Temperature coupling of mate attraction signals and female mate preferences in four populations of Enchenopa treehopper (Hemiptera: Membracidae)

Abstract

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.

Warm developmental temperatures induce non‐adaptive plasticity in the intrasexually selected colouration of a dragonfly

“…Overall, thermal plasticity in wing colouration appears to be non‐adaptive relative to the known production costs, as well as intrasexual selection, with respect to wing colouration in this population of P. longipennis (Moore & Martin, ; Moore et al ., ; Moore et al ., ). Thus, unlike some sexually selected signals in other insects (Beckers & Schul, ; Jocson et al ., ; Macchiano et al ., ), temperature‐mediated variation in intrasexual selection has not generated adaptive thermal plasticity for wing colouration. Without adaptation, this response in wing colouration may become particularly detrimental as the climate continues to warm: sexual and ecological sources of selection will favour less and less wing colour, whereas the developmental temperatures induce the expression of more and more.…”

Temperature‐related breakdowns in the coordination of mating in Enchenopa binotata treehoppers (Hemiptera: Membracidae)

“…To determine patterns of activity in male courtship, we tested the likelihood for males to produce courtship signals at seven ecologically relevant testing temperatures that span the range the insects naturally experience in the field (Jocson et al., 2019; 18, 21, 24, 27, 30, 33, and 36°C). We first acclimated each male to a randomly assigned testing temperature within a temperature‐controlled incubator for a minimum of 20 min (e.g., Greenfield & Medlock, 2007; Jocson et al., 2019). We then placed each male singly onto a host plant exemplar (which had also been acclimated for more than 20 min at the testing temperature) within a testing incubator set at the testing temperature.…”

“…We determined patterns of courtship activity for females in a similar manner, except that the playbacks involved three different vibratory primers. Both male signal frequency (Jocson et al., 2019; Sattman & Cocroft, 2003) and the frequency that females prefer (Jocson et al., 2019) increase with increased temperature in E. binotata . Furthermore, in some populations, females prefer male signal frequencies that differ from the average male signal across temperatures (Jocson et al., 2019).…”

“…Both male signal frequency (Jocson et al., 2019; Sattman & Cocroft, 2003) and the frequency that females prefer (Jocson et al., 2019) increase with increased temperature in E. binotata . Furthermore, in some populations, females prefer male signal frequencies that differ from the average male signal across temperatures (Jocson et al., 2019). Thus, to reduce the likelihood of females not responding because of a lack of preference for the male signal frequency, we played back six repetitions of three primers to each female.…”

“…We manipulated ambient temperature across a range of ecologically relevant temperatures (18–36ºC; Jocson, Smeester, Leith, Macchiano, & Fowler‐Finn, 2019) in a controlled laboratory setting and tested male courtship activity and female courtship activity in isolation using vibrational playbacks to simulate a reproductive context. We then paired males and females in live interactions across the same temperature range and determined mating success as well as the success and timing of each stage of the mating interaction.…”