Disentangling Interspecific and Intraspecific Trait Variability of Carex Species Across Different Habitats

Questions

Despite advances made in disentangling interspecific and intraspecific trait variability, little is known about their coordination. We explored intraspecific trait variability (ITV) of closely related species (to reduce phylogenetic effects) of the Carex genus growing over a broad environmental gradient. We asked whether (i) trait values of Carex species correlate with the community-weighted mean (CWM) of the same trait, (ii) to what extent Carex species turnover between localities and their ITV is responsible for this relationship, and (iii) the ITV of Carex species increases or decreases similarly to CWM, promoting either pattern of trait divergence or convergence.

Location

South Bohemia, Czech Republic.

Methods

We measured three key functional traits (height, specific leaf area—SLA, and leaf dry matter content—LDMC) on populations of 15 Carex species at 72 various localities. We also recorded species composition at each locality to compare Carex species traits with the respective CWMs of the rest of the community.

Results

SLA was the only trait showing significant correlation between Carex species and CWM. This relationship was largely driven by a turnover of Carex species along the gradient of CWM, but ITV strengthened this relationship and increased similarity to CWM. Plant height of Carex species did not correlate with CWM, and LDMC did not show a consistent pattern among Carex species.

Conclusion

ITV of SLA appears to be driven by trait convergence, which indicates environmental filtering for this trait. SLA is a highly variable trait, which was filtered toward optimal SLA values. This allows a more efficient capture of the energy from light and enables species to occupy a broader range of environmental conditions. The extension of conditions which species tolerate due to ITV is, however, limited compared to species turnover, which allows for a substantially broader spectrum of interspecific trait variability.