Phlegmariurus acerosus ­­­ (Swartz) B. Øllgaard (2012a: 480)

Øllgaard, Benjamin & Testo, Weston, 2021, The Lycopodiaceae of Panamá, Phytotaxa 526 (1), pp. 1-66 : 7-8

. Phlegmariurus acerosus ­­­ (Swartz) B. Øllgaard (2012a: 480) .—Fig. 1B

Lycopodium acerosum Swartz (1806b: 1575) .— Urostachys acerosus (Swartz) Nessel (1927: 399) .— Huperzia acerosa (Swartz) Holub (1985: 70) .— Lectotype (designated by Proctor (1977: 25): Plumier (1705: t. 166B); an authentic specimen possibly in Herb. Suriani no. 635 (P, not seen).

Very delicate plants, flaccidly pendulous, at least to 70 cm long. Shoots usually gradually heterophyllous, sometimes homophyllous, 3–6 mm in diameter including the leaves in basal divisions, tapering to 1–3 (–6) mm in terminal divisions. Stems excluding leaves 0.6–1 mm thick at the base, tapering to ca. 0.3–0.5 mm upward, somewhat concealed by the leaves, pale greenish to stramineous, at least to 10 times dichotomous, usually densely, unilaterally or omnilaterally sporangiate in separate, periodically produced zones of the terminal divisions, or continuously sporangiate from 15– 30 cm above the base and upward. Leaves gradually modified along the stems. Leaves of basal divisions densely crowded, borne in irregular alternating whorls of 6–7, these 0.5–2 mm apart, forming 12–14 indistinct longitudinal ranks, ascending and upward curved to appressed or somewhat secund, acicular-filiform, narrowly and prominently decurrent, 3.5–5 × 0.2–0.4 mm, soft herbaceous to subcoriaceous, convex below, canaliculate above, with involute margins. Vegetative leaves of terminal constricted divisions borne in irregular whorls of 4–6, these 0.5–2 mm apart, forming 8–12 indistinct longitudinal ranks, ascending to closely appressed, acicular-filiform to linear-lanceolate, 2–4 mm long, otherwise conform. Sporophylls borne in irregular, alternating whorls of 3–5, conform, or shorter and wider, linear-lanceolate and long acuminate to lanceolate, usually appressed, 1.5–4 × 0.3–0.8 mm, rounded to subcarinate abaxially. Sporangia 0.7–1 mm wide.

­­­ Distribution:— West Indies, Guatemala, Costa Rica, northern South America, south to Ecuador, Bolivia, northern Argentina and southeastern Brazil. This is the most widespread and apparently least specialized of the species in this group.

­­­ Habitats:— Epiphytic, in wet forest, 2100–3170 m elev.

­­­ Notes:— In older literature Phlegmariurus acerosus has often been referred to P. verticillatus (Linnaeus f. 1882: 448) Field et al. (2015: 21), or Lycopodium setaceum Lamarck (1792: 563) , both of which are based on material from Reìunion Island. The plants from the Paleotropics referred to Phlegmariurus verticillatus resemble P. acerosus but differ from this in a more robust growth habit, usually longer and more crowded leaves, and usually more densely and omnilaterally sporangiate terminal divisions. Sequence data indicate a close relationship between P. verticillatus from Réunion and Neotropical members of the P. acerosus clade (Bauret et al. 2018); it appears that the occurrence of P. verticillatus in the western Indian Ocean is the result of long-distance dispersal from South America. For a discussion of related species see P. curvifolius .

­­­ Specimens­­­examined:— Chiriquí: Ridge above Alto Pineda, 2750–3170 m, Hammel et al. 7101 (AAU, MO). 0.8 km up the main road from the center of the town Cerro Punta then 1.2 km SW along side road on ridge beyond end of road, primary forest, 2100–2300 m, Lellinger et al. 1928 (photo US).