Species richness

Short description: Variety of species in an ecological community, landscape or region

Global mammal richness (2015) Global amphibian richness (2015)

Species richness is the number of different species represented in an ecological community, landscape or region.[1] Species richness is simply a count of species, and it does not take into account the abundances of the species or their relative abundance distributions. Species richness is sometimes considered synonymous with species diversity, but the formal metric species diversity takes into account both species richness and species evenness.

## Contents

* 1 Sampling considerations
* 2 Trends in species richness
* 3 Applications
* 4 See also
* 5 References
* 6 Further reading

## Sampling considerations

Depending on the purposes of quantifying species richness, the individuals can be selected in different ways. They can be, for example, trees found in an inventory plot, birds observed from a monitoring point, or beetles collected in a pitfall trap. Once the set of individuals has been defined, its species richness can be exactly quantified, provided the species-level taxonomy of the organisms of interest is well enough known. Applying different species delimitations will lead to different species richness values for the same set of individuals.

In practice, people are usually interested in the species richness of areas so large that not all individuals in them can be observed and identified to species. Then applying different sampling methods will lead to different sets of individuals being observed for the same area of interest, and the species richness of each set may be different. When a new individual is added to a set, it may introduce a species that was not yet represented in the set, and thereby increase the species richness of the set. For this reason, sets with many individuals can be expected to contain more species than sets with fewer individuals.

If species richness of the obtained sample is taken to represent species richness of the underlying habitat or other larger unit, values are only comparable if sampling efforts are standardised in an appropriate way. Resampling methods can be used to bring samples of different sizes to a common footing.[2] Properties of the sample, especially the number of species only represented by one or a few individuals, can be used to help estimating the species richness in the population from which the sample was drawn.[3][4][5]

## Trends in species richness

The observed species richness is affected not only by the number of individuals but also by the heterogeneity of the sample. If individuals are drawn from different environmental conditions (or different habitats), the species richness of the resulting set can be expected to be higher than if all individuals are drawn from similar environments. The accumulation of new species with increasing sampling effort can be visualised with a species accumulation curve. Such curves can be constructed in different ways.[6] Increasing the area sampled increases observed species richness both because more individuals get included in the sample and because large areas are environmentally more heterogeneous than small areas.

Many organism groups have most species in the tropics, which leads to latitudinal gradients in species richness. There has been much discussion about the relationship between productivity and species richness. Results have varied among studies, such that no global consensus on either the pattern or its possible causes has emerged.[7]

## Applications

Species richness is often used as a criterion when assessing the relative conservation values of habitats or landscapes. However, species richness is blind to the identity of the species. An area with many endemic or rare species is generally considered to have higher conservation value than another area where species richness is similar, but all the species are common and widespread.

## See also

* Rapoport's rule
* Scaling pattern of occupancy
* Species-area curve
* Species discovery curve
* Storage effect

## References

1. ↑ Colwell, Robert K. (2009). "Biodiversity: Concepts, Patterns and Measurement". in Simon A. Levin. The Princeton Guide to Ecology. Princeton: Princeton University Press. pp. 257–263. https://archive.org/details/princetonguideto00levi.
2. ↑ Colwell, R. K. and Coddington, J. A. (1994) Estimating terrestrial biodiversity through extrapolation. Philosophical Transactions: Biological Sciences, 345, 101–118.
3. ↑ Chao, A. (1984) Non-parametric estimation of the number of classes in a population. Scandinavian Journal of Statistics, 11, 265–270.
4. ↑ Chao, A. (2005) Species richness estimation. Pages 7909–7916 in N. Balakrishnan, C. B. Read, and B. Vidakovic, eds. Encyclopedia of Statistical Sciences. New York, Wiley.
5. ↑ Webb, L. J.; Tracey, J. G.; Williams, W. T.; Lance, G. N. (1969), Studies in the Numerical Analysis of Complex Rain-Forest Communities: II. The Problem of Species-Sampling. Journal of Ecology, Vol. 55, No. 2, Jul., 1967, pp. 525-538, Journal of Ecology, British Ecological Society, https://www.jstor.org/stable/2257891
6. ↑ Scheiner, Samuel M. (October 17, 2003). "Six types of species-area curves". Global Ecology and Biogeography (Wiley) 12 (6): 441–447. doi:10.1046/j.1466-822x.2003.00061.x. ISSN 1466-822X. Bibcode: 2003GloEB..12..441S.
7. ↑ Waide, R. B. et al (1999) The relationship between productivity and species richness. Annual Review of Ecology and Systematics, 30, 257–300.

## Further reading

* Kevin J. Gaston & John I. Spicer. 2004. Biodiversity: an introduction, Blackwell Publishing. 2nd Ed., ISBN 1-4051-1857-1(pbk.)
* Diaz, et al. Ecosystems and Human Well-being: Current State and Trends, Volume 1. Millennium Ecosystem Assessment. 2005. Island Press.

