1500. 1200. 900. Number of species. 600. 300. 0. -80. -40. 0. 40. 80. Latitude. Latitudinal gradients. Species – latitude relationship of birds across the New World show the typical pattern of increased species diversity towards the equator. Coral reef fish. Labridae.
Number of species
Species – latitude relationship of birds across the New World show the typical pattern of increased species diversity towards the equator.
Mora et al. 2003
Diversity of coral reef fish declines from their centres of diversity.
There is also a strong correlation between distance and duration of the pelagic phase, which is a proxi of dispersal ability.
Latitudinal gradient in species diversity of mollusks on North and South American Pacific shelves (Valdovino et al. 2003)
Hillebrand (2004) conducted a meta-analysis about 581 published latitudinal gradients
The sawfly Arge coccinea, Photo by Tom Murray
Soybean aphid, Photo by David Voegtlin
The ichneumonid Arotes sp., Photo by Tom Murray
The aquatic macrophyte Hydrilla verticilliata, Photo by FAO
These taxa are most species rich in the northern Hemisphere
Some theories that try to explain observed latitudinal gradients in species diversity.
and Sanders 1969)
Latitudinal decrease in
angle of sun
et al.. 1986)
et al.. 1986)
Number of habitats
Time related explanations:
(Connor and McCoy 1979)
Temperature dependence of
Range size related explanation:
Random range sizes
(Gillooly et al. 2005)
Energy related explanations:
Ice age refuges
North American grasshoppers
Red data points: Multihabitat gradient in ant species diversity
Blue data points: Gradient for one habitat type
Latitudinal gradients can also be found within single habitat types
Energy or area per se
Ant species richness is significantly correlated to mean annual temperature and mean primary production, but not to area
The refuge theory of Pianka tries to explain the gradient in species diversity from ice age refuges in which speciation rates were fast. This process is thought to result in a multiplication of species numbers in the tropics. In the temperate regions without refuges species number remained more or less constant.
Western Atlantic gastropods
Eastern Pacific gastropods
Species diversity of marine gastropods is significantly correlated with mean surface water temperature
Metabolic theory and species latitudinal gradients in species richness
The inverse of time are rates.
Examples: Growth rates, mutation rates, species turnover rates, migration rates
Hence biological rates should scale to body weight and temperature by
Biological times should scale to body weight to the quarter power
Examples: Generation time, lifespan, age of maturation, average lifetime of a species
Body weight corrected energy use should exponentially scale to the inverse of temperature.
The slope –E/k should be a universal constant for all species independent of body size.
Body size specific metabolic rate M/W should scale to the quarter power to body weight and exponentially to temperature
Now assume that most mutations are neutral and occur randomly. That is we assume that the neutral theory of population genetics (Kimura 1983)
DNA substitution rate a should be proportional to M/W
The energy equivalence rule
The average abundance N of an assemblage of S species and J individuyals in areal A is N=J/SA
For standard areals and species of similar body size holds therefore
North American trees
North American amphibians
Prosobranchia species richness
Ectoparasites of marine teleosts
Fish species richness
Latitudinal gradients: http://en.wikipedia.org/wiki/Latitudinal_gradients_in_species_diversity
Gaston K. 2000 - Global patterns in biodiversity - Nature 405: 220-227
Allen A. P., Brown J. H., Gillooly J. F. 2002. Global biodiversity, biochemical kinetics, and the energy equivalence rule. Science 297: 1545-1548.