CATTLE DUNG AND THE FATE OF BISERRULA-PELECINUS L (LEGUMINOSAE) IN A MEDITERRANEAN PASTURE - SEED DISPERSAL, GERMINATION AND RECRUITMENT

Seed dispersal of Biserrula pelecinus via cattle dung in a semiarid pa sture is analysed by quantification of the viable seed content of catt le dung, assessment of the percentage of readily germinable seeds in g rowth chamber of seeds collected from the plant and from dung, monitor ing of the on-field frequency of the species in dung pats and in surro unding (control) pasture plots the four springs after dung deposition, and quantification of the pasture area occupied by dung pats. Large a mounts of seeds of the species are dispersed by cattle (up to 4 seeds g(-1) of dry manure in June 1991), and the germinability of the seeds increases significantly following their passage through the cattle gut (from 2.5% to 9.5%). In the first three springs after deposition, the frequency of adult plant of the species on dung almost tripled that f ound in the surrounding pasture. The effect on the pasture is scale-de pendent and Varies considerably between zones depending on the area co vered by dung. Thus, presence on dung may explain an average of 8% of the frequency of the species in the pasture at a 10x10 cm scale, and u p to 20% in some areas. The results are the first evidence of a herbac eous species being greatly favoured in a plant community by its disper sal through herbivore dung, a process that may have profound implicati ons for the interpretation of plant-herbivore relations and on the evo lution of plant traits. (C) 1995 The Linnean Society of London