Topic
Species richness
About: Species richness is a research topic. Over the lifetime, 61672 publications have been published within this topic receiving 2183796 citations.
Papers published on a yearly basis
Papers
More filters
TL;DR: A species-rich and abundant bee assemblage will facilitate high pollination success in lowland coffee and increase fruit set and coffee yield through simple management measures and by increasing the availability of nesting sites for solitary bees.
Abstract: Summary 1. Pollination of crops depends on local agricultural management and the quality of adjacent habitats. Lowland coffee Coffea canephora , is an important tropical cash crop. Fruit set depends on cross-pollination by bees, so inadequate pollination leads to reduced yield. In this study we analyse the relationship between bee pollinators, fruit set in coffee, and the local and regional agroforestry systems to identify the optimal conditions for pollinators. 2. We analysed the abundance and species composition of coffee flower-visiting bees in 15 agroforestry systems differing in distance to forest (important for wood-nesting species), light intensity (important for ground-nesting species), blossom cover of coffee and noncoffee-flowering plants, and species richness of flowering plants (as pollen and nectar resources) in Central Sulawesi (Indonesia). We examined which factors were most important for optimal pollination success. We carried out bagged and open pollination experiments in each agroforestry system, to measure the pollination efficiency of 15 bee species. 3. The number of social bee species decreased with distance to forest, whereas the number of solitary bee species increased with light intensity (less shade) and greater quantities of blossoms. 4. Fruit set of open pollinated flowers (as opposed to manually cross-pollinated flowers) increased with the diversity and abundance of flower-visiting bees. In the agroforestry systems studied, a bee community of 20 species or more led to a higher fruit set (95%) than a species-poor bee community of six species (70% fruit set). 5. Pollination activity by members of the species-rich solitary bee assemblage led to higher levels of fruit set than that arising from pollination activity by members of the more abundant social bee assemblage. 6. Synthesis and applications. A species-rich and abundant bee assemblage will facilitate high pollination success in lowland coffee. This will increase fruit set and coffee yield. Farmers can encourage different species of bees through simple management measures such as growing coffee in shade beneath a variety of trees; by pruning trees to increase levels of sunlight and numbers of flowering herbs; and by increasing the availability of nesting sites for solitary bees. Weed control and the use of herbicides should be kept to a minimum so that a diverse nectar and pollen resource is available to bees throughout the year. Natural forests and forest fragments should be preserved in the vicinity of coffee agroforestry systems (< 500 m) so that forest-nesting social bees can travel easily to the coffee fields to pollinate the flowers.
334 citations
TL;DR: Overall invasion success was negatively related to resident functional group richness, but there was only weak evidence that resident species repelled functionally similar invaders and other factors seem to have been more important to community in- vasibility.
Abstract: Although many theoretical and observational studies suggest that diverse systems are more resistant to invasion by novel species than are less diverse systems, experimental data are uncommon. In this experiment, I manipulated the functional group richness and composition of a grassland community to test two related hypotheses: (1) Diversity and invasion resistance are positively related through diversity's effects on the resources necessary for invading plants' growth. (2) Plant communities resist invasion by species in functional groups already present in the community. To test these hypotheses, I removed plant functional groups (forbs, C3 graminoids, and C4 graminoids) from existing grassland vegetation to create communities that contained all possible combinations of one, two, or three functional groups. After three years of growth, I added seeds of 16 different native prairie species (legumes, nonleguminous forbs, C3 graminoids, and C4 graminoids) to a1 3 1 m portion of each 4 3 8 m plot. Overall invasion success was negatively related to resident functional group richness, but there was only weak evidence that resident species repelled functionally similar invaders. A weak effect of functional group richness on some resources did not explain the significant diversity-invasibility relationship. Other factors, particularly the different responses of resident functional groups to the initial disturbance of the experimental manipulation, seem to have been more important to community in- vasibility.
334 citations
TL;DR: In this article, the authors use the potential of ANNs to deal with some of the persistent fuzzy and nonlinear problems that confound classical statistical methods for species diversity prediction, and show that riverine fish diversity patterns on a global scale can be successfully predicted by geographical patterns in local river conditions.
Abstract: ......... Processes governing patterns of richness of riverine fish species at the global level can be modelled using artificial neural network (ANN) procedures. These ANNs are the most recent development in computer-aided identification and are very different from conventional techniques 1,2 . Here we use the potential of ANNs to deal with some of the persistent fuzzy and nonlinear problems that confound classical statistical methods for species diversity prediction. We show that riverine fish diversity patterns on a global scale can be successfully predicted by geographical patterns in local river conditions. Nonlinear relationships, fitted by ANN methods, adequately describe the data, with up to 93 per cent of the total variation in species richness being explained by our results. These findings highlight the dominant effect of energy availability and habitat heterogeneity on patterns of global fish diversity. Our results reinforce the species-energy theory 3 and
334 citations
TL;DR: This work asks how fast do understory bird species disappear from experimentally isolated plots in the Biological Dynamics of Forest Fragments Project, central Amazon, Brazil, and derives a scaling rule for the time it takes to lose half the species in a fragment as a function of its area.
Abstract: In the face of worldwide habitat fragmentation, managers need to devise a time frame for action. We ask how fast do understory bird species disappear from experimentally isolated plots in the Biological Dynamics of Forest Fragments Project, central Amazon, Brazil. Our data consist of mist-net records obtained over a period of 13 years in 11 sites of 1, 10, and 100 hectares. The numbers of captures per species per unit time, analyzed under different simplifying assumptions, reveal a set of species-loss curves. From those declining numbers, we derive a scaling rule for the time it takes to lose half the species in a fragment as a function of its area. A 10-fold decrease in the rate of species loss requires a 1,000-fold increase in area. Fragments of 100 hectares lose one half of their species in <15 years, too short a time for implementing conservation measures.
334 citations
TL;DR: An approach to analysis of genotypic diversity in plant pathology that makes specific reference to the techniques used for identifying genotypes is developed, and a bootstrapping approach, where confidence intervals are calculated for indices of diversity and evenness is recommended.
Abstract: Grunwald, N. J., Goodwin, S. B., Milgroom, M. G., and Fry, W. E. 2003. Analysis of genotypic diversity data for populations of microorganisms. Phytopathology 93:738-746. Estimation of genotypic diversity is an important component of the analysis of the genetic structure of plant pathogen and microbial populations. Estimates of genotypic diversity are a function of both the number of genotypes observed in a sample (genotype richness) and the evenness of distribution of genotypes within the sample. Currently used measures of genotypic diversity have inherent problems that could lead to incorrect conclusions, particularly when diversity is low or sample sizes differ. The number of genotypes observed in a sample depends on the technique used to assay for genetic variation; each technique will affect the maximum number of genotypes that can be detected. We developed an approach to analysis of genotypic diversity in plant pathology that makes specific reference to the techniques used for identifying genotypes. Preferably, populations that are being compared should be very similar in sample size. In this case, the number of genotypes observed can be used directly for comparing richness. In most cases, sample sizes differ and use of the rarefaction method to calculate richness is more appropriate. In all cases, scaling either Stoddart and Taylor’s G or Shannon and Wiener’s H by sample size should be avoided. Under those circumstances where it might be important to distinguish whether richness or evenness contribute more to diversity, a bootstrapping approach, where confidence intervals are calculated for indices of diversity and evenness, is recommended.
333 citations