The pace-of-life syndrome hypothesis predicts that individual differences in behaviour should integrate with morphological, physiological, and life-history traits along a slow to fast pace-of-life continuum. For example, individuals with a "slow" pace-of-life are expected to exhibit a slower growth rate, delayed reproduction, longer lifespans, have stronger immune responses, and are expected to avoid risky situations relative to "fast" individuals.If supported this hypothesis would help resolve ecological and evolutionary questions regarding the origin and maintenance of phenotypic variation. Support for the pace-of-life syndrome hypothesis has, however, been mixed. Here we conducted a meta-analysis of 42 articles and 179 estimates testing the pace-of-life syndrome hypothesis as it applies to the integration of behaviours with physiological or life-history traits. We found little overall support for the pace-of-life syndrome hypothesis with the mean support estimated as r = 0.06. Support for the pace-of-life syndrome hypothesis was significantly higher in invertebrates (r = 0.23) than vertebrates (r = 0.02) and significantly higher when based onThe lack of overall support found in our analyses suggests that general assertions 24 regarding phenotypic integration due to "pace-of-life" and should be re-evaluated. 25 4 Significance StatementThe pace-of-life syndrome hypothesis has been proposed as an overall organizational framework for the integration of behavioural, life-history, and physiological traits. This hypothesis provides potentially profound insights into how and why phenotypic traits might covary and why phenotypic variation may be maintained within populations. Over the last seven years this organizational framework has been intensively investigated as it pertains to relationships between behaviour and other traits. Here we conducted an overall analysis of whether the hypothesis was supported. Despite considerable research investment across behavioural ecology, we did not find that available data supported the pace-of-life syndrome hypothesis. This suggests that either the hypothesis has been inappropriately tested or is not generally applicable.

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Sexual selection can drive the evolution of dramatic morphological and behavioral signals. This selection acts on both specific components of signals and overall signals that combine multiple sources of information. By studying the structure and variability of signals and their components we can improve our understanding of how sexual selection operates. Signal integration can be understood through the lens of classical signaling hypotheses or more recently defined systems approaches. Using crickets (Acheta domesticus), we evaluated competing hypotheses about signal integration and how observed patterns of signal integration fit into both systems approaches and classic signaling hypotheses. We measured three call types of 127 male crickets multiple times for a total of 930 observations. We found evidence for an underlying integrated signaling syndrome from which both intra- and intersexual signals stemmed. This syndrome was also affected by mass, suggesting honest signaling in the species. The presence of an integrated syndrome demonstrates that intra- and intersexual signals are incorporated in a redundant signal strategy in Acheta domesticus. This support for honest and redundant signaling is also consistent with a systems framework description of signals as degenerate and functionally modular—demonstrating one way in which classic hypotheses can be integrated with modern systems approaches.

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In many species, males produce signals to attract females. However, in some species and populations, only some males produce these signals with other males competing for and "sneaking" reproductive opportunities. In these systems, at least three tactics are expected: always signal, signal only when others are not (assessors), and never signal. The representation of these tactics within a population is unknown in part because the costs of signaling (C) and the fitness value of a single reproductive bout (V) are unknown. Using a game-theoretic model we predict that the always signal strategy only persists if the fitness value of calling is greater than twice the cost. We also show that always signal males are apparently absent in decorated crickets (Gryllodes sigillatus). Moreover, males of this species were not strict assessors and instead signaled infrequently (30% of the time) when signaling by others was constant. Males also exhibited substantial among-individual variation in the propensity to call when other males were not signaling (τ = 0.3). Our results suggest a high relative cost of signaling (2C > V) in this species. The presence of among-individual variation is indicative of underlying genetic variation and a mixed evolutionary stable strategy.