ミツガシワ科(キキョウ目)の珠皮の研究 Integumentary Studies in Menyanthaceae (Campanulales sensu lato)

ミツガシワ科3属に基づいて,この科が,ユガミウチワ科やキキョウ科にみられるような3から6細胞層の薄い珠皮ではなく,キク科やクサトベラ科に見られるような,10から25細胞層になる厚い珠皮をもつことがわかった。このことから,他で発表されたキキョウ目の分子系統図などに照らして,薄い珠皮から厚い珠皮への進化が,キク科,クサトベラ科,ミツガシワ科,カリケラ科(この科については珠皮の厚さはまた未定)に共通の祖先で起こったことが明らかになった。

On the basis of three species in three genera (Menyanthes, Nephrophyllidium and Nymphoides) of Menyanthaceae we found that the family has a thick, 10- to 25-cell-layered integument as in Asteraceae and Goodeniaceae, and not a thin, 3- to 6-cell-layered integument as in Pentaphragmataceae and Campanulaceae sensu lato. In the light of a molecular phylogenetic tree of Campanulales sensu lato published elsewhere, the result suggests that the evolution from the thin to the thick integument occurred in a common ancestor with Asteraceae, Goodeniaceae, and Calyceraceae although the last family is not known yet with respect to integumentary thickness.