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Analyses of species functional traits are suitable to better understand the coexistence of species in a given environment. Trait information can be applied to investigate diversity patterns along environmental gradients and subsequently to predict and mitigate threats associated with climate change and land use. Species traits are used to calculate community trait means, which can be related to environmental gradients. However, while species traits can provide insights into the mechanisms underlying community assembly, they can lead to erroneous inferences if mean trait values are used. An alternative is to incorporate intraspecific trait variability (ITV) into calculating the community trait means. This approach gains increasing acceptance in plant studies. For macrofungi, functional traits have recently been applied to examine their community ecology but, to our knowledge, ITV has yet to be incorporated within the framework of community trait means. Here, we present a conceptual summary of the use of ITV to investigate the community ecology of macrofungi, including the underlying ecological theory. Inferences regarding community trait means with or without the inclusion of ITV along environmental gradients are compared. Finally, an existing study is reconsidered to highlight the variety of possible outcomes when ITV is considered. We hope this Opinion will increase awareness of the potential for within-species trait variability and its importance for statistical inferences, interpretations, and predictions of the mechanisms structuring communities of macro- and other fungi.
Elevational gradients in high mountain ranges are particularly suitable to study and understand patterns and drivers of plant community diversity and composition, yet there are only few studies that explicitly addressed this topic for the European Alps. Here we analysed an elevational gradient in grasslands of the Gran Paradiso National Park (NW Italy) from c. 1,700 to 3,100 m a.s.l. We recorded vascular plant species composition in 13 100-m² plots, each with two series of nested subplots from 0.0001 to 10 m², as well as a set of environmental parameters (topography, soil). Beta-diversity was assessed via the z-values of power-law species-area relationships, both across all plot sizes and from one plot size to the next bigger one. Diversity-environment relationships were assessed with multi-model inference based on Akaike information criterion (AIC), while scale dependence in z-values across plot sizes was analysed with an ANOVA. Life forms and three major functional traits (specific leaf area = SLA, canopy height, seed mass) were derived from trait databases to calculate fractions of life forms and community-weighted means for the metric traits. Species richness on 100 m² ranged from 17 to 65, with a mean of 43.5. The z-values were within a typical range known for European grasslands (mean: 0.227), with non-significant scale dependence. The importance of environmental factors for richness changed across grain sizes, with inclination (positive effect), mean soil depth and soil skeleton content (both: negative effect) being most influential at grain sizes of 0.0001–1 m². By contrast, soil pH was most important (with a unimodal relationship) for 10 and 100 m². After account-ing for the other environmental factors, elevation showed a moderate unimodal relationship only for the two largest grain sizes. By contrast, functional composition showed strong and mostly significant rela-tionships with elevation: hemicryptophytes and geophytes became rarer and chamaephytes more fre-quent, while community-weighted means of SLA, canopy height and seed mass decreased. Our findings highlight the scale dependence of biodiversity patterns, thus pointing to the need of multi-scale sampling to reach comprehensive understanding. Further, we could provide one of the first documentations of biodiversity and functional composition along an elevational gradient in the Alps, some in agreement with expectations, others not. This suggests that more extensive studies with a similar design in this and other regions of the Alps could be a valuable contribution to the understanding of how environmental factors drive components of biodiversity as well a functional community assembly.