Tropical Bryology, Volume 6 (1992)
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Botanical history has recorded significant contributions of bryology to its conceptual development and to man’s scientific knowledge. The discovery of sexual chromosomes in plants by Allen and the production of the first polyploids by Wettstein are but two scientific achievments in which bryophytes had an outstanding role. Currently, their use in environmental monitoring and the identification of active principles, make bryophytes objects of great pragmatic interest.
214 Lichen and 38 bryophyte species are reported from Cerro Guaiquinima, a sandstone table mountain in southeastern Venezuela, thus fas almost unexplored for these groups and apparently undisturbed by man. Slightly over half of these species have also been reported from the north slope of Mount Roraima and surroundings, a nearby area with similar edaphic and climatological conditions.
The pleurocarpous moss genus Isopterygium (Hypnaceae) is revised for Latin America. Although as many as 92 species and varieties have been reported for the region over past years, these are currently accommodated by the present revision into only eight species. The most common taxon throughout most of Latin America, Isopterygium tenerum (Sw.) Mitt, is also the most polymorphic and presently 45 taxa are recognized as synonyms. The other seven species are I. affusum Mitt., I. acutifolium Irel., I. byssobolax Par., I. jamaicense Buck Broth., I. subglobosum Herz., and I. tenerifolium Mitt.+
References are made to cytotoxic and/or antitumor compounds that have been isolated - ansamitocin P-3 from Claopodium crispifolium (Hook.) Ren. & Card. and Anomodon attenuatus Hueb., or an associated actinomycete, and ohioensins and pallidisetums from Polytrichum spp. Several hundred collections, which have been obtained from temperate regions of North America during 1990 and 1991, are currently being screened in new bioassays; active sesquiterpene lactones have been recently isolated from species of Porella. The methodologies of collecting and screening bryophyte samples are discussed with consideration to costs based on expected number of samples that might be collected in a day, the diversity in the collections as related to phytogeography and vegetation types, and the bryophyte cover that is vanishing in many forest regions of the United States. The difficulties in obtaining large collections for isolation of active agents are also discussed by examplerecollection of Claopodium crispifolium.
Las comunidades de briofitas de troncos en descomposición del bosque subtropical mojado de Puerto Rico son descritas cuantitativamente. Los troncos en descomposición fueron clasificados de acuerdo a la presencia de corteza y textura de la madera. En los troncos con corteza dominan miembros de las Lejeuneáceas y Calymperáceas. En los de madera blanda son comunes Taxithelium planum e Isopterygium tenerum. De manera preliminar se sugiere que las briofitas higromórficas dominan en los troncos más descompuestos debido a la escasa fluctuación de la humedad en estos.
De las 21 especies neotropicales de Octoblepharum válidamente publicadas, se reconocen, al presente, sólo nueve. Estas son: O. albidum Hedw., O. ampullaceum Mitt., O. cocuiense Mitt., O. cylindricum Schimp. ex Mont., O. erectifolium Mitt., O. pulvinatum (Doz. & Molk.) Mitt., O. rhaphidostegium C. Müll., O. stramineum Mitt. y O. tatei (Williams) Bartr. Se distinguen dos líneas evolutivas de acuerdo al número de dientes del peristoma. Los miembros de la línea con 16 dientes son dioicos mientras que aquellos de la de 8 pueden ser autoicos o dioicos. Los estudios fenológicos en poblaciones de 3 especies en Panamá sugieren un pseudodioicismo en las especies autoicas con el desarrollo de gametoceos masculinos y anteridios en mayor número que los femeninos. En las poblaciones de O. albidum se presentan dos tipos de peristoma, uno verticalmente estriado y otro liso. Todas las especies ocurren en América del Sur la que se considera como el centro de origen y especiación del género.
Phenological observations and sex ratios in Marchantia chenopoda L. (Hepaticae: Marchantiaceae)
(1992)
Sex ratios were determined for 15 populations of Marchantia chenopoda L. along Puerto Rico. Sex was determined for twenty randomly selected individuals from each population. A female bias was observed in most populations. A census of reproductive structures of M. chenopoda was performed every two weeks in order to determine phenology. The highest archegoniophore count was observed to occur in January and February; minimum and maximum fertilization distances were 0.7 cm and 65 cm, respectively. Young sporophytes were most frequently observed at the beginning of the rainy season, in April and May. The highest frequency of mature sporophytes occurred during the dry season, in January and February. Capsules opened mostly during the heavy rainy season, from August to November. Protonemata were observed in the periphery of the population. Most young sporophytes aborted at the end of the moderate to heavy rainy season, from June to August. Immature gemmae cups were most frequent at the beginning of the rainy season, in April and May. Mature gemmae cups were observed throughout the rainy season, but were most frequent in September.
Cuba es uno de los países de las Antillas Mayores con mayor diversidad de musgos (383 taxa infragenéricos) los cuales se encuentran distribuidos fundamentalmente hacia las zonas montañosas. Aunque se han iniciado estudios en fitoquímica y antibiosis, los de sistemática deben continuar paralelamente.
Se presenta la ubicación taxonómica actualizada de 106 géneros de hepáticas y 233 géneros de musgos conocidos de Venezuela. Asimismo, se presenta una versión resumida de la distribución geográfica en Venezuela de 383 especies de hepáticas y 1009 especies de musgos. La información proviene principalmente de la revisión exhaustiva de las colecciones de briofitas en los herbarios venezolanos y de las publicaciones sobre briofitas colectadas en Venezuela. Se concluye que Venezuela, a pesar de haber sido poco explorada tiene una gran diversidad de briofitas, muchas de las cuales aún no se conocen y podrían extinguirse antes de haber sido colectadas, determinadas y analizadas científicamente.
Se comparan las características de una especie de Aphanolejeunea colectada en la Reserva Biológica de San Ramón, Alajuela, Costa Rica, con las dadas en la descripción de Lejeunea heterophylla de Puerto Rico; ambas pertenecen a la misma especie. A. heterophylla es esencialmente diferente de A. exigua Evans.
La lista preliminar de ácaros colectadas sobre musgos en México incluye 48 familias: 11 Mesostigmata, 17 Prostigmata (=Actinedida), 1 Astigmata y 19 Cryptostigmata (=Oribatei). Se presenta un análisis general de la relación entre las briofitas y su fauna asociada. El estudio detallado de estos grupos de animales seguramente dará a conocer un número mayor de especies asociadas con las briofitas.
Se analizan las relaciones filogenéticas de las especies de Anomodon y sus géneros más afines, Haplohymenium y Herpetineuron. Anomodon está restringido al hemisferio norte: hay cuatro especies en México (algunas de las cuales llegan a Guatemala y/o las islas del Caribe), dos en Estados Unidos y Canadá, una en Europa y el resto en el sur y este asiáticos. Se incluyen tres especies de Haplohymenium, Herpetineuron toccoae, H. acutifolium (=Anomodon acutifolius, Granzow-de la Cerda 1989) y Pterogonium gracile. Los 31 caracteres para los 17 taxa se analizaron con el programa PAUP, versión 3.0, para Macintosh (Swofford 1991). De acuerdo con los árboles resultantes, las 11 especies de Anomodon son monofiléticas, siempre que dicho taxon incluya las especies de Haplohymenium. Anomodon comprende dos clados, uno que coincide con el subgénero Pseudoanomodon constituido por A. longifolius, A. attenuatus, A. giraldii y A. rostratus; el otro coincide con el subgénero Anomodon el cual incluye las especies de Haplohymenium. Se propone la reducción de este último a la categoría de sección Haplohymenium.
Tropical deforestation, inevitably, leads to the local loss of bryophyte species. Recent studies show that the degree of species loss may vary considerably and depends on the scale or amount of habitat change that has occurred. Predictably, the shade epiphytes are most seriously affected by disturbance. An estimated 10% of the bryophyte species of neotropical rain forests are under threat. Based on data from recent monographs, a first list of 19 endangered and 27 rare species of these forests is presented. Critical areas for threatened species include Costa Rica and Panama, the Greater Antilles, the Chocó, southeastern Brazil, and parts of Amazonia. Protection of as much as possible of the remaining natural rain forest area seems the best approach to the conservation of the tropical bryophyte flora.
The Index of Atmospheric Purity (IAP) was used to make a preliminary evaluation of epiphytic moss response to atmospheric pollution in the urban area of Mexico City. Areal analysis indicates that there is a significant negative correlation (p < 0.5) between IAP values and SO2, NO2, NOx, Pb and temperature values of -0.45, -0.90, -0.80, -0.80, -0.90. Significant positive correlation (p < 0.05) between IAP values and O3, rainfall and relative atmospheric humidity with values of 0.70, 0.80, 0.90. Increase in atmospheric pollutants in Mexico City have promoted a gradual decrease in frequency and cover of epiphytic mosses even though some ecological factors may show the oposite effect.
Scanning electron microscopy and light microscopy were used to elucidate the morphology of Metzgeria conjutata Lindb. and confirm the presence of 2 rows of epidermal cells on the dorsal surface, (21-3) rows on the ventral surface, midrib with cells in (3-51-6) tiers; hirsute, short hairs, straight on the thallus-margin and on the ventral surface of midrib; marginal hairs paired, single or in groups of three; male branches globose or subglobose; female involucres obovate and hirsute at the margin, calyptra fleshy, pyriform to club-shaped, hirsute on the outer surface, hairs long and straight.
La enseñanza de la briología en México enfrenta varios problemas que impiden a los estudiantes obtener siquiera un panorama general de lo que son las briofitas; se han identificado tres problemas principales: la falta de infraestructura institucional, la carencia de bibliografía especializada y el desconocimiento de la estructura, biología e importancia de estas plantas por parte de los profesores. Para superar los problemas es necesario adquirir el equipo minímo indispensable (microscopios, material de laboratorio y literatura especializada) y pedir a los especialistas su participación en cursos, talleres y excursiones para ayudar a los profesores a comprender mejor a este grupo de plantas.
The vascular flora of Chiapas, Mexico, has been the subject of a long term study by Dennis Breedlove of the California Academy of Sciences. This has stimulated a related project dealing with the bryophyte flora of the region. A collecting expedition in 1988 generated 1420 collections of bryophytes. Specialists from 13 institutions assisted with identifications. Approximately 70% of the collections have been determined. Checklists of species of bryophytes of Chiapas are presented. These lists are based on collections at CAS and literature citations. A total of 364 species of mosses and 310 species of hepatics and hornworts are reported from Chiapas.
The bryophyte collection at MEXU was formally established in 1973 with about 3000 specimens; at present, it contains nearly 35000. Emphasis has been made on Mexican and tropical American localities, but herbarium holdings also include temperate areas. Herbarium information is now being stored in a database to assist floristic and taxonomic research in progress and for further reference.