Disentangling the roles of chance, abiotic factors and biotic interactions among epiphytic bryophyte communities in a tropical rainforest (Yunnan, China)
| center dot Epiphytes offer an appealing framework to disentangle the contributions of chance, biotic and abiotic drivers of species distributions. In the context of the stress-gradient theory, we test the hypotheses that (i) deterministic (i.e., non-random) factors play an increasing role in communities from young to old trees, (ii) negative biotic interac-tions increase on older trees and towards the tree base, and (iii) positive interactions show the reverse pattern. center dot Bryophyte species distributions and abiotic conditions were recorded on a 1.1 ha tropi-cal rainforest canopy crane site. We analysed co-occurrence patterns in a niche model-ling framework to disentangle the roles of chance, abiotic factors and putative biotic interactions among species pairs. center dot 76% of species pairs resulted from chance. Abiotic factors explained 78% of non-randomly associated species pairs, and co-occurrences prevailed over non-coincidences in the remaining species pairs. Positive and negative interactions mostly involved spe-cies pairs from the same versus different communities (mosses versus liverworts) and life forms, respectively. There was an increase in randomly associated pairs from large to small trees. No increase in negative interactions from young to old trees or from the canopy to the base was observed. center dot Our results suggest that epiphytic bryophyte community composition is primarily driven by environmental filtering, whose importance increases with niche complexity and diver-sity. Biotic interactions play a secondary role, with a very marginal contribution of com-petitive exclusion. Biotic interactions vary among communities (mosses versus liverworts) and life forms, facilitation prevailing among species from the same community and life form, and competition among species from different communities and life forms.
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| Shen, T; Collart, F
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