RESUMEN
Benthic macroinvertebrates of the Palo Verde wetland, Costa Rica. Palo Verde, Costa Rica, is one of the most important wetlands in the region now recovering from some invasive plants, especially Typha domingensis, and monitoring programs were started, including studies on the aquatic macoinvertebrate fauna. We sampled benthic macroinvertebrates monthly for more than a year with artificial substrates, and identified 116 taxa from 57 families and 18 orders, with 90 morfospecies of insects. The highest abundances were in the class Conchostraca (typical in seasonal wetlands) and in the family Chironomidae (Diptera, Insecta), which together represent almost half of all individuals collected. In contrast, 97 taxa were less than 1% of total abundance each. Number of individuals and number of species were higher at lower water levels (dry season). Cumulative species curves indicate that more species would be found if sampling had continued for more time. Rev. Biol. Trop. 57 (Suppl. 1): 275-284. Epub 2009 November 30.
El humedal de Palo Verde es uno de los más importantes de Centro America para aves acuáticas. Durante el período 2002 y 2005, se llevaron a cabo actividades de manejo para controlar la invasión de Typha domingensis. Con el fin de establecer una línea base para monitoreos futuros, en el 2003 se realizó una evaluación de macroinvertebrados acuáticos. Se efectuó un muestreo mensual durante un año, usando el método de sustratos artificiales. Se identificaron 116 táxones pertenecientes a 47 familias y a 18 órdenes. La mayor abundancia se encontró en la clase Conchostraca y la familia Chironomidae que juntas representaron casi la mitad de todos los individuos colectados. En contraste, el 97% de los táxones tuvieron, cada uno, menos del 1% del total de la abundancia. La diversidad de táxones, así como la abundancia de individuos y el número de especies, fueron mayores en la época seca que en la lluviosa. La curva acumulada de especies indicó que se hubiera registrado una mayor cantidad de táxones si los muestreos se hubieran extendido por más tiempo. Con este trabajo damos a conocer la primera lista de macroinvertebrados para el humedal de Palo Verde.
Asunto(s)
Fauna Béntica , Clasificación , Humedales , Invertebrados/clasificación , Costa RicaRESUMEN
Molecular phylogenetic studies have resolved placental mammals into four major groups, but have not established the full hierarchy of interordinal relationships, including the position of the root. The latter is critical for understanding the early biogeographic history of placentals. We investigated placental phylogeny using Bayesian and maximum-likelihood methods and a 16.4-kilobase molecular data set. Interordinal relationships are almost entirely resolved. The basal split is between Afrotheria and other placentals, at about 103 million years, and may be accounted for by the separation of South America and Africa in the Cretaceous. Crown-group Eutheria may have their most recent common ancestry in the Southern Hemisphere (Gondwana).
Asunto(s)
Teorema de Bayes , Mamíferos/clasificación , Mamíferos/genética , Filogenia , África , Animales , Emparejamiento Base , Evolución Biológica , Núcleo Celular/genética , Ecosistema , Fósiles , Genes , Genes de ARNr , Funciones de Verosimilitud , Cadenas de Markov , Marsupiales/clasificación , Marsupiales/genética , Mitocondrias/genética , Método de Montecarlo , Placenta , Probabilidad , Análisis de Secuencia de ADN , América del SurRESUMEN
On two different opportunities the distribution and diversity of the benthic macrofauna was studied at different depths in the Laguna del Cerro Chato crater lake, Alajuela, Costa Rica. For both surveys, the deep samples had significantly lower species diversity and evenness than the shallow samples. There was a drop in species diversity and evenness at 6 m, followed by an increase at 9 m. This pattern is associated with fluctuations in the lake's thermocline. Chironomids were the most abundant organism in both surveys and the genus Chironomus dominated at all depths. Analysis of the elements Ca, Cu, S, N, Fe, P and percentage of organic matter in the bottom sediments did not show a clear bathymetrical distribution. However, at a depth of 9 m the increase in both N content and percentage or organic matter could be related to the increase in abundance of organisms.
Asunto(s)
Biomasa , Insectos , Oligoelementos/análisis , Animales , Costa RicaRESUMEN
DNA hybridization was used to compare representatives of the major groups of marsupials and a eutherian outgroup. Because of the large genetic distances separating marsupial families, trees were calculated from normalized percentages of hybridization; thermal-melting statistics, however, gave identical topologies for the well-supported clades. The most notable results were the association of the only extant microbiotheriid, Dromiciops australis, an American marsupial, with the Australasian Diprotodontia, and of both together with the Dasyuridae. Estimates of the rate of divergence among marsupial genomes suggest that the Dromiciops-Diprotodontia split occurred approximately 50 million years ago, well after the establishment of the major clades of marsupials but before deep oceanic barriers prohibited dispersal among Australia, Antarctica, and South America. Because Dromiciops is nested within an Australasian group, it seems likely that dispersal from Australia accounts for its present distribution.