Rapoport’s rule is an ecological hypothesis that states that latitudinal ranges of plants and animals are generally smaller at lower than at high latitudes.

  Background

Stevens (1989)^[1] named the rule after Eduardo H. Rapoport, who had earlier provided evidence for the phenomenon for subspecies of mammals (Rapoport 1975^[2], 1982^[3]). Stevens used the rule to “explain” greater species diversity in the tropics in the sense that latitudinal gradients in species diversity and the rule have identical exceptional data and so must have the same underlying cause. Narrower ranges in the tropics would facilitate more species to coexist. He later extended the rule to altitudinal gradients, claiming that altitudinal ranges are greatest at greater altitudes (Stevens 1992 ^[4]), and to depth gradients in the oceans (Stevens 1996 ^[5]). The rule has been the focus of intense discussion and given much impetus to exploring distributional patterns of plants and animals. Stevens’ original paper has been cited about 330 times in the scientific literature.

  Generality of the rule

Support for the generality of the rule is at best equivocal^[6]. For example, marine teleost fishes have the greatest latitudinal ranges at low latitudes^[7][8]. In contrast, freshwater fishes do show the trend, although only above a latitude of about 40 degrees North^[8]. Some subsequent papers have found support for the rule, others, probably even more numerous, have found exceptions to it ^[6][9]. For most groups that have been shown to follow the rule, it is restricted to or at least most distinct above latitudes of about 40-50 degrees. Rohde therefore concluded that the rule describes a local phenomenon^[10]. Computer simulations using the Chowdhury Ecosystem Model did not find support for the rule.^[11]

  Explanations of the rule

Rohde (1996)^[10] explained the fact that the rule is restricted to very high latitudes by effects of glaciations which have wiped out species with narrow ranges, a view also expressed by Brown (1995)^[12]. Another explanation of Rapoport’s rule is the “climatic variability” or “seasonal variability hypothesis”^[13][5]. According to this hypothesis, seasonal variability selects for greater climatic tolerances and therefore wider latitudinal ranges (see also Fernandez and Vrba 2005^[14]).

  Methods used to demonstrate the rule

The methods used to demonstrate the rule have been subject to some controversy. Most commonly, authors plot means of latitudinal ranges in a particular 5° latitudinal band against latitude, although modal or median ranges have been used by some^[15]. In the original paper by Stevens, all species occurring in each band were counted, i.e., a species with a range of 50 degrees occurs in 10 or 11 bands. However, this may lead to an artificial inflation of latitudinal ranges of species occurring at high latitudes, because even a few tropical species with wide ranges will affect the means of ranges at high latitudes, whereas the opposite effect due to high latitude species extending into the tropics is negligible: species diversity is much smaller at high than low latitudes. – As an alternative method the “midpoint method” has been proposed, which avoids this problem. It counts only those species with the midpoint of their ranges in a particular latitudinal band^[8]. An additional complication in assessing Rapoport's rule for data based on field sampling is the possibility of a spurious pattern driven by a sample-size artifact. Equal sampling effort at species-rich and species-poor localities tends to underestimate range size at the richer localities relative to the poorer, when in fact range sizes might not differ among localities^[16].

  Biotic and abiotic factors which act against the rule

Marine benthic invertebrates and some parasites have been shown to have smaller dispersal abilities in cold seas (Thorson's rule), which would counteract Rapoport’s rule. The tropics have far more uniform temperatures over a far wider latitudinal range (about 45 degrees) than high latitude species. As temperature is one of the most important (if not the most important) factor determining geographical distribution, wider latitudinal ranges in the tropics might therefore be expected.

  Evolutionary age and Rapoport’s rule

The inconsistent results concerning Rapoport’s rule suggest that certain characteristics of species may be responsible for their different latitudinal ranges. These characteristics may include, for example, their evolutionary age: species that have evolved recently in the tropics may have small latitudinal ranges because they have not had the time to spread far from their origin, whereas older species have extended their ranges^[17].

  See also

• Biantitropical distribution
• Thorson's rule

  External links

• Rapoport's rule

  Literature

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 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 Mesopredator release hypothesis Omnivores Optimal foraging theory 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 Tidal pool Processes Ascendency Bioaccumulation Cascade effect 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 Herbivore adaptations to plant defense Mimicry Plant defense against herbivory Predator avoidance in schooling fish

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 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 Storage effect Spatial ecology Biogeography Cross-boundary subsidy Ecocline Ecotone Ecotype Disturbance Edge effect 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 Source–sink dynamics Niche Ecological niche Ecological trap Ecosystem engineer Environmental niche modelling Guild Habitat 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 Constructal theory 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 Systems ecology Theoretical ecology List of ecology topics