An evolutionary case for plant rarity: Eucalyptus as a model system

Area of Science:

• Ecology
• Evolutionary Biology
• Plant Science

Background:

• Species rarity is increasing globally, exacerbated by climate change.
• Rarity is often viewed as a stochastic outcome, but this study explores a natural selection hypothesis.
• Key descriptors of rarity include range size, habitat specificity, and population aggregation.

Purpose of the Study:

• To test if plant rarity results from natural selection on performance traits.
• To investigate the relationship between biomass, range size, habitat specificity, and population aggregation in rare species.
• To explore the role of phylogenetic and environmental factors in trait evolution associated with rarity.

Main Methods:

• A common garden experiment was conducted with 25 Tasmanian Eucalyptus species.
• Biomass allocation (aboveground vs. belowground) and overall biomass were measured.
• Phylogenetic comparative methods were used to analyze trait correlations.

Main Results:

• Rare Eucalyptus species had 70% lower biomass than common species.
• Rare species allocated proportionally more biomass aboveground.
• Significant positive correlations were found between biomass, range size, and habitat specificity.

Conclusions:

• Plant rarity can be an evolved trait influenced by natural selection on performance characteristics.
• Convergent evolution of rarity traits is evident across the Tasmanian Eucalyptus phylogeny.
• Understanding trait-based determinants of rarity may necessitate revised conservation strategies for rare species.