Evolutionary novelty in communication between the sexes

Abstract

The diversity of signalling traits within and across taxa is vast and striking, prompting us to consider how novelty evolves in the context of animal communication. Sexual selection contributes to diversification, and here we endeavour to understand the initial conditions that facilitate the maintenance or elimination of new sexual signals and receiver features. New sender and receiver variants can occur through mutation, plasticity, hybridization and cultural innovation, and the initial conditions of the sender, the receiver and the environment then dictate whether a novel cue becomes a signal. New features may arise in the sender, the receiver or both simultaneously. We contend that it may be easier than assumed to evolve new sexual signals because sexual signals may be arbitrary, sexual conflict is common and receivers are capable of perceiving much more of the world than just existing sexual signals. Additionally, changes in the signalling environment can approximate both signal and receiver changes through a change in transmission characteristics of a given environment or the use of new environments. The Anthropocene has led to wide-scale disruption of the environment and may thus generate opportunity to directly observe the evolution of new signals to address questions that are beyond the reach of phylogenetic approaches.

Behavioral responses of a parasitoid fly to rapidly evolving host signals

“…The exemplars in this study span most of the tremendous variation in purring song, offering more opportunity for flies to show preferences for diverse features of purring, yet we still found no preferences. This result is not surprising considering that preference evolution often lags behind signal evolution (Broder et al, 2021 ; Rosenthal, 2018 ). Since there is a large fitness cost of not locating a host, it stands to reason that parasitoids may be selected to accept any suitable host of that species, rather than expressing strong preferences for particular individual hosts (Kruitwagen et al, 2021 ).…”

“…The first possible hypothesis is that flies have no preference for particular purrs (preference functions are flat). This result seems likely for three reasons: (1) preference evolution may lag behind signal evolution (Broder et al, 2021 ; Rosenthal, 2018 ), (2) flies may be pre‐adapted to broadly attend to any new host signals because they parasitize at least 17 other cricket species in other parts of their range (Gray et al, 2019 ), and (3) there is a large fitness cost for flies that cannot locate a host, so parasitoids should accept any suitable host (Kruitwagen et al, 2021 ). Alternatively, flies may exhibit preferences for certain purring songs.…”

The persistence and evolutionary consequences of vestigial behaviours

“…The fate of associated behaviours is less well understood and has not often been studied but, like anti‐predator behaviours, lends itself to empirical study given the relative ease of inferring relaxed or reversed selection following the loss of the associated signal. This is an important gap in our understanding of sexual signals, as the retention of signalling behaviour components could play a vital role in facilitating their re‐emergence after evolutionary reversal (Broder et al ., 2021a).…”

Environmental Correlates of Sexual Signaling in the Heteroptera: A Prospective Study

“…Communication within the sexes in terms of sexual selection typically involves ritualized displays of dominance, fighting ability, or territory ownership, that precede, and potentially allow individuals to avoid, actual physical contests between rivals [3][4][5][6]. In terms of between-sex communication, whilst the focus has perhaps traditionally been on courtship displays and subsequent mate choice, for many organisms, communication is also an important part of (competitive) mate searching and will include signaling up to and during copulation [7][8][9][10]. The signals used to attract and entice a mate can vary greatly in complexity and signal content, including information associated with species discrimination, as well as one or more components of mate quality, and they can also vary in methods of transmission and sensory modality (visual, auditory, tactile, or olfactory).…”

“…Therefore, selection favors signals that optimize the signal to background noise ratio, whilst minimizing signal degradation [5]. This is highly dependent on the environment in which sexual communication occurs [9,[15][16][17][18][19][20]. Environmental conditions, both biotic and abiotic, spanning climate, seasonality, habitat structure, predators, and prey, interact via natural selection to influence how sexual selection acts, in terms of behavior, morphology, and key life-history allocation decisions [19].…”