Three new species of mangrove cyanobacteria from Thailand, with taxonomic revisions of Desikacharya (Nodulariaceae) and Baaleninema (Oscillatoriaceae)

Cryptic cyanobacterial diversity has increasingly been recognized in Thailand, which has emerged as a biodiversity hotspot for such taxa in recent years. Various new genera and species of heterocytous and simple filamentous cyanobacteria have been discovered from freshwater and man-made hypersaline habitats in northern and central Thailand, as well as from mangrove environments along the Andaman Sea. In this polyphasic study, Nostoc-like, Lyngbya-like and Geitlerinema-like mangrove-associated cyanobacteria from the provinces of Ranong, Trang and Satun along the west coast of Thailand were isolated and characterized. Our results supported the descriptions of three new species from mangrove habitats: Desikacharya salina sp. nov. Capilliphycus granulosus sp. nov. and Capilliphycus lohsawadkuliae sp. nov. A detailed reassessment of morphological and ecological characteristics, physio-chemical parameters, 16S rRNA gene phylogeny and genetic identity, 16S–23S rRNA ITS phylogeny, putative secondary structures and ITS per cent dissimilarity further supported the synonymization of ‘D. soli’ and ‘D. thermotolerans’’ with the type species D. nostocoides. Similarly, ‘D. raigadensis’ is regarded as a later synonym of D. kailashaharensis. Based on the 16S rRNA gene phylogeny, the nesting of Minunostoc and Reofilinostoc within the Desikacharya clade suggests that generic reassessment of Desikacharya, as currently circumscribed, is needed. Additionally, we provided an emended description of the genus Baaleninema and its type species, B. simplex. These findings expand our understanding of mangrove cyanobacterial diversity and highlight the need for continued taxonomic revision within the order Nostocales.