Latitudinal Diversity Gradients


The diversity of organisms tends to increase from the poles to the equator, a trend that is consistent over space and time. More than 30 hypotheses have been advanced to explain the phenomenon and although no consensus has yet been reached, support for the role of contemporary climate dominates the current literature. However, an integration of contemporary ecological and historical (phylogeny‚Äźbased) explanations is increasingly advocated. Most hypotheses are likely to be valid at some range of spatial scales, with mechanisms often showing interdependencies at different scales. With a continuing rise in the number of hypotheses, there is an increasing emphasis on empirical testing and falsification.

Keywords: scale; altitudinal diversity gradient; latitudinal gradient; diversity theories

Figure 1.

(a) Geographical patterns of species richness for Australian birds at a 27.5 km resolution. Reproduced from Hawkins et al. (2005) Water links the historical and contemporary components of the Australian bird diversity gradient. Journal of Biogeography 32: 1035–1042, by permission of Blackwell Publishing. (b) Geographical patterns of continental bird species richness in the Western Hemisphere at a 27.5 km resolution. Reproduced from Hawkins et al. (2006) Post‐Eocene climate change, niche conservatism, and the latitudinal diversity gradient of New World birds. Journal of Biogeography 33: 770–780, by permission of Blackwell Publishing.

Figure 2.

The ‘area hypothesis’ and biodiversity (circles represent species). (a) The tropics cover a greater area than high latitudes thus containing greater regional and local diversity. (b) If diversity gradients were purely the result of total area we would expect other great circles to have a higher diversity than their ‘poles’. Redrawn from Turner (2004) Explaining the global biodiversity gradient: energy, area, history and natural selection. Basic and Applied Ecology, 5: 435–448, copyright 2004, with permission from Elsevier.


Further Reading

Brown JH, Gillooly JF, Allen AP, Savage VM and West GB (2004) Toward a metabolic theory of ecology. Ecology 85: 1771–1789.

Colwell RK, Rahbek C and Gotelli NJ (2004) The mid‐domain effect and species richness patterns: what have we learned so far? The American Naturalist 163(3): E1–E23.

Currie DJ, Mittelbach MM, Cornell HV et al. (2004) Predictions and tests of climate‐based hypotheses of broad‐scale variation in taxonomic richness. Ecology Letters 7: 1121–1134.

Dungan JL, Perry JN and Dale MRT (2002) A balanced view of scale in spatial statistical analysis. Ecography 25: 626–640.

Field R, O'Brien EM and Whittaker RJ (2005) Global models for predicting woody plant richness from climate: development and evaluation. Ecology 86: 2263–2277.

Fine PVA and Ree RH (2006) Evidence for a time‐integrated species‐area effect on the latitudinal gradient in tree diversity. The American Naturalist 168(6): 796–804.

Hawkins BA, Field R, Cornell HV et al. (2003) Energy, water and broad‐scale geographic patterns of species richness. Ecology 84: 3105–3117.

Hurlbert AH and White EP (2005) Disparity between range map‐ and survey‐based analyses of species richness: patterns processes and implications. Ecology Letters 8: 319–327.

Jablonski D, Roy K and Valentine JW (2006) Out of the tropics: evolutionary dynamics of the latitudinal diversity gradient. Science 314: 102–106.

Lomolino MV and Heaney LR (eds) (2004) Frontiers of Biogeography: New Directions in the Geography of Nature, Part III, pp. 145–231. Sunderland, MA: Sinauer Associates.

Rahbek C (2005) The role of spatial scale and the perception of large‐scale species‐richness patterns. Ecology Letters 8: 224–239.

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

Wiens JJ and Donoghue MJ (2004) Historical biogeography, ecology and species richness. Trends in Ecology and Evolution 19: 639–644.

Willig MR, Kaufman DM and Stevens RD (2003) Latitudinal gradients of biodiversity: pattern, process, scale and synthesis. Annual Review of Ecology, Evolution and Systematics 34: 273–309.

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Gough, Lauren, and Field, Richard(Sep 2007) Latitudinal Diversity Gradients. In: eLS. John Wiley & Sons Ltd, Chichester. [doi: 10.1002/9780470015902.a0003233.pub2]