Species richness

About: Species richness is a research topic. Over the lifetime, 61672 publications have been published within this topic receiving 2183796 citations.

The contribution of species richness and composition to bacterial services

Abstract: Despite their importance, we are only beginning to understand how mixed communities of bacteria operate. There is a good reason for this: the microbial world is remarkably complex and dynamic so it is difficult to design experiments that ask the right questions. Laboratory microcosms are useful but involve small numbers of species in unreal situations. A natural ecosystem that can be manipulated experimentally is available, however. Rainpools that form in bark-lined depressions at the base of European beech trees are communities of up to 72 species, rather than the thousands found in, say, pond water. In this rainpool ecosystem the number of bacterial species (the biodiversity) strongly influences the rate at which the community provides a particular service (in this case, respiration). On this scale at least, species richness determines the level at which an ecosystem can function. Bacterial communities provide important services. They break down pollutants, municipal waste and ingested food, and they are the primary means by which organic matter is recycled to plants and other autotrophs. However, the processes that determine the rate at which these services are supplied are only starting to be identified. Biodiversity influences the way in which ecosystems function1, but the form of the relationship between bacterial biodiversity and functioning remains poorly understood. Here we describe a manipulative experiment that measured how biodiversity affects the functioning of communities containing up to 72 bacterial species constructed from a collection of naturally occurring culturable bacteria. The experimental design allowed us to manipulate large numbers of bacterial species selected at random from those that were culturable. We demonstrate that there is a decelerating relationship between community respiration and increasing bacterial diversity. We also show that both synergistic interactions among bacterial species and the composition of the bacterial community are important in determining the level of ecosystem functioning.

Habitat modification alters the structure of tropical host–parasitoid food webs

Abstract: Global conversion of natural habitats to agriculture has led to marked changes in species diversity and composition. However, it is less clear how habitat modification affects interactions among species. Networks of feeding interactions (food webs) describe the underlying structure of ecological communities, and might be crucially linked to their stability and function. Here, we analyse 48 quantitative food webs for cavity-nesting bees, wasps and their parasitoids across five tropical habitat types. We found marked changes in food-web structure across the modification gradient, despite little variation in species richness. The evenness of interaction frequencies declined with habitat modification, with most energy flowing along one or a few pathways in intensively managed agricultural habitats. In modified habitats there was a higher ratio of parasitoid to host species and increased parasitism rates, with implications for the important ecosystem services, such as pollination and biological control, that are performed by host bees and wasps. The most abundant parasitoid species was more specialized in modified habitats, with reduced attack rates on alternative hosts. Conventional community descriptors failed to discriminate adequately among habitats, indicating that perturbation of the structure and function of ecological communities might be overlooked in studies that do not document and quantify species interactions. Altered interaction structure therefore represents an insidious and functionally important hidden effect of habitat modification by humans.

Potential impact of climate change on vegetation in the European Alps: A review

Abstract: Based on conclusions drawn from general climatic impact assessmentin mountain regions, the review synthesizes results relevant to the European Alps published mainly from 1994 onward in the fields of population genetics, ecophysiology, phenology, phytogeography, modeling, paleoecology and vegetation dynamics Other important factors of global change interacting synergistically with climatic factors are also mentioned, such as atmospheric CO2 concentration, eutrophication, ozone or changes in land-use Topics addressed are general species distribution and populations (persistence, acclimation, genetic variability, dispersal, fragmentation, plant/animal interaction, species richness, conservation), potential response of vegetation (ecotonal shift – area, physiography – changes in the composition, structural changes), phenology, growth and productivity, and landscape In conclusion, the European Alps appear to have a natural inertia and thus to tolerate an increase of 1–2 K of mean air temperature as far as plant species and ecosystems are concerned in general However, the impact of land-use is very likely to negate this buffer in many areas For a change of the order of 3 K or more, profound changes may be expected

Diversity and host range of foliar fungal endophytes: are tropical leaves biodiversity hotspots?

Abstract: Fungal endophytes are found in asymptomatic photosynthetic tissues of all major lineages of land plants. The ubiquity of these cryptic symbionts is clear, but the scale of their diversity, host range, and geographic distributions are unknown. To explore the putative hyperdiversity of tropical leaf endophytes, we compared endophyte communities along a broad latitudinal gradient from the Canadian arctic to the lowland tropical forest of central Panama. Here, we use molecular sequence data from 1403 endophyte strains to show that endophytes increase in incidence, diversity, and host breadth from arctic to tropical sites. Endophyte communities from higher latitudes are characterized by relatively few species from many different classes of Ascomycota, whereas tropical endophyte assemblages are dominated by a small number of classes with a very large number of endophytic species. The most easily cultivated endophytes from tropical plants have wide host ranges, but communities are dominated by a large number of rare species whose host range is unclear. Even when only the most easily cultured species are considered, leaves of tropical trees represent hotspots of fungal species diversity, containing numerous species not yet recovered from other biomes. The challenge remains to recover and identify those elusive and rarely cultured taxa with narrower host ranges, and to elucidate the ecological roles of these little-known symbionts in tropical forests.

Community Patterns in Source‐Sink Metacommunities

Abstract: We present a model of a source‐sink competitive metacommunity, defined as a regional set of communities in which local diversity is maintained by dispersal. Although the conditions of local and regional coexistence have been well defined in such systems, no study has attempted to provide clear predictions of classical community‐wide patterns. Here we provide predictions for species richness, species relative abundances, and community‐level functional properties (productivity and space occupation) at the local and regional scales as functions of the proportion of dispersal between communities. Local (α) diversity is maximal at an intermediate level of dispersal, whereas between‐community (β) and regional (γ) diversity decline as dispersal increases because of increased homogenization of the metacommunity. The relationships between local and regional species richness and the species rank abundance distributions are strongly affected by the level of dispersal. Local productivity and space occupatio...