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Criticizing adaptive landscapes and the conflation between ecology and genealogy

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Presentation by Emanuele Serrelli …

Presentation by Emanuele Serrelli
ISHPSSB July 2011, Salt Lake City, Utah
http://www.conferences.utah.edu/ishpssb/index.html
Session: Hierarchy Theory of Evolution

Disentangling ecological vs. genealogical dimensions is a core task of hierarchy theory in evolutionary biology. As Eldredge repeatedly epitomized, organisms carry out (only) two distinct kinds of activities: they survive, and they reproduce. ! At the organismal level, the organism stays the same whether we consider it ecologically or genealogically - yet, differences can occur in what features we consider relevant, and what fitness measurement we use.
! At higher levels, the two dimensions diverge, realizing different systems. Reproductive (deme) may not coincide with ecological (avatar) population. Further upwards, along the ecological dimension, higher-level systems are grouped by energy- matter interconnection, whereas, along the genealogical dimension, higher taxa are assembled by relatedness.
! In Dobzhansky's (1937) use of the adaptive landscape visualization (Wright 1932), all living species are imagined as distributed on adaptive peaks which correspond to ecological niches in existing environments. Peaks are grouped forming genera and higher taxa (e.g., "feline", "carnivore" ranges), and geographic speciation is figured out - like adaptation - as movement on the landscape.
! In criticizing Dobzhansky's landscape, Eldredge wrote that species actually do not occupy ecological niches; demes don't, either; avatars do.
! I point out that neighborhood and movement need to be conceived separately in genealogical and ecological spaces. Indeed, ecology should be further split in at least two spaces: geographic and phenotypic/adaptive. Movement in one space may in fact result in stability in the other(s).
! I also comment on the adaptive landscape: technical limitations prevent it from being coherently used above the population level, even though as a metaphor. Finally, I emphasize the partiality of any landscape - based on the choice of relevant features and fitness components - and interpret partiality as the way of approaching complex multi- hierarchical structure in evolution.

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  • 1. Hierarchy Theory of Evolution• Dan BROOKS - Metaphors for the Extended Synthesis: Something Old, Something New.• Silvia CAIANIELLO - Modularity and Hierarchy Theory.• Linnda CAPORAEL - Grounding Human Social Cognition in Hierarchical Group Structure.• Telmo PIEVANI - The Evolving Structure of Evolutionary Theory: the role of Hierarchy Theory for an Extended Evolutionary Synthesis.• Niles ELDREDGE - A Matter of Individuality: Hierarchy Theory at the Dawn of Evolutionary Biology.• Ilya TËMKIN - Nested Networks and Biological Diversification.• Keynyn BRYSSE – Lessons from Interdisciplinary (Non-) Communication in the Mass Extinction Debate.• Emanuele SERRELLI - Criticizing Adaptive Landscapes and the Conflation Between Ecology and Genealogy.• Gregory DIETL- Toward a Unified Ecology in Macroevolution.• William MILLER - Macroevolutionary Consonance and expansion of the Modern Synthesis. 1
  • 2. Criticizing adaptive landscapes and the conflationbetween ecology and genealogyEmanuele SerrelliUniversity of Milano Bicocca, Italy 2
  • 3. Criticizing adaptive landscapes and the conflationbetween ecology and genealogy• There are habits of thinking evolution that have to do with conflating ecology and genealogy, and they can lead to inconsistencies in our thoughts.• Dobzhansky’s (1937) famous version of the adaptive landscape is a good instance of this conflation.• But, the tendency to conflate seems to be more general and lasting (independently from Dobzhansky’s work, and/or shaped by foundational works in the Modern Synthesis, among which Dobzhansky’s influent ideas).• Method: direct citations and comments 3
  • 4. Niles Eldredge - 40 years of evolutionary critique 4
  • 5. Niles Eldredge - 40 years of evolutionary critique• 1972 (with Steve Gould) - “Puctuated equilibria: an alternative to phyletic gradualism”, Models in Paleobiology• 1984 (with Stan Salthe) - “Hierarchy and evolution”, Oxford Surveys in Evol. Biol.• 1985 - Unfinished Synthesis. Biological Hierarchies and Modern Evolutionary Thought (OUP)• 1989 - Macroevolutionary Dynamics. Species, Niches, and Adaptive Peaks (McGraw- Hill)• 1992 (with Marjorie Grene) - Interactions. The Biological Context of Social Systems (CUP)• 1995 - Reinventing Darwin (Wiley)• 1999 - The Pattern of Evolution (Freeman)• 2008 - “Hierarchies and the Sloshing Bucket: Toward the unification of evolutionary biology”, Evolution: Education & Outreach• 2008 - “Some thoughts on ‘adaptive peaks’, ‘Dobzhansky’s dilemma’ - and how to think about evolution”, Evolution: Education & Outreach 5
