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Conspicuous sexual signals come with costs and benefits. Such signals increase reproductive success but may also reduce survival or viability. It has recently been suggested that non-signal traits may alleviate some of those costs (termed “compensatory traits”). In this perspective piece, we argue that biological rhythms should be considered in the milieu of compensatory traits, as they can reduce the natural selection burden of signaling. This may be particularly true for the many sexual signals that are ephemeral (i.e., only periodically present like a courtship dance). Biological rhythms (e.g., circadian and circannual rhythms) are ubiquitous in nature and help organisms perform the right activity at the right time—this includes the timing of many sexual signals and reproductive traits. Timing itself may, in fact, reduce the costs of such sexual signals. Here, we review sexual signals that are governed by biological rhythms and discuss how signal modality and type (ornament, weapon, dominance trait) account for differences in how chronobiology may act as a compensatory trait. We then consider how biologists might examine the untested role of chronobiology as a compensatory trait and set forth compelling questions for future work. 

Abstract Sensory drive can lead to the evolution of signals that are optimized to the environment in which they are perceived. However, when environmental conditions change, the interactions between signal, environment, and receiver may also shift, leading to the evolution of a new signal optimum or more categorical shifts in sexual signals (gains or losses). We evaluated how visual systems have evolved following a change in environment and male signal, and whether visual system divergence contributes to reproductive isolation between ancestral and derived types in red and black morphs of Pacific Northwest freshwater threespine stickleback. We found that opsin sequence was tuned to enhance the perceived contrast of black fish on a red-shifted light background, whereas opsin expression was not. Further, we found no evidence for homotypic preferences or assortative mating between colour morphs; males of both morphs were equally successful in no-choice mating contexts, perhaps because black males are more vigorous courters. Together, our results suggest that habitat transitions in black stickleback have led to a shift in sensory-drive dynamics with some aspects of the visual system and behaviour evolving in response to other factors (foraging or predation) or lagging behind the evolution of opsin sequences in red-shifted environments. 

Women and racially and ethnically minoritized populations are underrepresented in science, technology, engineering, and mathematics (STEM). Out-of-school time programs like summer camps can provide positive science experiences that may increase self-efficacy and awareness of STEM opportunities. Such programs often use the same high-impact practices used in K–12 classrooms including relating concepts to real-world examples, engaging students as active participants in inquiry-driven projects, and facilitating learning in a cooperative context. They additionally provide opportunities for engaging in STEM without fear of failure, offer a community of mentors, and allow families to become more involved. We designed a summer camp for middle schoolers who identified as girls, low-income, and as a minoritized race or ethnicity. We describe the design of the camp as well as the results from a simple pre- and post-camp questionnaire that examined each camper’s relationship to science, scientific self-efficacy, and interest in having a job in STEM. We found an increase in self-efficacy in camp participants, which is important because high scientific self-efficacy predicts student performance and persistence in STEM, especially for girls. We did not detect an increase in interest in pursuing a STEM job, likely because of already high values for this question on the pre-camp survey. We add to the growing body of work recognizing the potential of out-of-school time STEM programs to increase scientific self-efficacy for girls and racially minoritized students. Tweet: Summer camp for minoritized middle-school girls increases scientific self-efficacy, a characteristic that may be important for removing barriers to participation in STEM. 

Abstract Sexual signals are often transmitted through multiple modalities (e.g., visual and chemical) and under selection from both intended and unintended receivers. Each component of a multimodal signal may be more or less conspicuous to receivers, and signals may evolve to take advantage of available private channels. We recently documented percussive substrate-borne vibrations in the Pacific field cricket (Teleogryllus oceanicus), a species that uses airborne acoustic and chemical signals to attract and secure mates. The airborne signals of Hawaiian T. oceanicus are currently undergoing rapid evolution; at least five novel male morphs have arisen in the past 20 years. Nothing is yet known about the newly discovered percussive substrate-borne vibrations, so we ask “how” they are produced, “who” produces them (e.g., population, morph), “when” they produce them (e.g., whether they are plastic), and “why” (e.g., do they play a role in mating). We show that the vibrations are produced exclusively by males during courtship via foreleg drumming. One novel morph, purring, produces quieter airborne songs and is more likely to drum than the ancestral morph. However, drumming behavior is also contextually plastic for some males; when we removed the ability of males to produce airborne song, ancestral males became more likely to drum, whereas two novel morphs were equally likely to drum regardless of their ability to produce song. Opposite our prediction, females were less likely to mate with males who drummed. We discuss why that might be and describe what we can learn about complex signal evolution from this newly discovered behavior. 

