The origination time of diatoms: An analysis based on ribosomal RNA data

摘要

The nuclear encoded large and small-subunit ribosomal RNA indicate that diatoms originated sometime between 400 and 330 million years ago. This time interval is clearly in disagreement with a Late Precambrian or Early Paleozoic origin (Round 1981 a,b; Round and Crawford 1981, 1984) and with Pyxidicula representing a diatom form associated with the first evolutionary appearance of the group. Considering the fact that the slowest possible nucleotide substitution rates within Pennales and the largest distance values between the pennate diatoms and the outgroup/basal diatom taxa were used to infer the origination time interval, there is a possibility that the obtained values are overestimated.