The hypothesis of effective evolutionary time offers a causal explanation of diversity gradients, although it is recognized that many other factors can also contribute to and modulate them.
[5] Genera of Foraminifera in the Cretaceous and families of Brachiopoda in the Permian have greater evolutionary rates at low than at high latitudes.
[6] That mutation rates are greater at high temperatures has been known since the classical investigations of Nikolay Timofeev-Ressovsky et al. (1935),[7] although few later studies have been conducted.
It proposes that species diversity is a direct consequence of temperature-dependent processes and the time ecosystems have existed under more or less equal conditions.
[8] Thus, diversity of marine benthos, interrupted by some collapses and plateaus, has risen from the Cambrian to the Recent, and there is no evidence that saturation has been reached.
[11] Gillooly et al. (2002) described a general model also based on first principles of allometry and biochemical kinetics which makes predictions about generation times as a function of body size and temperature.
[12] Empirical findings support the predictions: in all cases that were investigated (birds, fish, amphibians, aquatic insects, zooplankton) generation times are negatively correlated with temperature.
[13] Indirect evidence points to increased mutation rates at higher temperatures,[14][15] and the energy-speciation hypothesis is the best predictor for species richness of ants.
[16] Finally, computer simulations using the Chowdhury ecosystem model have shown that results correspond most closely to empirical data when the number of vacant niches is kept large.
He also pointed out that exposure to irradiation including light is known to cause mutations in mammals, and that some homoiothermic animals have shorter generation times in the tropics, which - either separately or jointly - may explain the effect found by Gillman et al.[20] Gillman et al. (2010) extended their earlier study on plants [21] by determining whether the effect is also found within highly conserved DNA.
[25] Although our knowledge is still very fragmentary, some recent studies appear to suggest much greater species numbers (e.g., Grassle and Maciolek 1992: 10 million macroinvertebrates in soft bottom sediments of the deepsea).