Seed predation and dispersal in relict Scots pine forests in southern Spain

For two years, the seed rain and magnitude of seed losses due to predation were evaluated in Scots pine forests in southern Spain. The Crossbill was t he most important pre-dispersal predator, consuming more than 80% of ripeni ng seeds. In addition, other birds, mainly Tits and Siskin, also consumed s eeds just before seed dispersal, reaching values of 16 and 51% losses in 19 96 and 1997, respectively. Seed rain was monitored in different microhabita ts (under pine canopies, under shrubs and in open areas), and was most inte nse under the canopy of mother plants both years. Post-dispersal seed preda tors (rodents and birds) consumed up to 96% of seeds reaching the ground. B oth pre- and post-dispersal seed predators preferentially harvested filled seeds. Post-dispersal predation was similarly intense in all microhabitats, so predators did not change the spatial distribution of the seed rain. The se high predation rates were constant between years, localities and habitat s (woodland and treeline). We hypothesize that this high rate of seed preda tion is a major factor limiting the regeneration of these relict population s of Scots pine in its southernmost limit.