Résumé
(1) The spatial distribution of a clonal perennial weed, Rubia peregrina L., was analysed and modelled in a vineyard in southern France using a two-dimensional approach. The pattern, scale, intensity and directional compounds of the spatial distribution were detected and between-plant interactions were quantified in terms of their relative positions. (2) Spatial patterns showed clear aggregations along the rows of the vineyard. (3) Gibbs models were fitted to observed data to quantify plant interactions within clumps. In one zone of the vineyard, clumps were small, with high between-plant interactions, whereas in another zone clumps were large and characterized by weak between-plant interactions. These patterns corresponded to juvenile and senescent phases of the infestation, respectively. (4) Simulations of the probability of plant appearance agreed well with the observed data. (5) This spatial distribution can be related to the dispersal pattern of R. peregrina. Dispersal of seeds from the surrounding natural habitats created new infestation nuclei, whereas seed dispersal within the vineyard induced the extension of founder clumps.