Revisiting Darwin's hypothesis: Does greater intraspecific variability increase species' ecological breadth?

Area of Science:

• Ecology
• Evolutionary Biology
• Plant Trait Variation

Background:

• Darwin's hypothesis posits a link between ecological breadth and phenotypic variation.
• Understanding intraspecific variation is key to community assembly and species distribution theories.

Purpose of the Study:

• To test Darwin's hypothesis by examining the relationship between species' ecological breadth and intraspecific variation in specific leaf area (SLA).
• To assess the influence of abiotic factors on species' ecological breadth and trait variation.

Main Methods:

• Compared the coefficient of variation of SLA across 21 species against their local elevational ranges.
• Analyzed intraspecific SLA changes with elevation relative to community-level SLA shifts.

Main Results:

• Found a positive correlation between species' elevational range and intraspecific variation in SLA, supporting Darwin's hypothesis.
• Intraspecific SLA changes mirrored community mean SLA direction but had lower magnitude.

Conclusions:

• Wider-ranging species demonstrate greater intraspecific phenotypic variation.
• Species' phenotypes shift along environmental gradients consistently with community trends.
• Intraspecific trait plasticity/adaptation rates are limited compared to interspecific community assembly dynamics.