seed mass; functional traits; arable weeds; communities

Seed mass is widely considered to be one of the most important life history traits in plants. It is very diverse trait and it is not a coincidence that we also encounter this diversity in many ecologically specific groups. Here we present detected patterns in weed communities with regards to seed mass as a functional trait responsible for their coexistence. We analysed 430 relevés of arable field weed vegetation in the northeastern part of the Czech Republic. A total of 230 species were classified into the five categories according to their seed mass. Species from category 3 (seed mass 0.101-1 mg) tend to negatively correlate with all other categories (the strongest relationship with category 4 ? seed mass 1.01-10 mg). Further analyses showed optimal combination of proportions of each seed mass category resulting into the highest number of coexisting species in one relevé. These findings has further strengthened our conviction that seed mass clearly plays role in weed communities.