A Year at the Forefront of Streptophyte Algal Evolution

Abstract

Land plants originated from an algal ancestor ∼500 million years ago in one of the most important evolutionary events for life on Earth. Extant streptophyte algae, their closest living relatives, have subsequently received much attention to better understand this major evolutionary transition. Streptophyte algae occupy many different environments, have diverse genomes and display contrasting morphologies (e.g. unicellular, filamentous, three-dimensional). This has historically made inferring these evolutionary events challenging. This A Year at the Forefront Review focusses on research published between July 2023 and June 2024 and intends to provide a short overview of recent discoveries, innovations, resources, and hypotheses regarding streptophyte algal evolution. This work has provided mechanistic insights into ancient evolutionary events that prefigured the origin of land plants and raises new questions for future research into streptophyte algae.

Keywords: Algal evolution; Plant terrestrialisation; Streptophytes.

Fig. 1.

The evolution of streptophytes. A cladogram of the current understanding of streptophyte relationships. Taxa are highlighted in orange (land plants), blue (streptophyte algae) and green (chlorophyte algae). The origin of multicellularity as well as its loss and multiple independent regains in Zygnematophyceae are highlighted. Nodes with no commonly used nomenclature are highlighted with a question mark. Numbers at each internal node highlight divergence time in millions of years, with estimates derived from Harris et al. (2022). Silhouettes are sourced from Phylopic, with credit to Matt Crook (https://creativecommons.org/licenses/by-sa/3.0/).