Selection has led to the evolution of a variety of different mating strategies, each adapted to different competitive challenges. But what happens if the competitive challenges depend on the social environment? Here we discuss and review examples of socially cued anticipatory plasticity: irreversible developmental tactics in which resource allocation during the juvenile stage is altered to develop an appropriate phenotype for the competitive or mate choice environment that an individual encounters when mature. There are numerous theoretical and empirical examinations of the role of the social environment on the strength and direction of selection. However, only a handful of empirical studies examine how the social environment affects juvenile allocation and whether such tactics are adaptive. The goal of this review is to synthesize current knowledge about socially cued anticipatory plasticity, including the sensory modalities that individuals use to predict the adult competitive and mating environment. We then outline the various factors that are necessary for the evolution of socially cued anticipatory plasticity and discuss how this can affect phenotypic evolution. We conclude by suggesting some directions that future studies should take in order to understand how social variation can alter selection and the evolution of development.

Our understanding of selection in nature stems mainly from whole-season and cross-sectional estimates of selection gradients.These estimates suggest that selection is relatively constant within, but fluctuates between seasons. However, the strength of selection depends on demographics, and because demographics can vary within seasons, there is a gap in our understanding regarding the extent to which seasonal fluctuations in demographics may cause variation in selection. Here we use two populations of the golden orb-web spider (Nephila plumipes) that differ in density to examine how demographics change within a season and whether there are correlated shifts in selection. We demonstrate that there is within-season variation in sex ratio and density at multiple spatial and temporal scales. This variation led to changes in the competitive challenges that males encountered at different times of the season and was correlated with significant variation in selection gradients on male size and weight between sampling periods. We highlight the importance of understanding the biology of the organism under study to correctly determine the relevant scale in which to examine selection. We also argue that studies may underestimate the true variation in selection by averaging values, leading to misinterpretation of the effect of selection on phenotypic evolution. K E Y W O R D S : Demographic variation, Nephila plumipes, selection gradients, sexual selection.The strength and direction of selection pressures acting on heritable traits can predict the evolution of phenotypic distributions (Fisher 1930;Lande and Arnold 1983;Kingsolver et al. 2001). The advent of statistical methods to quantify phenotypic selection (Arnold and Wade 1984a,b;Lande and Arnold 1983;Brodie et al. 1995) has led to a better understanding of how selection shapes phenotypes through time. By using estimates of selection gradients derived from cross-sectional sampling or average fitness (longitudinal estimates) across a breeding season, a number of studies have provided information on variation in the strength of selection on a variety of traits associated with fitness (see Kingsolver et al. 2001 for a review). Comparisons of spatially 4 Current address:

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Assessment strategies are an important component in game theoretical models of contests. Strategies can be either based on one’s own abilities (self assessment) or on the relative abilities of two opponents (mutual assessment). Using statistical methodology that allows discrimination between assessment types, we examined contests in the jumping spider Phiddipus clarus. In this species, aggressive interactions can be divided into ‘pre-contact’ and ‘contact’ phases. Pre-contact phases consist of bouts of visual and vibratory signaling. Contact phases follow where males physically contact each other (leg fencing). Both weight and vibratory signaling differences predicted winners with heavier and more actively signaling males winning more contests. Vibratory behaviour predicted pre-contact phase duration, with higher signaling rates and larger differences between contestants leading to longer pre-contact interaction times. Contact phase duration was predicted most strongly by the weight of losing males relative to that of winning males, suggesting that P. clarus males use self-assessment in determining contest duration. While a self-assessment strategy was supported, our data suggest a secondary role for mutual assessment (“partial mutual assessment”). After initial contest bouts, male competitors changed their behaviour. Pre-contact and contact phase durations were reduced while vibratory signaling behaviour in winners was unchanged. In addition, only vibratory signaling differences predicted winners in subsequent bouts suggesting a role of experience in determining contest outcomes. We suggest that the rules and assessment strategies males use can change depending on experience and that assessment strategies are likely a continuum between self- and mutual assessment.