* v
* t
* e

Ecology: Modelling ecosystems: Trophic components

General|

* Abiotic component
* Abiotic stress
* Behaviour
* Biogeochemical cycle
* Biomass
* Biotic component
* Biotic stress
* Carrying capacity
* Competition
* Ecosystem
* Ecosystem ecology
* Ecosystem model
* Keystone species
* List of feeding behaviours
* Metabolic theory of ecology
* Productivity
* Resource

Producers|

* Autotrophs
* Chemosynthesis
* Chemotrophs
* Foundation species
* Mixotrophs
* Myco-heterotrophy
* Mycotroph
* Organotrophs
* Photoheterotrophs
* Photosynthesis
* Photosynthetic efficiency
* Phototrophs
* Primary nutritional groups
* Primary production

Consumers|

* Apex predator
* Bacterivore
* Carnivores
* Chemoorganotroph
* Foraging
* Generalist and specialist species
* Intraguild predation
* Herbivores
* Heterotroph
* Heterotrophic nutrition
* Insectivore
* Mesopredators
* Mesopredator release hypothesis
* Omnivores
* Optimal foraging theory
* Planktivore
* Predation
* Prey switching

Decomposers|

* Chemoorganoheterotrophy
* Decomposition
* Detritivores
* Detritus

Microorganisms|

* Archaea
* Bacteriophage
* Environmental microbiology
* Lithoautotroph
* Lithotrophy
* Microbial cooperation
* Microbial ecology
* Microbial food web
* Microbial intelligence
* Microbial loop
* Microbial mat
* Microbial metabolism
* Phage ecology

Food webs|

* Biomagnification
* Ecological efficiency
* Ecological pyramid
* Energy flow
* Food chain
* Trophic level

Example webs|

* Cold seeps
* Hydrothermal vents
* Intertidal
* Kelp forests
* Lakes
* North Pacific Subtropical Gyre
* Rivers
* San Francisco Estuary
* Soil
* Tide pool

Processes|

* Ascendency
* Bioaccumulation
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* Climax community
* Competitive exclusion principle
* Consumer-resource systems
* Copiotrophs
* Dominance
* Ecological network
* Ecological succession
* Energy quality
* Energy Systems Language
* f-ratio
* Feed conversion ratio
* Feeding frenzy
* Mesotrophic soil
* Nutrient cycle
* Oligotroph
* Paradox of the plankton
* Trophic cascade
* Trophic mutualism
* Trophic state index

Defense,
counter|

* Animal coloration
* Antipredator adaptations
* Camouflage
* Deimatic behaviour
* Herbivore adaptations to plant defense
* Mimicry
* Plant defense against herbivory
* Predator avoidance in schooling fish

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Ecology: Modelling ecosystems: Other components

Population
ecology|

* Abundance
* Allee effect
* Depensation
* Ecological yield
* Effective population size
* Intraspecific competition
* Logistic function
* Malthusian growth model
* Maximum sustainable yield
* Overpopulation in wild animals
* Overexploitation
* Population cycle
* Population dynamics
* Population modeling
* Population size
* Predator–prey (Lotka–Volterra) equations
* Recruitment
* Resilience
* Small population size
* Stability

Species|

* Biodiversity
* Density-dependent inhibition
* Ecological effects of biodiversity
* Ecological extinction
* Endemic species
* Flagship species
* Gradient analysis
* Indicator species
* Introduced species
* Invasive species
* Latitudinal gradients in species diversity
* Minimum viable population
* Neutral theory
* Occupancy–abundance relationship
* Population viability analysis
* Priority effect
* Rapoport's rule
* Relative abundance distribution
* Relative species abundance
* Species diversity
* Species homogeneity
* Species richness
* Species distribution
* Species-area curve
* Umbrella species

Species
interaction|

* Antibiosis
* Biological interaction
* Commensalism
* Community ecology
* Ecological facilitation
* Interspecific competition
* Mutualism
* Parasitism
* Storage effect
* Symbiosis

Spatial
ecology|

* Biogeography
* Cross-boundary subsidy
* Ecocline
* Ecotone
* Ecotype
* Disturbance
* Edge effects
* Foster's rule
* Habitat fragmentation
* Ideal free distribution
* Intermediate Disturbance Hypothesis
* Island biogeography
* Landscape ecology
* Landscape epidemiology
* Landscape limnology
* Metapopulation
* Patch dynamics
* r/K selection theory
* Resource selection function
* Source–sink dynamics

Niche|

* Ecological niche
* Ecological trap
* Ecosystem engineer
* Environmental niche modelling
* Guild
* Habitat
* Marine habitats
* Limiting similarity
* Niche apportionment models
* Niche construction
* Niche differentiation

Other
networks|

* Assembly rules
* Bateman's principle
* Bioluminescence
* Ecological collapse
* Ecological debt
* Ecological deficit
* Ecological energetics
* Ecological indicator
* Ecological threshold
* Ecosystem diversity
* Emergence
* Extinction debt
* Kleiber's law
* Liebig's law of the minimum
* Marginal value theorem
* Thorson's rule
* Xerosere

Other|

* Allometry
* Alternative stable state
* Balance of nature
* Biological data visualization
* Ecocline
* Ecological economics
* Ecological footprint
* Ecological forecasting
* Ecological humanities
* Ecological stoichiometry
* Ecopath
* Ecosystem based fisheries
* Endolith
* Evolutionary ecology
* Functional ecology
* Industrial ecology
* Macroecology
* Microecosystem
* Natural environment
* Regime shift
* Systems ecology
* Urban ecology
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List of ecology topics

cs:Druhová rozmanitost fr:Richesse spécifique ja:種多様性 sl:Vrstna diverziteta zh:物种多样性

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