Evidence for environmental and ecological selection in a microbe with no geographic limits to gene flow

This is the authors' abstract. We don't add key points for this paper.

Significance Marine microbes exhibit enormous genetic diversity and drive global biogeochemical processes. Diatoms are some of the most diverse and ecologically influential marine microbes, generating about 40% of global marine primary production. The physical and ecological processes that maintain diversity in marine microbes are widely debated. Here, using empirical evidence from a diatom species, we show that geographic distance between sites does not correlate with genetic divergence. Instead, environmental and ecological selection likely exert a stronger influence than dispersal on the divergence and connectivity of diatom populations throughout the globe. Understanding mechanisms driving divergence and selection of marine microbial populations has enormous potential for improving predictions of global productivity in response to a rapidly changing marine environment.