Ecological and evolutionary dynamics of chlamydiae endosymbionts in social amoeba host communities.

Across 1400+ dictyostelid social amoeba isolates spanning 1200 km, 41 chlamydiae haplotypes across 11 host species show prevalence that varies by host species and sampling location.

• Why it matters: It remains unclear how ecological processes shape endosymbioses that persist as segregating variation within host populations.
• What they did: The study surveyed chlamydiae haplotypes and tested links to geography and host diversification, then used laboratory passaging to assess vertical transmission and built a stochastic differential equation model of vertical plus environmental transmission with selection and drift.
• The result: Chlamydiae phylogenetic divergence was not linked to geographic dissimilarity but was linked to host diversification, and haplotype diversity was negatively associated with prevalence; the model recapitulated this relationship.