摘要:

We examined seasonal changes in microhabitat use by the murid rodents Akodon azarae and Calomys laucha in agroecosystems of the former pampa region of Argentina. In summer, trap data showed that both species had low densities and were almost equally distributed between the mature cropfields and their surrounding weedy borders. Analysis of vegetation at the trap sites revealed no selection for microhabitats at the borders, whereas in the cropfields both species shared preferences for covered microhabitats. In contrast, winter data revealed a sharp habitat segregation, being Calomys numerically dominant in post-harvest cropfields and Akodon more abundant in borders. Moreover, there were clear differences in microhabitat selection at the borders, A. azarae occupying the more covered microhabitats and C. laucha the less covered. Breadth and overlap of niches were calculated using principal component analysis, in order to recognize interspecific competition and its influence on community niche space. Available evidence indicates that the structure of this rodent community is strongly influenced by seasonal changes in habitat stucture and rodent abundance. The socially dominant A. azarae retains the best part of the available niche space, a fact becoming more evident under the harsh winter conditions.

ISSN:0165-0521    

DOI:10.1076/snfe.34.3.129.8913

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

In a field study carried out over one year in a secondary Araucaria forest in eastern ParanÝ State, Brazil, foraging was observed in a population of the squirrel Sciurus ingrami. Seeds of Araucaria and about ten more species of native and exotic trees were the main food items besides mushrooms and fruits. Not all seeds were consumed immediately. Especially in autumn and winter, a large portion was cached, in particular of the Araucaria seeds. The relevance of this behaviour, well known in squirrels, for seed dispersion and forest regeneration is discussed.

ISSN:0165-0521    

DOI:10.1076/snfe.34.3.137.8910

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

A new species, Microcavia criolloensis (Rodentia, Caviidae), from the Upper Pleistocene (Sopas Formation) of the northern basin of Uruguay (South America) is described. This species is characterised by an exclusive association of skull and dental state characters. An analysis of similarity including other species of the genus and the related genera of Caviidae was performed. The new species of Microcavia behaved in the phenogram obtained as a discrete unit closely associated to Microcavia chapalmalensis and Microcavia niata. A mosaic of habitats, ranging from open and arid or semiarid microhabitats to fluvial and riparian forests, is suggested here, mainly based on the current adaptations of the genus Microcavia and the records of several taxa of mammals in the Sopas Formation. The geographic area occupied by Microcavia in the Pleistocene was different, with fossil records located more than 500 km eastward with respect to its present distribution. This variation could have occurred as a response to environmental changes in the last interglacial and glacial cycles.

ISSN:0165-0521    

DOI:10.1076/snfe.34.3.141.8914

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

Molecular, morphometric, and distributional data are used to establish the taxonomic identity and differentiation of the South-American leptodactylid frogs Eupsophus calcaratus and E. roseus. Their geographical distribution in Chile suggests that the differentiation of these species occurred allopatrically. Molecular and morphometric data indicate a clear taxonomic identity of both taxa.

ISSN:0165-0521    

DOI:10.1076/snfe.34.3.150.8909

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

Three new species of terrestrial isopods from the leaf litter of a rain forest near Gamboa, canal zone, Panama, are described. They belong to the genera Ischioscia Verhoeff, 1928 and Andenoniscus Verhoeff, 1941, occurring in Central America and northern South America. I. panamensis spec. nov. is a typical member of the genus, whereas I. zebricolor spec. nov. differs remarkably from its congeners, both in colour and morphological aspects. Andenoniscus schmalfussi spec. nov. belongs to a different phyletic line of the so-called "Philosciidae", a paraphyletic group. The generic position of both I. zebricolor spec. nov. and A. schmalfussi spec. nov. is discussed, together with the evolution of specific characters and the biogeography of these Central American Oniscidea.

ISSN:0165-0521    

DOI:10.1076/snfe.34.3.156.8911

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

Pectiniunguis bollmani n. sp. (Chilopoda: Geophilomorpha: Schendylidae) is described from the Morrocoy National Park (State of Falc¢n, Venezuela) and considered as very closely related to P. halirrhytus Crabill, 1959. Additional data on P. halirrhytus Crabill and comments on the geographical distribution of the two taxa, both probably halophilous, are also given.

ISSN:0165-0521    

DOI:10.1076/snfe.34.3.176.8907

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

During quantitative samples of invertebrate fauna in two lakes in the Rio Doce State Park (Marliéria, MG) I found some individuals of the introduced aquatic snail Melanoides tuberculata. It was most abundant in areas with high human activity, where the original vegetation was removed from the shallow areas near the margin. Population structure inferred by size-class data suggests that the most impacted area was invaded first and that these snails maintain a viable population in Dom Helvécio lake. Potential spread of the snail in this lake system is tentatively related to the characteristics of the bank vegetation and I presume that the not yet invaded Carioca lake has better conditions for an exponential growth of this species.

ISSN:0165-0521    

DOI:10.1076/snfe.34.3.186.8908

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

ISSN:0165-0521    

DOI:10.1076/snfe.34.3.191.8912

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor