Trait divergence and trade-offs among Brassicaceae species differing in elevational distribution

Area of Science:

• Evolutionary Biology
• Ecology
• Plant Science

Background:

• Species geographic distributions are often restricted, with temperature being a key factor limiting climate niche evolution.
• Understanding the traits underlying these distribution limits is crucial for predicting species responses to climate change.

Purpose of the Study:

• To investigate the traits constraining species distributions using macroevolutionary comparisons in Brassicaceae.
• To identify how temperature influences phenological, morphological, and thermal resistance traits in relation to elevational distribution.

Main Methods:

• Macroevolutionary comparisons of 100 Brassicaceae species across elevational gradients.
• Controlled growth experiments under three temperature treatments (frost, mild, heat).
• Phenotyping for phenological, morphological, and thermal resistance traits, analyzed using mixed models, evolutionary models, and correlative approaches.

Main Results:

• Plant size, leaf morphology, and heat-induced growth were key traits differentiating low- and high-elevation species.
• High-elevation species exhibited faster growth under heat but were smaller in size, suggesting adaptive divergence and trade-offs.
• Trait evolution showed asymmetry, with less constraint under frost conditions, and moderate trade-offs were identified.

Conclusions:

• Adaptive divergence in traits like size and heat tolerance, coupled with trade-offs, contributes to the distinct elevational distributions of Brassicaceae species.
• Temperature plays a significant role in shaping plant traits and evolutionary trajectories, influencing species' geographic ranges.