Nonlinear changes in selection on a mating display across a continuous thermal gradient

Abstract

Understanding how animal communication varies across time and space is critical to understanding how animal signals have evolved and how they function. Changes in temperature, which occur across both time and space, can alter both the courtship and mate choice behaviour of ectothermic animals. In this study, we examine the effect of daily thermal variation on courtship and mate choice in the wolf spider Schizocosa floridana , which produces a complex song with vibrations from three distinct body parts. We test the hypothesis that different components of S. floridana' s courtship respond differently to daily changes in temperature and that corresponding mate choice patterns lead to complex, overlapping shifts in selection on the display itself. By manipulating the thermal environment of courting and choosing pairs, we found that several song components increased in production rate with increased temperature, whereas others decreased, or did not respond at all. We also found evidence that selection on courtship shifts with temperature in several ways, with some display components experiencing directional selection at higher temperatures, but not at lower temperatures. Our findings make it clear that understanding the effect of environmental variation on communication is critical to understanding how selection operates on mate choice and how signals, particularly complex signals, evolve.

Exploring a novel substrate‐borne vibratory signal in the wolf spider Schizocosa floridana

“…Likewise, S. floridana courtship changes across temperatures, but chirps change in a pattern opposite to the other courtship components. Specifically, chirp duration and the number of pulses within a chirp decrease with increasing temperature, whereas all other components increase in rate or duration with increasing temperature (Rosenthal & Elias, 2019). This finding suggests interesting future avenues of research in the study of complex signal function, which is often concerned with the relationships between multiple signal components.…”

“…One possibility is that it may encode information on signaler size or body condition, as is the case in many non‐spider species (e.g., Anurans: Gingras et al., 2012; Insects: Bennet‐Clark, 1998; Birds: Ryan & Brenowitz, 1985; Primates: Hauser, 1993). The production rate of thumps, taps, and chirps are known to affect mate choice (Rosenthal & Elias, 2019; Rosenthal & Hebets, 2012; Rosenthal et al., 2018; Rundus et al., 2011), but do not reflect male size or condition (Rosenthal & Hebets, 2012). It is possible that S. floridana body size is encoded in chirp frequency rather than in rate, and we are currently engaged in work testing this idea as well as exploring other potential roles of this novel acoustic component.…”

“…The production rate of thumps, taps, and chirps are known to affect mate choice (Rosenthal & Elias, 2019;Rosenthal & Hebets, 2012;Rosenthal et al, 2018;Rundus et al, 2011), but do not reflect male size or condition (Rosenthal & Hebets, 2012). It is possible that S. floridana body size is encoded in chirp frequency rather than in rate, and we are currently engaged in work testing this idea as well as exploring other potential roles of this novel acoustic component.…”

“…Using these recordings, we separately measured the tonality of each courtship component within the S. floridana song. For each male, we extracted three exemplars of each component (thumps, taps, chirps; see also Figure 1 from Rosenthal et al, 2018 or Figure 1 from Rosenthal & Elias, 2019). We quantified the spectral entropy from a power spectral density of each isolated component exemplar in MATLAB (see Chivers et al, 2017;Giannakopoulos & Pikrakis, 2014;Sueur et al, 2008; Supplemental file S1).…”

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

“…Many studies that describe behavioral responses to temperature focus on performance traits like sprint speed and locomotion (Bennett, 1980, 1990; Cullum, 1998; Green & Fisher, 2004; Hertz, Huey, & Nevo, 1983; Lailvaux, Alexander, & Whiting, 2003); in contrast, the thermal sensitivity of mating‐related traits has received less attention (Andrew et al., 2013; but see Brandt, Kelley, & Elias, 2018; Rosenthal & Elias, 2019; Macchiano, Sasson, Leith, & Fowler‐Finn, 2019). Because reproductive behaviors are closely tied to Darwinian fitness, understanding how temperature affects mating‐related behaviors is central to understanding the fitness effects of thermal variation (Sinclair et al., 2012; Visser, 2008).…”