Species of accidental woody epiphytes vary between host trees in Tasmanian wet forests

Abstract

Little is known about accidental epiphytes in Australian temperate forests. In western Tasmania, we determined whether: (1) the occurrence and abundance of accidental epiphytes increases with moisture availability and the size of host; (2) the species of host affects the occurrence of individual taxa of accidental epiphytes; (3) moist microhabitats favour accidental epiphytes. We recorded the accidental woody epiphytes on 21 trees in each of 20 locations and measured attributes of the host and the location and attachment height of the individual epiphytes. Epiphyte occurrence, but not abundance, was associated with the basal area of host tree, January rainfall and the taxon of the host. Eucalypts, gymnosperms and tree ferns were the outstanding hosts. The rainforest tree Nothofagus cunninghamii occurred as an epiphyte on eucalypts more than expected, while Proteaceae species occurred less than expected. In contrast, there was a strong positive association between the gymnosperm Athrotaxis selaginoides as a host and Proteaceae as epiphytes, possible reflecting their joint status as palaeoendemics. Accidental epiphytes were concentrated on the west and south-west of trees and near their bases, further indicating a strong effect of moisture availability on their occurrence. Our results reinforce the importance of conserving old growth forest to maintain ecosystem complexity.