Ludwigia sect. Seminudae

Herbs, annual or perennial, or shrubs, often forming pneumatophores when submerged. Stems erect or ascending, terete or angled. Leaves alternate. Flowers (4 or)5 or 6(or 7)-merous; petals present, orange-yellow; stamens 2 times as many as sepals; pollen shed in polyads. Capsules subcylindric [cylindric], angled or subterete [terete], with relatively thin walls, irregularly dehiscent. Seeds in 1 row per locule, embedded in horseshoe-shaped segment of endocarp from which it easily detaches, raphe inconspicuous. 2n = 32, 48, 64, 80.

Distribution

c, e United States, Mexico, West Indies, Central America, South America, Africa, Indian Ocean Islands (Madagascar).

Discussion

Species 5 (1 in the flora).

Section Seminudae consists of a polyploid complex of five species (P. H. Raven and W. Tai 1979), one [hexaploid (n = 24) L. africana (Brenan) H. Hara] endemic to Africa, two [hexaploid (n = 24) L. dodecandra (de Candolle) Zardini & P. H. Raven and chromosomally unknown L. quadrangularis (Micheli) H. Hara] endemic to Central America and South America, and two widely distributed multiploids in the New World but present also in Africa. Of the latter, L. affinis (de Candolle) H. Hara (n = 16, 24) occurs only in a small area of West Africa, probably as a recent introduction from South America (Raven 1963[1964]), whereas L. leptocarpa (n = 32, 40) is widespread and possibly native in sub-Saharan Africa. This section is distinctive among the diplostemonous taxa in having uniseriate seeds embedded in loose segments of endocarp. However, sect. Seminudae so far is poorly resolved by molecular analysis (Liu S. H. et al. 2017).

Selected References

None.

Lower Taxa

Ludwigia leptocarpa