PlantaeDB Logo
Login Sign-up

Genus Macroptilium in Subfamily Papilionoideae

In botanical taxonomy, a genus (plural genera) is a rank used to group closely related species within a family. In the hierarchy, genus sits below family and above species.

Genera are defined by shared morphological, anatomical, and genetic characteristics (for example, features of flowers, fruits, seeds, or leaves) that indicate a close evolutionary relationship among the species they contain.

Each genus can include one or more species. Examples include Rosa (roses) and Solanum (nightshades, including tomato and eggplant).

Do you wish to read more about plant taxonomy? Click here!

Genus Description

Suggest a correction!

Macroptilium (Leguminosae, subfamily Papilionoideae, tribe Phaseoleae, subtribe Phaseolinae) comprises about 15 species of herbs and vines native to the Americas from the southern United States to northern Argentina, with naturalized populations in the Old World tropics. The type species is Phaseolus lathyroides L., now accepted as Macroptilium lathyroides (L.) Urb. Plants are typically erect or climbing and bear trifoliolate leaves with entire to shallowly sinuate-dentate leaflets, a terminal leaflet on a distinct petiolule, and stipules that are often early deciduous; indumentum may be minute and appressed to long and spreading. Inflorescences are usually racemose, sometimes pseudoracemose, with papilionaceous flowers; the keel forms a narrow beak that typically projects from a narrow calyx throat, a diagnostic combination within Phaseolinae. Flowers are chasmogamous with a narrowly tubular standard that is often reflexed, and the ovary bears several ovules with axile placentation; fruits are dehiscent legumes with few to many seeds. Seed arils are absent, a feature that helps distinguish the genus from closely related Vigna.

Species richness concentrates in Mexico and the seasonally dry tropical forests of South America, with several endemics in the Caribbean and Brazil; widely pantropical weeds such as M. lathyroides occur from sea level to moderate elevations, often in disturbed sites, while drier, shrub-dominated and limestone habitats support several narrowly distributed taxa. Pollination is primarily entomophilous, and most species are short-lived annuals or perennials; wind dispersal of seeds is uncommon. Base chromosome number is consistently reported as x=11 across the genus (Turner & Fearing, 1964; Goldblatt, 1981), facilitating hybridization among closely related taxa and the polyploidy documented for some cultivated forms.

Taxonomically, the genus is well supported in molecular analyses of Phaseolinae (Delgado-Salinas et al., 2006; Lewis et al., 2000; Ramírez-Delgado et al., 2015), with a single, well-resolved clade treated as Macroptilium in recent treatments. Synonymizations include the reduction of Macroptilium bracteatum to M. lathyroides (Gómez-Santos et al., 2011), and M. pedunculare has been segregated within the closely related genus Eriosema (Grear, 1978), indicating minor but ongoing adjustments to circumscription. M. lathyroides is a widely cultivated forage and green manure, and M. atropurpureum (Siratro) has long been used as a pasture and ornamental; otherwise human relevance is limited, and the genus contains few serious weeds despite pantropical occurrences.

While most species are not threatened, habitat degradation and climate change pose regional risks, and a few narrowly endemic taxa remain poorly assessed. Continued phylogeographic and conservation-focused work, especially in South America, will refine estimates of species limits and inform future management. POWO, 2024; WFO, 2024.

Pick a Species to see its components: