Variation in temperature can affect the expression of a variety of important fitness‐related behaviours, including those involved with mate attraction and selection, with consequences for the coordination of mating across variable environments. We examined how temperature influences the expression of male mating signals and female mate preferences—as well as the relationship between how male signals and female mate preferences change across temperatures (signal–preference temperature coupling)—in Enchenopa binotata treehoppers. These small plant‐feeding insects communicate using plantborne vibrations, and our field surveys indicate they experience significant natural variation in temperature during the mating season. We tested for signal–preference temperature coupling in four populations of E. binotata by manipulating temperature in a controlled laboratory environment. We measured the frequency of male signals—the trait for which females show strongest preference—and female peak preference—the signal frequency most preferred by females—across a range of biologically relevant temperatures (18°C–36°C). We found a strong effect of temperature on both male signals and female preferences, which generated signal–preference temperature coupling within each population. Even in a population in which male signals mismatched female preferences, the temperature coupling reinforces predicted directional selection across all temperatures. Additionally, we found similar thermal sensitivity in signals and preferences across populations even though populations varied in the mean frequency of male signals and female peak preference. Together, these results suggest that temperature variation should not affect the action of sexual selection via female choice, but rather should reinforce stabilizing selection in populations with signal–preference matches, and directional selection in those with signal–preference mismatches. Finally, we do not predict that thermal variation will disrupt the coordination of mating in this species by generating signal–preference mismatches at thermal extremes.

Temperature influences the expression of a wide range of behavioral traits in ectotherms, including many involved in the initiation of pair formation and mating. Although opportunities to mate are thought to be greatest when male and female activity overlap, sex‐specific behaviors and physiology could result in mismatched thermal optima for male and female courtship. Here, we investigate how conflicts in the thermal sensitivity of male and female courtship activity affect patterns of mating across temperatures in Enchenopa binotata treehoppers (Hemiptera: Membracidae). These plant‐feeding insects coordinate mating with plant‐borne vibrational signals exchanged in male–female duets prior to pair formation. We manipulated temperature across an ecologically relevant range (18–36ºC) and tested the likelihood of individual male and female E. binotata to engage in courtship activity using vibrational playbacks. We then staged male–female mating interactions across the same temperature range and quantified the thermal sensitivity of mating‐related behaviors across stages of mating. Specifically, we measured the timing of duetting, the likelihood for key pre‐copulatory behaviors to occur, whether the pair mated, and copulation duration. We found sex‐specific thermal sensitivity in courtship activity: Males showed a clear peak of activity at intermediate temperatures (27–30ºC), while females showed highest activity at the hotter thermal extreme. Mating rates, courtship duets, and copulatory attempts were less likely to occur at thermal extremes. Also, duetting occurred earlier and copulation was shortest at higher temperatures. Overall, our data suggest that sexes differ in how temperature affects mating‐related activity and some processes involved in mate coordination may be more sensitive than others across variable thermal environments.

Predicting how insects will react to future thermal conditions requires understanding how temperature currently affects insect behavior, from performance traits to those involved in mating and reproduction. Many reproductive behaviors are thermally-sensitive, but little is known how temperature affects the behaviors used to find mates and coordinate mating. Here, we investigate how temperature influences courtship activity in two sympatric species of Enchenopa treehoppers (Hemiptera: Membracidae). Enchenopa use substrate-borne vibrational signals exchanged in male-female duets to facilitate pair formation prior to mating. In a controlled laboratory setting, we assessed the likelihood of males and females to produce courtship signals across a range of ecologically relevant temperatures. We found that changes in courtship activity across temperatures differed between the two species. We also found sex differences within species: in one species males were more likely to signal at higher temperatures, while in the other species females were more likely to signal at higher temperatures. Our results suggest that sex-specific responses to temperature may constrain mating to narrower ranges of temperatures. Furthermore, sympatric species may respond differently to changes in thermal variation despite sharing similar climactic history.

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Thermal ecology and mate competition are both pervasive features of ecological adaptation. A surge of recent work has uncovered the diversity of ways in which temperature affects mating interactions and sexual selection. However, the potential for thermal biology and reproductive ecology to evolve together as organisms adapt to their thermal environment has been underappreciated. Here, we develop a series of hypotheses regarding (1) not only how thermal ecology affects mating system dynamics, but also how mating dynamics can generate selection on thermal traits; and (2) how the thermal consequences of mate competition favour the reciprocal co-adaptation of thermal biology and sexual traits. We discuss our hypotheses in the context of both pre-copulatory and post-copulatory processes. We also call for future work integrating experimental and phylogenetic comparative approaches to understand evolutionary feedbacks between thermal ecology and sexual selection.Overall, studying reciprocal feedbacks between thermal ecology and sexual selection may be necessary to understand how organisms have adapted to the environments of the past and could persist in the environments of the future. K E Y W O R D Sclimate change, co-adaptation, mate choice, mate competition, mating systems, reciprocal causation, I N T RODUC T IONOrganisms must balance many demands as they adapt to their environments (Noordwijk & de Jong, 1986;Reznick et al., 2000;Ricklefs & Wikelski, 2002). Competing for mates, for example, often requires that animals use habitats or express traits that hinder survival (Andersson, 1994;Wiens & Tuschhoff, 2020;Zuk & Kolluru, 1998). Biologists have long understood that these survival costs can offset the benefits of mating success and limit the exaggeration of reproductive characters (