Fabrizio Panebianco and Emanuele Serrelli: A Niche Construction Model with Reaction Norms

Overview Niche Construction Plasticity Reactions Norm NCRN: Basic and Population NCRN and Economics Formalization A Niche Construction Model with Reaction Norms Fabrizio Panebianco and Emanuele Serrelli University of Milano - Bicocca May 6, 2011 CISEPS ANNUAL REPORT

Overview Niche Construction Plasticity Reactions Norm NCRN: Basic and Population NCRN and Economics Formalization Cultural Evolution Project

Overview Niche Construction Plasticity Reactions Norm NCRN: Basic and Population NCRN and Economics Formalization Outline • Niche construction • as a neglected major biological process • as modiﬁcation and innovation of existing models • Something missing in NC models: phenotypic plasticity • NCRN model: a niche construction model with reaction norm • Basic and population NCRN Models • NCRN, cultural evolution, and economical modeling • First Formalization

Overview Niche Construction Plasticity Reactions Norm NCRN: Basic and Population NCRN and Economics Formalization Niche Construction: «the selection pressures to which an organism is exposed exist partly as a consequence of the niche constructing activities of past and present generations of organisms»(Laland et al. (1996), p.294)

Overview Niche Construction Plasticity Reactions Norm NCRN: Basic and Population NCRN and Economics Formalization

Overview Niche Construction Plasticity Reactions Norm NCRN: Basic and Population NCRN and Economics Formalization That the activities of organisms lead to environmental modiﬁcations, on both on a local and global scale, can hardly be doubted; so much is obvious to even the most casual observer of the natural world. . . . if everyone agrees that niche-construction, i.e. organism-induced modiﬁcation of the environment, occurs, why does orthodox evolutionary theory fail to take account of it? (Okasha 2005, p. 1).

Overview Niche Construction Plasticity Reactions Norm NCRN: Basic and Population NCRN and Economics Formalization • Laland KN, Odling-Smee FJ, Feldman MW (1996). On the evolutionary consequences of niche construction. Journal of Evolutionary Biology 9: 293-316. • Laland KN, Odling-Smee FJ, Feldman MW (1999). The evolutionary consequences of niche construction and its implications for ecology. Proceedings of the National Academy of Sciences USA 96:10242- 47. • NC models are modification of multiplicative model (two loci) • Locus E (alleles E, e), Locus A (alleles A, a), Resources R • Frequency in E influences R, R influences A’s contribution to fitness The analysis confirms that niche construction can be a potent evolutionary agent by generating selection that leads to the fixation of otherwise deleterious alleles, supporting stable polymorphisms where none are expected, eliminating what would otherwise be stable polymorphisms, and generating unusual evolutionary dynamics. Even small amounts of niche construction, or niche construction that only weakly affects resource dynamics, can significantly alter both ecological and evolutionary patterns. (Laland et al. 1999, p. 10242).

Overview Niche Construction Plasticity Reactions Norm NCRN: Basic and Population NCRN and Economics Formalization Phenotypic Plasticity • The term phenotypic plasticity describes the property of a genotype to generate phenotypic variation in response to a given range of environmental conditions. • Various measures of plasticity exist and can be united within the framework of a polynomial function: the norm of reaction. • NC models do not allow factors other than genotypes to participate in the production of phenotypes. • Niche construction advocates always consider the classic idea of an inﬂuence on the population’s gene pool (frequency of alleles that correspond to determinate phenotypic traits or behaviours).

Overview Niche Construction Plasticity Reactions Norm NCRN: Basic and Population NCRN and Economics Formalization NC vc NCRN • Reaction Norm (G)≡ The rule imposed by the genotype, that determines the phenotype expressed in the population as a function of the environment and other factors, can be intended in different ways: it can go from simple mechanical reaction rules up to complex algorithms considering aspects of the environment, or from population either seen in the present or preceding generation. • Differences: Phenotypic outcome affects the environment. Current phenotype undergoes selection, which affects on population size. Future phenotypic outcomes depend on the environment by reaction norm, which takes into account at least the resource available in the environment and population size. • Common Feature: Aggregate Effect. NC models are constitutively concerned with selection pressures, and while selection pressures act on individuals, sorting them through generations, they make sense only at population level.

Overview Niche Construction Plasticity Reactions Norm NCRN: Basic and Population NCRN and Economics Formalization Basic and Population NCRN Models • The work with a basic NCRN model would be focused on the exploration of the dynamics resulting from diﬀerent kinds of reaction norms with no variation of G across the population. • Although basic NCRN studies seem insensitive to the particular explanation for the ubiquity of G, such studies might yield some results about the kinds of evolutionary norms that exhibit evolutionary stability. NCRN studies can be thought as preparatory to population models with multiple reaction norms (e.g. G1 and G2).

Overview Niche Construction Plasticity Reactions Norm NCRN: Basic and Population NCRN and Economics Formalization

Overview Niche Construction Plasticity Reactions Norm NCRN: Basic and Population NCRN and Economics Formalization NCRN, cultural evolution, and economical modeling • Reaction norm and Rational Choice are both Rules that share the picking of an element from a set of possibilities according to external constraints. • This picked up element is respectively the phenotype and the chosen action. • NCRN models introduce NC in a way that closes a gap between biological and economic modeling. vs • NC models traits are cultural and genetic, and both kinds are modeled by means of loci and alleles, where alleles correspond to phenotypic alternatives that are ﬁxed and there is no room for plasticity.

Overview Niche Construction Plasticity Reactions Norm NCRN: Basic and Population NCRN and Economics Formalization First Formalization • Resources Rt , • Population mass mt , • Genotype G , (reaction norm) • Phenotype At , At : (Rt , mt , G ) → [0, Rt ] Bt : (mt , At ) → + Ct : (Rt , At ) → + (1) Ft : (Bt − Ct ) → + Rt : (Rt−1 , At−1 ) → + mt : (mt−1 , Ft−1 ) → +

Fabrizio Panebianco and Emanuele Serrelli: A Niche Construction Model with Reaction Norms

by Emanuele Serrelli on May 26, 2011

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Fabrizio Panebianco and Emanuele Serrelli: A Niche Construction Model with Reaction Norms Presentation Transcript