This paper reports a study on species richness and composition of Tumbesian dry forest communities. We tested two alternative hypotheses about species assemblage processes in tropical dry forests: (1) species assemblage is determined by the filtering effect of environmental conditions and (2) species assemblage is determined by facilitative processes along the gradient of water availability, an...

Alien species are a major component of human-induced environmental change. Variation in the numbers of alien species found in different areas is likely to depend on a combination of anthropogenic and environmental factors, with anthropogenic factors affecting the number of species introduced to new locations, and when, and environmental factors influencing how many species are able to persist t...

Environmental (topography, climate) features have an important influence on plant diversity and richness of Iran. Topography is from –28m which is close to Caspian Sea to 5678m which is located on the Alborz Mountain. Two mountains (Alborz and Zagrosss) prevent moist air moving to the centre of Iran. On the basis of environmental factors, four ecological zones with specific plant richness from ...

The ability to predict spatial patterns of species richness using a few easily measured environmental variables would facilitate timely evaluation of potential impacts of anthropogenic and natural disturbances on biodiversity and ecosystem functions. Two common hypotheses maintain that faunal species richness can be explained in part by either local vegetation heterogeneity or primary productiv...

Invasions have increased the size of regional species pools, but are typically assumed to reduce native diversity. However, global-scale tests of this assumption have been elusive because of the focus on exotic species richness, rather than relative abundance. This is problematic because low invader richness can indicate invasion resistance by the native community or, alternatively, dominance b...

résuMé. — La richesse spécifique des rongeurs et celle des carnivores sont corrélées en Espagne. — La diversité des niches écologiques favorise la coexistence des espèces, accroissant la richesse spécifique. La richesse spécifique des carnivores devrait donc croître avec celle de leurs proies, en raison des niches trophiques ainsi ouvertes. cette hypothèse a été évaluée à l’aide de modèles liné...

1. Ecologists have generally focused on how species interactions and available niches control species richness. However, the number of species in the regional species pool may also control richness. Moreover, the relative influence of the species pool and species interactions on plant richness may change along productivity and disturbance gradients. 2. We test the hypothesis that many species f...

This study was aimed at finding the impacts of different tree species and individual trees of different sizes on species richness, diversity, and composition of the herbaceous layer. All the three tree species have greatly increased species richness and diversity both within and outside their crown zones compared with the open grassland. Both species richness and diversity were found to be high...

A number of species richness estimators have been developed under the model that individuals (or sampling units) are sampled with replacement. However, if sampling is done without replacement so that no sampled unit can be repeatedly observed, then the traditional estimators for sampling with replacement tend to overestimate richness for relatively high-sampling fractions (ratio of sample size ...