Flora of North America species comparison

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Ludwigia octovalvis

Ludwigia sect. Macrocarpon

Mexican primrose-willow
Habit Herbs (robust)or shrubs, herbs tap-rooted, often woody at base, with peeling bark. Herbs, perennial, or shrubs.Stems erect or spreading, terete, subterete, or ridged.
Stems

erect to spreading, terete or sometimes ridged, 60–250(–400) cm, densely branched, densely villous to glabrate, especially near base.

Leaves

stipules deltate, 0.5–0.8 × 0.6–0.7 mm, fleshy;

petiole 0–1 cm;

blade linear to oblong or oblanceolate, sometimes narrowly ovate, 0.7–14.5 × 0.1–4 cm, base tapered, margins entire, apex acute to acuminate, surfaces ± densely villous or strigillose;

bracts not or scarcely reduced.

alternate.
Inflorescences

open, leafy racemes, flowers solitary in axils, presentation often radial;

bracteoles ovate, 3–8 × 1.4–4 mm, apex acuminate, attached near base of ovary.

Flowers

sepals lanceolate to ovate, (6–)8–13 × 3–7 mm, apex acuminate, surfaces strigillose adaxially;

petals bright yellow, fan-shaped, (5–)10–20 × 5–20 mm, apex sometimes shallowly notched;

stamens 8 in 2 subequal series, yellowish white, filaments spreading, 4–6 mm, anthers oblong, 2.5–5 × 1–2 mm;

pollen shed in tetrads or sometimes polyads;

ovary cylindric, 4-angled, sometimes slightly twisted, 8–22 × 1–3 mm;

nectary disc elevated 0.4–0.5 mm on ovary apex, 1–2.4 mm diam., with 4 white-pubescent sunken lobes opposite petals;

style 2.5–3.5 mm, stigma capitate-globose, 1.8–3.5 × 2.5–3.5 mm, surrounded by anthers and pollen shed directly on it.

4-merous;

petals present, yellow;

stamens 2 times as many as sepals;

pollen shed in tetrads or polyads.
Capsules

cylindric to clavate-cylindric, subterete to ± 4-angled, 17–50 × 2.5–8 mm, thin-walled, irregularly dehiscent by 4–8 linear valves splitting from apex, short-villous, pedicel 5–25 mm.

cylindric to clavate-cylindric, ± angled to subterete, with thin walls, irregularly dehiscent.
Seeds

in several indistinct rows per locule, broad-cylindric with rounded ends, 0.6–0.9 × 0.5–0.8 mm, raphe inflated and nearly equal to seed body.

in several rows per locule, free, raphe enlarged, nearly equal to seed.
2n

= [16], 32, 48.

= 16, 32, 48.

Ludwigia octovalvis

Ludwigia sect. Macrocarpon
Phenology Flowering summer–early fall.
Habitat Wet or moist places, along coasts, streams, ditches, swamps, often near disturbance or cultivation.
Elevation 0–300[–2200] m. (0–1000[–7200] ft.)
Distribution
from FNA
AL; FL; GA; LA; MS; NC; SC; TX; Mexico; Central America; South America; West Indies; s Asia; e Asia (Burma, China, India, Japan, Thailand, Vietnam); Africa; Indian Ocean Islands (Comoros Islands, Madagascar); Pacific Islands (New Caledonia, Papua New Guinea, Philippines)
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[BONAP county map]
se United States; Mexico; Central America; South America; s United States; West Indies; Eurasia; Africa; Indian Ocean Islands; Pacific Islands; Australasia
Discussion

Ludwigia octovalvis is perhaps the most widespread species of Ludwigia worldwide and exhibits a very complex pattern of morphological and ecological variation, correlated only in part with multiple ploidy levels; this complexity is reflected in its extensive synonymy. P. H. Raven (1963[1964]), P. A. Munz (1942, 1965), and others have proposed formal classifications to account for this variation, with mixed results and additional study using more powerful analytical tools is clearly needed in order to develop a more stable classification. In the absence of better understanding, and despite some correlated patterns of morphological and geographical variation on a global scale, this treatment does not recognize infraspecific taxa.

