Species–Area Relationship

Abstract

The species–area relationship (SAR) describes the increase in species numbers with increasing area and is often referred to as one of ecology's few genuine laws. Different (mathematical) regression models can be fitted to species–area data to generate a species–area curve. The power model, S = cAz, is the most commonly used, but more than 20 models have been proposed. Community ecologists of the early nineteenth century were the first to propose a mathematical model. Subsequently, the SAR has become an important part of biogeography, macroecology and conservation. Two main types of SARs are described: those generated from sample areas (mainlands) and those generated from isolates (islands), more or less isolated from each other. There are many applications of the SAR: to identify, explain and compare patterns in nature, to extrapolate (upscale) species numbers and to forecast changes in species numbers – for example extinctions from habitat loss.

Key Concepts

  • Species‐area curves result from graphing the model, typically either the power model or the logarithmic model, fitted to species‐area data.
  • Isolate species–area relationships (iSARs) result from a comparison of the number of species on oceanic islands or other types of isolates, for example mountain tops (‘sky islands’) or forest remnants.
  • Sample‐area species–area relationships (saSARs) result by accumulating the number of species when adding new, typically continuous, sample areas (or increase the surveyed area) on mainlands (also referred to as ‘mainland SARs’).
  • Nested sampling areas are spatially organised so that each smaller area is completely contained within the next area, larger than the previous.
  • The z‐value is the exponent of the power‐law SAR and the most preferred SAR measurement. It is often described as the ‘slope’, because it becomes the slope in log–log space, although in reality, z is the rate at which the species–area curve decelerates.
  • Self‐similarity (or scale invariance), resulting if the species–area relationship is power law, causes the same proportional (or percentage) increase in species number for each doubling of area size. The z‐value controls this proportion.
  • Minimum‐area effects (MAEs) result from resource restrictions, when the isolate (or island) becomes too small to sustain viable populations of some species.
  • The equilibrium theory of island biogeography was proposed by MacArthur and Wilson in 1967 to explain species richness of oceanic islands, and also applies to other isolates.

Keywords: species diversity; species area; sample area; isolate; island biogeography; community ecology; power law; z‐value; species extinction; extrapolation

Figure 1. Species–area relationships (SARs) in log–log space, where power‐law SARs become straight lines and logarithmic SARs become convex. We see that one of Gleason's data sets is power law, contrary to his claims. The data points from Gleason's ‘scattered’ (continuous) sample areas fits the logarithmic model, and the data points from the continuous (nested) sample areas fit the power model.
Figure 2. (a) The expected difference between the curve shapes of sample‐area (mainland) and isolate (island) SARs. Islands and other isolates typically have fewer species than same‐size sample areas, because of minimum‐area effects (represented by grey shading). (b) The two processes of species extinction from habitat loss: (1) the original number of species, (2) the number after the immediate extinctions from decreased area and (3) the number after relaxation of species numbers down to equilibrium.
Figure 3. (a) The P2‐model fitted in transformed (log–log) space to Deshaye and Morisset's (1988) data of plants on Canadian island (Richmond Gulf). This SAR is distinctly sigmoid (though convex upward in log–log space, wherefore the inflection point is indicated), and the sigmoid P2‐model fits better than for example the convex power model. (b) Illustration of how log‐transforming the dependent variable (S) can affect the shape of the fitted SAR, based on Wright's data from the West Indies. The unbroken species–area curve is fitted with log S and the dashed line with (untransformed) S.
Figure 4. (a) The expected variation of the z‐value (slope in log–log space) between small (local), provincial (regional) and interprovincial (continental) scales to form a triphasic sample‐area SAR. From Preston's original bird data set. (b) A logarithmic breakpoint regression fitted to Nierings data on plants of the Kapingamaringi Atoll, illustrating how researchers have chosen to identify what is called the small‐island effect. Note that the curve in (b) is plotted in log‐linear space (whereas the curves in (a) are plotted in log–log space).
Figure 5. (a) The differences between power‐law species–area curves (plotted in log–log space) for birds (open squares and dashed lines) and reptiles (filled circles and unbroken line), recalculated from Wright's data of the West Indies. (b) The difference between mainland (filled squares and dashed line) and island (open circles and unbroken line) power‐law species–area curves, calculated from Heaney's data for mammalians in parts of Central Asia.
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References

Arrhenius O (1921) Species and area. Journal of Ecology 9: 95–99.

