Pellaea villosa

Pellaea villosa (Windham) Windham & Yatsk.
(Latin: villosus, softly hairy)

Local names: villose cliff-brake

Plant to 60 cm tall; rhizome scales with 2 colors, black in center with brown along margins; petioles dark purple to black, shiny; leaf blades 2-pinnate-pinnatifid and distally 1-pinnate, monomorphic; rachis villous, especially in axils of pinnae; pinnae attached to rachis so that their tips point } straight out or slightly towards tip of leaf, at least some and often many distal pinnae marginally completely entire, those in proximal 1⁄2–2⁄3 of leaf deeply ternately divided (= into three portions), the ultimate leaf segments (either portions of the ternately divided proximal pinnae or the undivided, entire, distal pinnae) linear-oblong, apically mucronate, leathery, with hairs scattered along main veins on lower surface; 2n = 116 (Windham 1993c). Various rocky substrates; in TX known only from the Davis Mts., Jeff Davis Co. (R. Magill 101, TEX-LL [annotated M.D. Windham]; Windham 1993c; P. Zelazny 217, SRSC) in the Trans-Pecos; known in the U.S. only from AZ (Fishbein et al. 2861, ARIZ) and TX; also rather widespread in n Mexico. Sporulating summer–fall. [Pellaea ternifolia (Cav.) Link subsp. villosa Windham] When Windham (1993e) named this taxon as a variety of P. ternifolia (var. villosa) he suggested that P. ternifolia was represented by “three genetically distinct taxa characterized by differences in leaf morphology and chromosome number.” He further noted that subsp. villosa was probably an allotetraploid resulting from hybridization between typical P. ternifolia and some other as yet unidentified species. Since 1993, a new species, P. ribae Mendoza & Windham, has been discovered in the Mexican state of San Luis Potosi (Mendoza et al. 2001) and appears to be the previously unidentified missing parent (Windham & Yatskievych 2003a). Windham and Yatskievych (2003a) have argued that since the entity going by the name P. ternifolia subsp. villosa is a morphologically distinct, “reproductively competent” allotetraploid of hybrid origin “it should be recognized as a distinct species.” We are thus following Windham and Yatskievych (2003a) in treating it at the species level. They marshalled evidence demonstrating that it is “morphologically intermediate” between the two proposed parents “in nearly every character examined.” For example, P. ternifolia has all pinnae deeply ternately divided and P. ribae has all pinnae entire; P. villosa, however, has proximal pinnae ternately divided and distal pinnae entire. Such reproductively isolated allotetraploid species are well known among ferns (Wagner 1954). This taxon was previously known in the U.S. from only a single individual in the Davis Mts. of TX; however, “recent botanical surveys of the Madrean ‘sky islands’ of southern Arizona have identified a second U.S. population.” (These Madrean “sky islands,” are isolated high elevation areas [e.g., Chisos Mts., Davis Mts., Guadalupe Peak] similar to habitats found in the Sierra Madre Mountains of Mexico). Pellaea villosa is one of a small group of species including Cheilanthes lendigera, Notholaena aschenborniana, N. neglecta, and Pellaea ternifolia subsp. arizonica, “that are known from Arizona and Trans-Pecos Texas but not from the intervening regions of New Mexico” (which has fewer of the Madrean “sky island” habitats) (Windham & Yatskievych 2003a). Because of its rareness and limited distribution in the state, we consider this species to be of conservation concern in TX.

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