  • 6. Criticizing adaptive landscapes and the conflationbetween ecology and genealogy• There are habits of thinking evolution that have to do with conflating ecology and genealogy, and they can lead to inconsistencies in our thoughts.• Dobzhansky’s (1937) famous version of the adaptive landscape is a good instance of this conflation.• But, the tendency to conflate seems to be more general and lasting (independently from Dobzhansky’s work, and/or shaped by foundational works in the Modern Synthesis, among which Dobzhansky’s influent ideas).• Method: direct quotations and comments 6
  • 7. Different versions of adaptive landscapes:interesting issues Theodosius Dobzhansky Sewall Wright (1937) (1932) 7
  • 8. Dobzhansky’s adaptive landscape (1937) 8
  • 9. Dobzhansky’s adaptive landscape (1937)• «In an organism possessing only 1000 genes each capable of producing ten allelomorphs, the number of the possible gene combinations that may be formed is 101000. Some, probably a great majority, of these combinations are discordand and have no survival value, but still very numerous ones may be supposed to be harmonious in the different ecological niches of the same environment, as well as in different environments. If the entire ideal field of possible gene combinations is graded with respect to adaptive value, we may find numerous “adaptive peaks” separated by “valleys”. The “peaks” are the groups of related gene combinations that make their carriers fit for survival in a given environment; the “valleys” are the more or less unfavourable gene combinations. Each living species or race may be thought of as occupying one of the available peaks in the field of gene combinations» (Dobzhansky 1937 p. 187; cf. Wright 1932 p. 356, Eldredge 1985 p. 27). 9
  • 10. Dobzhansky’s adaptive landscape (1937)• «In an organism possessing only 1000 genes each capable of producing ten allelomorphs, the number of the possible gene combinations that may be formed is 101000. Some, probably a great majority, of these combinations are discordand and have no survival value, genetic map but still very numerous ones may be supposed to be harmonious in the different ecological niches of the same environment, as well as in different environments. If the entire ideal field of possible gene combinations is graded with respect to adaptive value, we may find numerous “adaptive peaks” separated by “valleys”. The “peaks” are the groups of related gene combinations that make their carriers fit for survival in a given environment; the “valleys” are the more or less unfavourable gene combinations. Each living species or race may be thought of as occupying one of the available peaks in the field of gene combinations» (Dobzhansky 1937 p. 187; cf. Wright 1932 p. 356, Eldredge 1985 p. 27). 10
  • 11. Dobzhansky’s adaptive landscape (1937)• «In an organism possessing only 1000 genes each capable of producing ten allelomorphs, the number of the possible gene combinations that may be formed is 101000. Some, probably a great majority, of these combinations are discordand and have no survival value, but still very numerous ones may be supposed to be harmonious in the different ecological niches of the same environment, as well as in different environments. If the entire ideal field of possible gene combinations is graded with respect to adaptive value, we may find numerous “adaptive peaks” separated by “valleys”. The “peaks” are fitness the groups of related gene combinations that make their carriers fit for survival in a given environment; the “valleys” are the more or less unfavourable gene combinations. Each living species or race may be thought of as occupying one of the available peaks in the field of gene combinations» (Dobzhansky 1937 p. 187; cf. Wright 1932 p. 356, Eldredge 1985 p. 27). 11
  • 12. Dobzhansky’s adaptive landscape (1937)• «In an organism possessing only 1000 genes each capable of producing ten allelomorphs, the number of the possible gene combinations that may be formed is 101000. Some, probably a great majority, of these combinations are discordand and have no survival value, but still very numerous ones may be supposed to be harmonious in the different ecological niches of the same environment, as well as in different environments. If the entire ideal field of possible gene combinations is graded with respect to adaptive value, we may find numerous “adaptive peaks” separated by “valleys”. The “peaks” are the groups of related gene combinations that make their carriers fit for survival in a given environment; the “valleys” are the more or less unfavourable gene metaphor combinations. Each living species or race may be thought of as occupying one of the available peaks in the field of gene combinations» (Dobzhansky 1937 p. 187; cf. Wright 1932 p. 356, Eldredge 1985 p. 27). 12
