The Importance of Female Choice, Male-Male Competition, and Signal Transmission as Causes of Selection on Male Mating Signals

Abstract

Selection on advertisement signals arises from interacting sources including female choice, male-male competition, and the communication channel (i.e., the signaling environment). To identify the contribution of individual sources of selection, we used previously quantified relationships between signal traits and each putative source to predict relationships between signal variation and fitness in Enchenopa binotata treehoppers (Hemiptera: Membracidae). We then measured phenotypic selection on signals and compared predicted and realized relationships between signal traits and mating success. We recorded male signals, then measured lifetime mating success at two population densities in a realistic environment in which sources of selection could interact. We identified which sources best predicted the relationship between signal variation and mating success using a multiple regression approach. All signal traits were under selection in at least one of the two breeding seasons measured, and in some cases selection was variable between years. Female preference was the strongest source of selection shaping male signals. The E. binotata species complex is a model of ecological speciation initiated by host shifts. Signal and preference divergence contribute to behavioral isolation within the complex, and the finding that female mate preferences drive signal evolution suggests that speciation in this group results from both ecological divergence and sexual selection.

Genotype × environment interaction is weaker in genitalia than in mating signals and body traits in Enchenopa treehoppers (Hemiptera: Membracidae)

“…Our estimates of H 2 were higher in body and genitalia than in signals, a pattern that fits the trend for behaviour to show lower heritability than morphology (Stirling et al 2002). It is also consistent with the expected erosion of genetic variation by selection, since E. binotata signals have diverged rapidly under strong sexual selection (Rodríguez et al , 2006Cocroft et al 2010;Sullivan-Beckers and Cocroft 2010). Medium-tohigh H 2 in genitalia is in line with other studies (Arnqvist and Thornhill 1998;Zeng et al 2000;Andrade et al 2009;Higgins et al 2009;Kamimura and Iwase 2010).…”

“…The above analyses view traits as independent from each other, since we were interested in specific traits; e.g., some signal traits are the most divergent aspects of adult phenotypes in the E. binotata complex, and targets of sexual selection (Rodríguez et al 2006;Cocroft et al 2010;Sullivan-Beckers and Cocroft 2010). Also, the body and genitalia traits encompass the subtle variation present in the complex (Pratt and Wood 1993;Hamilton and Cocroft 2009).…”

Palomena prasina (Hemiptera: Pentatomidae) vibratory signals and their tuning with plant substrates

“…The difference in this case is in the range of several hundred Hz and is likely to be a result of micro-habitat choice that determines the most efficient signal frequency [15], as well as divergent evolution due to shaping of female preference [29,30]. However, this not the adaptive phenotypic plasticity that is implied by our results.…”

Genetic variation in social influence on mate preferences

“…For example, which aspects of social interactions are responsible for the variation that is generated in, say, mate preferences? We find that, for Enchenopa females, experimental manipulation of social groupings has stronger effects than manipulation in the experience of signals alone ( [32,33], this study). What is the cause of these differences?…”

“…We note that Enchenopa females mate only once [31,33]. Consequently, the broods of the females that we collected constitute full-sibling families.…”