Seed Coat Anatomy and Relationships of Ludwigia Sects. Microcarpium, Dantia, and Miquelia (Onagraceae), and Notes on Fossil Seeds of Ludwigia from Europe

Abstract

Seed coat anatomy was investigated in all species of three closely related sections of Ludwigia, i.e., sects. Microcarpium (14 species), Dantia (five species), and Miquelia (one species), and in two fossil seeds of Ludwigia from Europe. Eight species of sect. Microcarpium have a thin endotesta, as do other Ludwigia, whereas the other six species of the section have a thick endotesta, as do sects. Dantia and Miquelia. The thin endotesta, also found in other Onagraceae, is clearly a plesiomorphic characteristic, and the thick endotesta is an apomorphic one. The present study supports the hypothesis that sects. Dantia and Miquelia were independently derived from a common ancestor from within sect. Microcarpium, specifically from those species with thick endotesta. On the basis of different character state combinations of capsule wall structure, capsule dehiscence, and seed coat structure, we recognize five species groups within sect. Microcarpium: group 1, which comprises species with plesiomorphies alone-L....