Testing the niche-breadth-range-size hypothesis: habitat specialization vs. performance in Australian alpine daisies

Area of Science:

• Ecology
• Evolutionary Biology
• Plant Science

Background:

• The niche-breadth-range-size hypothesis predicts common species outperform rare ones across diverse environments.
• Experimental evidence for this hypothesis, particularly in alpine ecosystems, is limited.
• Species rarity may result from trade-offs between environmental specialization and broad performance.

Purpose of the Study:

• To test the niche-breadth-range-size hypothesis using common and rare alpine daisies (Brachyscome spp.) from the Australian Alps.
• To compare seedling survival, growth, phenotypic plasticity, and seed germination/viability across different alpine habitats and a common garden.

Main Methods:

• Common garden experiment in a warm climate to assess growth and plasticity.
• Reciprocal transplant experiments in three alpine habitats to evaluate seedling survival and seed germination/viability.
• Focus on four common and three rare endemic Brachyscome species.

Main Results:

• All species survived best in productive, low-stress open heathland habitats.
• Common daisies showed greater growth and biomass in the warm common garden, though some rare species performed comparably.
• Common daisies had higher germination rates, while rare species maintained higher seed viability across conditions.

Conclusions:

• Results offer partial support for the niche-breadth-range-size hypothesis, with common species generally outperforming rare ones in growth.
• Rare alpine endemics may possess stress tolerance at the expense of growth in less stressful environments.
• The seed stage appears crucial for the persistence of rare alpine species.