Cope's Rule and the Dynamics of Body Mass Evolution in North American Fossil Mammals

Alroy, John

doi:10.1126/science.280.5364.731

Cited by 480 publications

(596 citation statements)

References 30 publications

(42 reference statements)

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“…2). Discovery of Titanoboa extends the known range of body lengths in snakes by more than two orders of magnitude, between TBLs of 10 cm (Leptotyphlops carlae) and 12.8 m. Our estimates of body size also demonstrate that Titanoboa is the largest known nonmarine vertebrate from the Palaeocene and early Eocene 17 .…”

supporting

confidence: 56%

Giant boid snake from the Palaeocene neotropics reveals hotter past equatorial temperatures

Head

Bloch

Hastings

et al. 2009

Nature

203

141

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supporting

confidence: 56%

Giant boid snake from the Palaeocene neotropics reveals hotter past equatorial temperatures

Head

Bloch

Hastings

et al. 2009

Nature

203

141

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“…27): morphogenera recover biological signal even where only paraphyletic or polyphyletic morphogenera are sampled (highly unlikely, given our results showing monophyly to be far more common than expected by chance). The strength of these correlations probably derives from the significant phylogenetic component recorded for the interspecific evolution of geographic range and body size (33,37,47). However, the tighter correlations for body size suggest this character carries a strong phylogenetic signal, such that related species tend to be similar in size, regardless of whether they are direct sister taxa.…”

Section: Discussionmentioning

confidence: 99%

“…32), this issue has yet to be addressed quantitatively. Here, we evaluate the phylogenetic status of morphogenera relative to molecular phylogenies in 2 paleobiologically and ecologically important clades, Mammalia and Mollusca, and assess the potential impact of incorrect assumption of generic monophyly on 2 key macroevolutionary and macroecological variables: body size (9,(33)(34)(35) and latitudinal range (36)(37)(38)(39)(40)(41).…”

mentioning

confidence: 99%

Congruence of morphologically-defined genera with molecular phylogenies

Jablonski

Finarelli

2009

Proc. Natl. Acad. Sci. U.S.A.

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Morphologically-defined mammalian and molluscan genera (herein ''morphogenera'') are significantly more likely to be monophyletic relative to molecular phylogenies than random, under 3 different models of expected monophyly rates: Ϸ63% of 425 surveyed morphogenera are monophyletic and 19% are polyphyletic, although certain groups appear to be problematic (e.g., nonmarine, unionoid bivalves). Compiled nonmonophyly rates are probably extreme values, because molecular analyses have focused on ''problem'' taxa, and molecular topologies (treated herein as error-free) contain contradictory groupings across analyses for 10% of molluscan morphogenera and 37% of mammalian morphogenera. Both body size and geographic range, 2 key macroevolutionary and macroecological variables, show significant rank correlations between values for morphogenera and molecularlydefined clades, even when strictly monophyletic morphogenera are excluded from analyses. Thus, although morphogenera can be imperfect reflections of phylogeny, large-scale statistical treatments of diversity dynamics or macroevolutionary variables in time and space are unlikely to be misleading.biogeography ͉ body size ͉ macroecology ͉ macroevolution ͉ systematics M orphologically-defined genera are the primary analytical units for a wide range of large-scale paleontological and neontological analyses, across topics such as global diversity dynamics (1-8), macroevolutionary trends (9-11), paleoecology (12-14), systematics (15, 16), biogeography (17-19), and conservation biology (20-23). Although assigning rank to sets of species sharing close morphological affinities (usually with 1 or more diagnostic characters) lacks rigorous criteria, analyses of genus-level operational units are less subject to sampling and other biases than species-level analyses (24-26) and generally capture a damped record of species-level patterns (4, 27, 28). However, the proliferation of phylogenetic analyses using molecular data has uncovered an increasing number of paraphyletic or polyphyletic morphogenera (e.g., refs. 29 and 30), calling into question their analytic utility. Yet, despite alarming cases (e.g., ref. 31) and gross generalizations on the value of morphology (e.g., ref. 32), this issue has yet to be addressed quantitatively. Here, we evaluate the phylogenetic status of morphogenera relative to molecular phylogenies in 2 paleobiologically and ecologically important clades, Mammalia and Mollusca, and assess the potential impact of incorrect assumption of generic monophyly on 2 key macroevolutionary and macroecological variables: body size (9, 33-35) and latitudinal range (36-41). ResultsRates of Paraphyly and Polyphyly. We coded each of the 425 genera in our database (Table S1) as monophyletic, paraphyletic, or polyphyletic (42) (Fig. 1). The probability of randomly drawing a cladogram consistent with monophyly for a particular morphogenus from the set of all potential cladograms varies with the number of species in each analysis and in each morphogenus, but does not exceed 4.7% ...