Arrhenius O (1923) On the relation between species and area – a reply. Ecology 4: 90–91.

Brooks TM, Pimm SL and Oyugi JO (1999) Time lag between deforestation and bird extinction in tropical forest fragments. Conservation Biology 13: 1140–1150.

Coleman B (1981) On random placement and species‐area relations. Mathematical Biosciences 54: 191–215.

Darlington PJ (1957) Zoogeography: The Geographical Distribution of Animals. New York, NY: John Wiley & Sons, Inc.

de Candole A (1855) Géographie botanique raisonnée: ou l'exposition des faits principaux et des lois concernant la distribution géographique des plates de l'epoque actuelle. Paris: Maisson.

Dengler J (2009) Which function describes the species‐area relationship best? A review and empirical evaluation. Journal of Biogeography 36: 728–744.

Dengler J (2010) Robust methods for detecting a small‐island effect. Diversity and Distributions 16: 256–266.

Deshaye J and Morisset P and (1988) Floristic richness, area and habitat diversity in an hemiarctic archipelago. Journal of Biogeography 15: 747–757.

Drakare S, Lennon JJ and Hillebrand H (2006) The imprint of geographical, evolutionary and ecological context on species‐area relationships. Ecology Letters 9: 215–227.

Fattorini S (2006) Detecting biodiversity hotspots by species‐area relationships: a case study of Mediterranean beetles. Conservation Biology 20: 1169–1180.

Fisher RA, Corbet AS and Williams CB (1943) The relation between the number of species and the number of individuals in a random sample of an animal population. Journal of Animal Ecology 12: 42–58.

Gleason HA (1922) On the relation between species and area. Ecology 3: 158–162.

Harte J, Kinzig A and Green J (1999) Self‐similarity in the distribution and abundance of species. Science 284: 334–336.

He F and Hubbell SP (2011) Species‐area relationships always overestimate extinction rates from habitat loss. Nature 473: 368–371.

Heaney L (1984) Mamalian species richness on islands on the Sunda Shelf, Southeast Asia. Oecologia 61: 11–17.

Hubbell SP (2001) The Unified Neutral Theory of Biodiversity and Biogeography. Princeton, NJ: Princeton University Press.

Lomolino MV and Weiser MD (2001) Towards a more general species‐area relationship: diversity of all islands, great and small. Journal of Biogeography 28: 431–445.

MacArthur RH and Wilson EO (1967) The Theory of Island Biogeography. Princeton, NJ: Princeton University Press.

Martin HG and Goldenfeld N (2006) On the origin and robustness of power‐law species‐area relationships in ecology. Proceedings of the National Academy of Sciences of the United States of America 103: 10310–10315.

May RM (1975) Patterns of species abundance and diversity. In: Cody ML and Diamond JM (eds) Ecology and Evolution of Communities, pp. 81–120. Cambridge, MA: Belknap Harvard University.

Niering WA (1963) Terrestrial ecology of Kapingamarangi Atoll, Caroline Islands. Ecological Monographs 33: 131–160.

Pimm SL and Raven P (2000) Extinction by numbers. Nature 403: 843–845.

Plotkin JB, Potts MD, Yu DW, et al. (2000) Predicting species diversity in tropical forests. Proceedings of the National Academy of Sciences of the United States of America 97: 10850–10854.

Preston FW (1960) Time and space and the variation of species. Ecology 41: 611–627.

Preston FW (1962) The canonical distribution of commonness and rarity: Part I & II. Ecology 43: 185–215, 410–432.

Romell L‐G (1920) Sur la régle de distribution de fréquences. Svensk Botanisk Tidsskrift 14: 1–20.

Rosenzweig ML (1995) Species Diversity in Space and Time. Cambridge, UK: Cambridge University Press.

Rybicki J and Hanski I (2013) Species‐area relationships and extinctions caused by habitat loss and fragmentation. Ecology Letters 16 (Suppl): 27–38.

Santos AMC, Whittaker RJ, Triantis KA, et al. (2010) Are species‐area relationships from entire archipelagos congruent with those of their constituent islands? Global Ecology & Biogeography 19: 527–540.

Scheiner SM (2003) Six types of species‐area curves. Global Ecology & Biogeography 12: 441–447.

Schoener TW (1976) The species‐area relations within archipelagoes: models and evidence from island land birds. Proceedings of the XVI International Ornithological Congress, pp 629–642.