  • 13. Dobzhansky’s adaptive landscape (1937)• «In an organism possessing only 1000 genes each capable of producing ten allelomorphs, the number of the possible gene combinations that may be formed is 101000. Some, probably a great majority, of these combinations are discordand and have no survival value, but still very numerous ones may be supposed to be harmonious in the different ecological niches of the same environment, as well as in different environments. If the entire ideal field of possible gene combinations is graded with respect to adaptive value, we may find numerous “adaptive peaks” separated by “valleys”. The “peaks” are the groups of related gene combinations that make their carriers fit for survival in a given environment; the “valleys” are the more or less unfavourable gene combinations. Each living species or race may be thought of as occupying one of the available peaks in the field of gene combinations» (Dobzhansky 1937 p. 187; cf. relatedness Wright 1932 p. 356, Eldredge 1985 p. 27). 13
  • 14. Dobzhansky’s adaptive landscape (1937)• «In an organism possessing only 1000 genes each capable of producing ten allelomorphs, the number of the possible gene combinations that may be formed is 101000. Some, probably a great majority, of these combinations are discordand and have no survival value, genetic map but still very numerous ones may be supposed to be harmonious in the different ecological niches of the same environment, as well as in different environments. If the entire ideal field of possible gene combinations is graded with respect to adaptive value, we may find numerous fitness “adaptive peaks” separated by “valleys”. The “peaks” are the groups of related gene combinations that make their carriers fit for survival in a given environment; the “valleys” are the more or less unfavourable gene metaphor combinations. Each living species or race may be thought of as occupying one of the available peaks in the field of relatedness gene combinations» (Dobzhansky 1937 p. 187; cf. Wright 1932 p. 356, Eldredge 1985 p. 27). 14
  • 15. Dobzhansky’s adaptive landscape (1937)• «...species tend to be subdivided into numerous isolated colonies of different size, with the exchange of individuals between the colonies prevented [...] such a situation is by no means imaginary; on the contrary, it is very frequently encountered in nature» (e.g., p. 133; cf. Wright 1932, Eldredge 1985 p. 21).• Above the species level:• «...the adaptive peaks and valleys are not interspersed at random. “Adjacent” adaptive peaks are arranged in groups, which may be likened to mountain ranges in which the separate pinnacles are divided by relatively shallow notches. Thus, the ecological niche occupied by the species “lion” is relatively much closer to those occupied by tiger, puma, and leopard than to those occupied by wolf, coyote, and jackal. The feline adaptive peaks form a group different from the group of the canine “peaks.” But the feline, canine, ursine, musteline, and certain other groups of peaks form together the adaptive “range” of carnivores, which is separated by deep adaptive valleys from the “ranges” of rodents, bats, ungulates, primates, and others» (1951, p. 10). 15
  • 16. Dobzhansky’s adaptive landscape (1937)• «...species tend to be subdivided into numerous isolated colonies of different size, with the exchange of individuals between the genetic map??? colonies prevented [...] such a situation is by no means imaginary; on the contrary, it is very frequently encountered in nature» (e.g., p. 133; cf. Wright 1932, Eldredge 1985 p. 21).• Above the species level:• «...the adaptive peaks and valleys are not interspersed at random. “Adjacent” adaptive peaks are arranged in groups, which may be likened to mountain ranges in which the separate pinnacles are divided by relatively shallow notches. Thus, the ecological niche occupied by the species “lion” is relatively much closer to those occupied by tiger, puma, and leopard than to those occupied by wolf, coyote, and jackal. The feline adaptive peaks form a group different from the group of the canine “peaks.” But the feline, canine, ursine, musteline, and certain other groups of peaks form together the adaptive “range” of carnivores, which is separated by deep adaptive valleys from the “ranges” of rodents, bats, ungulates, primates, and others» (1951, p. 10). 16
