Asplenium L.
Descripción
Terrestrial, epipetric, or epiphytic; rhizomes usually compact, very short-creeping to suberect or erect, rarely long-creeping, usually unbranched, scaly; rhizome scales usually concolorous, clathrate, lanceolate; fronds often clumped (occasionally spaced), usually monomorphic (rarely slightly dimorphic, as in A. dentatum), small to medium-sized, rarely large, erect, spreading, pendent, or flat on ground or rocks; stipes green to atropurpureous or black, dull to lustrous, often slightly winged; blades simple to 3-pinnate, most often 1-pinnate; veins free, stopping short of margins in clavate tips (as seen adaxially); indument on both sides seemingly absent in most species, but blades in most (all?) species with minute appressed whitish to brownish, clavate, multicellular (3–6 very short cells sometimes with a terminal enlarged glandular cell) hairs 0.1–0.3 mm between veins, rarely with longer hyaline septate hairs on axes (A. pumilum), sometimes with a few narrow, hair-like scales on rachises, in a few species the scales more numerous, broader, and decidedly clathrate; sori abaxial, along the veins, usually one per ultimate vein, rarely back-to-back or opposing one another (A. scolopendrium), oblong to linear, indusiate; indusia persistent, extending the length of sori, whitish when young, tan to light brown with age, thin, margins entire to erose, occasionally ciliate or fimbriate; sporangia with slender, uniseriate stalks; spores bilateral, brown to blackish, with distinct perispore, usually 64 per sporangium (32 and globose in apogamous spp.); x=36 (39 or occasionally 38 in species of sect. Hymenasplenium).
A
A
Forma de vida
Terrestre, EpífitaA
Distribución
México (Country) native and not endemicB
Categoría IUCN
No incluidaC
Categoría NOM-059-SEMARNAT-2010
No incluidaD
Discusión taxonómica
Asplenium is a cosmopolitan genus of about 700 species, mostly of the tropics, 86 in Mexico. It includes some of the most difficult taxonomic problems for Mexican ferns. Hybridization is common among the temperate aspleniums and may also be common among tropical species, but there are no studies that document this in the Neotropics. In addition apogamy appears to be prevalent in Asplenium, as judged by life cycle studies on temperate and a few tropical groups, as well as spore morphology and number per sporangium, often 32 globose spores in apogamous species or specimens, instead of 64 reniform spores within a sporangium in sexually reproducing species (Braithwaite, 1986; Murakami & Moran, 1993). In studies on the A. aethiopicum group in Africa (closely related to A. praemorsum in Mexico), Braithwaite suggested that the apomictic taxa were able to tolerate more extreme environmental conditions than their sexual progenitors. We include minimal, but incomplete observational data on spore morphology and number per sporangium in the species descriptions below, as an impetus to further work.
One of the characters sometimes used in descriptions of spleenworts concerns the presence or absence and color of scattered whitish to tan (or sometimes brown) hairs, on the abaxial lamina, on and between the veins, as well as sometimes on the stipes and rachises. On casual inspection, the laminae of most aspleniums appears perfectly glabrous, but a closer look reveals that they bear inconspicuous, multicellular (3–6 cells), uniseriate, usually closely appressed hairs mostly 0.1–0.3 mm long on the abaxial surfaces. We have found such hairs in nearly all species examined from Mexico, and suspect that this feature is an autapomorphy for the entire family. Consequently, it seems to us of little use in characterizing individual species, unless differences in cell number, density, presence or absence of a darkened glandular tip, or color are diagnostic. We have so far not found this to be the case.
Several groups of Asplenium are well represented in the Mexican fern flora, in particular, the A. monanthes group, with 23 species. This number makes Mexico probably the center of greatest species diversity in the world in this cosmopolitan group. Other well represented groups are A. miradorense and allies, with ca. 13 species, and A. cuspidatum/auritum and allies, with 6 species. Several distinctive predominantly extraterritorial groups are also represented, e.g., A. exiguum and A. dalhousiae, both closely related to, or the same as, species in the Himalayas.
In addition, there is the occurrence of several predominantly temperate species, especially in northern Mexico: A. chihuahuense, A. scolopendrium, A. septentrionale, and A. trichomanes.
