02400nas a2200193 4500008004100000245014000041210006900181520172100250653001601971653002701987653002302014653001402037653001802051653002502069100002202094700002402116700002302140856004302163 2018 eng d00aSeasonal variation in abundance and diversity of eavesdropping frog-biting midges (Diptera, Corethrellidae) in a neotropical rainforest0 aSeasonal variation in abundance and diversity of eavesdropping f3 a

In the tropics, precipitation patterns result in seasonal fluctuations in the abundance and distribution of plant and animal species. Tropical predators and parasites are therefore faced with seasonal changes in prey and host availability.
2. This study investigates the seasonal interaction among a specialised ectoparasite, eavesdropping frog-biting midges (Corethrella spp.), and their anuran hosts, examining how the abundance and diversity of the frog-biting midge community fluctuate between the rainy (host abundant) and dry (host sparse) seasons.
3. Midges were captured in both the rainy and dry seasons using acoustic playbacks of calls from a common frog species that breeds during the rainy season, the túngara frog (Engystomops, Physalaemus, pustulosus). During the dry season túngara frog choruses are absent. To explore seasonal shifts in host preference or changes in the midge community due to host specificity, midges were also captured using playbacks of calls from a frog that breeds during the dry season, the pug-nosed tree frog (Smilisca sila).
4. While the overall abundance of midges decreased in the dry season, only slight differences in the relative abundance between midge species were found. These results suggest that midge populations can shift between hosts as they become available across seasons, allowing adult populations of frog-biting midges to persist year-round. To overcome the challenge of detecting and localising different host species, it is proposed that frog-biting midges have evolved a generalised acoustic template, allowing them to respond to a broad range of available hosts, regardless of seasonal host composition.

10aCorethrella10aEngystomops pustulosus10afrog-biting midges10aphenology10aSmilisca sila10atropical seasonality1 aLegett, Henry, D.1 aBARANOV, VIKTOR, A.1 aBernal, Ximena, E. uhttp://doi.wiley.com/10.1111/een.1249205028nas a2200121 4500008004100000245003200041210003000073520469600103100002104799700002204820700002304842856004104865 2014 eng d00aBe loved, be prey, be eaten0 aBe loved be prey be eaten3 a

Animal communication is one of the most fundamental of all social behaviors. It modulates interactions among neighbors and strangers, siblings and parents, and individuals and their prospective mates. One of the most fundamental functions of communication is to enhance the sender’s conspicuousness, to cause the sender to stand out against the background so it can be detected by the receiver. This is a challenge for signals that function over long distances, such as those that function in territorial advertisement and mate attraction, because signal intensity and fidelity decrease with distance from the sender. At longer distances a signal is less likely to be above the receiver’s threshold for detection and recognition, and it is also more likely to be masked by noise as the intensity of noise at the receiver is independent of its distance from the sender.

Another type of noise is generated by conspecifics signaling in the same channel. We may perceive a chorus of frogs or insects as a melodious, even co- operative unit. But to members of the chorus the calls of their neighbors are every bit as deleterious to their own call’s ability to be detected as is environ- mental noise. There is also “noise” within the perceptual systems of the receiver that ameliorates signal detection. One example is habituation. Upon continual exposure to a signal, an animal will tend to ignore it, and some of the animal’s neurons will cease to fire. Another type of perceptual noise is incremental forgetting of a signal once it is perceived. Some signals are more memorable than others, surviving longer in the receiver’s memory. The importance of conspecific noise and perceptual noise is usually less appreciated in animal communication studies than is environmental noise.

Selection often will favor senders to produce communication signals that stand out against these three types of background noise. Conspicuousness is accomplished in a variety of ways. In the acoustic domain animals can use fre- quency bands that contain less noise; they can call longer, at a faster rate, or at a higher amplitude; they can call during periods when others are silent; and they can produce calls that are more complex. Visual signals can stand out more against background when their spectral properties and spatial patterns differ from those in the background, when colors are brighter and patterns are more complex, and when motion patterns associated with the signal, such as push-up displays in lizards, are different than the pattern of background movement, such as vegetation being blow in the wind (e.g., Fleishman, 1992). Increasing signal complexity in both the acoustic and visual domains can to some extent remedy the receiver habituating to and forgetting a signal. There is less known about how chemical, tactile, and electrical signals can enhance contrast with the background.

In a survey of preferences for sexual signals, Michael Ryan and Anne Keddy-Hector (1992) showed that across modalities prospective mates tended to prefer sexual signals that were greater in magnitude: longer and louder, faster and brighter, more complex and with more background contrast. Although there were numerous cases in which prospective mates preferred signals that were near the population mean, there were few cases in which there was a preference for signals of lesser magnitude. A simple rule of thumb for sexual signals is that more is better. Selection for signal efficacy, however, creates a dilemma for the sender: the curse of unintended receivers. In general, each signal has evolved under selection to communi- cate with a specific intended receiver. In the case of sexual advertisement sig- nals, the intended receivers are prospective mates, usually female conspecifics. Other receivers can also detect and respond to signals even if there was no selection on the sender to communicate with them. We refer to these receivers as eavesdroppers or unintended receivers. It is important to note that the terms intended and unintended should not imply intention- ality but instead refer to hypotheses about the selection forces that favored the evolution of these signals. With few exceptions, senders and receivers do not communicate in a private channel. The world is populated by unin- tended receivers, eavesdroppers who are attendant to the signals of senders, often to the demise of senders. In this chapter we explore the tension that exists in sexual communication systems between being conspicuous to potential mates and attracting eavesdroppers, between being loved, being prey, and being eaten.

1 aPage, Rachel, A.1 aRyan, Michael, J.1 aBernal, Ximena, E. uhttps://bio.acousti.ca/it/node/5755502040nas a2200181 4500008004100000245011900041210006900160520139000229653002701619653002601646653001801672653002201690653001401712100002201726700002101748700002301769856006601792 2019 eng d00aSynchronized mating signals in a communication network: the challenge of avoiding predators while attracting mates0 aSynchronized mating signals in a communication network the chall3 a

Conspicuous mating signals attract mates but also expose signallers to predators and parasites. Signal evolution, therefore, is driven by conflicting selective pressures from multiple receivers, both target and non-target. Synchronization of mating signals, for example, is an evolutionary puzzle, given the assumed high cost of reduced female attraction when signals over- lap. Synchronization may be beneficial, however, if overlapping signals reduce attraction of non-target receivers. We investigate how signal synchro- nization is shaped by the trade-off between natural and sexual selection in two anuran species: pug-nosed tree frogs (Smilisca sila), in which males pro- duce mating calls in near-perfect synchrony, and túngara frogs (Engystomops pustulosus), in which males alternate their calls. To examine the trade-off imposed by signal synchronization, we conducted field and laboratory play- back experiments on eavesdropping enemies (bats and midges) and target receivers (female frogs). Our results suggest that, while synchronization can be a general strategy for signallers to reduce their exposure to eavesdrop- pers, relaxed selection by females for unsynchronized calls is key to the evolution and maintenance of signal synchrony. This study highlights the role of relaxed selection in our understanding of the origin of mating signals and displays.

10aacoustic communication10acommunication network10aeavesdroppers10arelaxed selection10asynchrony1 aLegett, Henry, D.1 aPage, Rachel, A.1 aBernal, Ximena, E. uhttps://royalsocietypublishing.org/doi/10.1098/rspb.2019.1067