FLOWERING, FRUITING AND SEED-GERMINATION IN CHILEAN RAIN-FOREST MYRTACEAE - ECOLOGICAL AND PHYLOGENETIC CONSTRAINTS

Phenological studies in plant communities have generally focused on ta xonomically heterogeneous species assemblages, and have only occasiona lly examined the evolutionary and ecological constraints on the phenol ogical patterns of species within a single family or a genus. Here, we determine relative importance of phylogenetic versus other constraint s on the flowering and fruiting periods of 12 species and the germinat ion ecology of 10 species of Myrtaceae sympatric to the temperate rain forest of Isla Grande de Chiloe (42 degrees 30' S), in southern Chile. We found that, for most species in the family Myrtaceae, flowering wa s strongly aggregated in January and February. Although this pattern i s consistent with the expectation of the 'facilitation' hypothesis (i. e., interspecific overlaps are maximized to attract pollinators), avai lable evidence suggests that pollinators, mainly hymenopterans and dip terans, do not limit fruit production in these species of Myrtaceae in the temperate rainforest. In contrast to flowering, fruiting occurred all-year-round, showing greater segregation in time among the species . According to the their temporal patterns of fruit ripening, two func tional groups were defined within the Myrtaceae: those that ripen thei r fruits immediately after flowering (species in the subtribe Myrtinae ) and those in which green fruit develops slowly for several months be fore ripening (subtribe Myrciinae). Seed germination in the field occu rred mainly between August and October. Lab assays showed that the spe cies of Myrtaceae, subtribe Myrtinae, exhibited a long seed dormancy ( >40 days), while the seeds of species in the subtribe Myrciinae often germinated within one week after harvesting. The analysis of the pheno logy of reproductive events in the species of Myrtaceae in this rainfo rest suggests that: (1) flowering periods patterns are constrained mai nly by phylogenetic inertia at the family level, and (2) differences i n fruiting patterns and dormancy periods are determined mainly by frui t and seed size, which in turn are associated primarily with phylogene tic closeness within the family, and secondarily with the activity of vertebrate seed dispersers.