Biodiversity, temperature, and energy David Storch Center for Theoretical Study & Department of Ecology, Faculty of Science Charles University, Czech Republic
Global diversity gradients energy-related variables are consistent predictors of diversity latitudinal diversity gradient is fully attributable to energy-related variables birds 600 7 Model residuals 400 200 0-200 -400 log number log (počet of druhů) species 6 5 4 3 2 1-600 Latitude 0 0 1 2 3 4 5 6 7 8 Log AET
The more-individuals hypothesis more energy higher total number of individuals N more species with viable populations spp rich (1km x1km) 50 40 30 20 10 0 7 9 11 13 15 sqrt total density (1km x1km) 60 40 20 0 7 9 11 13 15 summer temperature ( C) summer temperature ( C) lower extinction probability more species S Evans KL, Newson SE, Storch D et al. (2008) J.Anim.Ecol. 77: 395-405.
Storch D (2012) in Metabolic ecology: The scaling approach. ed. Sibly, Brown, Kodric-Brown, Wiley-Blackwell. The more-individuals hypothesis Species-energy relationship does not seem to be mediated by the number of individuals Theory (the More Individuals Hypothesis) Gentry forest plots Birds on productivity gradient in SA environment (productivity) total number of individuals number of species
Metabolic theory of biodiversity history of ideas Allen et al. 2002 assumptions predictions Allen et al. 2006 assumptions metabolic rate increases with temperature B ~ e -E/kT energy equivalence rule holds across temperature gradients total numbers of individuals does not depend on T population densities of ectotherms decreases with T molecular evolution rate increases with T R e ~ e -E/kT speciation rate increases with T R s ~ e -E/kT Allen, Brown & Gillooly 2002 Science 297: 1545 species richness scales with T S ~ e -E/kT logs ~ -E(1/kT) Allen, Gillooly, Savage & Brown 2006 PNAS 103: 9130
Metabolic theory of biodiversity current version Allen, Gillooly & Brown 2007 Scaling biodiversity (eds. Storch, Brown & Marquet) Cambridge UP
Metabolic theory of biodiversity - predictions Predictions if everything else is equal: S ~ e -E/kT, logs ~ -E(1/kT) Wang, Brown, Tang & Fang 2009 PNAS 106: 13388
Metabolic theory of biodiversity empirical patterns are often different Predictions if everything else is equal: S ~ e -E/kT, logs ~ -E(1/kT) Hawkins et al. 2007 Ecology 88: 1877
Metabolic theory of biodiversity testing through spatial patterns is problematic Predictions if everything else is equal: S ~ e -E/kT, logs ~ -E(1/kT) Hawkins et al. 2007 Ecology 88: 1877
Metabolic theory of biodiversity predicted slope sometimes holds Predictions if everything else is equal: S ~ e -E/kT, logs ~ -E(1/kT) Stegen, Enquist & Ferriere 2009 Ecology Letters, 12: 1001-1015 Hawkins et al. 2007 Ecology 88: 1877
Metabolic theory of biodiversity predicts actually diversification Predictions if everything else is equal: S ~ e -E/kT, logs ~ -E(1/kT) environmental temperature affects diversification only in ectotherms
Metabolic theory of biodiversity tests using endotherms x ectotherms Predictions if everything else is equal: S ~ e -E/kT, logs ~ -E(1/kT) environmental temperature affects diversification only in ectotherms Plethodontid salamanders x Carnivora well-resolved phylogenies + distribution two major approaches which relate traits to diversification: (1) ancestral reconstruction+pglm & (2) QuaSSE (Quantitative State Speciation and Extinction) results mutually consistent (also for other methods) Macháč, Zrzavý, Smrčková & Storch 2012 J.Evol.Biol. 25: 2449-2456
Metabolic theory of biodiversity or diversification? Predictions if everything else is equal: S ~ e -E/kT, logs ~ -E(1/kT) environmental temperature affects diversification only in ectotherms Problem: diversity patterns are just opposite! MTE may be rather a theory of diversification than of diversity patterns Macháč, Zrzavý, Smrčková & Storch 2012 J.Evol.Biol. 25: 2449-2456 Kozak & Wiens 2012 Ecology 93: S167-S181
When is diversity decoupled from diversification? Non-equilibrium situation (time-for-diversification hypothesis) diversifica!on rates (tropics as a cradle)!me for diversifica!on (tropics as a museum) temperate tropics
When is diversity decoupled from diversification? Non-equilibrium situation (time-for-diversification hypothesis) Equilibrium situation diversity is bounded, and speciation is balanced by extinction But diversity patterns often emerge regardless of particular evolutionary history Hawkins et al. 2012 J.Biogeogr. 39: 825-841
Is diversity bounded? evolutionary diversification have a tendency to slow-down Rabosky & Glor 2010 PNAS 107: 22178-22183
Is diversity bounded? evolutionary diversification have a tendency to slow-down there is no relationship between taxon age and number of species Rabosky et al. 2012 PLoS Biology 10: e1001381
