Speciation within blidingia minima (chlorophyta) in japan: evidence from morphology, ontogeny, and analyses of nuclear rdna its sequence

The genus Blidingia is a common, sometimes abundant, component of northern hemisphere temperate and subarctic shores. Species determination relies on characteristic differences in morphology and early ontogenic development. Within the species Blidingia minima (Naegeli ex Kuetzing) Kylin in Japan, however, there appear to be three distinct types, the F‐, D‐, and M‐types, which are differentiated in early ontogeny. The M‐type can be further categorized into three subtypes. Results of intensive field and culture studies supported the view that morphological characteristics do not reliably separate the F‐, D‐, and M‐types and that all three may potentially cross breed. The F‐type has characteristics in early ontogeny of the species B. chadefaudii (  J. Feldmann) Bliding in European waters and this, combined with the morphological and cross breeding studies, suggest that B. chadefaudii should be merged with B. minima. In this study, molecular analyses of nuclear rDNA from samples of the F‐ and D‐types indicated that both have a distinctive and characteristic identity. Sequence data also examined from two of the M‐type subtypes indicated that each of these also has a characteristic molecular identity clearly distinguished from that of the F‐ and D‐types. Analyses indicated that there is a close relationship between the D‐type and one of the M‐type subtypes, and that these are more closely related to the F‐type than to the other M‐type examined. Comparison with studies of this gene region in other ulvophytic algae indicated a wide range of variation within B. minima. Such variation may be useful in assessing distribution patterns in Japanese waters of the developmental types within this species.