Do New World pitvipers "scale-down" at high elevations? Macroecological patterns of scale characters and body size

Area of Science:

• Macroecology
• Herpetology
• Evolutionary Biology

Background:

• Bergmann's rule predicts larger body size at higher elevations, but this is inconsistent in ectotherms like reptiles.
• Epidermal traits, such as scales, are understudied in relation to Bergmann's rule despite their role in thermoregulation.

Purpose of the Study:

• To investigate the relationship between body size, elevation, and scale characters in New World pitvipers.
• To examine macroecological patterns in reptiles, considering taxonomic scope and adaptive traits.

Main Methods:

• Analyzed body size and scale counts across 122 New World pitviper species (15 genera).
• Assessed correlations between body size, elevation, and scale characters, including clade-level analyses.

Main Results:

• A contra-Bergmann's pattern was observed: smaller body size at higher elevations.
• This pattern was influenced by the distribution of small-bodied clades at high elevations and large-bodied clades at low elevations.
• Scale counts positively correlated with body size, but elevation did not independently affect scale numbers.

Conclusions:

• Macroecological patterns in reptiles, like Bergmann's rule, are influenced by taxonomic scope and clade distribution.
• Scale characters correlate with body size but not independently with elevation in pitvipers.
• Reptile macroecology requires reevaluation, incorporating traits like squamation.