COS 63-1 - Eco-evolutionary causes and consequences of rarity in plants: a meta-analysis

Background/Question/Methods

Species differ dramatically in their prevalence in the natural world, with many species characterized as rare due to restricted geographic distribution, low local abundance, and/or habitat specialization. Investigating the ecological and evolutionary causes and consequences of rarity could advance ecological theory and guide conservation efforts, especially in the context of rapid global change. We investigated eco-evolutionary causes and consequences of rarity with a comprehensive phylogenetically-controlled meta-analysis examining population genetic diversity, fitness, and functional traits in rare and common congeneric plant species. Our syntheses included 252 rare species and 267 common congeners reported in 152 peer-reviewed articles and one manuscript in press.

Results/Conclusions

Discerning the reasons for rarity is a challenging task, but such understanding could inform robust plans for the conservation of rare species and overall biodiversity against the pressures of contemporary environmental change. Our results reveal that rare species have reduced population genetic diversity, depressed fitness, and smaller reproductive structures than common congeners. A preliminary mating system meta-analysis also suggests that rare species could suffer from inbreeding depression and reduced fertilization efficiency. These characteristics could influence patterns of rarity and increase susceptibility of rare species to environmental change by limiting their adaptive and migratory potential. We recommend that future studies present more detail on the extent of rarity in focal species, expose rare and common species to ecologically-relevant treatments, and conduct quantitative genetic and population genomic analyses across a greater array of systems. This research could yield insights into processes that contribute to rarity and generate more robust predictions of extinction risks under global change.