Microlepia C.Presl, Tent. Pterid.

Triana-Moreno, Luz A., Yañez, Agustina, Kuo, Li-Yaung, Rothfels, Carl J., Pena, Nelson Túlio L., Schwartsburd, Pedro B. & Sundue, Michael, 2023, Phylogenetic revision of Dennstaedtioideae (Dennstaedtiaceae: Polypodiales) with description of Mucura, gen. nov., TAXON 72 (1), pp. 20-46 : 31

I. Microlepia C.Presl, Tent. Pterid. : 124, t. 4, fig. 21–23. 1836, nom. cons. prop.

– Type (designated by Smith, Hist. Fil.: 260. 1875): Microlepia polypodioides (Sw.) C.Presl.

(≡ Dicksonia polypodioides Sw. ) (= Microlepia speluncae (L.) T.Moore ≡ Polypodium speluncae L.).

= Scyphofilix Thouars , Gen. Nov. Madagasc.: 1. 1806, nom. rej. prop. – Type (designated by Farwell in Amer. Midl. Naturalist 12: 237. 1931): Polypodium speluncae L. (≡ Microlepia speluncae (L.) T.Moore).

Description. – Plants terrestrial or rarely rupestral; rhizomes short to long creeping, with trichomes or bristles, branching (or unknown); petioles grooved, lacking epipetiolar buds, rarely aculeate; leaves large, erect, decompound, usually distant, or sometimes closely spaced, lamina 1–4-pinnate with strigose, acicular hairs, axes inalate; veins free, with slender apices; sori generally abaxial and protected by an abaxial indusium, indusium half cup-shaped directed outward, or rarely sori cup-shaped, protected by adaxial and abaxial indusia, and directed downward; spores trilete with perispore ornamentation of rodlets. ( Fig. 5 )

Synopsis. – Microlepia is a monophyletic group of about 60 species resolved as sister to Sitobolium . Microlepia can be diagnosed by its distinctive perispore ornamentation of rodlets ( Fig. 4D ), and by petioles that lack epipetiolar buds ( Mickel, 1973). The sori are generally abaxial and protected by an abaxial indusium, but marginal sori with both abaxial and adaxial indusia evolved at least twice as demonstrated by our results and those of Wang & al. (2021). Although nearly all Dennstaedtiaceae bear catenate hairs, those of Microlepia are often distinctively strigose and acicular, and never glandular. Microlepia is essentially an Old-World genus, distributed primarily in tropical and east Asia but extending to Africa and Madagascar, Australia, the western Pacific, and Hawaii. One species, M. speluncae , is widespread in the Neotropics where it appears to be adventive ( Tryon & Tryon, 1982).

History of use. – Microlepia has been in use since it was described by Presl (1836). The largely overlooked name Scyphofilix Thouars was published 30 years before Microlepia and would have priority ( Farwell, 1931), had Schwartsburd’ s (2017) proposal to conserve Microlepia against it not been approved by the General Committee. Similarly, our proposal to conserve Dennstaedtia with a new type aims to maintain nomenclatural stability of Microlepia .

Taxonomic treatments. – Wang & al. (2017) reported this as one of the most taxonomically challenging clades. Species estimates vary widely, from 33 ( Moore, 2010) to 60 (PPG-I, 2016), or 100 ( Yuan & al., 2012). Important regional treatments include Cambodia ( Sun, 2014), China ( Yan & al., 2013), India ( Fraser-Jenkins & al., 2017), Japan ( Nakaike, 1975), Nepal ( Fraser-Jenkins & al., 2015), Taiwan ( Knapp, 2011; TPG, 2019, 2021), and Thailand ( Tagawa & Iwatsuki, 1979). We include 44 species and 4 named hybrids here based upon molecular phylogenetic and morphological evidence. We list an additional 25 species and 1 named hybrid that remain insufficiently known to us at this time.

Figures

Fig. 5. Characters of Microlepia. A, Lower leaf surface; B, Detail of abaxial sori; C, Upper leaf surface; D, Detail of pinna costae. — All from Microlepia strigosa, Philippines, Sundue 3163 (CMUH, TAIF, VT). All photos by M. Sundue.

Fig. 4. Examples of perispore morphology of spores in distal view. A, Verrucae and irregular reticles with prominent ridges covering the corners, Mucura globulifera (Yañez & Márquez 86, LP); B, Tubercles, Sitobolium wilfordii (Unknown coll. s.n., UVMVT192145, VT); C, Verrucae and prominent ridges to the spore sides, Sitobolium hirsutum (Rothfels & al. 5282, VT); D, Network of rodlets, Microlepia speluncae (Rojas 4878, MO); E, Regular reticle, Dennstaedtia glabrata (James & Sundue 1593, VT); F, Prominent ridges, Dennstaedtia distenta (Mickel 4163, LP); G, Verrucae and ridges, Dennstaedtia dissecta (Palacios 1296, LP). — Scale bars = 10 μm.