Morphological variations in a widely distributed Eastern Asian passerine cannot be consistently explained by...

Area of Science:

• * Ecology and Evolutionary Biology
• * Zoology
• * Biogeography

Background:

• * Ecogeographic rules link animal morphology to climate, aiding predictions of climate change impacts.
• * These rules are well-tested in Europe and North America but less so in other regions.
• * The vinous-throated parrotbill (Sinosuthora webbiana), an East Asian passerine, serves as a model for studying regional ecogeographic variation.

Purpose of the Study:

• * To investigate the morphometric variation of Sinosuthora webbiana.
• * To test conformity to Bergmann's rule, Allen's rules, and Gloger's rule in this species.
• * To assess the applicability of ecogeographic rules in understudied regions.

Main Methods:

• * Described the climatic niche of S. webbiana using occurrence (n=7838) and specimen (n=290) records.
• * Analyzed morphometric variation (plumage coloration, appendage size, body size) against climatic factors.
• * Employed analysis of covariance (ANCOVA) to evaluate relationships between morphology and climate.

Main Results:

• * Plumage coloration was darker in wetter/warmer environments, supporting Gloger's rule.
• * Appendage size (culmen length, beak volume, tarsi length) was larger in colder environments, contradicting Allen's rule.
• * Body size (wing length) was larger in warmer environments, contradicting Bergmann's rule.

Conclusions:

• * Morphological variation in S. webbiana deviates from predictions of Bergmann's and Allen's rules.
• * This suggests multiple selection pressures, not just thermoregulation, shape evolution.
• * Ecogeographic rules require validation in less-studied regions before predicting climate change responses.