  • 17. Dobzhansky’s adaptive landscape (1937)• «...species tend to be subdivided into numerous isolated colonies of different size, with the exchange of individuals between the genetic map??? colonies prevented [...] such a situation is by no means imaginary; on the contrary, it is very frequently encountered in nature» (e.g., p. 133; cf. Wright 1932, Eldredge 1985 p. 21).• Above the species level:• «...the adaptive peaks and valleys are not interspersed at random. “Adjacent” adaptive peaks are arranged in groups, which may be likened to mountain ranges in which the separate pinnacles are divided by relatively shallow notches. Thus, the ecological niche occupied by the species “lion” is relatively much closer to those occupied by tiger, puma, and leopard than to those occupied by wolf, coyote, and jackal. The feline adaptive peaks form a group different from the group of the canine “peaks.” But the feline, niche??? canine, ursine, musteline, and certain other groups of peaks form together the adaptive “range” of carnivores, which is separated by deep adaptive valleys from the “ranges” of rodents, bats, ungulates, primates, and others» (1951, p. 10). 17
  • 18. Dobzhansky’s adaptive landscape (1937)• «In an organism possessing only 1000 genes each capable of producing ten allelomorphs, the number of the possible gene combinations that may be formed is 101000. Some, probably a great majority, of these combinations are discordand and have no survival value, but still very numerous ones may be supposed to be harmonious in the different ecological niches of the same environment, as well as in different environments. If the entire ideal field of possible gene combinations is graded with respect to adaptive value, we may find numerous “adaptive peaks” separated by “valleys”. The “peaks” are the groups of related gene combinations that make their niche carriers fit for survival in a given environment; the “valleys” are the more or less unfavourable gene combinations. Each living species or race may be thought of as occupying one of the available peaks in the field of gene combinations» (Dobzhansky 1937 p. 187; cf. Wright 1932 p. 356, Eldredge 1985 p. 27). 18
  • 19. Niches and landscapes (environment) • ...in the different ecological niches of the same environment, as well as in different environments... • ...the ecological niche occupied by the species “lion” is relatively much closer to those occupied by tiger... 19
  • 20. Niches and landscapes (environment) • ...in the different ecological niches of the same environment, as well as in different environments... ??? • ...the ecological niche occupied by the species “lion” is relatively much closer to those occupied by tiger... ??? 20
  • 21. Niches and landscapes (environment) 21
  • 22. Niches and landscapes (environment) We have been (or, for some reasons, we are) brought to identify, to conflate a discrete and scattered distibution in the genotypic space (i.e., the space of possible genotypic combinations) and a discrete array of different sets of selective pressures. 22
  • 23. Speciation and landscapes Dobzhansky, Modern Synthesis 1) environmental changes make Sewall Wright populations move geographically (1932) 2) geographical isolation can happen 3) geographical isolation is evolutionarily important because it can eventually bring to genetic isolation (hybrid unviability or sterility) 4) moving in a new environment can result in novel adaptations 23
  • 24. Speciation, adaptation, and landscapes Geographic speciation, geographic adaptation... 24
  • 25. THREE COORDINATING SPACES 25
  • 26. Criticizing adaptive landscapes and the conflationbetween ecology and genealogy• There are habits of thinking evolution that have to do with conflating ecology and genealogy, and they can lead to inconsistencies in our thoughts.• Dobzhansky’s (1937) famous version of the adaptive landscape is a good instance of this conflation.• Its influence may constrain our though in perpetuating these conflations.• I see three coordinated spaces (genotypic, geographical, selective pressures) conflated in the landscape.• To avoid inconsistencies, geographic and genealogical groups should be grouped on different hierarchies (disentanglement).• OPEN ENDED ON HIERARCHY THEORY: • Where selective pressures (not a proper space)? 26
  • 27. Criticizing adaptive landscapes and the conflationbetween ecology and genealogyEmanuele SerrelliUniversity of Milano Bicocca, Italy 27