Dennstaedtia Bernh., 1982

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 : 34-36

II. Dennstaedtia Bernh.

in J. Bot. (Schrader) 1800(2): 124. 1801, nom. cons. prop.

– Type: Dennstaeaedtia dissecta (Sw.) T.Moore ( Dicksonia dissecta Sw. ), typ. cons. prop.

= Patania C.Presl, Tent. Pterid: 137, t. 5, fig. 12–14. 1836 – Type (designated by Christensen, Index Filic.: xxix. 1906): Patania obtusifolia (Willd.) C.Presl (≡ Dicksonia obtusifolia Willd. ).

= Leptolepia Prantl in Arbeiten Königl. Bot. Gart. Breslau 1: 23. 1892 – Type (designated by Christensen, Index Filic.: xxviii. 1960): Leptolepia novae-zelandiae (Colenso) Mett. ex Diels. (≡ Davallia novae-zelandiae Colenso ).

= Costaricia Christ in Bull. Soc. Bot. Genève, ser. 2, 1(5): 229. 1909 – Type: Costaricia werckleana Christ.

= Oenotrichia Copel. in Univ. Calif. Publ. Bot. 16: 82. 1929 – Type: Oenotrichia maxima (E.Fourn.) Copel. (≡ Leucostegia maxima E.Fourn. ).

= Paradennstaedtia Tagawa in J. Jap. Bot. 27(6): 213. 1952 – Type: Paradennstaedtia glabrata (Ces.) Tagawa (≡ Dicksonia glabrata Ces. ).

Description. – Plants terrestrial or rupestral (or rarely epiphytic); rhizomes short to long creeping, unbranched, with catenate hairs; petioles grooved, adaxially sulcate, usually bearing epipetiolar buds, rarely aculeate; leaves large, erect, decompound, 2–4-pinnate, often with proliferous buds, axes inalate; veins free, with enlarged or slender apices; sori usually marginal, usually provided with abaxial and adaxial indusia fused into purse- or cup-shaped involucre; spores trilete, perispore regular reticles, ridges and verrucate. ( Fig. 6 )

Synopsis. – As defined here, Dennstaedtia is generally a pantropical genus but absent from continental Africa. It includes ca. 55 species sister to all other Dennstaedtioideae. Dennstaedtia is recognized by having rhizomes that are usually unbranched, petioles bearing epipetiolar buds, and by often bearing proliferous buds upon the leaves. The leaves of most species are large, and some species such as D. scandens are indeterminate and scandent over other vegetation. The spores of Neotropical species exhibit verrucae and ridges ( Fig. 4F,G ), whereas regular reticles are found among Paleotropical species ( Fig. 4E ). Neotropical species of Dennstaedtia are fairly morphologically homogenous, whereas Paleotropical species exhibit more trait variation, at least in our analysis. This is particularly true of species formerly treated in the small genera Leptolepia ( Dennstaedtia novae-zelandiae ) and Oenotrichia ( Dennstaedtia maxima ) which differ by branched rhizomes, the lack of epipetiolar buds, and abaxial sori along with the constituent loss of the adaxial indusia. Dennstaedtia maxima further differs by rhizomes provided with scales instead of hairs and by having monolete (rarely trilete) spores. These taxa are part of an unresolved polytomy. If they prove to be sister to the remainder of Dennstaedtia , some users may prefer to recognize them as small genera.

The early Eocene Dennstaedtia christophelii Pigg & al. (2021) has been placed in this clade based upon its similarity to D. mathewsii (Hook.) C.Chr. and D. producta Mett. This age sits between two recent clade age estimates; Testo & Sundue (2016) estimated the crown group of Dennstaedtia to have diverged during the late Eocene, and Schwartsburd & al. (2020) estimated it to diverge during the mid-Miocene.

History of use. – This circumscription retains the familiar circumscription of Dennstaedtia minus the two species of Mucura gen. nov., the two species moved to Microlepia , and the temperate clade here recognized as Sitobolium . The oldest available name for this clade is Patania Presl (1836) , but our proposal ( Triana-Moreno & al., 2022) to conserve Dennstaedtia with D. dissecta as the type would permit its continued use and avoid further name changes. The New Zealand endemic D. novae-zelandiae was previously recognized as the monotypic genus Leptolepia . Dennstaedtia maxima , endemic to New Caledonia, was previously recognized as Oenotrichia .

Taxonomic treatments. – The Neotropical species of Ecuador were revised by Navarrete & Øllgaard (2000), who pioneered the emphasis of rhizome characters. Schwartsburd & al. (2017) treated the Bolivian species, and Mexican and Mesoamerican species were treated by Mickel & Smith (2004) and Moran (1995), respectively. Brownsey & Perrie (2018) treated the species from New Zealand, and those from the Western Pacific were treated by Nakamura (2008). Copeland (1958) recognized several narrowly distributed species in his treatment of Philippine ferns that presumably belong here, but which are insufficiently known by us. We include 37 constituent species of Dennstaedtia based upon molecular phylogenetic and morphological evidence, and we make necessary combinations for two of them. We list an additional 15 that remain insufficiently known to us at this time.

Figures

Fig. 6. Characters of Dennstaedtia. A, Upper Leaf surface with leaf buds present in pinna axils; B, Upper leaf surface and grooved rachis-costa axes without raised wings; C, Lower leaf surface and marginal sori; D, Creeping unbranched rhizome; E, Subterete petioles with prominent epipetiolar buds. — All photos by M. Sundue except E by P.H. Hovenkamp.

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.