Higher ploidy is associated with reduced range breadth in the Potentilleae tribe

Area of Science:

• Evolutionary Biology
• Ecology
• Genetics

Background:

• Polyploids are hypothesized to possess greater niche breadth and larger geographic ranges than diploids.
• This prediction stems from increased ecological tolerances, self-compatibility, and genetic variation in polyploids.
• However, empirical evidence is mixed, and few studies examine quantitative variation in ploidy.

Purpose of the Study:

• To test the prediction that species with higher ploidy exhibit greater range breadth and abiotic breadth.
• To investigate the relationship between quantitative variation in ploidy and ecological/geographical range.
• To assess the contribution of ploidy to range variation, controlling for evolutionary history.

Main Methods:

• Estimated range breadth (latitudinal, altitudinal, overall size) and abiotic breadth (temperature, precipitation, UV-B) for 109 Potentilleae (Rosaceae) species.
• Employed phylogenetic comparative methods to account for evolutionary relatedness and divergence times.
• Analyzed the contribution of ploidy to variation in range and abiotic breadth.

Main Results:

• Ploidy levels ranged from 2× to 12×, with phylogenetic relatedness explaining little variation.
• Transitions to higher ploidy were significantly associated with reduced latitudinal and altitudinal ranges.
• Higher ploidy correlated with smaller overall range size and decreased abiotic breadth for temperature and UV-B.

Conclusions:

• Contrary to predictions, higher ploidy is linked to reduced range size and abiotic breadth.
• Emphasizes the importance of considering continuous variation in ploidy for ecological studies.
• Suggests genome duplication may contribute to a negative relationship between ploidy and range breadth.