Incorporating intraspecific trait variation into functional diversity: Impacts of selective logging on birds in Borneo

Abstract

Summary As conservation increasingly recognizes the importance of species’ functional roles in ecosystem processes, studies are shifting away from measuring species richness towards measures that account for the functional differences between species in a community. These functional diversity (FD) indices have received much recent attention and refinement, but their greatest limitation remains their inability to incorporate information about intraspecific trait variation (ITV). We use an individual‐based model to account for ITV when calculating the functional diversity of two avian communities in Borneo; one in primary (unlogged) forest and one in selectively logged forest. We deal with the scarcity of trait data for individual species by developing a simulation approach, taking data from the literature where necessary. Using a bootstrapping procedure, we produce a range of ecologically feasible FD values taking account of ITV for five commonly used FD indices, and we quantify the confidence that can be placed in these values, using a newly developed bootstrapping method: btFD. We find that incorporating ITV significantly alters the FD values of all indices used in our models. The rank order of FD for the two communities, indicating whether diversity was higher in primary or selectively logged forest, is largely unchanged by the inclusion of ITV. However, by accounting for ITV, we are able to reveal previously unrecognized impacts of selective logging on avian functional diversity through a narrower dispersion of individuals in functional trait space in logged forest. Our results highlight the importance of incorporating ITV into measures of functional diversity, whilst our simulation approach addresses the frequently encountered difficulty of working with sparse trait data and quantifies the confidence that should be placed in such findings.

A test of trophic and functional island biogeography theory with the avifauna of a continental archipelago

“…We selected 15 functional traits previously recognized to be functionally important in the partitioning of niche space based on resource requirements, foraging substrate use and dietary composition (Sekercioglu, ). Trait data were collected from Wilman et al () and Del Hoyo, Elliott, Sargatal, Christie, and Juana () following methods in Ross et al (), and no traits were assumed a priori to contribute more to ecosystem functioning than others (for a full list of traits and their sources, see Table S1). We first down‐weighted correlated traits and scaled continuous traits (body mass and clutch size) so they approximated a Gaussian distribution.…”

“…(2014) and Del Hoyo, Elliott, Sargatal, Christie, and Juana (2017) following methods in Ross et al (2017), and no traits were assumed a priori to contribute more to ecosystem functioning than others (for a full list of traits and their sources, see Table S1). We first down-weighted correlated traits and scaled continuous traits (body mass and clutch size) so they approximated a Gaussian distribution.…”

Trait‐based ecology of terrestrial arthropods

“…Bennett et al ., ), as well as animals (e.g. Ross et al ., ) including terrestrial arthropods. Studies on wild bee communities have shown that intraspecific variation in body size may shape assembly along climatic gradients (Classen et al ., ), and mediate the effects of habitat fragmentation on community structure and the ecosystem function of pollination (Warzecha et al ., ).…”

Selective logging intensity in an East African rain forest predicts reductions in ant diversity

“…, Ross et al . ). Yet these relationships may not be so one‐dimensional; in some cases, habitat fragmentation and selective logging have been found to have neutral or even positive relationships with certain components of biodiversity, particularly after a recovery time of several decades (Azevedo‐Ramos et al .…”

“…Habitat fragmentation and selective logging have frequently been shown to reduce biodiversity across a range of taxa (Heydon & Bulloh 1997, Ewers et al 2015, Hamer et al 2015, Ross et al 2017). Yet these relationships may not be so one-dimensional; in some cases, habitat fragmentation and selective logging have been found to have neutral or even positive relationships with certain components of biodiversity, particularly after a recovery time of several decades (Azevedo-Ramos et al 2006, Gunawardene et al 2010, Edwards et al 2013.…”