Phylogenetic relationships among taxa of the liverwort Conocephalum conicum (Conocephalaceae) revealed by psbA sequence

摘要

The 5' flanking and coding regions of the psbA gene were sequenced to clarify relationships among several taxa discovered recently in thalloid liverwort Conocephalum conicum. Twenty six samples included in this study represent five "cryptic species" detected in worldwide collection, five groups discovered from Japan and finally three "chemo-types" with different dominant volatile component. Pairwise differences in nucleotide sequences of coding region between samples of Conocephalum conicum varied greatly depending on the combination, ranging from 0.001 to 0.018 per site. In total, seven amino acid substitutions were found among all samples. NJ and parsimony trees among the taxa were constructed for the first time. The phylogenetic relationships among taxa were basically consistent with those inferred from isozyme and morphological studies. Conocephalum conicum species FS and T taxon found in Japan have identical sequence of psbA gene, suggesting that they are conspecific. Similarly, YFS and KYT taxa cluster together with FS cryptic species, and "chemo-types" I and II with "cryptic species" J. A chemotype III was very different from any other taxa of C. conicum. These results suggest that morphological species, Conocephalum conicum is highly differentiated at the molecular level and some of the taxa may in fact represents different species as previous studies suggested.