Species traits and plant performance: functional trade-offs in a large set of species in a botanical garden

Earlier research has established a number of relationships between community structure and plant traits. However, these relationships are mediated by demographic processes that are constrained, but not determined, by the trait values, and involve responses of plants to their environments. In particular, life-history costs and associated trade-offs need to be examined at the level of demographic processes such as plant survival and reproduction, not only at the level of individual trait values. We examined these demographic trade-offs using data on vegetative and seed reproduction from 951 species of the Central European flora kept in the Botanical Garden of Charles University in Prague. With each species grown under conditions close to its natural habitat, we view the data as information on vegetative and seed reproduction under favourable conditions. We used nonparametric tests and ordinal regressions to examine relationships of the vegetative and seed reproduction to each other, as well as to commonly used traits such as plant height, leaf size, specific leaf area, seed size and clonal traits. There was an overall negative correlation between seed and vegetative reproduction, indicating trade-off between these two modes of reproduction. In contrast, there was no evidence of a trade-off between clonal and seed traits. Traits of clonal growth were related to vegetative reproduction in the garden and seed trait to seed reproduction in the garden. Further, there were correlations between seed reproduction and clonal traits and vice versa. These results suggest that seed reproduction is associated with a wider array of traits than only seed traits, and vegetative reproduction with a wider array than clonal traits again indicating complex life-history relationships. These relationships did not change substantially after the incorporation of phylogenetic information. Synthesis. The results suggest that trade-offs between vegetative and seed reproduction are not revealed by analysis of species traits, probably due to the fact that trade-offs often only arise due to life-history costs that are shaped by the local environment. This highlights the importance of examining life-history processes associated with trait values.