Intraspecific trait variation shapes macro-scale patterns ofniche breadth and range size

Morphological trait variation within 161 bulbuls predicts both ecological niche breadth and geographic range size, with widespread species showing greater variation than restricted-range species.

• Why it matters: Intraspecific morphological variation is still poorly measured across broad taxa and geography, limiting tests of whether trait flexibility shapes ecological and biogeographic patterns.
• What they did: Using global sampling of beak shape, tarsus length, and wing length for 161 species, the study modeled niche breadth and range size with phylogenetic models from 8,251 museum specimens and 5,627 live captures.
• The result: Trait variation is linked to wider niches and larger ranges, and widespread bulbuls show greater morphological variation than restricted-range species even when geographic extents are matched.

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