Taxonomic Delimitation of the Monostromatic Green Algal Genera Monostroma Thuret 1854 and Gayralia Vinogradova 1969 (Ulotrichales, Chlorophyta)

Abstract

The genera Monostroma and Gayralia belong to the order of monostromatic green algae; however, their taxonomic delimitation remains controversial at the genus level. This study attempts to address this issue through the combined analysis of the morphology and nuclear-encoded Internal Transcribed Spacer region sequences of monostromatic green algal samples collected in the South China Sea. Our phylogenetic data revealed that the monostromatic specimens were separated into the M. nitidum clade, G. brasiliensis clade, and a single Monostroma sp. clade, and that the inter-genera genetic distance between the Monostroma and Gayralia genera was lower than that observed within the Monostroma genus. All the specimens presented similar morphology in their single cell-layered thallus, with irregularly arranged cells, rounded cell corners, a parietal chloroplast, and predominantly one (>90%) pyrenoid. Their most obvious morphological difference was in thallus thickness and size. Moreover, the monostromatic specimens of the M. nitidum clade corresponded to the morphological description of the M. nitidum-type specimens. The genus Monostroma was erected earlier than the genus Gayralia. Therefore, we propose to assign the genus Gayralia to Monostroma based on the morphological and phylogenetic analysis and genetic distance data presented here.

Taxonomic identification and life cycle comparison of two populations of the monostromatic green algae Monostroma nitidum

“…( 2013 ) and Cui et al. ( 2022 ), the ITS sequences of G. oxysperma and G. brasiliensis exhibited genetic differences of at least 0.3 and 0.2, respectively. Pellizzari advocated for the retention of the genus Gayralia by proposing a new Brazilian species, G. brasiliensis .…”

“…An earlier study by our group analyzed the external morphological features and ITSs sequences of MGA from various locations along the coast of Guangdong, China (Cui et al., 2022 ). The results of the phylogenetic analysis revealed that MGA could be categorized into three branches: Monostroma nitidum , Gayralia brasiliensis , and Monostroma sp.…”

Algal growth and morphogenesis-promoting factors released by cold-adapted bacteria contribute to the resilience and morphogenesis of the seaweedUlva(Chlorophyta) in Antarctica (Potter Cove)

“…strain BPC-108 under controlled conditions and propagation of gametophytes similar to those of U. mutabilis. Finally, our study did not participate in the controversial taxonomic reclassification of Monostroma (Cui et al 2022).…”