Ecology of Foliicolous Lichens at the ‘Botarrama’ Trail (Costa Rica), a Neotropical Rainforest. IV. Species Associations, their Salient Features and Their Dependence on Environmental Variables

A community ecology approach using an association of species test and a principal component analysis resulted in the recognition of two major and two minor foliicolous lichen communities in a neotropical rainforest. The major communities arc governed by microclimatic factors, one characteristic of the shady understorcy and the other confined to light gaps. The minor communities are due to subtle phorophyte preferences towards palm and dicot leaves. The shady understorey community is dominated by the families Anhoniaceae, Opegraphaceae, Tnchoihdiaceae and Pilocarpaceae, which predominantly have Phycepeltis as their phycobiont, thin thalli, abundant sexual reproduction, small ascospores produced in high numbers, and pyenidial conidiomata. The light-gap community is mainly composed of the families Gomphillaceae and Ectolechiaceae, with Trebouxia as their phycobiont, thickly crystalline or whitish, dispersed thalli, frequent asexual reproduction, large ascospores produced in low numbers, and specialized campylidia and hyphophores as conidiomata. Phycobiont, thallus structure, and the mode of reproduction are considered as adaptations to different microsites, whereas the shape and size of ascospores and conidia seem to be of less importance. The foliicolous lichen communities reflect the spatial and temporal structure of the forest, in particular the continuity of the shady understorey in comparison to the discontinuity of the light gaps. While the formation of the shady understorey community follows more deterministic patterns, the light-gap community exhibits high stochasticity.

Input of wind–dispersed seeds into light–gaps and forest sites in a Neotropical forest

ABSTRACTA total of 52,467 wind-dispersed seeds from 14 tree and 32 liana species fell into 1720 seed traps in 43 paired light-gap and adjacent forest sites on Barro Colorado Island, Panama. Summed at the community level, many more wind-dispersed seeds were collected from light-gaps (61%) than from forest sites (39%). They accumulated from March through May, 1984 to a density of 328 m-2 in gaps and 207 m-2 in forest sites. In contrast, only 33% of the total of 2782 non-wind-dispersed seeds were collected in gaps. Due to the extreme heterogeneity of the seed rain, these differences between gap and forest sites were not statistically significant at the community-level. Gap sites received more wind-dispersed seeds than adjacent forest sites in only 20 of 43 locations and in 13 of 20 species, especially those with individuals of high fecundity near gap sites. Of the estimated 105 million wind-dispersed seeds contributing to the seed rain of the 50 ha study plot, only 4.1% were dispersed to the rare gap sites that enhance the establishment and growth of seedlings for many of these species.