Institut de biologie de l'École normale supérieure (IBENS), École Normale Supérieure, CNRS, INSERM, Université PSL, Paris, France.
Institut de Systématique, Évolution, Biodiversité (ISYEB), Muséum National d'histoire Naturelle, CNRS, Sorbonne Université, EPHE, UA, CP39, Paris, France.
Mol Ecol. 2022 Jun;31(12):3496-3512. doi: 10.1111/mec.16478. Epub 2022 May 5.
Analysing diversification dynamics is key to understanding the past evolutionary history of clades that led to present-day biodiversity patterns. While such analyses are widespread in well-characterized groups of species, they are much more challenging in groups for which diversity is mostly known through molecular techniques. Here, we use the largest global database on the small subunit (SSU) rRNA gene of Glomeromycotina, a subphylum of microscopic arbuscular mycorrhizal fungi that provide mineral nutrients to most land plants by forming one of the oldest terrestrial symbioses, to analyse the diversification dynamics of this clade in the past 500 million years. We perform a range of sensitivity analyses and simulations to control for potential biases linked to the nature of the data. We find that Glomeromycotina tend to have low speciation rates compared to other eukaryotes. After a peak of speciations between 200 and 100 million years ago, they experienced an important decline in speciation rates toward the present. Such a decline could be at least partially related to a shrinking of their mycorrhizal niches and to their limited ability to colonize new niches. Our analyses identify patterns of diversification in a group of obligate symbionts of major ecological and evolutionary importance and illustrate that short molecular markers combined with intensive sensitivity analyses can be useful for studying diversification dynamics in microbial groups.
分析多样化动态是理解导致当今生物多样性模式的进化历史的关键。虽然这种分析在特征明确的物种群体中很普遍，但在多样性主要通过分子技术来了解的群体中，这种分析就更具挑战性了。在这里，我们利用 Glomeromycotina （一种微小的丛枝菌根真菌的亚门）的小亚基（SSU）rRNA 基因的最大全球数据库，该数据库分析了该丛枝菌根真菌亚门在过去 5 亿年中的多样化动态。我们进行了一系列敏感性分析和模拟，以控制与数据性质相关的潜在偏差。我们发现，与其他真核生物相比，Glomeromycotina 的物种形成率较低。在 2 亿至 1 亿年前达到物种形成的高峰期后，它们的物种形成率在接近现在时经历了重要的下降。这种下降至少部分与它们的菌根生态位缩小以及它们有限的能力向新生态位殖民有关。我们的分析确定了一个具有重要生态和进化意义的专性共生体群体的多样化模式，并表明短的分子标记物结合密集的敏感性分析可以用于研究微生物群体的多样化动态。
