Ampelopteris, Kunze, Kunze

Fawcett, Susan & Smith, Alan R., 2021, A Generic Classification of the Thelypteridaceae, Fort Worth, Texas, USA: BRIT Press : 30-31

AMPELOPTERIS

Ampelopteris Kunze, Bot. Zeit. 6:114. 1848.

— TYPE: Ampelopteris elegans Kunze = A. prolifera (Retz.) Copel. [= Cyclosorus proliferus (Retz.) Tardieu & C.Chr.]

For additional generic synonymy, see Holttum (1974a).

Etymology.—Gr. ampelos, vine + pteris, fern, in reference to the indeterminate growth of the rachis, and vine-like habit.

Plants terrestrial, with proliferous fronds of indefinite growth, sometimes with climbing rhizomes, typically medium-sized, mostly (8–)15–75(–100+) cm tall; rhizomes short- to long-creeping, with scales primarily at apices, these setulose and/or glandular at margins, older parts of rhizomes becoming scaleless; fronds typically clustered, weakly dimorphic with fertile fronds often taller than non-fertile fronds and with narrower, shorter pinnae, erect or arching, once-pinnate; stipes 30–60 cm long, grooved adaxially, stramineous to dull brown, sometimes with short, blackish spines to 3 mm long; stipe scales ovate-deltate to lanceolate, appressed, brown, 2–3 mm long, typically with hairs on scales; blades chartaceous to subcoriaceous, with apex pinna-like, or blades ± indeterminate, rachises prolonged and whip-like, irregularly producing 20+ pairs of much reduced pinnae <2 cm, and also bearing buds and plantlets in axils of pinnae, sometimes with clusters of plantlets in a single pinna axis, these proliferous plantlets sometimes well developed, fertile, and with fronds over 15 cm long; proximal pinnae of well-developed fronds not reduced or with a few pairs slightly reduced, but lacking greatly reduced or glanduliform pinnae; rachises adaxially grooved, bearing simple and sometimes forked or branched acicular hairs, often glabrescent; pinnae grooved adaxially, truncate or slightly cordate at bases, acute at tips, to ca. 15(–20) × 2(–3) cm wide, margins entire, subentire, crenate, or shallowly lobed about 1/4 the distance to costae, lacking acroscopic or basiscopic basal auricles, sessile or often short-petiolulate to ca. 1 mm, with truncate bases, symmetric, sometimes fertile at a very small size (ca. 3 × 0.6 cm); veins prominent adaxially and abaxially, with up to ca. 12 pairs of veins from a costule, 5–6 pairs alternately anastomosing with veins from an adjacent costule and producing a ± straight (toward the base) or often zig-zag (toward pinna margins) excurrent vein to sinus, areoles lacking included free veinlets; vein ends reaching margins; aerophores absent or at most a small darkened swelling at pinna bases; indument abaxially, if present, of sparse hyaline acicular hairs, shorter hairs sometimes shallowly forked or branched (most hairs restricted to costae), costae and sometimes also costules with scattered, tan, peltate, ovate, or lanceolate setulose scales, orangish spherical glands occasionally also present, blades often glabrescent with age; indument adaxially of hyaline acicular to ca. 0.5 mm long on costae, seldom with hairs on costules or ultimate veins, never on laminar tissue between veins; pustules absent on abaxial laminae between veins; sori ± medial to supramedial, round to often oblong or elongate, exindusiate, paired on either side of excurrent vein, not confluent, not appearing acrostichoid; sporangia glabrous or often with a reddish globose gland adjacent to annulus on the capsule; sporangial stalks short, with a stalked often reddish globose or pear-shaped gland(s) at the tip; spores tan, with numerous short and narrow ridges and small echinulate elements ( Tryon & Lugardon 1991); x = 36, only diploids known. No hybridization with any other genus has been demonstrated.

Diagnosis.—The axillary plantlets of proliferous fronds produce rootlets that aid in clinging tightly to trees in thickets ( Holttum et al. 1970). Other paleotropical genera with proliferous fronds include species of Grypothrix and Menisorus s.l., and these genera appear to have no close affinity with Ampelopteris . Ampelopteris is unusual in Thelypteridaceae in having indeterminate growth of its fronds, a feature shared with the distantly related Hawaiian endemic Pseudophegopteris keraudreniana , and the Antillean Goniopteris reptans . The forked or branched hairs in Ampelopteris (see Holttum et al. 1970) are inconspicuous and easily abraded, and are not indicative of a close relationship with neotropical Goniopteris ; the proliferous nature of the fronds of many Goniopteris has also been considered an indication of affinity to Ampelopteris by some, but this trait is likely independently derived in the two genera. Characteristics shared between Ampelopteris and Cyclosorus s.s. include the very similar spore morphology ( Tryon & Lugardon 1991), stalked, multicellular glands with a globose, often reddish tip, and the presence of costal scales. Characteristics shared with Mesophlebion include the similar sporangial stalk glands, but spores of Mesophlebion have much broader, higher, and fewer ridges and lack the dense echinulate elements ( Tryon & Lugardon 1991). Ampelopteris differs from both in having proliferous fronds, more copiously anastomosing veins, and short (to ca. 0.3 mm) forked, branched, or stellate hairs on the axes, these most easily seen along the adaxial ridges of young fronds.

Biogeography and ecology.— Ampelopteris comprises a single species, A. prolifera (Retz.) Copel. , widely distributed from tropical West Africa to northeastern Australia and New Caledonia, including mainland southeastern Asia and throughout Malesia. It occurs on riverbanks, and in wet ditches, sometimes forming thickets, often in open places.

Taxonomic and phylogenetic studies.—Most workers have thought Ampelopteris to be most closely related to Cyclosorus s.s. and Mesophlebion ( Holttum 1982; Smith 1990), and this hypothesis is now supported by molecular data, which show Ampelopteris forms a clade with these two genera ( Almeida et al. 2016; Fawcett et al. in press; Fig. 1 ), though the relationship among them is poorly resolved. The sole species of Ampelopteris has sometimes been placed in a more broadly defined Cyclosorus or in Goniopteris (e.g., Christensen 1913), a neotropical genus having many proliferous species, as well as similar stellate hairs.

Notes.—Fossils of Cyclosorus eoproliferus (Prasad) Prasad et al. from mid-late Miocene strata in northeastern India (ca. 10 Ma), appear to be very similar to or conspecific with Ampelopteris prolifera ( Mehrotra et al. 2011) . The same or a similar taxon was previously described as Goniopteris prolifera (Retz.) C. Presl ( Prasad 1991) , a homotypic synonym of the extant species, and the fossil Thelypteridaceophyllum tertiarum Joshi & Mehrotra (2003).

Young tips of Ampelopteris are edible, but supposedly inferior to those of Diplazium esculentum (Retz.) Sw. ( Copeland 1947).

Constituent species.—* Ampelopteris prolifera (Retz.) Copel.

Figures

FIG. 1. A synoptical treeillustrating relationships among genera of Thelypteridaceae based on Fawcett et al.(in press).