Phyllitis has traditionally been recognized as genus of 3 (to 5) species, largely of temperate regions, in Europe (common), Asia, North America (rare), and the Neotropics (rare in southern Mexico and Hispaniola). The species are difficult to distinguish. The genus is marginally distinct from Asplenium, and there are several intergeneric hybrids, a primary reason for its inclusion in Asplenium in this treatment. Recent molecular work by Schneider et al. (ms.) and by Van den Heede et al. (2003) indicates that Phyllitis is nested deeply within Asplenium, and allied to A. dalhousiae (often treated in the segregate and polyphyletic genus Ceterach). Phyllitis is traditionally distinguished by its simple elongate blades (also in some aspleniums) and opposing pairs (opening towards each other) of sori.
Two other genera of Mexican ferns, both rare and with undivided blades, are closely allied to Asplenium. Holodictyum can be easily distinguished by its net venation, and Schaffneria by its simple, round blades with lustrous atropurpureous to black stipes and paired sori facing each other from adjacent veins. These two genera are kept separate in this treatment because their relationship to and origin from any extant species is obscure and because they have been regarded as distinct in many other taxonomic accounts, rather than through any conviction that they deserve generic rank.
Phylogenetic studies on Asplenium and the Aspleniaceae are ongoing, but preliminary evidence suggests that the group diverged from a larger cluster of families and genera that include the athyrioid, thelypteroid, onocleoid, and blechnoid ferns. The family Aspleniaceae in the sense maintained by most systematists (e.g., Copeland, 1947; Tryon & Tryon, 1982; Kramer & Viane in Kubitzki, 1990) is clearly monophyletic, on the basis of both molecular and morphological evidence, but the delimitation of genera within the family is still unsettled and likely to undergo change. It appears now that the only element that can be clearly separated at generic rank, apart from Asplenium s.l. , is Hymenasplenium Hayata, distinguished in part by its different chromosome base numbers (x=38, 39), and creeping rhizomes (see Mitui et al., 1989; Murakami & Moran, 1993; Schneider et al., 2002).
Unplaced Names
Asplenium coriaceum Fée,Mém. Foug. 5: 193. 1852, non Desv., 1827. A. pycnophyllum T. Moore, Index Fil. 159. 1859. Type. Mexico. Galeotti s.n. (RB).
Asplenium auritum Sw. var. dissectum E. Fourn., Mexic. Pl. 1: 107. 1872. Syntypes. Mexico. Veracruz: S. Cristóbal, Botteri 1428; S. Andrés, Botteri 1429 (both Herb. va. Heurck, presumably BR).
Excluded Species
Asplenium lividum Mett. ex Kuhn, Linnaea 36: 100. 1869. Type. Venezuela. Aragua: San Carlos River valley, Fendler 156 (B; isotypes F, MO!, US!).
This was attributed to Chiapas by Adams (in Davidse et al., 1995) on the basis of Ghiesbreght s.n. (BM), which we have not seen. Otherwise, the species has been reported from Venezuela, Peru (Tryon & Stolze, 1993), and Africa (Burrows, 1990; Jacobsen, 1983; Schelpe & Anthony, 1986). It is very closely related to A. praemorsum, differing by the less dissected blades (merely pinnate-pinnatifid), fewer scales on the blades, and the scales without a long-attenuate tip. We doubt the conspecificity of the Ghiesbreght collection with the Venezuelan type, and the distinctness of the species is also open to question. Therefore, it is here excluded from the Mexican flora.
A
One of the characters sometimes used in descriptions of spleenworts concerns the presence or absence and color of scattered whitish to tan (or sometimes brown) hairs, on the abaxial lamina, on and between the veins, as well as sometimes on the stipes and rachises. On casual inspection, the laminae of most aspleniums appears perfectly glabrous, but a closer look reveals that they bear inconspicuous, multicellular (3–6 cells), uniseriate, usually closely appressed hairs mostly 0.1–0.3 mm long on the abaxial surfaces. We have found such hairs in nearly all species examined from Mexico, and suspect that this feature is an autapomorphy for the entire family. Consequently, it seems to us of little use in characterizing individual species, unless differences in cell number, density, presence or absence of a darkened glandular tip, or color are diagnostic. We have so far not found this to be the case.