Simberloff DS and Abele LG (1976) Island biogeography and conservation practice. Science 191: 285–286.

Šizling AL and Storch D (2004) Power‐law species‐area relationships and self‐similar distributions within finite areas. Ecology Letters 7: 60–68.

Šizling AL and Storch D (2007) Geometry of species distributions: random clustering and scale invariance. In: Storch D, Marquet PA and Brown JH (eds) Scaling Biodiversity, pp. 77–1000. Cambridge, UK: Cambridge University Press.

Tjørve E (2003) Shapes and functions of species‐area curves: a review of possible models. Journal of Biogeography 30: 827–835.

Tjørve E and Tjørve KMC (2008) The species–area relationship, self‐similarity, and the true meaning of the z‐value. Ecology 89: 3528–3533.

Tjørve E, Kunin WE, Polce C and Tjørve KMC (2008) The species–area relationship: separating the effects of species‐abundance and spatial distribution. Journal of Ecology 96: 1141–1151.

Tjørve E (2009) Shapes and functions of species‐area curves (II): a review of new models and parameterizations. Journal of Biogeography 36: 1435–1445.

Tjørve E and Turner WR (2009) The importance of samples and isolates for species‐area relationships. Ecography 32: 391–400.

Tjørve E (2010) How to resolve the SLOSS debate: Lessons from species‐diversity models. Journal of Theoretical Biology 264: 604–612.

Tjørve E and Tjørve KMC (2011) Subjecting the theory of the small‐island effect to Ockham's razor. Journal of Biogeography 38: 1834–1839.

Triantis KA, Guilhaumon F and Whittaker RJ (2012) The island species‐area relationship: biology and statistics. Journal of Biogeography 39: 215–231.

Turner WR and Tjørve E (2005) Scale‐dependence in species‐area relationships. Ecography 28: 721–730.

Ulrich W and Buszko J (2005) Detecting biodiversity hotspots using species‐area and endemics‐area relationships. Biodiversity and Conservation 14: 1977–1988.

Veech JA (2000) Choice of species‐area function affects identification of hotspots. Conservation Biology 14: 140–147.

Watson HC (1859) Cybele Britannica, or British plants and their geographical relations. London, UK: Longman and Company.

Whitehead DR and Jones CE (1969) Small islands and the equilibrium theory of insular biogeography. Evolution 23: 171–179.

Wiens HJ (1962) Atoll Environment and Ecology. New Haven, CT: Yale University Press.

Williams CB (1964) Patterns in the Balance of Nature. London, UK: Academic Press.

Wright SJ (1981) Intra‐archipelago vertebrate distributions; the slope of the species‐area relation. American Naturalist 118: 726–748.

Further Reading

Connor EF and McCoy ED (1979) The statistics and biology of the species‐area relationship. American Naturalist 113: 791–833.

Connor EF and McCoy ED (2001) Species‐area relationships. In: Levin SA (ed.) Encyclopedia of Biodiversity, vol. 5, pp. 397–411. San Diego, CA: Academic Press.

Griffin DA (2011) Diversity theories. In: Millington A, Blumer M and Schickhoff U (eds) The SAGE Handbook of Biogeography, pp. 43–56. London, UK: SAGE Publications.

Lomolino MV (2000) Ecology's most general, yet protean pattern: the species‐area relationship. Journal of Biogeography 27: 17–26.

Lomolino MV and Weiser MD (2001) Towards a more general species‐area relationship: diversity of all islands, great and small. Journal of Biogeography 28: 431–445.

Lomolino MV, Sax DF and Brown JH (eds) (2004) Foundations of Biogeography: Classic Papers with Commentaries. Chicago, IL: University of Chicago Press.

Lomolino MV, Riddle BR, Whittaker RJ and Brown JH (2010) Biogeography, 4th edn. Sunderland, MA: Sinauer Associates.

Rosenzweig M (2004) Applying species‐area relationships to the conservation of species diversity. In: Lomolino MV and Heaney L (eds) Frontiers in Biogeography : New Directions in the Geography of Nature, pp. 325–344. Sunderland, MA: Sinauer.

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Tjørve, Even, and Tjørve, Kathleen MC(Jan 2017) Species–Area Relationship. In: eLS. John Wiley & Sons Ltd, Chichester. http://www.els.net [doi: 10.1002/9780470015902.a0026330]