The Closest Living Relatives of Land Plants

TLDR

The evolutionary relationship between land plants and green algae, particularly the Charophyta, has been unclear. The authors performed a four‑gene phylogenetic analysis to resolve these relationships. The analysis places land plants within Charophyta, identifies stoneworts (Charales) as their closest living relatives, shows Coleochaetales as sister to the Charales/land‑plant clade, and places the unicellular flagellate Mesostigma as the earliest charophyte branch, offering insights into plant ancestry and the aquatic‑to‑terrestrial transition.

Abstract

The embryophytes (land plants) have long been thought to be related to the green algal group Charophyta, though the nature of this relationship and the origin of the land plants have remained unresolved. A four-gene phylogenetic analysis was conducted to investigate these relationships. This analysis supports the hypothesis that the land plants are placed phylogenetically within the Charophyta, identifies the Charales (stoneworts) as the closest living relatives of plants, and shows the Coleochaetales as sister to this Charales/land plant assemblage. The results also support the unicellular flagellate Mesostigma as the earliest branch of the charophyte lineage. These findings provide insight into the nature of the ancestor of plants, and have broad implications for understanding the transition from aquatic green algae to terrestrial plants.