Elías R. de la Sota

Análisis biogeográfico de la diversidad pteridofítica en Argentina y Chile continental

Las Pteridofitas de Chile continental estan representadas por 116 especies nativas (43 generos, 20 familias), y en Argentina continental por 346 (86 generos, 27 familias). Ambos paises comparten 89 especies (41 generos, 20 familias). La menor diversidad pteridofitica y el mayor endemismo en Chile (11,2 %) que en Argentina (3,5 %) estan relacionados probablemente con extinciones historicas y su actual aislamiento geoclimatico. Sin embargo, se destaca que el endemismo en los helechos es cinco a seis veces menor que en Angiospermas. Los generos con mas especies en Argentina son Thelypteris (34), Asplenium (32), Cheilanthes (21), Blechnum (19) e Hymenophyllum (16). Los dos ultimos tambien son los mas diversificados en Chile (Hymenophyllum, 18 y Blechnum, 10). En la region estudiada la diversidad muestra incrementos latitudinales opuestos, concentrandose en tres centros, dos subtropicales en el noroeste y noreste de Argentina y uno templado-lluvioso en el sur argentino-chileno alrededor de los 40o latitud sur. Los tres centros de diversidad concentran el 93 % de las especies y el 95 % de los endemismos, compartiendo pocas especies entre ellos. En los centros subtropicales las familias Aspleniaceae, Polypodiaceae, Pteridaceae, Thelypteridaceae y Selaginellaceae son sus componentes mas importantes, y comparten un gran numero de especies con Bolivia y Brasil, respectivamente. El centro templado sur tiene una menor diversidad pteridofitica, pero se hallan en el mayor cantidad de endemismos (77 %) que en los centros subtropicales, a consecuencia de un fuerte aislamiento. Sin embargo, presenta altos indices de similitud e intercambio floristico entre ambas vertientes de Los Andes. Alli las Blechnaceae y Hymenophyllaceae son las familias mejor representadas. Los taxa que presentan una distribucion disyunta encontrandose en los tres centros de diversidad, nos indican que la pteridoflora del Cono Sur fue historicamente mas extensa y continua, y que sus limites han retrocedido a causa de los impactantes cambios climaticos y geomorfologicos que sucedieron durante el Terciario y el Pleistoceno.

Two cytotypes and a new hybrid in Salvinia Séguier

Two cytotypes (2n=4x=36 and 2n=6x=54) found in Salvinia minima Bak. are discussed, the first from Brazil and the second from Argentina. The hexaploid cytotype, presumably a hybrid between Salvinia minima and S. sprucei Kuhn, was collected from the Solimoes River near Manaus, Brazil and from Trinidad. Discussing its intermediate morphology, the authors attemp to explain the hybridization as a result of the seasonal and sporadic occurrence of Salvinia sprucei in the Amazonian basin, assuming that the still unknown chromosome number of the latter species would correspond to the diploid level (2n=2x=18).

Revision of the Genus Salpichlaena J. Sm. (Blechnaceae, Pteridophyta)

ABSTRACT Salpichlaena J. Sm. (Blechnaceae) is a genus of climbing fern that grows in Central and South America. The number of species recognized for this genus varies according to different authors from one to four. The goal of this work was to provide a systematic revision of the genus Salpichlaena in order to contribute to the knowledge of the fern biodiversity in America. For this purpose morphological, anatomical and palynological characters were analyzed in material from the geographical distribution of Salpichlaena. Herbarium specimens were treated according to the standard techniques for LM and SEM studies. The type specimens and the original descriptions were consulted to determine the applications of names. Two species are recognized, S. volubilis (Kaulf.) J. Sm. and S. hookeriana (Kuntze) Alston. Salpichlaena hookeriana differs from S. volubilis by pronounced foliar dimorphism (the fertile pinnules are much reduced), the presence of foliar buds on sterile basal pinnules, ovate costular scales and the presence of glandular hairs on the abaxial surface of the costa. The spores are monolete in both taxa, with rugulate-granulate perispore and superficial spherules. Salpichlaena volubilis is widely distributed in Central and South America, from Guatemala and Caribbean Islands, up to southern Brazil and Bolivia, across a wide altitudinal range of 200 to 1900 m. Salpichlaena hookeriana grows from Colombia, Venezuelan Guyana, Suriname, British Guiana, North Brazil to Peru and Bolivia, at altitudes up to 800 m. The diagnostic characters, illustrations and distribution maps of both species are given.

Biogeographic analysis and key to the genera of ferns and lycophytes of Mburucuyá National Park, Corrientes, Argentina

Fil: Meza Torres, Esteban Ismael. Consejo Nacional de Invest.cientif.y Tecnicas. Centro Cientifico Tecnol.conicet - Nordeste. Instituto de Botanica del Nordeste (i); Argentina;

Observations on Tracheary Elements in Salpichlaena J. Sm. (Blechnaceae, Pteridophyta)

ABSTRACT The morphology of the tracheary elements of the climbing fern Salpichlaena (Blechnaceae) were analyzed by means of LM and SEM. Two preparative techniques were employed: maceration and sectioning. Under SEM macerated tracheary elements from roots, rhizomes and leaf rachises showed large scalariform perforations lacking pit membranes, thus constituting apparent perforation plates. The perforations showed terminal as well as lateral positions. “Multiple end-wall” and “intermittent” perforation plates were also observed. In sectioned material tracheary cells exhibited mostly intact pit membranes conforming tracheids with scalariform and circular to oval wall pitting. In roots, true perforations seemed to be present in some tracheary cells. A different degree of pit membrane perforations were registered in both macerated and sectioned material, thus suggesting the existence of “incipient vessel elements”. According to our observations macerations produce alterations in the xylem tissue, which can lead to misinterpretations.

A New Species of Pecluma (Pteridophyta–Polypodiaceae)

ABSTRACT A new species of Pecluma M. G. Price, P. barituensis O. Martínez & de la Sota, is described from material collected from the northwestern forests and mountain woods in Argentina. This taxon is related to Pecluma oranensis (de la Sota) de la Sota, from which it differs with its pinnae narrower at mid-rachis, thereby appearing farther apart, and its auriculiform basal pinnae.

Una Nueva Combinación en Microgramma C. Presl (Pteridophyta–Polypodiaceae)

ABSTRACT A new combination in Microgramma C. Presl (Pteridophyta–Polypodiaceae) is proposed instead of M. fuscopunctata (Hooker) Vareschi, after the analysis of the type of Polypodium dictyophyllum Kunze ex Mettenius. Through the study of additional specimens and recent bibliography, the distributional pattern of this taxon for tropical America is specified.A new combination in Microgramma C. Presl (Pteridophyta–Polypodiaceae) is proposed instead of M. fuscopunctata (Hooker) Vareschi, after the analysis of the type of Polypodium dictyophyllum Kunze ex Mettenius. Through the study of additional specimens and recent bibliography, the distributional pattern of this taxon for tropical America is specified. RESUMEN . Se propone una nueva combinación en Microgramma C. Presl (Pteridophyta–Polypodiaceae), sobre la base de Polypodium dictyophyllum Kunze ex Mettenius, en lugar de M. fuscopunctata (Hooker) Vareschi, después de analizar el tipo del primer taxón nombrado. Estudiando otros especimenes y consultando bibliografı́a reciente, se precisa el área de distribución de esta especie en América tropical.