & Brosse, 2014). Previous studies failed to find a consistent relationship between functional and taxonomic homogenization with results varying between location, environmental pressures, and focal taxa (Abadie, Machon, Muratet & Porcher, 2011; Devictor, Julliard, Couvet, Lee & Jiguet, 2007; Monnet et al., 2014; Reif et al., 2013; Sonnier, Johnson, Amatangelo, Rogers & Waller, 2014). Many of these only use a proxy for functional homogenization, that is, mean community specialization.…”

“…Using mean specialization, however, ignores similarity between communities (Gosselin, 2012), which is integral to the general definition of homogenization as an increase in spatial similarity of genetic, functional, or taxonomic diversity in time (Olden & Rooney, 2006; Olden et al., 2004). More recently, a handful of studies have measured functional homogenization by calculating the difference in functional (dis)similarity between communities over time (Baiser & Lockwood, 2011; Monnet et al., 2014; Sonnier et al., 2014). Here, we use a similar “difference in turnover” method to incorporate a variety of ecological traits into a measure comparable with that of taxonomic homogenization.…”

“…Climate modifies the local environment, leading to both taxonomic and functional homogenization (Meynard et al., 2011; Sonnier et al., 2014). For example, areas which have undergone a long‐term increase in minimum temperature are expected to exhibit homogenization as species adapted to warmer conditions dominate the landscape by shifting their range (Devictor, Julliard, Couvet & Jiguet, 2008; Powney, Cham, Smallshire & Isaac, 2015).…”

The Homogocene: a research prospectus for the study of biotic homogenisation

“…Studies comparing patterns in taxonomic and functional homogenisation have been particularly intuitive in this regard (e.g. Smart et al 2006, Pool and Olden 2012, Sonnier et al 2014, Villéger et al 2014.…”