LAUSR

ABSTRACT Host-parasite interactions between plants may reduce the vegetative and reproductive performance of the host plant. Although it is well established that parasitic plants may negatively aff ect the metabolism and the number of vegetative/reproductive structures of their hosts, the eff ects of this interaction on the reproductive characteristics of the host plant are poorly understood. Here we document the interaction between Cuscuta partita (Convolvulaceae) and its main host, Zornia diphylla (Fabaceae), in the Caatinga of northeastern Brazil. We measured diverse reproductive/vegetative attributes of Z. diphylla in 60 plots randomly distributed in patches that were parasitized and not parasitized by C. partita . Both vegetative and reproductive attributes, such as the number of branches, leaves and fl owers, and the individual biomass of Z. diphylla were signifi cantly reduced by the parasitism. Th e number of pollen grains and ovules per fl ower were not aff ected by the parasitism, but since the parasitism reduced fl ower production, the total number of pollen and ovules per individual and population may also be reduced. Additionally, pollen viability was signifi cantly reduced in the fl owers of parasitized individuals. We conclude that