PlantaeDB Logo
Login Sign-up

Genus Atrichum in Family Polytrichaceae

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!

Atrichum (authority P.Beauv.) is a moss genus placed in the family Polytrichaceae (Polytrichales). Molecular and morphological evidence consistently supports this placement and its separation from the closely related Polytrichum (Hedenäs, 1992; Huttunen et al., 2016). Approximately 70 species are recognized worldwide, a number confirmed by the global moss checklist (Söderström et al., 2016) and distribution data (GBIF, 2024). Its members are primarily temperate, occurring in boreal and montane forests, peatlands, and alpine meadows across the Northern Hemisphere, with a secondary radiation in tropical highlands. The type species is Atrichum undulatum (P.Beauv.) (Hedenäs, 1992).

The genus is recognised by narrow, lanceolate leaves with a hyaline awn and a strong, excurrent costa. Leaves bear 2–5 shallow lamellae on the adaxial surface, a reduction relative to Polytrichum. Margins are usually entire to weakly dentate, and sporophytes lack a true peristome, a diagnostic trait in Polytrichaceae (Hedenäs, 1992; Laaka‑Lindberg et al., 2006).

Richness peaks in Asian mountains—Himalayas and Hengduan—and the Pacific Northwest of North America. Several taxa are narrowly endemic across elevations from lowland peatlands to subalpine tundra. A secondary centre lies in tropical highlands of Southeast Asia and New Guinea, reflected in distribution data (GBIF, 2024) and phylogenies (Huttunen et al., 2016).

Reproduction occurs via wind‑dispersed spores released from capsules lacking a peristome. Gametophytes are dioicous, bearing separate male and female shoots that produce antheridia and archegonia on specialized leaves. Chromosome counts consistently show a base number of x = 7, matching the family pattern (Newton, 1979).

Taxonomically, Atrichum is divided into two informal groups—broad‑leaf (sect. Macrophyllae) and narrow‑leaf (sect. Angustatae). Molecular phylogenies confirm its monophyly and reveal cryptic lineages, leading to synonymisations such as A. crispum with A. undulatum (Hedenäs, 1992; Söderström et al., 2016). An alternative treatment merging Atrichum with Lyellia (Hyvönen & He, 2003) remains contested.

No Atrichum species provide timber or food, but a few, notably A. undulatum with its gently wavy leaves, are cultivated as ornamental groundcovers in rock gardens and terraria. Conversely, several weedy taxa occasionally colonise greenhouse substrates and are considered minor horticultural weeds (World Flora Online, 2024).

Many Atrichum taxa have limited ranges and are vulnerable to habitat loss, warming, and hydrological changes in peatlands. Global assessments remain incomplete, but several endemic species are listed as vulnerable in national red data books. Integrating molecular, morphological, and ecological data is essential to refine species limits and guide conservation actions.

Pick a Species to see its components: