The Effect of Rain Forest Canopy Architecture on the Distribution of Epiphytic Ferns (<i>Asplenium</i> spp.) in Sabah, Malaysia

<jats:title>ABSTRACT</jats:title><jats:p>Epiphytic plants are a dominant component of the rain forest canopy biota. They represent a significant proportion of canopy plant biomass and diversity, play a key role in nutrient cycling, and support highly abundant and diverse animal communities. Understanding the factors affecting their distribution in this three‐dimensional habitat is consequently of great importance, not least because they may be particularly vulnerable to climate change and habitat conversion. Here we investigate how canopy architecture affects the distribution of two species of bird's nest fern (<jats:italic>Asplenium</jats:italic> spp.) in pristine rain forest. Both species were found at high abundances (<jats:italic>Asplenium phyllitidis</jats:italic>: 136/ha, SE ± 31.6, <jats:italic>Asplenium nidus</jats:italic>: 44/ha, SE ± 9.2) and their distributions were differentially affected by canopy architecture. <jats:italic>Asplenium phyllitidis</jats:italic> was found only at heights &lt; 30 m in areas with a thicker lower canopy layer. <jats:italic>Asplenium nidus</jats:italic> was found at all heights in the canopy and was associated with emergent trees and areas with an open understory. Larger <jats:italic>A. phyllitidis</jats:italic> were found higher in the canopy while larger <jats:italic>A. nidus</jats:italic> were found on trunks and branches with a wider diameter. <jats:italic>Asplenium nidus</jats:italic> seems adapted to withstand the hot dry conditions in the upper canopy and in gaps, and its size is consequently limited only by the size of its support. <jats:italic>Asplenium phyllitidis</jats:italic> is dominant in areas that are cooler and damper, and so the growth rate of individuals may be limited by light levels. We discuss possible implications of this partitioning for epiphyte communities in the face of climate change and habitat conversion.</jats:p>