Intraspecific variability and trait‐based community assembly

Abstract

Summary 1.Trait-based approaches applied to community ecology have led to a considerable advance in understanding the effect of environmental filters on species assembly. Although plant traits are known to vary both between and within species, little is known about the role of intraspecific trait variability in the non-random assembly mechanisms controlling the coexistence of species, including habitat filtering and niche differentiation. 2. We investigate the role of intraspecific variability in three key functional traits -specific leaf area (SLA), leaf dry matter content (LDMC) and height -in structuring grassland communities distributed along a flooding gradient. We quantified the contribution of intraspecific variability relative to interspecific differences in the trait-gradient relationship, and we used a null model approach to detect patterns of habitat filtering and niche differentiation, with and without intraspecific variability. 3. Community mean SLA and height varied significantly along the flooding gradient and intraspecific variability accounted for 44% and 32%, respectively, of these trait-gradient relationships. LDMC did not vary along the gradient, with and without accounting for intraspecific variability. Our null model approach revealed significant patterns of habitat filtering and niche differentiation for SLA and height, but not for LDMC. More strikingly, considering intraspecific trait variability greatly increased the detection of habitat filtering and was necessary to detect niche differentiation processes. 4. Synthesis. Our study provides evidence for a strong role of intraspecific trait variability in community assembly. Our findings suggest that intraspecific trait variability promotes species coexistence, by enabling species to pass through both abiotic and biotic filters. We argue that community ecology would benefit from more attention to intraspecific variability.

Trait-based community assembly of understory palms along a soil nutrient gradient in a lower montane tropical forest

“…When comparing across species mean trait values in this study, we found differences for most physiological traits as well as for morphological and biochemical traits among the species, indicating that our sampling regime, a compromise between the number of species, traits, and sites, was able to detect differences in trait means at all but the smallest scales (within site) for conserved traits. For example, coefficient of variation of the nearest neighbor trait values (CV_NND; trait values more evenly spaced) has been developed as a measure of niche differentiation of trait values among coexisting species (Stubbs and Wilson 2004;Kraft et al 2008;Jung et al 2010). We were unable to detect significantly lower CV_NND than expected under a null model (following Jung et al 2010) with the limited sample sizes in this study (data not shown).…”

“…For example, SLA, a key plant functional trait, has been found to differ among environmentally defined habitats. At the same time, SLA values within habitats have been found to be more evenly dispersed, or divergent, than expected from null models in a variety of ecosystems (Kraft et al 2008;Cornwell and Ackerly 2009;Jung et al 2010). Thus, multiple processes may frequently shape trait distributions in diverse plant communities.…”

“…The importance of intraspecific variation in determining trait-environmental relationships and trait-based community assembly is becoming increasingly recognized (Ashton et al 2010;Jung et al 2010;Sandel et al 2010). We examined trait plasticity in G. cuneata, which occurred across all sites examined here and was also the most abundant species at most sites (Andersen et al 2010a).…”

“…Habitat filtering can lead to changes in trait composition along environmental gradients as a result of either turnover in species composition or differences in species abundance (Keddy 1992;Cornwell and Ackerly 2009;Sandel et al 2010) or intraspecific variation due to plasticity or genetic variation (Cornwell and Ackerly 2009;Hulshof and Swenson 2010;Jung et al 2010). Whereas most trait-based studies focus on species mean trait values, recent work has incorporated intraspecific variation to trait-based frameworks, adding a greater power to detect trait-environment linkages (Cornwell and Ackerly 2009;Hulshof and Swenson 2010;Jung et al 2010).…”

“…Whereas most trait-based studies focus on species mean trait values, recent work has incorporated intraspecific variation to trait-based frameworks, adding a greater power to detect trait-environment linkages (Cornwell and Ackerly 2009;Hulshof and Swenson 2010;Jung et al 2010). Furthermore, the incorporation of intraspecific variation allows a mechanistic approach to predicting species losses due to environmental change and its impact on ecosystem function (Hooper et al 2005;Jung et al 2010).…”