Several groups of Asplenium are well represented in the Mexican fern flora, in particular, the A. monanthes group, with 23 species. This number makes Mexico probably the center of greatest species diversity in the world in this cosmopolitan group. Other well represented groups are A. miradorense and allies, with ca. 13 species, and A. cuspidatum/auritum and allies, with 6 species. Several distinctive predominantly extraterritorial groups are also represented, e.g., A. exiguum and A. dalhousiae, both closely related to, or the same as, species in the Himalayas.
In addition, there is the occurrence of several predominantly temperate species, especially in northern Mexico: A. chihuahuense, A. scolopendrium, A. septentrionale, and A. trichomanes.
Phyllitis has traditionally been recognized as genus of 3 (to 5) species, largely of temperate regions, in Europe (common), Asia, North America (rare), and the Neotropics (rare in southern Mexico and Hispaniola). The species are difficult to distinguish. The genus is marginally distinct from Asplenium, and there are several intergeneric hybrids, a primary reason for its inclusion in Asplenium in this treatment. Recent molecular work by Schneider et al. (ms.) and by Van den Heede et al. (2003) indicates that Phyllitis is nested deeply within Asplenium, and allied to A. dalhousiae (often treated in the segregate and polyphyletic genus Ceterach). Phyllitis is traditionally distinguished by its simple elongate blades (also in some aspleniums) and opposing pairs (opening towards each other) of sori.
Two other genera of Mexican ferns, both rare and with undivided blades, are closely allied to Asplenium. Holodictyum can be easily distinguished by its net venation, and Schaffneria by its simple, round blades with lustrous atropurpureous to black stipes and paired sori facing each other from adjacent veins. These two genera are kept separate in this treatment because their relationship to and origin from any extant species is obscure and because they have been regarded as distinct in many other taxonomic accounts, rather than through any conviction that they deserve generic rank.
Phylogenetic studies on Asplenium and the Aspleniaceae are ongoing, but preliminary evidence suggests that the group diverged from a larger cluster of families and genera that include the athyrioid, thelypteroid, onocleoid, and blechnoid ferns. The family Aspleniaceae in the sense maintained by most systematists (e.g., Copeland, 1947; Tryon & Tryon, 1982; Kramer & Viane in Kubitzki, 1990) is clearly monophyletic, on the basis of both molecular and morphological evidence, but the delimitation of genera within the family is still unsettled and likely to undergo change. It appears now that the only element that can be clearly separated at generic rank, apart from Asplenium s.l. , is Hymenasplenium Hayata, distinguished in part by its different chromosome base numbers (x=38, 39), and creeping rhizomes (see Mitui et al., 1989; Murakami & Moran, 1993; Schneider et al., 2002).
Unplaced Names
Asplenium coriaceum Fée,Mém. Foug. 5: 193. 1852, non Desv., 1827. A. pycnophyllum T. Moore, Index Fil. 159. 1859. Type. Mexico. Galeotti s.n. (RB).
Asplenium auritum Sw. var. dissectum E. Fourn., Mexic. Pl. 1: 107. 1872. Syntypes. Mexico. Veracruz: S. Cristóbal, Botteri 1428; S. Andrés, Botteri 1429 (both Herb. va. Heurck, presumably BR).
Excluded Species
Asplenium lividum Mett. ex Kuhn, Linnaea 36: 100. 1869. Type. Venezuela. Aragua: San Carlos River valley, Fendler 156 (B; isotypes F, MO!, US!).
This was attributed to Chiapas by Adams (in Davidse et al., 1995) on the basis of Ghiesbreght s.n. (BM), which we have not seen. Otherwise, the species has been reported from Venezuela, Peru (Tryon & Stolze, 1993), and Africa (Burrows, 1990; Jacobsen, 1983; Schelpe & Anthony, 1986). It is very closely related to A. praemorsum, differing by the less dissected blades (merely pinnate-pinnatifid), fewer scales on the blades, and the scales without a long-attenuate tip. We doubt the conspecificity of the Ghiesbreght collection with the Venezuelan type, and the distinctness of the species is also open to question. Therefore, it is here excluded from the Mexican flora.
A