Increasing arboreality with altitude: a novel biogeographic dimension

Area of Science:

• Ecology
• Biogeography
• Zoology

Background:

• Biodiversity patterns are typically linked to climatic gradients along elevation and latitude.
• The role of other potential gradients, such as vertical rainforest strata, in shaping biogeographic patterns remains less understood.

Purpose of the Study:

• To investigate if rainforest vertical strata create climatic gradients that organize arboreal species distribution.
• To propose and test the 'arboreality hypothesis' explaining how vertical habitat use influences species' geographical ranges.

Main Methods:

• Comparing climatic gradients across rainforest vertical strata, elevation, and latitude.
• Analyzing frog distribution and arboreality in relation to altitude in Philippine and Singaporean rainforests.
• Utilizing a Philippine-wide dataset of frog distributions to assess broad-scale patterns.

Main Results:

• Rainforest vertical strata exhibit steeper climatic gradients than elevation or latitude.
• Frog distribution shifts upward in rainforest strata with increasing altitude.
• Increased arboreality with elevation was observed at both local and broad biogeographic scales.

Conclusions:

• The 'arboreality hypothesis' suggests arboreal species may have larger distributions by vertically adjusting to temperature changes.
• Vertical microclimatic gradients in vegetation can explain species richness and abundance patterns.
• Global warming may reduce rainforest biodiversity by forcing arboreal species to lower strata, impacting forest function and survival.