# Population bottlenecks and sexual recombination shape diatom microevolution

## TL;DR

The study explores how diatoms evolve through population bottlenecks and sexual recombination, showing non-bloom phases help maintain genetic diversity.

## Contribution

The novel contribution is a model showing non-bloom phases counteract bloom-related genetic divergence in diatoms.

## Key findings

- Non-bloom phases maintain sex-generated diversity from blooms.
- Populations return to pre-bloom states despite genetic differentiation during blooms.
- Model insights help understand diatom microevolution and ecological roles.

## Abstract

Diatoms are single‐celled organisms that contribute approximately 20% of the global primary production and play a crucial role in biogeochemical cycles and trophic chains. Despite their ecological importance, our knowledge of microevolution is limited. We developed a model using the SLiM evolutionary framework to address this knowledge gap. As a reference, we used the diatom Pseudo‐nitzschia multistriata, which has been extensively studied in the Gulf of Naples. Our model recapitulates what we observe in natural populations, with microevolutionary processes that occur annually during a three‐stage bloom phase. Interestingly, we found that non‐bloom phases allow the population to maintain sex‐generated diversity produced during blooms. This finding suggests that non‐bloom phases are critical to counteract bloom‐related pressures and mitigate genetic divergence at the species level. Moreover, our model showed that despite the consistent genetic differentiation during bloom phases, the population tends to return to pre‐bloom states. While our model is limited to neutral dynamics, our study provides valuable insights into diatoms' microevolution, paving the way to explore the ecological implications of the life history dynamics of these organisms.

Diatoms are single‐celled organisms producing blooms crucial in biogeochemical cycles and trophic chains. We simulated neutral microevolutionary dynamics of synthetic diatom populations observing that non‐bloom phases are critical to counteract bloom‐related pressures and mitigate genetic divergence at the species level. Our work contributes to understanding microbial communities' roles in aquatic ecosystems and global biogeochemical cycles.