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P matrices for the male song. The correlation among carrier frequency (cf), pulse rate (pr), pulse duty cycle (pdc), trill rate (tr) and trill duty cycle (tdc) are given for Gryllus rubens (a), Gryllus texensis (b), and the F1 (c) and F2 (d) hybrids. The intensity of the colour of the heat plots indicates the strength of the positive (blue) or negative (red) correlation. The diagonals show the variances of the standardized variables (in white). Correlations are shown above and covariances below the diagonal.
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Studying the genetic architecture of sexual traits provides insight into the rate and direction at which traits can respond to selection. Traits associated with few loci and limited genetic and phenotypic constraints tend to evolve at high rates typically observed for secondary sexual characters. Here, we examined the genetic architecture of song t...
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... estimated the individual-level P matrices for G. rubens, G. texensis and F1 and F2 hybrids. Among male song traits, several parameters showed strong correlations in the parental lines (Fig. 3a,b), most notably trill duty cycle and trill rate (strong, negative in both species) and pulse and trill rate (strong, positive in G. texensis but not in G. rubens). In the F1 and F2 hybrid lines, strong, posi- tive correlations were observed among carrier frequency, pulse rate and trill duty cycle (Fig. 3c,d). Phenotypic inte- gration ...
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... correlations in the parental lines (Fig. 3a,b), most notably trill duty cycle and trill rate (strong, negative in both species) and pulse and trill rate (strong, positive in G. texensis but not in G. rubens). In the F1 and F2 hybrid lines, strong, posi- tive correlations were observed among carrier frequency, pulse rate and trill duty cycle (Fig. 3c,d). Phenotypic inte- gration (relative variance of the eigenvalues, Var rel [k]) was much stronger in G. texensis (Var rel [k] = 0.21) compared to G. rubens (Var rel [k] = 0.08, Table 4a) and not significantly lower among F1 (Var rel [k] = 0.18) or F2 (Var rel [k] = 0.17) hybrids compared to the parental lines (Table 4a). The ...
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... strong negative correlation was observed between trill rate and trill duty cycle (À0.54/À0.34 for G. rubens/ G. texensis; Fig. 3). Although both trill duty cycle and trill rate can be derived from the trill period mathemati- cally, they can be varied independently through the (independent) variation of the trill duration and trill pause. Potentially, the negative correlation between trill rate and trill duty cycle represents a trade-off between trill duration ...
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... G. texensis (but not G. rubens), we also observed a strong correlation between pulse rate and trill rate (0.80) and both traits had strong vector loadings on the first eigenvector of the covariance matrix (Fig. 3, Table S3). In an earlier study comparing P among four cricket species (including G. texensis), the authors reported strong dependence of pulse duration on trill du- ration as well as a (somewhat weaker) correlation between pulse pause and trill pause ( Bertram et al., 2012). Although the authors analysed different traits of the ...
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... strong negative correlation was observed between trill rate and trill duty cycle (À0.54/À0.34 for G. rubens/ G. texensis; Fig. 3). Although both trill duty cycle and trill rate can be derived from the trill period mathemati- cally, they can be varied independently through the (independent) variation of the trill duration and trill pause. Potentially, the negative correlation between trill rate and trill duty cycle represents a trade-off between trill duration and trill rate, as has been shown for the grey treefrog (Wells & Taigen, 1986;Reichert & Gerhardt, 2012). In this case, selection for higher trill duty cycles would result in lower trill rates, which would affect G. rubens more strongly than G. texensis (because the strength of directional selection on trill duty cycle is lower in G. texensis and the correlation between trill duty cycle and trill rate is higher in G. rubens, see Blan- kers et al., 2015 and Fig. S1 in this ...
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... G. texensis (but not G. rubens), we also observed a strong correlation between pulse rate and trill rate (0.80) and both traits had strong vector loadings on the first eigenvector of the covariance matrix (Fig. 3, Table S3). In an earlier study comparing P among four cricket species (including G. texensis), the authors reported strong dependence of pulse duration on trill du- ration as well as a (somewhat weaker) correlation between pulse pause and trill pause ( Bertram et al., 2012). Although the authors analysed different traits of the calling song (duration and pause vs. rate and duty cycle), a positive correlation between the temporal pattern of the pulse and that of the trill supports our finding of a positive correlation between pulse rate and trill rate. Interestingly, the other three Gryllus species analysed by Bertram et al. (2012) showed the same pat- tern, further strengthening the hypothesis of correlated evolution of pulse rate and trill (or chirp) rate in crick- ...
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... estimated the individual-level P matrices for G. rubens, G. texensis and F1 and F2 hybrids. Among male song traits, several parameters showed strong correlations in the parental lines (Fig. 3a,b), most notably trill duty cycle and trill rate (strong, negative in both species) and pulse and trill rate (strong, positive in G. texensis but not in G. rubens). In the F1 and F2 hybrid lines, strong, posi- tive correlations were observed among carrier frequency, pulse rate and trill duty cycle (Fig. 3c,d). Phenotypic inte- gration (relative variance of the eigenvalues, Var rel [k]) was much stronger in G. texensis (Var rel [k] = 0.21) compared to G. rubens (Var rel [k] = 0.08, Table 4a) and not significantly lower among F1 (Var rel [k] = 0.18) or F2 (Var rel [k] = 0.17) hybrids compared to the parental lines (Table 4a). The eigenvectors of P indicate that pulse rate, carrier frequency and trill duty cycle can vary indepen- dently; variation in the trill rate is coupled to variation either in carrier frequency (G. rubens) or pulse rate (G. texensis; Table ...
