Within‐species variability is the main driver of community‐level responses of traits of epiphytes across a long‐term chronosequence

Abstract

Summary1. There has been growing recent interest in the relative importance of within-species trait variation vs. across-species trait variation in vascular plants in determining total community-level trait variation across communities and environmental gradients. Recent studies on plant communities have generally found across-species variation to be more important than within-species variation, but comparable studies involving other functionally important biota, such as lichens, are largely lacking. 2. We used a fire-driven chronosequence involving 30 lake islands in northern Sweden to study how declining soil fertility during retrogression affects the functional traits of each of the dominant epiphytic lichen species growing on the trunks of the tree Betula pubescens. We measured several functional traits for the commonest lichen species on each island and used communityweighted measures to study the community-level responses of lichens to the gradient. 3. We found that as retrogression proceeds and soil fertility declines, thallus N and P concentrations and specific thallus mass (STM) increase, both within species and at the community level. Lichen secondary compounds showed contrasting within-species responses and were non-responsive at the whole community level. 4. By decomposing community-level measures of these traits across the gradient, we showed that for the three most responsive traits (N, P and STM), within-species variation was substantially more important than across-species variation. This emerges in part because lichen species composition was not very responsive to ecosystem retrogression, and because unlike vascular plants, lichens easily absorb elements over their entire surface, meaning that nutrient concentrations within lichen species are likely to more closely reflect nutrient availability. 5. We found that within-species variability drove the changes in community-weighted measures of lichen traits across a strong environmental gradient, which contrasts strongly with what we know from studies of vascular plants where across-species variation and species turnover is much more important. To understand how lichen functional traits at the community level respond to environmental factors, it is therefore essential to consider the responses of individual species, and the application of traits-based approaches to lichen communities needs to account for their considerable intraspecific variability.

Changes in functional traits of the terricolous lichen Peltigera aphthosa across a retrogressive boreal forest chronosequence

“…Although previous work has revealed that traits of epiphytic lichens and of vascular plants respond strongly to this gradient (Asplund et al 2012;Asplund & Wardle 2014;Kumordzi et al 2014), we found that most traits of P. aphthosa are relatively unresponsive. Furthermore, most traits were unaffected by changes in light availability across the gradient, which contrasts with what has been previously shown for responses of epiphytic lichens in this system (Asplund et al 2012;Asplund & Wardle 2014). These contrasting findings between epiphytic and ground-dwelling lichens highlight the importance of studying different functional groups of primary producers along the same gradient.…”

“…Until recently, studies on functional trait variability have focused on interspecific variation, and the importance of intraspecific trait variability has been recognized as an important ecological driver only in the past few years (Albert et al 2010;Messier et al 2010;Kichenin et al 2013). We have recently shown that functional traits of epiphytic lichens are highly responsive to ecosystem retrogression, and at the withinspecies level are much more responsive than those of vascular plant species (Asplund et al 2012;Asplund & Wardle 2014). …”

Why species tell more about traits than traits about species: predictive analysis

“…Ecological traits are attributes of organisms that vary within individuals, between individuals, and between species (Wright et al 2004, 2007, Westoby and Wright 2006, Lavorel et al 2008, Albert et al 2010, Asplund and Wardle 2014, Mitchell and Bakker 2014, Stahl et al 2014), but they are most often analyzed as attributes of locations (Fig. Ecological traits are attributes of organisms that vary within individuals, between individuals, and between species (Wright et al 2004, 2007, Westoby and Wright 2006, Lavorel et al 2008, Albert et al 2010, Asplund and Wardle 2014, Mitchell and Bakker 2014, Stahl et al 2014), but they are most often analyzed as attributes of locations (Fig.…”

“…Model-based analysis is developed here to quantify the variation in traits that comes from (1) trait syndromes, (2) the diversity of species that possess them, and (3) the environmental variation that affects both species and trait diversity. Ecological traits are attributes of organisms that vary within individuals, between individuals, and between species (Wright et al 2004, 2007, Westoby and Wright 2006, Lavorel et al 2008, Albert et al 2010, Asplund and Wardle 2014, Mitchell and Bakker 2014, Stahl et al 2014), but they are most often analyzed as attributes of locations ( Fig. 1a).…”

Grazing‐induced shifts in community functional composition and soil nutrient availability in Tibetan alpine meadows

“…We then used a nested anova (grazing nested in site) to decompose the total sum of squares (SS) into CWM variance components attributable to the site effect, grazing effect and plot effect, and finally quantified the relative contribution of ITV and change in species occurrence and abundance and their covariance for each component effect (Lepš et al . ; Asplund & Wardle ; Jung et al . ; de la Riva et al .…”