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“…If smaller is better (higher fitness), why has natural selection resulted in the evolution of larger-sized organisms [e.g., Cope's rule in mammals (19)]. Suppose a mutation for larger body size occurs in a community in which the species with the largest body size is at position Y in Fig.…”

Section: Evolution Of Larger Body Sizementioning

confidence: 99%

“…It is easy to imagine how sexual selection for larger size in males could lead to evolution of larger size in females as a correlated trait. This has likely played a major role in certain lineages of mammals, where there have been evolutionary trends for the body size to increase [Cope's rule (19)] and with increasing overall size for the ratio of male to female size also to increase [Rensch's rule (29,31)]. Eventually, species of very large size may go extinct, because their lower reproductive capacities and smaller populations increase their vulnerability to environmental change.…”

Section: Evolution Of Larger Body Sizementioning

confidence: 99%

Life-history evolution under a production constraint

Brown

Sibly

2006

Proc. Natl. Acad. Sci. U.S.A.

143

134

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The recently formulated metabolic theory of ecology has profound implications for the evolution of life histories. Metabolic rate constrains the scaling of production with body mass, so that larger organisms have lower rates of production on a mass-specific basis than smaller ones. Here, we explore the implications of this constraint for life-history evolution. We show that for a range of very simple life histories, Darwinian fitness is equal to birth rate minus death rate. So, natural selection maximizes birth and production rates and minimizes death rates. This implies that decreased body size will generally be favored because it increases production, so long as mortality is unaffected. Alternatively, increased body size will be favored only if it decreases mortality or enhances reproductive success sufficiently to override the preexisting production constraint. Adaptations that may favor evolution of larger size include niche shifts that decrease mortality by escaping predation or that increase fecundity by exploiting new abundant food sources. These principles can be generalized to better understand the intimate relationship between the genetic currency of evolution and the metabolic currency of ecology.allometry ͉ life-history theory ͉ metabolic ecology T he recently formulated metabolic theory of ecology (1) predicts that many attributes of individuals, populations, communities, and ecosystems should be relatively straightforward consequences of the metabolic processes of the relevant organisms. Specifically, many rate processes should scale with body size and temperature in the same way as mass-specific metabolic rate:where R is the rate of some biological process, R 0 is a normalization constant, the M Ϫ1/4 term gives the power-function dependence on body mass M, and the e ϪE/kT term or Boltzmann factor gives the exponential temperature dependence in terms of an ''activation energy'', E, Boltzmann's constant, k, and temperature, T, in Kelvin. This very general relationship holds both within and between species. It can be applied to the rate of production of biomass per unit mass, which is predicted to scale as M Ϫ1/4 (e.g., refs. 2-4). If we ignore temperature or assume for the moment that it does not vary, the Boltzmann factor is a constant. Then, taking logarithms of Eq. 1 we have log (mass-specific production rate) log (body mass). [2]This prediction appears to be generally supported, although for some traits, the empirically measured scaling exponents appear to deviate from the predicted Ϫ1͞4, sometimes being closer to Ϫ1͞3 (e.g., ref. 5). For our argument here, however, the exact value of the exponent is not an issue; what is important is that it is negative. The consequence of the negative exponent is that in a log-log plot, mass-specific production rate is a declining straight-line function of body mass, as shown schematically by the solid black line in Fig. 2 A. We take this to be a fundamental causal constraint limiting life-history options as suggested by metabolic theory. The result is that sm...

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Cope's Rule and the Dynamics of Body Mass Evolution in North American Fossil Mammals

Cited by 480 publications

References 30 publications

Giant boid snake from the Palaeocene neotropics reveals hotter past equatorial temperatures

Giant boid snake from the Palaeocene neotropics reveals hotter past equatorial temperatures

Congruence of morphologically-defined genera with molecular phylogenies

Life-history evolution under a production constraint

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