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

Robert C. Jadin, Joseph R. Mihaljevic, Sarah A. Orlofske

Research output: Contribution to journalArticlepeer-review

5 Scopus citations


Bergmann's rule describes the macroecological pattern of increasing body size in response to higher latitudes and elevations. This pattern is extensively documented in endothermic vertebrates, within and among species; however, studies involving ectotherms are less common and suggest no consistent pattern for amphibians and reptiles. Moreover, adaptive traits, such as epidermal features like scales, have not been widely examined in conjunction with Bergmann's rule, even though these traits affect physiological processes, such as thermoregulation, which are hypothesized as underlying mechanisms for the pattern. Here, we investigate how scale characters correlate with elevation among 122 New World pitviper species, representing 15 genera. We found a contra-Bergmann's pattern, where body size is smaller at higher elevations. This pattern was mainly driven by the presence of small-bodied clades at high elevations and large-bodied clades at low elevations, emphasizing the importance of taxonomic scope in studying macroecological patterns. Within a subset of speciose clades, we found that only Crotalus demonstrated a significant negative relationship between body size and elevation, perhaps because of its wide elevational range. In addition, we found a positive correlation between scale counts and body size but no independent effect of elevation on scale numbers. Our study increases our knowledge of Bergmann's rule in reptiles by specifically examining characters of squamation and suggests a need to reexamine macroecological patterns for this group.

Original languageEnglish (US)
Pages (from-to)9362-9375
Number of pages14
JournalEcology and Evolution
Issue number16
StatePublished - Aug 2019
Externally publishedYes


  • Bergmann's rule
  • Crotalinae
  • Viperidae
  • biogeography
  • body size
  • macroecology

ASJC Scopus subject areas

  • Ecology, Evolution, Behavior and Systematics
  • Ecology
  • Nature and Landscape Conservation


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