Increasing arboreality with altitude: a novel biogeographic dimension

Abstract

Biodiversity is spatially organized by climatic gradients across elevation and latitude. But do other gradients exist that might drive biogeographic patterns? Here, we show that rainforest's vertical strata provide climatic gradients much steeper than those offered by elevation and latitude, and biodiversity of arboreal species is organized along this gradient. In Philippine and Singaporean rainforests, we demonstrate that rainforest frogs tend to shift up in the rainforest strata as altitude increases. Moreover, a Philippine-wide dataset of frog distributions shows that frog assemblages become increasingly arboreal at higher elevations. Thus, increased arboreality with elevation at broad biogeographic scales mirrors patterns we observed at local scales. Our proposed 'arboreality hypothesis' suggests that the ability to exploit arboreal habitats confers the potential for larger geographical distributions because species can shift their location in the rainforest strata to compensate for shifts in temperature associated with elevation and latitude. This novel finding may help explain patterns of species richness and abundance wherever vegetation produces a vertical microclimatic gradient. Our results further suggest that global warming will 'flatten' the biodiversity in rainforests by pushing arboreal species towards the cooler and wetter ground. This 'flattening' could potentially have serious impacts on forest functioning and species survival.

First report on the amphibians and reptiles of a remote mountain, Gunung Tebu in northeastern Peninsular Malaysia

“…Flattening could seriously alter the forest ecosystem and impact the survival of numerous species (Scheffers et al 2013). It is imperative to consider that our study did not focus specifically on frog arborality like Scheffers et al (2013). Therefore we cannot rule out the possibility that frog arborality peaked between 500-800 m and future studies are required to determine this.…”

“…We report 50 species of frogs from 20 genera and six families, 35 species of lizards from 19 genera and four families, 18 species of snakes from 12 genera and six families, and three species of turtle from three genera and three families ( Scheffers et al (2013) identified arborality (vertical stratification) as a key determinant of rainforests species richness and abundance patterns in Mount Banahaw, Phillipines and Singaporean lowlands especially for ectothermic and hydrophilic species such as frogs. They indicated that arboreal frog richness peaked between 600 m and 800 m and that increased elevation resulted in increased vertical species stratification.…”

“…We can infer from our results that 600-750 m on Gunung Tebu is an ideal climate for the majority of the species collected. It is possible that climate change could cause a shift in this altitudinal distribution and Scheffers et al (2013) suggested that global warming could cause arboreal species to migrate downslope to cooler and wetter ground creating a "flattening" effect in their stratification. Flattening could seriously alter the forest ecosystem and impact the survival of numerous species (Scheffers et al 2013).…”

“…It is possible that climate change could cause a shift in this altitudinal distribution and Scheffers et al (2013) suggested that global warming could cause arboreal species to migrate downslope to cooler and wetter ground creating a "flattening" effect in their stratification. Flattening could seriously alter the forest ecosystem and impact the survival of numerous species (Scheffers et al 2013). It is imperative to consider that our study did not focus specifically on frog arborality like Scheffers et al (2013).…”

Environmental change: prospects for conservation and agriculture in a southwest Australia biodiversity hotspot

“…Moritz and Agudo (2013) reported range movements of plants and animals on mountains during rising temperatures that were counterintuitive: ranges shifted downslope and sideways indicating not all distributions are climate limited. In a similar vein two recent studies have suggested biota might use the inherent, small-scale variability in ecological systems to avoid modeled climate shifts (e.g., Scheffers et al 2013Scheffers et al , 2014. Southwestern Australia now consists of a mosaic of largely intact to highly altered ecosystems, with a long, complex evolutionary history offering a useful setting to examine opportunities for integrating resource use and conservation at a bioregional scale (Cheng et al 2003, Campbell 2008, Donovan et al 2009).…”