Integrating species traits into species pools

Abstract

Despite decades of research on the species-pool concept and the recent explosion of interest in trait-based frameworks in ecology and biogeography, surprisingly little is known about how spatial and temporal changes in species-pool functional diversity (SPFD) influence biodiversity and the processes underlying community assembly. Current trait-based frameworks focus primarily on community assembly from a static regional species pool, without considering how spatial or temporal variation in SPFD alters the relative importance of deterministic and stochastic assembly processes. Likewise, species-pool concepts primarily focus on how the number of species in the species pool influences local biodiversity. However, species pools with similar richness can vary substantially in functional-trait diversity, which can strongly influence community assembly and biodiversity responses to environmental change. Here, we integrate recent advances in community ecology, trait-based ecology, and biogeography to provide a more comprehensive framework that explicitly considers how variation in SPFD, among regions and within regions through time, influences the relative importance of community assembly processes and patterns of biodiversity. First, we provide a brief overview of the primary ecological and evolutionary processes that create differences in SPFD among regions and within regions through time. We then illustrate how SPFD may influence fundamental processes of local community assembly (dispersal, ecological drift, niche selection). Higher SPFD may increase the relative importance of deterministic community assembly when greater functional diversity in the species pool increases niche selection across environmental gradients. In contrast, lower SPFD may increase the relative importance of stochastic community assembly when high functional redundancy in the species pool increases the influence of dispersal history or ecological drift. Next, we outline experimental and observational approaches for testing the influence of SPFD on assembly processes and biodiversity. Finally, we highlight applications of this framework for restoration and conservation. This species-pool functional diversity framework has the potential to advance our understanding of how local- and regional-scale processes jointly influence patterns of biodiversity across biogeographic regions, changes in biodiversity within regions over time, and restoration outcomes and conservation efforts in ecosystems altered by environmental change.

A model study of terraced riverbeds as novel ecosystems

“…We adopted in this study a trait-based modeling approach, which directly bears on functional diversity and ecosystem function [36][37][38] . The approach allowed us to study the filtering of species traits from a set of species pools and the local community structures that emerge from interspecific competition for water and light under various rainfall regimes.…”

“…Prevailing trait-based frameworks 38 focus primarily on community assembly from a fixed species pool, paying little attention to species pools that differ in the nonlinear forms of the tradeoffs that characterize them. Our results show that convex and concave tradeoffs result in significantly different community-level properties.…”

Distinguishing the signatures of local environmental filtering and regional trait range limits in the study of trait–environment relationships

“…These two influences need to be disentangled in order to identify the specific role of local environmental filtering. However, while much emphasis has been put on the idea that environmental filtering can be more intense at the extremes of environmental gradients (Weiher et al 2011), far less attention has been devoted to how the functional composition of species pools influences local community composition (Spasojevic et al 2018). To address the issue, we used a simulation-based, Approximate Bayesian Computation (ABC) approach (ecolottery package, Munoz et al 2018).…”

“…Further investigation of the influence of trait range limits with different definitions of the species pool should help address under which conditions TGBE can be reliably detected. Furthermore, the influence of the shape of the trait distribution in the pool should be addressed in more details in the future (Spasojevic et al 2018) and appears essential since it can vary from a biogeographical context to another even though local environmental filtering can operate in a similar way. For sake of simplicity, we considered a uniform distribution of trait values among species at regional scale, and two types of distribution of regional abundances, uniform and log-series.…”

Greater local diversity under older species pools may arise from enhanced competitive equivalence

“…If competitive interactions favored co-occurrence of species with greater trait differences in the past, niche filling through diversification and immigration could increase functional diversity in the regional species pool (8,(15)(16)(17). Greater functional diversity in the species pool could then contribute to greater local diversity by reducing trait overlap among members of the species pool.…”