Lycopodiella is a genus in the clubmoss family Lycopodiaceae. The genus members are commonly called bog clubmosses, describing their wetland habitat. The genus has a cosmopolitan distribution,[1] with centers of diversity in the tropical New World and New Guinea. In the past, the genus was often incorporated within the related genus Lycopodium, but was segregated in 1964.[2] In the Pteridophyte Phylogeny Group classification of 2016 (PPG I), Lycopodiella is placed in the subfamily Lycopodielloideae, along with three other genera. In this circumscription, the genus has about 15 species.[3] Other sources use a wider circumscription, in which the genus is equivalent to the Lycopodielloideae of PPG I, in which case about 40 species and hybrids are accepted.
Lycopodiella are non-flowering plants. They have leafy rhizomes that grow along the ground and vertical, leafy shoots, also known as peduncles.[4] Fertile peduncles have strobili at the top of the shoot.[4] Individuals can have short, creeping rhizomes with simple strobili, branching rhizomes with many strobili, or anywhere in between.[1] The North American specimens are typically shorter, have thinner shoots, and have fewer vertical shoots in the North than specimen in the South.[5]
Lycopodiella life cycles include an independent sporophyte stage and a long-lived gametophyte stage.[6] Individuals reproduce by single-celled spores that disperse and germinate into small plants when in suitable conditions.[2] This part of the plant is called the gametophyte; it produces the eggs and sperm.[2] In Lycopodiella the gametophytes grow on the surface of the soil and are partially photosynthetic.[7] After fertilization, the embryos grow into sporophytes, which are larger spore-bearing plants.[2] The sporophyte is the vegetative part of the plant seen in nature. Juvenile individuals typically re-sprout in the spring or after a fire.[4] Individuals have a base chromosome number of 78.[8]
In the Pteridophyte Phylogeny Group classification of 2016 (PPG I), Lycopodiella is placed in the subfamily Lycopodielloideae, along with three other genera (Lateristachys, Palhinhaea and Pseudolycopodiella).[3] In 2022, an additional monotypic genus, Brownseya, was segregated from Pseudolycopodiella to render the latter monophyletic.[9] Other sources do not recognize these genera, submerging them into Lycopodiella.[10][11]
As of February 2023[update], the Checklist of Ferns and Lycophytes of the World recognized the following species:[12]
Lycopodiella is found worldwide, but typically in temperate and tropical areas, a majority of which are found in North and South America.[13] Individuals are typically found in terrestrial lowlands or montane forests on poor soils.[14] Much of the soils are sandy and saturated and have little to no organic layer.[2]