Where less may be more: how the rare biosphere pulls ecosystems strings

Summary

This review synthesises ecological principles governing the rare microbial biosphere, arguing that microbial taxa at low relative abundance frequently act as overlooked keystone species regulating ecosystem function. Rather than treating rarity as passive consequence of ecological competition, the authors present evidence that rare microbes exhibit phylogenetically conserved features and disproportionately influence nutrient cycling and community assembly. The paper provides a conceptual framework and research recommendations for investigating rare microbes in host-associated, terrestrial and aquatic environments.

UK applicability

This conceptual review is applicable to UK soil and environmental microbiology research programmes, particularly those investigating soil health, crop productivity and microbiome-mediated ecosystem services. The framework could inform UK agricultural research strategies seeking to understand mechanisms underlying soil resilience and function.

Key measures

Conceptual framework of rare biosphere ecology; relative abundance thresholds for rarity; functional roles in biogeochemical cycles; phylogenetic patterns in rarity; ecosystem functioning impacts

Outcomes reported

The review synthesises evidence that rare microbial species play disproportionately important roles in biogeochemical cycling and microbiome function across terrestrial, aquatic and host-associated ecosystems. It identifies causes of microbial rarity and mechanisms by which rare taxa may regulate ecosystem processes despite low abundance.

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