Lycopodiella is a genus in the clubmoss family Lycopodiaceae. The genus members are commonly called bog clubmosses, describing their wetland habitat. In the past, the genus was often incorporated within the related genus Lycopodium, but was segregated in 1964. 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. Individuals reproduce by single-celled spores that disperse and germinate into small plants when in suitable conditions. After fertilization, the embryos grow into sporophytes, which are larger spore-bearing plants. Individuals have a base chromosome number of 78.
Taxonomy
The distinctness of these species was recognized by John Gilbert Baker, who placed species of both the current Lycopodiella s.s. and Pseudolycopodiella (including Brownseya) in an informal "group of L. inundatum", within subgenus Lepidotis; like most of his contemporaries, he placed all clubmosses and firmosses in a very broadly circumscribed Lycopodium. Ernst Georg Pritzel gave this group sectional rank within subgenus Rhopalostachya in 1902 in his treatment for Die Natürlichen Pflanzenfamilien. Wilhelm Gustav Franz Herter treated the group as subgenus Inundatostachys, after removing the doubtfully placed Lycopodium cruentum. In 1944, Werner Rothmaler began to raise some of the groups formerly included in Lycopodium to generic rank. He raised Baker & Pritzel's group to a subgenus of Lepidotis. Josef Ludwig Holub felt that Lepidotis, as circumscribed by Rothmaler, was still too heterogenous, and founded the genus Lycopodiella to accommodate these species in 1964. The name, a diminutive of Lycopodium, was inspired by the Czech common name (and diminutive) "plavuňka". The type species of the genus is Lycopodiella inundata.
Holub would subsequently subdivide the group by erecting the genus Pseudolycopodiella in 1983, typified on Pseudolycopodiella caroliniana. He distinguished them based on features such as the dimorphic stem leaves projecting on either side of the horizontal stem and the lack of veinal mucilage canals (versus leaves of uniform shape and veinal mucilage canals present in Lycopodiella s.s.). Holub's disintegration of Lycopodium into smaller genera was not universally accepted. Benjamin Øllgaard's global classification in 1987 treated Lycopodiella in a broader sense, including not only Pseudolycopodiella but Lateristachys and Palhinhaea, although he recognized Holub's four genera at sectional level. However, North American treatments by Herb Wagner and Joe Beitel in 1992 and Arthur Haines in 2003 both accepted Holub's recognition of Lycopodiella and Pseudolycopodiella.
The molecular phylogeny of Wikström and Kendrick published in 2000 supported the monophyly of sect. Lycopodiella (Lycopodiella s.s.) and sect. Campylostachys (Palhinhaea) but could not resolve consistent relationships among Øllgaard's four sections. Surprisingly, sect. Caroliniana (Pseudolycopodiella), felt to be the most "primitive" anatomically, did not diverge before the rest of the group.
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). Other sources do not recognize these genera, submerging them into Lycopodiella. All but one species of Lycopodiella, Lycopodiella inundata, are limited to the East coast, Gulf of Mexico, and/or Great Lakes region.