Summary 1We develop and test a game-theoretic model for considering the effects of intra-and interplant competition on root proliferation and reproductive yield. 2 We predict that if space and resources per individual are held constant, plants should produce more roots per individual and less reproductive yield per individual as the number of plants sharing the combined space increases. 3 We tested the predictions using soybean plants ( Glycine max ) cultivated in the glasshouse either as owners or as two individuals sharing twice the space and nutrients. 4 Sharing individuals produced 85% more root mass than owners. Owners, however, produced 30% more reproductive yield per plant (dry mass of seeds), as a result of significantly more seed pods (8.70 vs. 7.66), more seeds per pod (1.87 vs. 1.72) and larger seeds (0.205 vs. 0.195 g seed -1 ), than did sharing individuals. 5 Total plant biomass did not differ between owners and sharing individuals, but owners had significantly higher shoot to root ratios, produced significantly more seeds per unit root mass, and allocated a significantly higher percentage of total biomass production to seeds. 6 Possession of an evolutionarily stable strategy (ESS) of root competition suggests that different roots and parts of a plant assess and respond to opportunities in a manner that maximizes the good of the whole plant. Thus, plants may be more sophisticated and share more in common with animals in their non-cognitive behaviours than previously thought. A plant operating as a co-ordinated whole should, all else being equal, first proliferate roots in unoccupied soil, then in soil occupied by a conspecific competitor, and lastly in soil already occupied by its own roots.

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Here, we tested the predictions of a 'tragedy of the commons' model of below-ground plant competition in annual plants that experience spatial heterogeneity in their competitive environment. Under interplant competition, the model predicts that a plant should over-proliferate roots relative to what would maximize the collective yield of the plants. We predict that a plant will tailor its root proliferation to local patch conditions, restraining root production when alone and over-proliferating in the presence of other plants. A series of experiments were conducted using pairs of pea (Pisum sativum) plants occupying two or three pots in which the presence or absence of interplant root competition was varied while nutrient availability per plant was held constant. In two-pot experiments, competing plants produced more root mass and less pod mass per individual than plants grown in isolation. In three-pot experiments, peas modulated this response to conditions at the scale of individual pots. Root proliferation in the shared pot was higher compared with the exclusively occupied pot. Plants appear to display sophisticated nutrient foraging with outcomes that permit insights into interplant competition.

Recent years have seen a dramatic increase in state legislation likely to reduce access for some voters, including photo identification and proof of citizenship requirements, registration restrictions, absentee ballot voting restrictions, and reductions in early voting. Political operatives often ascribe malicious motives when their opponents either endorse or oppose such legislation. In an effort to bring empirical clarity and epistemological standards to what has been a deeply-charged, partisan, and frequently anecdotal debate, we use multiple specialized regression approaches to examine factors associated with both the proposal and adoption of restrictive voter access legislation from 2006–2011. Our results indicate that proposal and passage are highly partisan, strategic, and racialized affairs. These findings are consistent with a scenario in which the targeted demobilization of minority voters and African Americans is a central driver of recent legislative developments. We discuss the implications of these results for current partisan and legal debates regarding voter restrictions and our understanding of the conditions incentivizing modern suppression efforts. Further, we situate these policies within developments in social welfare and criminal justice policy that collectively reduce electoral access among the socially marginalized.

Game theory provides an untapped framework for predicting how below-ground competition will influence root proliferation in a spatially explicit environment. We model root competition for space as an evolutionary game. In response to nutrient competition between plants, an individual's optimal strategy (the spatial distribution of root proliferation) depends on the rooting strategies of neighbouring plants. The model defines and predicts the fundamental (in the absence of competition) and realized (in the presence of competition) root space of an individual plant. Overlapping fundamental root spaces guarantee smaller, yet still overlapping, realized root spaces as individuals concede some but not all space to a neighbour's roots. Root overlap becomes an intentional consequence of the neighbouring plants playing a nutrient foraging game. Root proliferation and regions of root overlap should increase with soil fertility, decline with the distance cost of root production (e.g. soil compactness) and shift with competitive asymmetries. Seemingly erratic patterns of root proliferation and root overlap become the expected outcome of nutrient foraging games played in soils with small-scale heterogeneities in nutrient availability.

Summary 1.A growing body of literature suggests that some plants may engage in a game of Tragedy of the Commons when competing for soil resources. Two annual plants sharing a whole space will produce more roots per individual and less reproductive yield per individual than one plant with half the space to itself. 2. Several papers have recently suggested that the increase in soil volume in going from a single plant to two competitor plants (as has been the case in empirical tests of the above prediction) may produce the increased root proliferation independent of the competitor. 3. We extend the Tragedy of the Commons model of Gersani et al . (2001) to explicitly consider the separate effects of volume per plant ( V ) and nutrient concentration per unit volume ( N ) on root proliferation and yield of plants that 'own' their space relative to plants that share their space with a competitor. We then use simulations resulting from the model to evaluate existing data and the new perspectives provided by recent challenges to the conceptual basis for the Tragedy of the Commons. 4. When N is held constant, increasing V should produce an almost linear increase in root proliferation and net nutrient profit for reproduction. The increase in roots should be more pronounced for two plants sharing their space, and the increase in yield should be more pronounced for plants with exclusive access to half the space. When V × N is held constant, roots per plant should at first increase and then decline with increased volume. The difference between a plant that 'owns' its space vs. one that shares its space with a competitor should be less pronounced as V increases. 5. Synthesis . We use this model to help clarify some confusion surrounding the Tragedy of the Commons theory of below-ground competition by showing how issues raised by others are not incompatible with the approach used to generate the Tragedy of the Commons theory and highlight future opportunities for research on root growth strategies.

Research investigating whether female legislators provide more effective substantive representation on women's issues than their male colleagues faces a significant methodological hurdle. Models used to estimate the effect of gender on representation inevitably omit constituency variables that affect the character of legislators' decisions and are also correlated with gender, potentially biasing the estimates of the effect of gender. Employing a quasi-experimental research design as an alternative strategy, the authors remove this hurdle and estimate the influence of gender on representation free from this potential bias. The authors find that gender does affect representation and observe critical mass effects.

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