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Local Species Diversity (local + species_diversity)
Selected AbstractsArctiid moth ensembles along a successional gradient in the Ecuadorian montane rain forest zone: how different are subfamilies and tribes?JOURNAL OF BIOGEOGRAPHY, Issue 1 2006Nadine Hilt Abstract Aim, We examined changes in the species diversity and faunal composition of arctiid moths along a successional gradient at a fine spatial scale in one of the world's hot spots for moths, the Andean montane rain forest zone. We specifically aimed to discover whether moth groups with divergent life histories respond differentially to forest recovery. Location, Southern Ecuador (province Zamora-Chinchipe) along a gradient from early successional stages to mature forest understorey at elevations of 1800,2005 m a.s.l. Methods, Moths were sampled with weak light traps at 21 sites representing three habitat categories (early and late succession, mature forest understorey), and were analysed at species level. Relative proportions were calculated from species numbers as well as from specimen numbers. Fisher's , was used as a measure of local diversity, and for ordination analyses non-metric multidimensional scaling (NMDS) was carried out. Results, Proportions of higher arctiid taxa changed distinctly along the successional gradient. Ctenuchini (wasp moths) contributed more strongly to ensembles in natural forest, whereas Lithosiinae (lichen moths) decreased numerically with forest recovery. Arctiid species diversity (measured as Fisher's ,) was high in all habitats sampled. The three larger subordinated taxa contributed differentially to richness: Phaegopterini (tiger moths) were always the most diverse clade, followed by Ctenuchini and Lithosiinae. Local species diversity was higher in successional habitats than in forest understorey, and this was most pronounced for the Phaegopterini. Dominance of a few common species was higher, and the proportion of species represented as singletons was lower, than reported for many other tropical arthropod communities. NMDS revealed a significant segregation between ensembles from successional sites and from forest understorey for all larger subordinated taxa (Phaegopterini, Ctenuchini, Lithosiinae). Abandoned pastures held an impoverished, distinct fauna. Faunal segregation was more pronounced for rare species. Ordination axes reflected primarily the degree of habitat disturbance (openness of vegetation, distance of sites from mature forest) and, to a lesser extent, altitude, but not distance between sampling sites. Main conclusions, Despite the geographical proximity of the 21 sites and the pronounced dispersal abilities of adult arctiid moths, local ecological processes were strong enough to allow differentiation between ensembles from mature forest and disturbed sites, even at the level of subfamilies and tribes. Differences in morphology and life-history characteristics of higher arctiid taxa were reflected in their differential representation (proportions of species and individuals) at the sites, whereas patterns of alpha and beta diversity were concordant. However, concordance was too low to allow for reliable extrapolation, in terms of biodiversity indication, from one tribe or subfamily to the entire family Arctiidae. Phaegopterini (comprising more putative generalist feeders during the larval stages) benefited from habitat disturbance, whereas Ctenuchini (with host-specialist larvae) were more strongly affiliated with forest habitats. [source] Plant species richness and environmental heterogeneity in a mountain landscape: effects of variability and spatial configurationECOGRAPHY, Issue 4 2006Alexia Dufour The loss of biodiversity has become a matter of urgent concern and a better understanding of local drivers is crucial for conservation. Although environmental heterogeneity is recognized as an important determinant of biodiversity, this has rarely been tested using field data at management scale. We propose and provide evidence for the simple hypothesis that local species diversity is related to spatial environmental heterogeneity. Species partition the environment into habitats. Biodiversity is therefore expected to be influenced by two aspects of spatial heterogeneity: 1) the variability of environmental conditions, which will affect the number of types of habitat, and 2) the spatial configuration of habitats, which will affect the rates of ecological processes, such as dispersal or competition. Earlier, simulation experiments predicted that both aspects of heterogeneity will influence plant species richness at a particular site. For the first time, these predictions were tested for plant communities using field data, which we collected in a wooded pasture in the Swiss Jura mountains using a four-level hierarchical sampling design. Richness generally increased with increasing environmental variability and "roughness" (i.e. decreasing spatial aggregation). Effects occurred at all scales, but the nature of the effect changed with scale, suggesting a change in the underlying mechanisms, which will need to be taken into account if scaling up to larger landscapes. Although we found significant effects of environmental heterogeneity, other factors such as history could also be important determinants. If a relationship between environmental heterogeneity and species richness can be shown to be general, recently available high-resolution environmental data can be used to complement the assessment of patterns of local richness and improve the prediction of the effects of land use change based on mean site conditions or land use history. [source] Anthropogenic