Diversity and phylogeny of Chaetoceros species (Bacillariophyceae) with a central valve linking protuberance

ABSTRACT

Chaetoceros Ehrenberg is one of the most diverse genera of planktonic diatoms and includes important primary producers in marine waters. A valve linking protuberance is a unique character that has only been recorded in Chaetoceros rostratus and C. rostratus var. glandazii. However the taxonomical relationship between the two taxa needs to be clarified. In order to clarify species delimitations, monoclonal strains were established from Chinese southeastern coastal waters. Vegetative cells were observed using light microscopy and electron microscopy of the frustule. The region D1–D3 of the nuclear-encoded large subunit ribosomal DNA and the small subunit ribosomal DNA were sequenced to determine phylogenetic relationships. The phylogenetic analyses inferred from both SSU and LSU rDNA showed that the strains bearing valve linking protuberance clustered into two groups, which corresponded to different morphotypes. One group included the strains isolated from Hong Kong, the type locality of C. rostratus, and matched the original description; this was used herein to delineate the characters of C. rostratus. Another group is described as a new species, Chaetoceros separatus sp. nov., characterized by a long tubular valve linking protuberance and disjoint sibling setae. Previous reports of C. rostratus and C. rostratus var. glandazii were re-examined. The phylogenetic results showed C. peruvianus grouping with species of Chaetoceros sect. Rostrata, thereby suggesting the synonymy between this section and Chaetoceros sect. Peruviana. However, the identity and morphological variability of C. peruvianus need to be re-examined.

KEYWORDS:

• Chaetoceros rostratus
• Chaetoceros separatus
• Chinese coastal waters
• LSU rDNA
• SSU rDNA
• Valve linking protuberance

ACKNOWLEDGEMENTS

We thank two anonymous reviewers and editors for their insightful comments and suggestions on the manuscript.

DISCLOSURE STATEMENT

No potential conflict of interest was reported by the authors.

SUPPLEMENTARY MATERIAL

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Additional information

Funding

This work was supported by grants from National Science Foundation of China [32170206] and Nature Science Foundation of Guangdong Province, China [2021A1515010786].