Weedy Setaria Seed Life History Jack Dekker Weed Biology Laboratory Agronomy Department Iowa State University Ames, Iowa 50010 USA Email: [email protected] KEYWORDS: biological algorithms; bristly foxtail; communication theory; community assembly; complex adaptive systems; complexity; emergent behavior; giant foxtail; green foxtail; information theory; knotroot foxtail; phenotypic plasticity; plant model system; seed biology; seed dormancy; seed germinability; seed germination; seed heteroblasty; seed polymorphism; seedling emergence; seedling recruitment; self-organization; self-similarity; Setaria faberi; Setaria geniculata; Setaria italica; Setaria pumila; Setaria verticillata; Setaria viridis; Shannon communication system; somatic polymorphism; weed biology; weed model system; yellow foxtail Summary. The nature of weeds is a complex adaptive, soil-seed communication system. The nature of weedy Setaria life history is an adaptable, changeable system in which complex behaviors emerge when self-similar plant components self-organize into functional traits possessing biological information about spatial structure and temporal behavior. The nature of the weedy Setaria is revealed in the physical (morphological and genetic spatial structures) and the phenomenal (life history behavior instigated by functional traits). Structural self-similarity in morphology is revealed in seed envelope compartmentalization and individual plant tillering; in genetics by local populations and Setaria species-associations forming the global metapopulation. Behavioral self-organization is revealed in the self-pollenating mating system controlling genetic novelty, seed heteroblasty blueprinting seedling recruitment, and phenotypic plasticity and somatic polymorphism optimizing seed fecundity. The weedy Setaria phenotype can be described in terms of the spatial structure of its seed and plant morphology, and by its genotypes and population genetic structure. This spatial structure extends from the cells and tissues of the embryo axes, the surrounding seed envelopes, the individual seed and then plant, the local deme, and ending with the aggregation of local populations forming the global metapopulation. Setaria plant spatial structure is the foundation for emergent life history behavior: self-similar timing of life history processes regulated by functional traits expressed via environment-plant communication. Temporal life history behavior begins in anthesis, fertilization and embryogenesis; development continues with inflorescence tillering, seed dispersal in space and time, and resumption of embryo growth with seedling emergence. Setaria life history behavior is a Markov chain of irreversible (dormancy induction; seed dispersal, 1 germination, seedling emergence, neighbor interactions) and reversible (seed after-ripening, dormancy re-induction) processes of seed-plant state changes (flowering plants, dormant seed, seed germination candidate, germinated seed, seedling) regulated by morpho-physiological traits acting through environment-plant communication systems (environment-plant-seed, soil-seed). Heritable functional traits are the physical reservoirs of information guiding life history development, emergent behavior. Information contained in structural and behavioral traits is communicated directly between soil environment and seed during development. Functional traits controlling seed-seedling behavior are physical information that has evolved in ongoing communication between organism and environment leading to local adaption. The consequence of structural self-similarity and behavioral self-organization has been the evolution of a complex adaptive seed-soil communication system. Weedy Setaria life history is represented in algorithmic form as FoxPatch, a model to forecast seed behavior. The environment-biological informational system with which weedy Setaria life history unfolds is represented in the soil- seed communication system. CONTENTS 1. The nature of weed seeds and seedlings 1.1 Weed complexity 1.2 Biological communication 1.3 The general nature of weeds, the specific nature of weedy Setaria 2. The nature of weedy Setaria seed-seedling life history 2.1 Seed-seedling life history 2.2 The nature of Setaria: spatial structure and temporal behavior 2.3 Setaria model system of exemplar species 3. Setaria spatial structure 3.1 Plant morphological structure 3.2 Plant genetic structure 4. Setaria seed-seedling life history behavior 4.1 Life history behaviors: functions, traits and information 4.2 Seed formation and dormancy induction 4.3 Seed rain dispersal 4.4 Seed behavior in the soil 4.5 Seedling recruitment 5. Setaria seed life history as complex adaptive soil-seed communication system 5.1 Forecasting Setaria seed behavior: