A Study of Avian Frugivores, Bird-Dispersed Plants, and Their Interaction in Mediterranean Scrublands

摘要: Fruit production and patterns of seed dispersal by birds were studied at two elevations in the Mediterranean scrublands southern Spain. Fleshy-fruit-producing species represent a very prominent fraction woody plants terms cover (57-76%) number (49-66%). occurs year round lowland site but is confined to August-February upslope. Ripe fruits are most abundant (>105 ripe fruits/ha) November-December. abundance fluctuates widely between years highland locality only slightly lowlands. In both communities, dominant ripen autumn-winter, display highest within-plant fruit densities, tend have lipid-rich fruits. Fruits differ pulp nutritive value, seediness, relative amount among remarkably uniform size (mostly 5-10 mm transverse di- ameter). Two-thirds passerine each eat some fruit. Of these species, 69% (highland) 26% (lowland) resident "fruit predators," feeding on either or seeds alone, damaging when eating together. The rest overwintering migratory dispersers that ingest whole without seeds. Seed common late autumn- winter, coincident with peak predominance A few small (12-18 g body mass) disperser (Erithacus rubecula, Sylvia atricapilla, melano- cephala) account for frugivory disperse majority predators relatively scarce infrequently, negligible their diets. removal was high (89-100% crops) smaller than gape width small-sized dispersers, low larger width. Removal success negatively correlated having dispersers' No relation has been found quality, fruiting time, ripening rate, density. principal ate mainly nutritious fruits, although not exclusion less Substantial pairwise plant-bird reciprocity common. (The avian disperses substantial plant's seeds, which turn provide bulk bird's energy supply.) Current bird-plant interactions result evolutionary, climatic, geo- graphical factors Mediterranean. Mutualistic congruency largely is, cases, an epiphe- nomenon factors, resulting necessarily from mutual adaptations (coevolution). It sug- gested actual coevolution involving set bird plant may facilitate persistence noncoevolving (or slowly coevolving) thus favoring existence chronic "anachronism load" (with regard dispersal) community.