The importance of tree species and size for the epiphytic bromeliad Fascicularia bicolor in a South-American temperate rainforest (Chile)

Bromeliads are a numerous family of vascular epiphytes, though only one epiphytic species inhabits South-American temperate rainforests: the endemic Fascicularia bicolor. This bromeliad is an important driver of canopy biodiversity, but attributes of its hosts are mostly unknown. Here we report (i) the tree species colonized by F. bicolor, (ii) the relationship between tree size and presence of F. bicolor and (iii) the relation between tree size and the number of mats of F. bicolor inhabiting each colonized tree. We sampled 231 trees in seven forest plots recording their species, diameter, heights, and the number of F. bicolor mats growing on them. The dataset was analyzed with a zero-inflated model to relate host tree attributes with F. bicolor occurrence and abundance in a single statistical approach. The occurrence and abundance of F. bicolor depend on host-species identity and diameter. F. bicolor colonization in slow-growing trees started at smaller DBH than that required for other tree species. Nonetheless, the overall occurrence of F. bicolor relies on large trees above 50 cm DBH for most host species. The number of mats occurring on each colonized tree depends on the interaction between tree height and species suggesting the importance of space available for colonization along the tree-trunk, and differential effects due to species' traits. Currently, large trees and old-growth forests are scarce within the distribution range of F. bicolor, which could seriously affect the long-term conservation of this endemic epiphyte, along with the canopy properties and species associated with it.