FoxPatch 5.2 Setaria soil-seed communication system 5.3 Seed memory and adaptive evolution 6. References Cited 2 1. THE NATURE OF WEED SEEDS AND SEEDLINGS “Present knowledge of the behavior of invading species, both successful and unsuccessful, suggests that it is in phases of germination and seedling establishment that their success or failure is most critically determined and it would seem reasonable therefore, to look particularly closely at seeds and seedlings of invading species. The considerations set out in this paper lead one to expect that it is in properties such as seed number, seed size, seed polymorphisms, and precise germination requirements that the most sensitive reactions of a species to an alien environment are likely to occur.” (Harper, 1964) The nature of weeds is a complex adaptive system. Weed life history is an adaptable, changeable system in which complex behaviors emerge as a consequence of structural self- similarity and behavioral self-organization. The nature of weeds is an environment-biology communication system. Biology is information. Information comes via evolution, an ongoing exchange between organism and environment. Information is physical. Biology is physical information with quantifiable complexity. 1.1 WEED COMPLEXITY "The plant population that is found growing at a point in space and time is the consequence of a catena of past events. The climate and the substrate provide the scenery and the stage for the cast of plant and animal players that come and go. The cast is large and many members play no part, remaining dormant. The remainder act out a tragedy dominated by hazard, struggle and death in which there are few survivors. The appearance of the stage at any moment can only be understood in relation to previous scenes and acts, though it can be described and, like a photograph of a point in the performance of a play, can be compared with points in other plays. Such comparisons are dominated by the scenery, the relative unchanging backcloth of the action. It is not possible to make much sense of the plot or the action as it is seen at such a point in time. Most of our knowledge of the structure and diversity of plant communities comes from describing areas of vegetation at points in time and imposing for the purpose a human value of scale on a system to which this may be irrelevant." (Harper, 1977) A complex adaptative system (CAS) is a dynamic network of many interacting adaptive agents acting in parallel (Axelrod and Cohen, 1999). The overall system behavior is a result of a huge number of decisions, made every moment, by many individual agents acting and reacting in competition and cooperation to what other agents are doing, in which control is highly dispersed and decentralized. A CAS is a complex, self-similar collectivity of interacting adaptive agents with emergent and macroscopic properties. Complex adaptive systems are open, defining system boundaries is difficult or impossible. CASs operate far from equilibrium conditions, a constant flow of energy is needed to maintain the organization of the system. CASs are living, adaptable, changeable systems in which complexity, self-similarity and self-organization occur. 3 1.1.1 Complexity Complexity arises in a system composed of many elements in an intricate arrangement. The numerous elements interact with each other by which numerous relationships are formed among the elements. The relationship among system parts is differentiated from other parts outside of system. A key principle of CAS behavior and evolution is that the basic system units are agents (e.g phenotypes, strategic traits, cells) which scan/sense/perceive their environment (opportunity spacetime, Dekker, 2011b) and develop schema/plans/traits representing interpretive and action rules (e.g. seed heteroblasty). These schema/plans/traits are subject to change and evolution. Agents are a collection of properties, strategies and capabilities for interacting with local opportunity and other agents. Agents and the complex system are adaptable, with a high degree of adaptive capacity providing resilience to disturbance. The number of elements in a CAS is large such that a conventional description is impractical, and does not assist in understanding the system (e.g. Colbach et al., 2001a, b). A second key principle of CAS behavior and evolution is that system order is emergent, not predetermined. Emergence is the way complex systems and patterns arise out of a multiplicity of relatively simple interactions. Interactions are non-linear: small causes can have large effects (e.g. pleiotropy in triazine resistant plants; Dekker, 1992, 1993). Interaction is physical or involves exchange of information. Systems emerge from the moment-to-moment decisions made by many