Alsophila gastonyi Lehnert
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Authority
Lehnert, Marcus. 2011. The Cyatheaceae (Polypodiopsida) of Peru. Brittonia. 63 (1): 11-45.
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Family
Cyatheaceae
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Scientific Name
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Description
Description - Ab Alsophila erinacea (H. Karst.) D. S. Conant et Alsophila cuspidata (Kunze) D. S. Conant squamis petiolorum lanceolatis atrobrunneis costisque abaxia- liter abundante et persistente pilosis (vs. squamis linealo-lanceolatis pallide brunneis costisque abaxia- liter glabrescentibus vel parce pilosis), ab Alsophila engelii R. M. Tryon et Alsophila minervae Lehnert in presentía pilorum persistentium indusiis (vs. absentia pilorum persistentium indusiis) absentiaque alarum in parte distale pinnarum differt. Trunks to 4 m high, 4 cm diam., otherwise unknown. Fronds of unknown dimensions, presumably 2-3 m long, patent to arching. Petioles 27-56 cm long, basally dark brown to blackish, distally paler brown to dark stramineous, with persistent scales and scurf of appressed lacerate squamules; aphlebiae or skeletonized basal pinnae absent. Petiole scales to 7 X 2 mm, lanceolate to ovate-lanceolate, with differentiated margins of differently orientated cells, dark brown with somewhat paler margins with only one dark apical setae to 1 mm, no or few marginal setae, concolorous (Fig. 1A), of variable texture, larger scales papery, smaller ones firm, intergrading with scurf squamules and marginate squaminate spines to 6 mm long, black, with broad bases and acuminate, curved tips. Laminae to ca. 130 cm broad, broadly ovate, bipinnate-pinnatifid, opaque dark green adaxially, opaque pale green abaxially, apices abruptly reduced, non-conform to conform, i.e., pinna-like (Fig. 1С). Rachises and costae brown to dark stramineous, inermous, abaxially with fugacious flattish brown squamules to 0.5 mm long, white pericellular hairs to 1.5 mm long at least on distal parts, adaxially more abundant than abaxially, insertions of costae into rachises slightly raised abaxially, bearing a lunular, flat to concave blackish pneumathode to 5x2.5 mm. Pinnae to 65 cm long, stalked to 1.5 cm, not green-alate distally; basal ones reduced, more ore less patent. Largest pinnules to 10.5x1.8 cm, sessile, truncate basally, attenuate apically (Fig. ID); costules stramineous to tan abaxially and adaxially, with flat brown, setate scales to 1 mm long, no búllate scales present, with white to tan pluricellular hairs to 1 .5 mm long abaxially and adaxially, abaxially denser and less spreading than abaxially (Fig. IE); seg- ments to 10x2.5 mm, adnate, sessile, weakly ascending, straight (Fig. IE) to weakly falcate, the margins subentire to weakly crenate basally in the proximal segments, flat in sterile and fertile segments; midveins weakly protruding adaxially and adaxially, with white pluricellular hairs identical to those on the costules (Fig. IE), fertile veins forked once, rarely twice, sterile ones forked to simple (Fig. IE), hardly discern- able adaxially, dark gray abaxially, glabrous on both sides (Fig. IE). Sori to 0.8 mm diam., 1-3 per segment, costal, in vein forks (Fig. IE); indusia urceolate to subsphaeropteroid, either irregularly or not rupturing at maturity, firm, lustrous dark brown to tan, with persistent pluricellular hairs to 0.6 mm long (Fig. IE), receptacles 0.2-0.3 mm diam., columellar, black, paraphyses much shorter than the spor- angia, 0.1-0.2 mm long, blackish to tan. Spores not examined.
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Discussion
Etymology. - The name honors Gerald J. Gastony in acknowledgment of his contributions to pteridology.
The trunk morphology was not described on the specimen labels but presumably is like in the majority of Neotropical Alsophila species, i.e., densely covered with thin lanceolate scales and without persistent old petiole bases. Among its Andean congeners, the species is similar and supposedly related to Alsophila engelii R. M. Tryon and A. minervae Lehnert but differs from these in having long, relatively straight, presistent hairs on both sides of the midveins and on the indusia. The other two species have no hairs on the indusia and on the midveins adaxially, but may have hairs or trichomidia on the lateral veins abaxially where A. gastonyiis glabrous; Alsophila engelii has appressed tortuous hairs and thin squamules on the leaf axes abaxially but no spreading straight hairs as they occur in the same places in A. gastonyii in varying density. Further, A. gastonyi commonly has abruptly reduced (but usually not pinna-like) laminar apices and occurs below 1000 m, whereas A. engelii and A. minervae have gradually reduced laminar apices and occur mainly above 1500 m. Using the general key to the genus (Conant 1983), Alsophila gastonyi will key out to A. portoricensis (Spreng, ex Kuhn) D. S. Conant, a species restricted to Puerto Rico, and both populations may well be united under one species morphologically. Such a biogeograpical pattern would be unequalled among Neotropical ferns. Other tree ferns that span such distances do so in a more or less continuous population (e.g., C. microdonta and C. delgadii ). Either this Alsophila species has been left undetected in most of its range, or, a hypothesis favored here, A. gastonyi and A. portoricensis are an example of convergent evolution.