Jussiaea hirsuta Velloso, J. suffruticosa var. angustifolia Chodat & Hassler, J. velutina Kunze, and Ludwigia suffruticosa (Linnaeus) M. Gómez are later homonyms; these four names pertain here.

(Discussion copyrighted by Flora of North America; reprinted with permission.)

Species 4 (2 in the flora).

Section Macrocarpon consists of four species, all of which occur in Argentina, Brazil, and Paraguay. Ludwigia bonariensis also occurs as a disjunct in Mexico and the southern United States; L. octovalvis is found worldwide in subtropical and tropical areas and is widely distributed in the southern United States. Section Macrocarpon, which is supported as monophyletic by molecular data (Liu S. H. et al. 2017), differs from sect. Myrtocarpus by having strictly 4-merous (versus 4+-merous) flowers, cylindric (versus obconic) capsules, and distinctive seeds with an enlarged raphe.

Ludwigia bonariensis and L. lagunae are diploid (n = 8) and self-incompatible; L. neograndiflora is tetraploid (n = 16; Liu S. H. et al. 2017), but compatibility is unknown. In contrast, most populations of the multiploid L. octovalvis are polyploid, with some reports of diploids in the New World (P. H. Raven and W. Tai 1979), and self-compatible. Ludwigia octovalvis is extremely variable in morphology and ploidy level, and the entire section is in need of taxonomic revision.

(Discussion copyrighted by Flora of North America; reprinted with permission.)
Source FNA vol. 10. FNA vol. 10.
Parent taxa Onagraceae > subfam. Ludwigioideae > Ludwigia > sect. Macrocarpon Onagraceae > subfam. Ludwigioideae > Ludwigia
Sibling taxa
L. alata, L. alternifolia, L. arcuata, L. bonariensis, L. brevipes, L. curtissii, L. decurrens, L. erecta, L. glandulosa, L. grandiflora, L. hexapetala, L. hirtella, L. lanceolata, L. leptocarpa, L. linearis, L. linifolia, L. maritima, L. microcarpa, L. palustris, L. peploides, L. peruviana, L. pilosa, L. polycarpa, L. ravenii, L. repens, L. simpsonii, L. spathulata, L. sphaerocarpa, L. suffruticosa, L. virgata
Subordinate taxa
Synonyms Oenothera octovalvis, Jussiaea calycina, J. clavata, J. frutescens, J. haenkeana, J. hirta, J. ligustrifolia, J. occidentalis, J. octofila, J. octonervia, J. octonervia var. sessiliflora, J. octovalvis, J. parviflora, J. peruviana var. octofila, J. pubescens, J. sagrana, J. salicifolia, J. scabra, J. suffruticosa, J. suffruticosa var. ligustrifolia, J. suffruticosa var. linearifolia, J. suffruticosa var. octofila, J. suffruticosa subsp. octonervia, J. suffruticosa var. octonervia, J. suffruticosa var. sessiliflora, J. suffruticosa var. sintenisii, J. venosa, J. villosa, L. octovalvis var. ligustrifolia, L. octovalvis var. octofila, L. octovalvis subsp. sessiliflora, L. octovalvis var. sessiliflora, L. pubescens, L. pubescens var. ligustrifolia, L. pubescens var. linearifolia, L. pubescens var. sessiliflora, L. sagrana Jussiaea section macrocarpon
Name authority (Jacquin) P. H. Raven: Kew Bull. 15: 476. (1962) (Micheli) H. Hara: J. Jap. Bot. 28: 291. (1953)
Web links 
Unless otherwise noted, all data comes from the online version of the Flora of North America, who have made most of their content available via a Creative Commons license (CC BY 4.0).



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