How novel phenotypes evolve is challenging to imagine because traits are often underlain by numerous integrated phenotypic components, and changes to any one form can disrupt the function of the entire module. Yet novel phenotypes do emerge, and research on adaptive phenotypic evolution suggests that complex traits can diverge while either maintaining existing form–function relationships or through innovations that alter form–function relationships. How these alternate routes contribute to sexual signal evolution is poorly understood, despite the role of sexual signals in generating biodiversity. In Hawaiian populations of the Pacific field cricket, male song attracts both female crickets and a deadly acoustically orienting parasitoid fly. In response to this conflict between natural and sexual selection, male crickets have evolved altered wing morphologies multiple times, resulting in loss and dramatic alteration of sexual signals. More recently, we and others have observed a radical increase in sexual signal variation and the underlying morphological structures that produce song. We conducted the first combined analysis of form (wing morphology), function (emergent signal), and receiver responses to characterize novel variation, test alternative hypotheses about form–function relationships (Form–Function Continuity vs. Form–Function Decoupling), and investigate underlying mechanistic changes and fitness consequences of novel signals. We identified three sound-producing male morphs (one previously undescribed, named “rattling”) and found that relationships between morphology and signals have been rewired (Form–Function Decoupling), rapidly and repeatedly, through the gain, loss, and alteration of morphological structures, facilitating the production of signals that exist in novel phenotypic space. By integrating across a hierarchy of phenotypes, we uncovered divergent morphs with unique solutions to the challenge of attracting mates while evading fatal parasitism. 

Abstract Sexual selection can contribute to speciation when signals and preferences expressed during mate choice are coupled within groups, but come to differ across groups (generating assortative mating). When new sexual signals evolve, it is important to investigate their roles in both mate location and courtship contexts, as both signaling functions are critical in mate choice. In previous work, researchers identified two new male morphs (silent and purring) in Hawaiian populations of the Pacific field cricket, Teleogryllus oceanicus. These morphs likely evolved because they protect males from an acoustically orienting parasitoid, yet still obtain some reproductive success. But, it remains unknown how the purring morph functions in close courtship encounters. We compared the relative success of the very recently evolved purring morph to that of the ancestral and silent morphs during courtship encounters. Purring males produce a novel courtship song and were not as successful in courtship as the ancestral type, but were mounted by females as often and as quickly as the obligately silent morph that arose and spread ~20 years ago. Purring males initiate courtship more quickly than other morphs, and females from populations where purring is common exhibit higher overall mounting rates. Thus, differences in the behavior of purring males and of females from populations where purring is common may have facilitated the origin of this novel sexual signal. We found no assortative mating between males of a given morph and females from their own population, and so we hypothesize that multiple male types will be maintained within the species because each achieves fitness in different ways. 

Course-based undergraduate research experiences (CUREs) are high-impact practices that allow students to conduct research during class time. Benefits of a CURE can be maximized when integrated into a faculty member’s ongoing research. However, this can be particularly challenging for field biologists, especially when field sites are not situated near their university. Indeed, few existing CUREs are field based. One solution is to partner with a collaborator near the field site. We describe a semester-long CURE in an animal behavior class that involved collaboration among three institutions: researchers from two “distant” institutions have ongoing research at the “local” institution where the CURE took place. This model uses remote conferencing and strategic collaboration to meet all stakeholders’ needs. Undergraduate students engaged as active participants in collaborative inquiry-based work, learned in a cooperative context, and even participated in the publication process. The local principal investigator and their institution generated a high-impact course that integrated research and teaching. Likewise, the distant principal investigators were able to collect more extensive and longer-term field-based data than otherwise possible, and they gained valuable input from the local researchers that contributed to future projects. Remote collaborations open the door to international collaboration with smaller institutions, promoting greater inclusion in science.