Are latitudinal clines in body size adaptive?

Area of Science:

• Ecology
• Evolutionary Biology
• Zoology

Background:

• Latitudinal clines in animal body size are a long-standing biological observation.
• Temperature gradients are implicated in body size variation across latitudes.
• Phenotypic data often confound genetic and plastic influences on size.

Purpose of the Study:

• To demonstrate the risks of inferring adaptation from phenotypic measures of body size.
• To illustrate how plasticity, specifically the temperature-size rule, complicates understanding of latitudinal size clines.
• To emphasize the necessity of genetic basis for adaptive conclusions.

Main Methods:

• Review of studies on latitudinal clines in body size.
• Analysis of phenotypic data and its limitations.
• Examination of the temperature-size rule in ectotherms.

Main Results:

• Phenotypic measures of body size can lead to erroneous adaptive inferences.
• Plasticity, like the temperature-size rule, obscures the genetic underpinnings of size variation.
• Current research often fails to distinguish between plastic and genetic contributions to size.

Conclusions:

• Adaptive conclusions about latitudinal body size clines require demonstrating a genetic basis.
• Distinguishing plasticity from genetic variation is crucial for understanding evolutionary patterns.
• Future research must incorporate genetic analyses to validate adaptive hypotheses.