impacts upon plant species richness and net primary productivity in CaliforniaECOLOGY LETTERS, Issue 2 2005John W. Williams Abstract We assess the importance of anthropogenic land-use, altered productivity, and species invasions for observed productivity,richness relationships in California. To this end, we model net primary productivity (NPP) c. 1750 AD and at present (1982,1999) and map native and exotic vascular plant richness for 230 subecoregions. NPP has increased up to 105% in semi-arid areas and decreased up to 48% in coastal urbanized areas. Exotic invasions have increased local species diversity up to 15%. Human activities have reinforced historical gradients in species richness but reduced the spatial heterogeneity of NPP. Structural equation modelling suggests that, prior to European settlement, NPP and richness were primarily controlled by precipitation and other abiotic variables, with NPP mediating richness. Abiotic variables remain the strongest predictors of present NPP and richness, but intermodel comparisons indicate a significant anthropogenic impact upon statewide distributions of NPP and richness. Exotic and native species each positively correlate to NPP after controlling for other variables, which may help explain recent reports of positively associated native and exotic richness. [source] Beta diversity of frogs in the forests of New Guinea, Amazonia and Europe: contrasting tropical and temperate communitiesJOURNAL OF BIOGEOGRAPHY, Issue 5 2009Chris Dahl Abstract Aim, To test the hypothesis that animal communities within environmentally relatively uniform lowland forests are characterized by low beta diversity, both in tropical and in temperate areas. Location, Lowland forests in the basins of the Sepik and Ramu rivers in New Guinea, the Amazon river in Bolivia, and the Elbe and Dyje rivers in the Czech Republic. Methods, A network of 5,6 study sites spanning distances from 20,80 to 300,500 km in each study area was systematically surveyed for all frogs, using visual detection and call tracking. The community data were analysed for alpha and beta diversity. Results, Local (alpha) diversity of frog communities was similar in the two tropical areas, New Guinea (mean ± SE of 22 ± 1.4 species per site) and Amazonia (24 ± 1.7 species), but was significantly lower in Europe (8 ± 0.8 species). In Amazonia, 36 of the total of 70 species were recorded from single sites. In contrast, widespread species dominated in Europe, whereas New Guinea exhibited an intermediate pattern with both local and widespread species well represented. The rate of species accumulation across different sites was lowest in Europe, intermediate in New Guinea and highest in Amazonia. The regional species diversity, expressed as the combined number of species from five study sites, was 1.5 times higher than the local species diversity at a single site in Europe, 2.0 times higher in New Guinea and 2.7 times higher in Amazonia. The proportion of species shared between communities decreased with geographic distance in New Guinea and Europe, but not in Amazonia. Main conclusions, Frog communities in the lowland tropical rain forests of New Guinea and Amazonia had similar numbers of species, but differed in their beta diversity. More species in Amazonia had restricted distributions than in New Guinea. Both tropical areas had markedly higher alpha and beta diversity than the temperate area in Europe. [source] Genetic identity of interspecific neighbours mediates plant responses to competition and environmental variation in a species-rich grasslandJOURNAL OF ECOLOGY, Issue 5 2007JASON D. FRIDLEY Summary 1Although outbreeding populations of many grassland plants exhibit substantial genetic and phenotypic variation at fine spatial scales (< 100 m2), the implications of local genetic diversity for community structure are poorly understood. Genetic diversity could contribute to local species diversity by mediating the effects of competition between species and by enhancing species persistence in the face of environmental variation. 2We assayed the performance of three genotypes each of a dominant tussock grass (Koeleria macrantha [Ledeb.] J.A. Schultes) and dominant sedge (Carex caryophyllea Lat.) derived from a single 10 × 10 m quadrat within a limestone grassland in Derbyshire, UK. Genotypes were grown in monoculture and grass,sedge mixtures of different genetic composition in two environments of contrasting fertility. Species mixtures also included one genotype of the subordinate forb Campanula rotundifolia L. 3When grown without neighbours, intraspecific genotypes responded similarly to environmental treatments. One genotype of the sedge performed worse in both environments than the other two sedge genotypes. 4When grown in species mixtures, genotype performance was significantly influenced by the genetic identity of the neighbouring species for both the sedge and the grass. At high fertility, differential genotype performance was not sufficient to alter the expectation of competitive exclusion of the sedge by the grass. However, at low fertility, the competitive dominant depended on the genetic identity of both the grass and the sedge. In addition, each genotype of the grass performed best next to a different genotype of the sedge, and the identity of the best genotype pairings switched with environment. 5Performance of a single genotype of the subordinate Campanula was not predictable by fertility alone, but by how fertility interacted with different neighbouring genotypes of both the grass and the sedge. 