Species richness

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

Community structure of ectomycorrhizal fungi in a Pinus muricata forest: minimal overlap between the mature forest and resistant propagule communities.

Abstract: We have investigated colonization strategies by comparing the abundance and frequency of ectomycorrhizal fungal species on roots in a mature Pinus muricata forest with those present as resistant propagules colonizing potted seedlings grown in the same soil samples. Thirty-seven fungal species were distinguished by internal transcribed spacer (ITS) restriction fragment length polymorphisms (RFLPs); most were identified to species level by sporocarp RFLP matches or to genus/family level by using sequence databases for the mitochondrial and nuclear large-subunit rRNA genes. The below-ground fungal community found in the mature forest contrasted markedly with the resistant propagule community, as only four species were found in both communities. The dominant species in the mature forest were members of the Russulaceae, Thelephorales and Amanitaceae. In contrast, the resistant propagule community was dominated by Rhizopogon species and by species of the Ascomycota. Only one species, Tomentella sublilacina (Thelephorales), was common in both communities. The spatial distribution of mycorrhizae on mature roots and propagules in the soil differed among the dominant species. For example, T. sublilacina mycorrhizae exhibited a unique bias toward the organic horizons, Russula brevipes mycorrhizae were denser and more clumped than those of other species and Cenococcum propagules were localized, whereas R. subcaerulescens propagules were evenly distributed. We suggest that species differences in resource preferences and colonization strategies, such as those documented here, contribute to the maintenance of species richness in the ectomycorrhizal community.

Biodiversity effects in the wild are common and as strong as key drivers of productivity

Abstract: More than 500 controlled experiments have collectively suggested that biodiversity loss reduces ecosystem productivity and stability. Yet the importance of biodiversity in sustaining the world's ecosystems remains controversial, largely because of the lack of validation in nature, where strong abiotic forcing and complex interactions are assumed to swamp biodiversity effects. Here we test this assumption by analysing 133 estimates reported in 67 field studies that statistically separated the effects of biodiversity on biomass production from those of abiotic forcing. Contrary to the prevailing opinion of the previous two decades that biodiversity would have rare or weak effects in nature, we show that biomass production increases with species richness in a wide range of wild taxa and ecosystems. In fact, after controlling for environmental covariates, increases in biomass with biodiversity are stronger in nature than has previously been documented in experiments and comparable to or stronger than the effects of other well-known drivers of productivity, including climate and nutrient availability. These results are consistent with the collective experimental evidence that species richness increases community biomass production, and suggest that the role of biodiversity in maintaining productive ecosystems should figure prominently in global change science and policy.

Estimating species richness and accumulation by modeling species occurrence and detectability

Abstract: A statistical model is developed for estimating species richness and accumulation by formulating these community-level attributes as functions of model-based estimators of species occurrence while accounting for imperfect detection of individual species. The model requires a sampling protocol wherein repeated observations are made at a collection of sample locations selected to be representative of the community. This temporal replication provides the data needed to resolve the ambiguity between species absence and nondetection when species are unobserved at sample locations. Estimates of species richness and accumulation are computed for two communities, an avian community and a butterfly community. Our model-based estimates suggest that detection failures in many bird species were attributed to low rates of occurrence, as opposed to simply low rates of detection. We estimate that the avian community contains a substantial number of uncommon species and that species richness greatly exceeds the number of species actually observed in the sample. In fact, predictions of species accumulation suggest that even doubling the number of sample locations would not have revealed all of the species in the community. In contrast, our analysis of the butterfly community suggests that many species are relatively common and that the estimated richness of species in the community is nearly equal to the number of species actually detected in the sample. Our predictions of species accumulation suggest that the number of sample locations actually used in the butterfly survey could have been cut in half and the asymptotic richness of species still would have been attained. Our approach of developing occurrence-based summaries of communities while allowing for imperfect detection of species is broadly applicable and should prove useful in the design and analysis of surveys of biodiversity.

Species-Area Relationship for Stream Fishes

Abstract: We sampled riffle and pool habitats of small streams in Minnesota, Illinois, and Panama to examine variation in species-area relationships within and between the respective fish faunas. For six of the seven steams studied, habitat volume was a better predictor of species richness than was habitat area, and number of individuals was a better predictor of species richness than habitat volume. Slopes of species-volume relationships were similar among regions, but the number of species per unit volume was greater in Panama. Multiple regression analyses indicated that knowledge of habitat complexity and volume did not enhance appreciably the capability of linear models to predict species richness from number of individuals in the sample. These results support the hypothesis that species-area relationships may often be epiphenomena stemming from the more com- prehensive community "samples" intercepted by larger habitat patches. Although number of individuals was the best single predictor of species richness, habitat structure and type clearly influenced species' distributions in some streams, thereby indicating that species- area relationships were not strictly sampling phenomena. An index of habitat complexity based on depth, current, and bottom type was correlated with species richness in two Panama streams. Also, the abundance of individual species was more likely to be correlated with habitat volume in Panama than in Illinois or Minnesota, and species relative abun- dances were more similar between years in Panama than in Illinois or Minnesota streams, especially in pools. These patterns suggest that in streams subject to strong seasonal and annual environmental variation, habitat features are poorer predictors of fish distribution and abundance than in streams subject to less environmental variability. We speculate that annual variability in reproductive success and harsh winters interact to maintain imbalance between the fish assemblages and their habitat in Minnesota. Weak relationships between species richness and habitat volume or complexity may be indicative of population vari- ability and the predominance of extinction/recolonization processes in community orga- nization.