Factors Affecting the Distribution and Abundance of Asplenium nidus L. in a Tropical Lowland Rain Forest in Peninsular Malaysia

Abstract

Asplenium nidus is an abundant epiphytic fern of tropical rain forests in the Old World, where it plays an important ecological role in the forest canopy as host to diverse arthropod communities. We investigated the factors that determine the distribution and abundance of A. nidus in the canopy of an aseasonal lowland dipterocarp forest at Pasoh Forest Reserve, Malaysia. We found that A. nidus was more abundant in the understory, and on hosts with smooth bark and relatively flat branch angles. Ferns were found on a wide diversity and size range of host taxa. However, both host taxa and host diameter at breast height had a significant effect on A. nidus occupancy. Asplenium nidus had an aggregated spatial distribution at all scales within the study area. Spatial aggregation at larger scales appears to be driven by habitat preference, as A. nidus abundance was positively associated with swampy areas and negatively associated with hilly areas. At smaller scales, limited dispersal of their wind-dispersed spores most likely explains the aggregated distribution. Larger individuals occurred higher in the canopy and were more common in the hilly area. Thus, the distribution of A. nidus may represent a trade-off between the availability of suitable microsites for establishment in the understory and better growth conditions higher in the canopy. However, A. nidus is known to comprise a complex of cryptic species, and future studies should incorporate molecular techniques to elucidate the potential role of speciation in explaining these patterns. Abstract in Malaysian is available at

Analysis of Tropical Forest Landscape Fragmentation in Batang Toru Watershed, North Sumatra

“…Forest landscape of Batang Toru Hilir watershed is remained in hill and mountain area. This result inline with the reseacrh conducted by Zhang et al (2010) that found the forest landscape tend to be clustered in hill and mountained area.…”

Distributional Patterns of Epiphytic Ferns are Explained by the Presence of Cryptic Species

“…We suggest that this smaller species is either A. phyllitidis, as is the case in our study (Fayle et al 2009), or another species with a similar ecology. This explains both the vertical gradient of abundance observed by Zhang et al (2010), with large numbers of the A. phyllitidis-like species being present in the understory but none in the high canopy, and the gradient in fern size, with larger A. phyllitidis-like ferns (but not larger A. nidus) in higher strata. There is some indirect evidence that the high light levels found in the upper canopy can lead to fast rates of growth of bird's nest ferns: ferns in oil palm plantations where light levels are comparable to those found in the upper canopy can reach sizes of 3.6 m diam (frond tip to frond tip) after only 14 yr (E. Turner, unpubl.…”

“…In a paper in press at Biotropica at the time that the study of Zhang et al (2010) was submitted, we demonstrated that the latter of these two (non-mutually exclusive) hypotheses is likely to be true for bird's nest ferns in Southeast Asia (Fayle et al 2009). We collected field samples of Asplenium from lowland rain forest in Malaysian Borneo and sequenced the plastid trnL intron.…”

“…LITTER-TRAPPING ASPLENIUM FERNS, COMMONLY KNOWN AS BIRD'S NEST FERNS, ARE abundant in rain forests from east Africa to northern Australia, and provide an important habitat in the canopy for arthropods and other animals (Ellwood & Foster 2004). Zhang et al (2010) show that Asplenium nidus are present at high abundances in the forest understory, with lower abundances but larger individuals in the canopy and in emergent trees. They pose two possible explanations for these (and other) patterns: (1) trade-offs between light and water requirements lead to high recruitment but slow growth in the understory, and the reverse pattern in the high canopy;…”

“…As Zhang et al (2010) state, it is vital that we continue to integrate molecular techniques into ecological studies in order to properly define subject species where morphological identification is problematic. Doing so may reveal many further instances of multiple cryptic species where only one was assumed to exist.…”