Morphological and molecular characterization within 26 strains of the genus Cylindrospermum (Nostocaceae, Cyanobacteria), with descriptions of three new species

Twenty-six strains morphologically identified as Cylindrospermum as well as the closely related taxon Cronbergia siamensis were examined microscopically as well as phylogenetically using sequence data for the 16S rRNA gene and the 16S-23S ITS region. Phylogenetic analysis of the 16S rRNA revealed three distinct clades. The clade we designate as Cylindrospermum sensu stricto had all five of the foundational species, C. maius, C. stagnale, C. licheniforme, C. muscicola, and C. catenatum. In addition to these taxa, three species new to science in this clade were described: C. badium, C. moravicum, and C. pellucidum. Our evidence indicates that Cronbergia is a later synonym of Cylindrospermum. The phylogenetic position of Cylindrospermum within the Nostocaceae was not clearly resolved in our analyses. Cylindrospermum is unusual among cyanobacterial genera in that the morphological diversity appears to be more evident than sequence divergence. Taxa were clearly separable using morphol...本研究对26株经形态学鉴定为柱孢藻属（Cylindrospermum）及其近缘类群暹罗克伦伯格藻（Cronbergia siamensis）的菌株，分别开展了显微观察与基于16S核糖体RNA基因（16S rRNA gene）和16S-23S转录间隔区（16S-23S ITS region）序列数据的系统发育分析。16S rRNA基因的系统发育分析结果显示存在三个独立的演化支。我们将其命名为狭义柱孢藻演化支（Cylindrospermum sensu stricto）的类群，包含该属全部5个核心物种：C. maius、C. stagnale、C. licheniforme、C. muscicola及C. catenatum。除上述类群外，该演化支中还描述了3个科学新种：C. badium、C. moravicum和C. pellucidum。本研究证据表明，克伦伯格藻属（Cronbergia）实为柱孢藻属（Cylindrospermum）的晚出同物异名。本分析尚未明确柱孢藻属在念珠藻科（Nostocaceae）中的系统发育位置。柱孢藻属在蓝细菌属中较为特殊，其形态多样性相较于序列分歧更为显著，利用形态学特征可清晰区分各类群……