Topic
Species richness
About: Species richness is a research topic. Over the lifetime, 61672 publications have been published within this topic receiving 2183796 citations.
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TL;DR: In this paper, a comprehensive review of 73 historical reports of insect declines from across the globe, and systematically assess the underlying drivers of insect extinction, reveals dramatic rates of decline that may lead to the extinction of 40% of the world's insect species over the next few decades.
1,754 citations
TL;DR: An extensive survey of the literature is conducted and a synthetic assessment of the degree to which variation in patterns is a consequence of characteristics of scale or taxon is provided.
Abstract: ▪ Abstract The latitudinal gradient of decreasing richness from tropical to extratropical areas is ecology's longest recognized pattern. Nonetheless, notable exceptions to the general pattern exist, and it is well recognized that patterns may be dependent on characteristics of spatial scale and taxonomic hierarchy. We conducted an extensive survey of the literature and provide a synthetic assessment of the degree to which variation in patterns (positive linear, negative linear, modal, or nonsignificant) is a consequence of characteristics of scale (extent or focus) or taxon. In addition, we considered latitudinal gradients with respect to generic and familial richness, as well as species evenness and diversity. We provide a classification of the over 30 hypotheses advanced to account for the latitudinal gradient, and we discuss seven hypotheses with most promise for advancing ecological, biogeographic, and evolutionary understanding. We conclude with a forward-looking synthesis and list of fertile areas f...
1,730 citations
TL;DR: A formal meta-analysis of studies that have experimentally manipulated species diversity to examine how it affects the functioning of numerous trophic groups in multiple types of ecosystem suggests that the average effect of decreasing species richness is to decrease the abundance or biomass of the focal Trophic group, leading to less complete depletion of resources used by that group.
Abstract: Over the past decade, accelerating rates of species extinction have prompted an increasing number of studies to reduce species diversityexperimentallyandexaminehowthisalterstheefficiency by which communities capture resources and convert those into biomass 1,2 . So far, the generality of patterns and processes observed in individual studies have been the subjects of considerable debate 3–7 .Here wepresent aformal meta-analysis of studies thathaveexperimentallymanipulatedspeciesdiversitytoexamine how it affects the functioning of numerous trophic groups in multiple types of ecosystem. We show that the average effect of decreasing species richness is to decrease the abundance or biomass of the focal trophic group, leading to less complete depletion of resources used by that group. At the same time, analyses reveal that the standing stock of, and resource depletion by, the most species-rich polyculture tends to be no different from that of the single most productive species used in an experiment. Of the known mechanisms that might explain these trends, results are most consistent with what is called the ‘sampling effect’, which occurs when diverse communities are more likely to contain and become dominated by the most productive species. Whether this mechanism is widespread in natural communities is currently controversial. Patterns we report are remarkably consistent for four different trophic groups (producers, herbivores, detritivores and predators) and two major ecosystem types (aquatic and terrestrial). Collectively, ouranalysessuggestthat theaverage species loss does indeed affect the functioning of a wide variety of organisms and ecosystems, but the magnitude of these effects is ultimatelydeterminedbytheidentityofspeciesthataregoingextinct.
1,691 citations
TL;DR: The methods proposed to identify prior- ity areas for conservation of the genetic resources of the argan tree are compared to those sometimes advo- cated in the case of reserve design, where one of the goals is to maximize species richness.
Abstract: To select candidate populations of wild species to be given priority for conservation, genetic criteria gained from the study of molecular markers may be useful. Traditionally, diversity measures such as ex- pected heterozygosity or percentage of polymorphic loci have been considered. For conservation we propose instead that priority should be given to measures of allelic richness. To standardize the results of allelic rich- ness across populations, we used the technique of rarefaction. This technique allows evaluation of the ex- pected number of different alleles among equal-sized samples drawn from several different populations. We also show how the contribution of each population to total diversity can be partitioned into two components. The first is related to the level of diversity of the population and the second to its divergence from the other populations. For conservation purposes the uniqueness of a population-in terms of its allelic composition- may be at least as important as its diversity level. These new descriptors are illustrated by means of isozyme and chloroplast DNA data obtainedfor an endangered tree species, the argan tree of Morocco (Argania spinosa (L.) Skeels). With these analyses the conservation value of the argan tree populations, especially those of two isolates present in the north of the country, can be better appreciated. The methods proposed to identify prior- ity areas for conservation of the genetic resources of the argan tree are compared to those sometimes advo- cated in the case of reserve design, where one of the goals is to maximize species richness.
1,621 citations
TL;DR: The abundance of individuals in microbial species is so large that dispersal is rarely (if ever) restricted by geographical barriers, and this “ubiquitous” dispersal requires an alternative view of the scale and dynamics of biodiversity at the microbial level.
Abstract: The abundance of individuals in microbial species is so large that dispersal is rarely (if ever) restricted by geographical barriers. This “ubiquitous” dispersal requires an alternative view of the scale and dynamics of biodiversity at the microbial level, wherein global species number is relatively low and local species richness is always sufficient to drive ecosystem functions.
1,614 citations