Is diversity bounded? What then checks an indefinite increase in the number of species? The amount of life (I do not mean the number of specific forms) supported on an area must have a limit, depending so largely as it does on physical condifons; therefore, if an area be inhabited by very many species, each or nearly each species will be represented by few individuals; and such species will be liable to exterminafon from accidental fluctuafons in the nature of the seasons or in the number of their enemies. Darwin 1859; 6th edi!on speciation or extinction per species number of species temperate (lower N) tropics (higher N)
Is diversity bounded? Diversity may be in equilibrium, but it is not clear at which spatial and phylogenetic scale this equilibrium takes place residual bird diversity aner controlling for the effect of AET Storch et al. 2006 Ecology LeLers 9: 1308-1320 speciation or extinction per species number of species temperate (lower N) tropics (higher N) number of species tropics (faster speciation) temperate (slower speciation)
When is diversity decoupled from diversification? Non-equilibrium situation (age/time-for-diversification hypothesis) Equilibrium with particular relationship between origination/extinction and diversity Even if diversity variation is due to speciation rate variation, it is not ensured that diversity is proportional to speciation rate temperate temperate tropics temperate tropics tropics tropics temperate temperate tropics temperate tropics speciation or extinction per species number of species temperate (lower N) tropics (higher N) number of species tropics (faster speciation) temperate (slower speciation)
Conceptual problems of the Metabolic Theory of Biodiversity the original assumption concerning energy equivalence rule is unjustified species richness is proportional to speciation rate only under very restrictive conditions speciation/extinction rates speciation extinction number of species
Conceptual problems of the Metabolic Theory of Biodiversity the original assumption concerning energy equivalence rule is unjustified and flawed species richness is proportional to speciation rate only under very restrictive conditions speciation/extinction rates speciation extinction T5 T4 T3 T2 T1 number of species, S
Conceptual problems of the Metabolic Theory of Biodiversity the original assumption concerning energy equivalence rule is unjustified and flawed species richness is proportional to speciation rate only under very restrictive conditions universal slope of species-temperature relationship would appear only if speciesarea curve had constant slope slope 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0 theory: anchor N/S = 10 theory: anchor N/S = 2 wet tropical forest temperate understory serpentine grassland S. Af. birds dry tropical forest 0 2 4 6 8 10 ln(n/s) Harte, Smith & Storch 2009 Ecology Letters 12: 789 Wang, Brown, Tang & Fang 2009 PNAS 106: 13388
Merits of the MTB Fuhrman, et al. 2008 PNAS 105: 7774-7778 The only quantitative theory which predicts exponential species-temperature relationship The slopes seem to converge to the predicted value Temperature (together with water availability) is more important factor than productivity
Merits of the MTB The only quantitative theory which predicts exponential species-temperature relationship The slopes seem to converge to the predicted value Temperature (together with water availability) is more important factor than productivity (especially at large scales) Belmaker & Jetz 2011 GEB 20:464-474
Merits of the MTB The only quantitative theory which predicts exponential species-temperature relationship The slopes seem to converge to the predicted value Temperature (together with water availability) is more important factor than productivity (especially at large scales) Šímová et al. (2011) Global Ecology and Biogeography
Metabolic theory of biodiversity pros and cons + - The only quantitative theory which predicts exponential species-temperature relationship Many empirical patterns have different form and differ between taxa Diversification is often higher in low latitudes/high temperatures Diversification may be largely decoupled from diversity patterns Temperature (together with water availability) is the most important factor (especially at large scales) The theory is poorly conceptually founded and do not specify scales at which it operates Number of individuals is not sufficient for explaining diversity variation, but may be responsible for its stabilization Metabolic Theory of Biodiversity is not a consistent theory of spatial diversity variation, althoug it properly predicts temperature-dependence of diversification Temperature is the most important factor affecting diversity variation, although the quantitative predictions do not (and cannot) hold exactly Diversity dynamic is diversity-dependent, so that it is necessary to study factors that affect the interaction between species origination and extinction Spatial dynamics of species ranges is important, and so far unaccounted by all these theories