To what extent does plant clonality contribute to the assemblage of species in communities? Two apparently contrasting, and largely untested, hypotheses envisage the potential role of plant clonal traits in community assembly: (i) environmental filters constrain coexisting species to have functionally similar traits (i.e. trait convergence); (ii) niche differentiation selects for functionally dissimilar species (i.e. trait divergence) allowing them to exploit different spatial and temporal niches. These hypotheses are assessed using a large dataset of 369 plots (100 m2) covering altitudes between 4100 and 5800 m a.s.l. and including the major vegetation types found in Ladakh, NW Himalaya. Patterns of clonal traits, coexistence and turnover were assessed using a functional diversity partitioning framework in the context of different null models. Functional diversity was expressed both for morphologically delimited clonal growth forms (17 categorical growth forms) and for functionally delimited clonal characters (combining 16 different traits differentiating the 17 growth forms). PERMANOVA revealed that both α (within-plots) and β (between-plots) functional diversity varied across environmental conditions and vegetation types highlighting a filtering effect on clonal traits. Alpha diversity, however, was more stable across habitats than β diversity. Despite the significant turnover of clonal traits across habitats, most of the diversity of clonal traits was found within plots, with a higher trait divergence than expected by chance, which suggests that niche differences determine species coexistence. While both trait convergence and trait divergence were detected, convergence was stronger when using null models that shuffled all species in the regional pool across plots and functional diversity expressed in terms of different clonal growth forms. Divergence, in contrast, was detected mostly when using null models that shuffled species cover across species co-occurring in given plots and considering functional diversity in terms of clonal traits. By detecting both trait convergence and trait divergence this study supports both initial hypotheses and brings new evidence on the relevance of clonal traits as a function of species that both inhabit different environments and coexist.
Plants’ abilities to function are difficult to evaluate directly in the field. Therefore, a number of attempts have been made to determine easily measurable surrogates – plant functional traits (PFTs). In particular, the value of PFTs as tools for predicting vegetation responses to management (i.e., grazing and mowing) is the focus of a large number of studies. However, recent studies using PFTs to predict the effect of pasture management in different regions did not give consistent predictions for the same set of PFTs. This lead to the suggestion that more specific traits better suited for a specific region be used in the future. We consider the identification of the most adaptative traits for surviving grazing and mowing in different biomes an important goal. Using temperate grasslands in Europe as an example, we show that (i) plant height, often considered as the best predictor of species response to grassland management, is coupled with other more relevant functional traits, and that (ii) clonal traits have important, often neglected functions in the response of species to grassland management. We conclude that single traits cannot be the only basis for predicting vegetation changes under pasture management and, therefore, a functional analysis of the trade-off between key traits is needed.