PARENT SESSION
Poster Session #49: Reproductive Ecology.
Friday, August 10, 2001. Presentation from 10:30 AM to 12:00 PM. Exhibition Hall
115
Reproductive ecology of two closely related species of Rhamnus (a widespread and an endemic species): from buds to seedling establishment.
Traveset, Anna1, Gulías, Javier1, Riera, Nuria1, Mus, Maurici2, 1 2
ABSTRACT- The different stages in the reproductive cycle (from bud to seedling recruitment) of two dioecious species in the genus Rhamnus, one widespread in the western Mediterranean (R. alaternus) and the other endemic to the Balearic Islands (R. ludovici-salvatoris), were compared to determine possible causes of their different distributions and abundances. For each species, fruit set, seed viability, seed rain patterns, post-dispersal seed predation, germination and one-year seedling survival were examined in two populations in the island of Mallorca. Both species are mainly entomophilous, although wind can play a non-negligible role (up to 22% fruitset). Hand-pollination experiments were performed to determine pollen limitation during both 1999 and 2000. Seed rain, predation, and one-year seedling survival were monitored in different microhabitats. Pollen limitation was found in both species, although only in one year. Seed viability (45-70%) did not differ between the two species. For both Rhamnus, the largest seed fall (67-87%) occurred under female conspecifics. Post-dispersal seed predation represented 90-95% of losses; ants were the most important predators although rodents also removed some of the seeds. Of the remaining seeds, only an average of c. 0.3% for R. alaternus and 0% for R. ludovici-salvatoris were established as seedlings after one year. For both species, but especially for the endemic Rhamnus, recruitment is most strongly limited by seed failure to establish after arrival than by failure to arrive.
KEY WORDS: western Mediterranean shrubs, pollen limitation, seed dispersal, seedling recruitment