A new preferentially outcrossing monoicous species of Volvox sect. Volvox (Chlorophyta) from Thailand.

Hisayoshi Nozaki,Wirawan Heman,Ryo Matsuzaki,Masanobu Kawachi,Wuttipong Mahakham,James G Umen

doi:10.1371/journal.pone.0235622

Abstract

Volvox sect. Volvox is an interesting group of green algae; it comprises mostly monoicous species, but evidence suggests an evolution towards dioicy. Based on cultured strains originating from Thailand, we describe Volvox longispiniferus, a novel species in Volvox sect. Volvox. This species is distinguished from others in the section by the large number of sperm packets in its monoicous sexual spheroids and by the long spines on its zygote wall. Phylogenetic analyses indicate that V. longispiniferus is distinct from the other species of two monophyletic groups within Volvox sect. Volvox. In addition, the novel species produces more zygotes when different cultures are combined compared with a single culture, suggesting a preference for outcrossing.

Highlights

Sex is recognized in various eukaryotic lineages and contributes to the mixing of genomes between two individuals, normally designated as male or female based on the production of sperm or eggs, respectively
Monoecism in flowering plants has been of interest to evolutionary biologists since the time of Charles Darwin, as self-fertilization rapidly leads to inbreeding depression [4]
Mature asexual spheroids of V. longispiniferus in the present cultures were subspherical or ovoid in shape, with 5600–8200 somatic cells embedded in individual sheaths at the periphery of the gelatinous matrix (Fig 1A–1C)

Summary

Introduction

Sex is recognized in various eukaryotic lineages and contributes to the mixing of genomes between two individuals, normally designated as male or female based on the production of sperm or eggs, respectively. In some invertebrates, flowering plants, fungi, and algae, both sperm and eggs are produced by the same individual; this is known as “hermaphroditism”, “monoecism”, “monoicy”, or “homothallism” [1,2,3]. Volvox exhibits interesting sexual features, with seven monoicous and three dioicous species [5,6,7], and ancestral state reconstruction suggests its evolution from monoicy toward dioicy [3]. Hanschen et al [8] studied a dioicous species of Volvox sect. Volvox (V. perglobator) and further explored the evolution of dioicy

Methods

Results

Conclusion