PlantaeDB Logo
Login Sign-up

Genus Acaena in Family Rosaceae

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!

A member of Rosaceae subfamily Rosoideae (APG IV, 2016), Acaena comprises about 200 to 250 species and is widely distributed across temperate and subantarctic regions of the Southern Hemisphere, with secondary centers in Malesia and Hawai‘i; the name stems from a diminutive Greek word for “thorn” (Darwin, 1988). The type species is Acaena spinosa (L. f.) Mutis ex L.

Low-growing perennial herbs, sometimes annuals, form mats or cushions. Leaves are imparipinnate to subpalmate, with serrate leaflets and a persistent, stipular base; indumentum ranges from glabrous to sparsely hairy. The inflorescence is usually a terminal spike or raceme; the corolla is minute or absent, replaced by short, persistent calyx lobes. Carpels are distinct; styles persist as hooks, and the fruiting hypanthium enlarges into a burr-like indurated structure bearing retrorse spines that aid epizoochorous dispersal. Fruit is a small achene enclosed in the burr. Ovules are typically solitary and pendulous.

Centers of diversity include New Zealand, temperate South America (especially the Andes and Patagonia), and the subantarctic islands, with numerous endemics at higher elevations and in coastal habitats; widespread A. novae-zelandiae is typical of drier open ground, while many Andean and New Zealand species occupy alpine fellfields and cushion fields (Darwin, 1988; WFO, 2024).

Pollination is predominantly wind assisted, with nectarless, often apetalous flowers; dispersal is primarily by epizoochory via hooked burrs, and occasionally hydrochory in coastal settings. Chromosome numbers reported across the genus are consistent with a base number of x = 14, and polyploidy appears frequent (Webb et al., 1988). Seed dormancy patterns vary with habitat, with cold-induced germination cues documented in some temperate taxa (Michaels et al., 1999).

Taxonomically, Acaena is placed in tribe Potentilleae; recent phylogenies in Rosoideae support the generic distinctness and its position within the Agrimonia group (Eriksson et al., 1998; Töpel et al., 2012). Sections widely used include sect. Hippophæstum (mostly Andean and Patagonian) and sect. Acaena (widely Southern Hemisphere). In the 19th century Ancistrum was sometimes merged, but modern treatments recognize Acaena as distinct (Darwin, 1988; POWO, 2024; WFO, 2024).

Several weedy taxa, such as A. novae-zelandiae and A. microphylla, have local horticultural nuisance value due to burr entanglement; most species are not cultivated widely, though a few are used as groundcovers in native plantings. No taxa are major timber or food crops.

Loss of alpine and coastal habitats, competition with invasive grasses, and collection pressure threaten numerous narrow endemics; a standardized phylogenetic framework integrating Andean and New Zealand clades remains incomplete, and finer-scale conservation assessments are needed (POWO, 2024; WFO, 2024).

Pick a Species to see its components: