Flowering, fruiting and seed germination in Chilean rain forest myrtaceae: ecological and phylogenetic constraints

Phenological studies in plant communities have generally focused on taxonomically heterogeneous species assemblages, and have only occasionally examined the evolutionary and ecological constraints on the phenological patterns of species within a single family or a genus. Here, we determine relative importance of phylogenetic versus other constraints on the flowering and fruiting periods of 12 species and the germination ecology of 10 species of Myrtaceae sympatric to the temperate rainforest of Isla Grande de Chiloe (42 degrees 30' S), in southern Chile. We found that, for most species in the family Myrtaceae, flowering was strongly aggregated in January and February. Although this pattern is consistent with the expectation of the 'facilitation' hypothesis (i.e., interspecific overlaps are maximized to attract pollinators), available evidence suggests that pollinators, mainly hymenopterans and dipterans, 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 functional groups were defined within the Myrtaceae: those that ripen their fruits immediately after flowering (species in the subtribe Myrtinae) and those in which green fruit develops slowly for several months before ripening (subtribe Myrciinae). Seed germination in the field occurred mainly between August and October. Lab assays showed that the species 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 phenology of reproductive events in the species of Myrtaceae in this rainforest suggests that: (1) flowering periods patterns are constrained mainly by phylogenetic inertia at the family level, and (2) differences in fruiting patterns and dormancy periods are determined mainly by fruit and seed size, which in turn are associated primarily with phylogenetic closeness within the family, and secondarily with the activity of vertebrate seed dispersers.