Next steps for understanding the selective relevance of female-female competition

After decades of neglect, recent empirical research on exaggerated female traits (e.g., ornaments, armaments, aggression, acoustic signals, etc.) has revived interest in this widespread but poorly understood phenomenon, and shown that these traits often function in the context of female-female competition (West-Eberhard, 1983; Amundsen, 2000; Clutton-Brock, 2009; Rosvall, 2011a; Stockley and Bro-Jørgensen, 2011; Rubenstein, 2012 [Theme issue]; Stockley and Campbell, 2013 [Theme issue]). However, recent reviews have emphasized the applicability of sexual vs. social selection, rather than rigorously examining the role of different ecological contexts in shaping the evolution of traits used in competitive contexts (hereafter, “competitive traits”) in females. Thus, we still lack a solid understanding of the ecological and evolutionary mechanisms driving the evolution of female trait expression, in particular whether, how, and why these mechanisms vary among species, and between the sexes

Flexible arms provide constant force for pressure switch calibration

In-place calibration of a pressure switch is provided by a system of radially oriented flexing arms which, when rotated at a known velocity, convert the centrifugal force of the arms to a linear force along the shaft. The linear force, when applied to a pressure switch diaphragm, can then be calculated

Costs and benefits of competitive traits in females: aggression, maternal care and reproductive success

Recent research has shown that female expression of competitive traits can be advantageous, providing greater access to limited reproductive resources. In males increased competitive trait expression often comes at a cost, e.g. trading off with parental effort. However, it is currently unclear whether, and to what extent, females also face such tradeoffs, whether the costs associated with that tradeoff overwhelm the potential benefits of resource acquisition, and how environmental factors might alter those relationships. To address this gap, we examine the relationships between aggression, maternal effort, offspring quality and reproductive success in a common songbird, the dark-eyed junco (Junco hyemalis), over two breeding seasons. We found that compared to less aggressive females, more aggressive females spent less time brooding nestlings, but fed nestlings more frequently. In the year with better breeding conditions, more aggressive females produced smaller eggs and lighter hatchlings, but in the year with poorer breeding conditions they produced larger eggs and achieved greater nest success. There was no relationship between aggression and nestling mass after hatch day in either year. These findings suggest that though females appear to tradeoff competitive ability with some forms of maternal care, the costs may be less than previously thought. Further, the observed year effects suggest that costs and benefits vary according to environmental variables, which may help to account for variation in the level of trait expression.Research was supported by National Science Foundation (NSF) grants to EK (BSC 05-19211 and IOS 08-20055) and an NSF Doctoral Dissertation Improvement Grant to KC (09-10036). KC was also supported by NSF Graduate Research Fellowship (www.nsfgrfp.org)

Shifts in U.S. Relative Wages: The Role of Trade, Technology, and Factor Endowments

This paper investigates three hypotheses to account for the observed shifts in U.S. relative wages of less educated workers compared to more educated workers during the period from 1967 to 1992: (1) increased import competition, (2) changes in the relative supplies of labor of different educational levels, and (3) changes in technology. Our analysis relies on a basic relationship of the standard general equilibrium trade model that relates changes in product prices to factor price changes and factor shares, together with information about changes in the composition of output and trade, within-industry factor use, and factor supplies. For the period from 1967 to 1973, we conclude that the relative increase in the supply of well-educated labor was the dominant economic force that narrowed the wage gap among workers of different educational levels. In the 1980s and early 1990s, however, the wage gap between more educated and less educated workers widened sharply, despite the continued relative increase in the supply of workers with more education. We conclude that increased import competition cannot account for the observed increase in inequality among the major education groups, although it could have been a contributory cause of the decrease in the relative wages of the least educated workers. Instead, we find support for technical progress that is saving of less educated labor and that is more rapid in some manufacturing sectors intensively using highly educated labor as the dominant force in widening the wage gaps among college-educated workers, workers with a completed high school education, and workers with 1–11 years of schooling. Finally, we use the Deardorff-Staiger model, which allows changes in the factor content of trade to reveal the effects of trade on relative factor prices. Our empirical tests reinforce the conclusion that increased import competition between 1977 and 1987 was not the dominant force in widening the wage

Dynamic and Static Components of Political Support in Britain

This paper will consider a model of the British electorate which tries to account for both exogenous structural and endogenous political factors. The specification of the proposed model will be discussed in some detail and compared with the Butler and Stokes paradigm, which places almost exclusive emphasis on exogenous structural factors. The estimates obtained from a multivariate regression are then used to measure the relative impact of structural and political components on individual preferences and to draw inferences about the sources of electoral change in Britain. We will then confront the other half of the problem; namely, can a model which incorporates a significant endogenous component successfully account for electoral stability. The estimates of issue and lagged partisan components from a second set of regressions will form the basis of some observations about the stability of preferences across individuals in this model

Assessing the Partisan Effects of Redistricting

The purpose of this paper is to assess the reality behind the politician's perception that redistricting matters. There are, of course, many dimensions to that perception since redistricting has many effects. This paper will focus on the impact that boundary changes have on the partisan composition of seats. In order to do this, it will be necessary to specify what the expected partisan effects of redistricting are and how they can be measure. Thus, the paper first explains how the impact of redistricting will vary with the strategy of particular plans. Following this, there is an exploration of some techniques for measuring the partisan impact of boundary changes, and then a detailed analysis of the most important Congressional redistricting in 1982—the Burton plan in California

Blessed Be the Tie that Unbinds: Constituency Pressures and National Party Forces in Great Britain

This study looks at the relationship between constituency service and party ties at the local and national levels. The data come from two surveys: one of the British electorate in May 1979 and the other of Members and their agents in those constituencies sampled in the voter study. Pressures at the local party level, it is argued, reinforce the electoral incentive for Members to perform constituency services diligently. Members widely believe that constituency work improves relations with activists and bolsters local party morale. For their part, core constituents—activists and strong party identifiers—value constituency work very highly and are more likely than other groups in the electorate to make use of the Member's services. The effect of constituency effort at the local level is to weaken party ties at the national level. Ivor Crewe noted that Labour fought very well in its marginal seats in 1979, and this study argues that this was because Labour MPs in marginal seats worked hard to establish a local identity. MPs in marginal seats tend to have more favourable voter ratings than do those in safer seats. Moreover, MPs who were active in their constituencies had better swings in 1979 than MPs who were inactive. For Labour Members, constituency work "cushioned" the swing, and for Conservative Members, it "amplified" the swing. The paper concludes with some speculation about why non-policy pressures might increase at the local level

Dynamic and Static Components of Political Support in Britain

Many studies in British politics in particular and comparative politics more generally have shown a strong relation between personal attributes and voting behavior. Such studies have tended to assume an excessively static picture of party support. "Issue-voting" models, on the other hand, have not adequately accounted for sources of electoral stability. This paper attempts to link structural and political factors in a single model of political preference, and to show the implications of this for the study of broader questions such as why political systems remain stable or change over time. Two routes by which the social structure affects political preferences are posited, estimated, and compared. The strength of the endogenous political component raises the question of the source of stability in the British political system. The proposed model thus estimates the importance of lagged judgments and socialization biases in maintaining a core of "partisan" support for the parties