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Genus Laggera in Tribe Inuleae

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).

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Genus Description

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Laggera (Sch.Bip. ex Benth.) is a genus in Asteraceae, tribe Inuleae (subtribe Plucheinae), with about 115 accepted species (POWO, 2024). It occurs throughout tropical and subtropical Africa, the Arabian Peninsula, South and Southeast Asia, in grasslands, open woodlands and riverine margins. The type species is Laggera alata (D. Don) Sch.Bip. ex Benth.

The genus has opposite, decurrent leaves giving a winged stem, erect herbs or shrubs, and a dense tomentose indumentum. Flower heads are discoid with reflexed imbricate bracts; the receptacle bears paleae. Fruits are oblong achenes with a pappus of many bristles, a wind‑dispersal adaptation unusual among Inuleae. Anthers are obovate; style short (Funk et al., 2020).

Species richness peaks in the Eastern Arc of Tanzania and Ethiopian highlands, with many narrow endemics (WFO, 2024). Secondary centres lie in the Himalayas, Western Ghats and New Guinea (Nebel & Müller, 2022). The altitudinal range spans sea level to ~2 500 m, on well‑drained sandy or loamy soils of savanna, forest edge or riparian habitats.

Pollination is mainly by bees and flies, while the pappus enables wind dispersal of achenes. The base chromosome number is x = 9; 2n = 36 has been recorded for L. alata and related taxa (Schmidt, 2018). Many taxa exhibit pronounced phenotypic plasticity across altitudinal gradients, with leaf size and indumentum density increasing at higher elevations.

Molecular data place Laggera as sister to Pluchea in Plucheinae (Nebel & Müller, 2022). Some authors have proposed merging the genera, but major checklists retain Laggera as distinct (POWO, 2024; WFO, 2024). A two‑subgenus scheme (subg. Laggera and subg. Eriocoma) is occasionally used but not universally accepted (Funk et al., 2020).

L. alata is cultivated for ornamental foliage; L. tomentosa is a weed in fields and roadsides, and the plant is grazed in parts of East Africa (WFO, 2024). The species is also used in xeriscaping and as a low‑maintenance groundcover in tropical and subtropical gardens.

Habitat loss and overgrazing threaten many endemics; fewer than 20 % of species have IUCN assessments (WFO, 2024). Future work should combine genomic data with distribution modelling to guide conservation. Conservation actions should prioritize the East African hotspots, where high species richness coincides with ongoing habitat loss, and integrate molecular data to clarify taxonomic uncertainties.

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