6Results support the hypothesis that the genetic identity of interspecific neighbours influences plant performance in multispecies assemblages and mediates species' responses to environmental variation. Such interactions could be a key factor in the contribution of local intraspecific genetic diversity to species diversity. [source] Experimental evidence of habitat provision by aggregations of Riftia pachyptila at hydrothermal vents on the East Pacific RiseMARINE ECOLOGY, Issue 1 2007Breea Govenar Abstract Habitat created or modified by the physical architecture of large or spatially dominant species plays an important role in structuring communities in a variety of terrestrial, aquatic, and marine habitats. At hydrothermal vents, the giant tubeworm Riftia pachyptila forms large and dense aggregations in a spatially and temporally variable environment. The density and diversity of smaller invertebrates is higher in association with aggregations of R. pachyptila than on the surrounding basalt rock seafloor. Artificial substrata designed to mimic R. pachyptila aggregations were deployed along a gradient of productivity to test the hypothesis that high local species diversity is maintained by the provision of complex physical structure in areas of diffuse hydrothermal flow. After 1 year, species assemblages were compared among artificial aggregations in low-, intermediate-, and high-productivity zones and compared to natural aggregations of R. pachyptila from the same site. Hydrothermal vent fauna colonized every artificial aggregation, and both epifaunal density and species richness were highest in areas of high chemosynthetic primary production. The species richness was also similar between natural aggregations of R. pachyptila and artificial aggregations in intermediate- and high-productivity zones, suggesting that complex physical structure alone can support local species diversity in areas of chemosynthetic primary production. Differences in the community composition between natural and artificial aggregations reflect the variability in microhabitat conditions and biological interactions associated with hydrothermal fluid flux at low-temperature hydrothermal vents. Moreover, these local ecological factors may further contribute to the maintenance of regional species diversity in hydrothermal vent communities on the East Pacific Rise. [source] Species-specific Seedling Responses to Hurricane Disturbance in a Puerto Rican Rain Forest1BIOTROPICA, Issue 4 2003Lawrence R. Walker ABSTRACT Seedling dynamics were followed in a Puerto Rican forest for 20 months following a severe hurricane to study the interactive effects of hurricane debris, nutrients, and light on seedling diversity, density, growth, and mortality. Three treatments (debris removal, an unaltered control with hurricane debris, and chemical fertilization added to hurricane debris) altered levels of forest debris and soil nutrients. Canopy openness was measured twice using hemispherical photographs of the canopy. We examined the demographic responses of six common species to treatments over time. Seedling densities increased for all six species but the only significant treatment effects were increased densities of the pioneer tree Cecropia and the shrub Palicourea in the debris removal treatment. Seedling growth declined with declining light levels for four species but not for the pioneer tree Alchornea or the non-pioneer tree Dacryodes. Only Cecropia and the non-pioneer tree Chionanthus had treatment effects on growth. Mortality also differed among species and tended to be highest in the fertilized plots for all but Cecropia and Dacryodes. We found only some of the expected differences between pioneer and non-pioneer plants, as each species had a unique response to the patchy distributions of organic debris, nutrients, and light following the hurricane. High local species diversity was maintained through the individualistic responses of seedlings after a disturbance. RESUMEN Seguimos la dinámica de plántulas en un bosque en Puerto Rico durante 20 meses después del huracán Hugo para estudiar el efecto de la interacción de hojarasca de huracán, nutrientes, y luz sobre la diversidad de especies, la densidad, el crecimiento, y la mortalidad. Establecimos tres tratamientos (remoción de hojarasca, control con la hojarasca de huracán inalterada, y fertilizante químico añadido a la hojarasca del huracán) para alterar los niveles de hojarasca en el bosque y los nutrientes en el suelo. Medimos luz directa e indirecta dos veces usando fotografias hemisféricas del dosel. La diversidad y la uniformidad en la distribución de especies pero no la riqueza de especies fueron reducidas en presencia de fertilización. Durante el estudio examinamos respuestas demográficas de seis especies communes a los tratamientos. La densidad de plántulas aumentó para todas las seis especies pero el único efecto de tratamiento fue el aumento en la densidad del árbol pionero Cecropia y el arbusto Palicourea en el tratamiento de remoción de hojarasca. El crecimiento de plántulas disminuyó según los niveles de luz disminuyeron para cuatro de las especies pero no para el árbol pionero Alchornea o el árbol nopionero Dacryodes. Sólo el crecimiento de Cecropia y del árbol no-pionero Chionanthus fue affectado por los tratamientos. La mortalidad fue diferente entre las especies y tuvo una tendencia a ser mayor en las parcelas fertilizadas. Sólo encontramos algunas de las diferencias esperadas entre plantas pioneras y no-pioneras. Cada especie respondió de forma única a la distribución en parches de hojarasca, nutrientes, y luz luego del huracán. La aha diversidad local de especies se mantuvo a través de las respuestas individualizadas de las plántulas después de la perturbación. [source] | ||||||||||