10 research outputs found
Floral neighbourhoods in the sea: how floral density, opportunity for outcrossing and population fragmentation affect seed set in Zostera marina
Podostemum rutifolium subsp. rutifolium como estruturador da comunidade de algas perifĂticas em um rio neotropical
A phallus for free? Quantitative genetics of sexual trade-offs in the snail Bulinus truncatus
Diet of Astyanax species (Teleostei, Characidae) in an Atlantic Forest River in Southern Brazil
Feeding habits of six species of Astyanax from river MaquinĂ© are described. Fishes were sampled bi-monthly from November/95 to September/96 in two zones of the river. Items were identified, counted and had their abundance estimated according to a semi-quantitative scale. Frequency of occurrence, alimentary importance index (IFI) values and a similarity analysis of diets for each species-river zone sample were examined. All the species were considered typically omnivorous, with insects and vegetal matter being the most important items in their diet. These species could act as seed dispersers, particularly for macrophytes. Intra-specific spatial differences were not observed in comparisons of samples from two diferent regions of the river, except for A. fasciatus. The presence of Podostemaceae macrophytes in the mid-course of the river seemed to be important both as an autochthonous food resource and as habitat for several organisms preyed by the Astyanax species.<br>Seis espĂ©cies do gĂŞnero Astyanax, presentes no rio MaquinĂ©, RS, foram estudadas quanto aos seus hábitos alimentares. Os exemplares foram amostrados bimensalmente de novembro de 1995 a setembro de 1996 nas zonas ritral e potamal do rio. Os itens alimentares foram identificados e quantificados de acordo com uma escala semi-quantitativa de abundância, utilizando-se para análise a frequĂŞncia de ocorrĂŞncia e um Ăndice de importância alimentar para cada espĂ©cie e zona do rio. Análises multivariadas de agrupamento e ordenação foram utilizadas para comparar as dietas intra e interespecĂficas. Todas as espĂ©cies foram consideradas onivoras, sendo que os itens mais importantes foram os insetos e restos de vegetais superiores. Sugere-se que as espĂ©cies estudadas possam atuar como dispersoras de sementes, particularmente para macrĂłfitas. Diferenças espaciais intraespecĂficas nĂŁo foram encontradas, exceto para A. fasciatus. A presença de Podostemaceae no curso mĂ©dio do rio parece ser uma fonte importante de alimento para as espĂ©cies, alĂ©m de servir de refĂşgio para diversos organismos que sĂŁo predados por Astyanax sp
A systematic survey of floral nectaries
The construction of classifications, as well as the understanding of biological diversity, depends upon a careful comparison of attributes of the organisms studied (Stuessy, 1990). It is widely known that data from diverse sources showing differences from taxon to taxon are of systematic significance. Dur-ing the 20th century, systematists have emphasized that their discipline involves a synthesis of all knowledge (Stevens, 1994) or, in other words, the variation of as many relevant characters as possible should be incorporated into the natural system to be constructed. The extent to which particular characters are constant or labile will determine their usefulness to syste-matics. In general, more conservative characters will be valuable in defining families and orders, whereas more labile characters may be useful at the ge-neric and specific levels (Webb, 1984). There is no doubt that floral characters are among the most used in the classification of flowering plants. At the same time, they constitute essential features in diagnostic keys to taxa in both taxonomic treatments and Floras (Cronquist, 1981, 1988).Fil: Bernardello, Gabriel Luis Mario. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Centro CientĂfico TecnolĂłgico Conicet - CĂłrdoba. Instituto Multidisciplinario de BiologĂa Vegetal. Universidad Nacional de CĂłrdoba. Facultad de Ciencias Exactas FĂsicas y Naturales. Instituto Multidisciplinario de BiologĂa Vegetal; Argentin