[B-CG05] Frontier in diversity and ecology of protists and microfossils

[BCG05-01] Diversity and phylogeny of coccolithophores

★Invited Papers

*萩野 恭子¹ (1.高知大学)

キーワード：円石藻、ハプト藻、石灰質ナノ化石

Coccolithophores are unicellular marine haptophytes that possess calcified scales called coccoliths. They have extensive fossil records making them an attractive group for study of microevolutionary patterns through combined study of molecular genetics, the morphology of living species and the fossil record. Classification of coccolithophores is based on the morphology of the coccoliths and the crystallographic orientation of the calcite elements that form coccoliths. Molecular phylogenetic studies of living coccolithophores largely supported the morphological and crystallographic classification, and revealed that many coccolithophore morpho-species consist of multiple pseudo-cryptic species: discrete species only differing from each other in minor morphological features or the size range of coccoliths. Molecular phylogenetic analyses are therefore a powerful tool for understanding the evolutionary process and diversity of coccolithophores, but the feasibility of molecular analyses depends fundamentally on the availability of culture strains. Since less than 1/4 of described species have been cultured and sequenced, molecular phylogenetic tree of the coccolithophores lacks most uncultured species. Molecular data from uncultured phytoplankton can be obtained using the single cell PCR technique, although the sequence regions that can be determined from single cells are limited. In this presentation, I will introduce an update on the diversity and phylogenetic studies of coccolithophores, and discuss the remaining issues that need to be resolved.