Increased host diversity limits bacterial generalism but may promote microbe-microbe interactions.

Area of Science:

• Microbiology
• Ecology
• Evolutionary Biology

Background:

• Host-associated bacteria exhibit varying host specificity, with generalists potentially having greater ecological impact.
• Previous research indicates many bacterial lineages are host-specific, but constraints on generalism may differ by ecological context.

Purpose of the Study:

• To investigate how ecological context, specifically host diversity, influences bacterial host generalism and specialization.
• To assess patterns of diversity and specialization in reptile cloacal microbiomes across a gradient of host species richness.

Main Methods:

• Analysis of cloacal microbiomes from reptile communities spanning temperate to tropical zones.
• Quantification of bacterial lineage richness and host prevalence across varying host diversity levels.

Main Results:

• Host-specific bacterial lineages increased in richness with host species, while generalist lineages did not.
• Generalist bacterial lineages achieved highest prevalence in lower host diversity environments.
• In high-diversity communities, successful generalists (Proteobacteria) frequently co-occurred across disparate hosts.

Conclusions:

• Bacterial lineages adapt to high host diversity by either specializing on hosts or forming co-occurring cohorts.
• The study supports the prevalence of mutually beneficial relationships among bacterial lineages within diverse host microbiomes.