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... estimated the individual-level P matrices for G. rubens, G. texensis and F1 and F2 hybrids. Among male song traits, several parameters showed strong correlations in the parental lines (Fig. 3a,b), most notably trill duty cycle and trill rate (strong, negative in both species) and pulse and trill rate (strong, positive in G. texensis but not in G. rubens). In the F1 and F2 hybrid lines, strong, posi- tive correlations were observed among carrier frequency, pulse rate and trill duty cycle (Fig. 3c,d). Phenotypic inte- gration (relative variance of the eigenvalues, Var rel [k]) was much stronger in G. texensis (Var rel [k] = 0.21) compared to G. rubens (Var rel [k] = 0.08, Table 4a) and not significantly lower among F1 (Var rel [k] = 0.18) or F2 (Var rel [k] = 0.17) hybrids compared to the parental lines (Table 4a). The eigenvectors of P indicate that pulse rate, carrier frequency and trill duty cycle can vary indepen- dently; variation in the trill rate is coupled to variation either in carrier frequency (G. rubens) or pulse rate (G. texensis; Table ...
Citations
... Many animals -monkeys, mice, bats, birds, frogs, crickets, grasshoppers, katydids, fruit flies -produce species-specific songs to attract and woo conspecifics of the other sex (Baker et al., 2019;Bradbury and Vehrencamp, 2011;Kostarakos and Hedwig, 2014;Neunuebel et al., 2015;Schöneich et al., 2015). During the evolution of acoustic communication, the structure of songs as well as behavioral preferences can evolve rapidly during speciation events (Blankers et al., 2015;Mendelson and Shaw, 2005), giving rise to the large diversity of species-specific songs. Since the evolution of song is mainly driven by the female (Gray and Cade, 2000), the females' song recognition must be selective and modifiable in order to drive the evolution of distinct, species-specific song patterns in males (Wagner, 2007). ...
... Our modeling study of the song recognition network in the cricket brain provides first evidence that the underlying neuronal network is computationally flexible: by adapting physiological parameters, the network can produce all preference types described in crickets ( Figure 4B-E). The computational flexibility of the recognition mechanism may explain the species richness as well as the speed of evolution in a particular taxon like crickets (Alexander, 1962;Blankers et al., 2015;Desutter-Grandcolas and Robillard, 2003;Oh and Shaw, 2013;Otte, 1992): female preferences drift around with little constraint in signal space, maybe pushed by abiotic (environmental noise selects against preferences for very short pauses) and biotic factors (avoid overlap with heterospecifics, Amezquita et al., 2011). The male song evolution follows changes in the female's preference since only males that sing attractive song will reproduce. ...
... Computational flexibility also needs evolvability -the ability to generate specific and robust phenotypes during evolution (Blankers et al., 2015). The 'mechanistic degeneracy' of computation in biological neural networks -the fact that specific network outputs can be obtained by tuning disparate parameters -is thought to be a prerequisite for evolvability (Wagner, 2011, see also Hasson et al., 2020Leonardo, 2005;Schneider et al., 2021). ...
How neural networks evolved to generate the diversity of species-specific communication signals is unknown. For receivers of the signals one hypothesis is that novel recognition phenotypes arise from parameter variation in computationally flexible feature detection networks. We test this hypothesis in crickets, where males generate and females recognize the mating songs with a species-specific pulse pattern, by investigating whether the song recognition network in the cricket brain has the computational flexibility to recognize different temporal features. Using electrophysiological recordings from the network that recognizes crucial properties of the pulse pattern on the short timescale in the cricket Gryllus bimaculatus, we built a computational model that reproduces the neuronal and behavioral tuning of that species. An analysis of the model's parameter space reveals that the network can provide all recognition phenotypes for pulse duration and pause known in crickets and even other insects. Phenotypic diversity in the model is consistent with known preference types in crickets and other insects, and arise from computations that likely evolved to increase energy efficiency and robustness of pattern recognition. The model's parameter to phenotype mapping is degenerate-different network parameters can create similar changes in the phenotype-which likely supports evolutionary plasticity. Our study suggests that computationally flexible networks underlie the diverse pattern recognition phenotypes and we reveal network properties that constrain and support behavioral diversity.
... The variation in acoustic communication (i.e. in mating signals) has been well studied among certain groups of insects such as crickets, treehoppers and lacewings because it is involved in mating processes and consequently in sexual selection (Wilkins et al. 2013). As an example, the two sibling species of crickets Gryllus rubens and G. texensis diverge whereas they share gene flow; differences in males' mating calls and strong female preferences for certain sound traits were promoters of such divergence (Blankers et al. 2015(Blankers et al. , 2019. Despite sexual selection has been proposed as the primary driver of acoustic divergence in this group of crickets, the mechanisms for the divergence are not well understood (Wilkins et al. 2013). ...
To describe and understand biodiversity, the identification of species is essential. Because some species diversify without revealing any morphologic change, the use of different taxonomic tools is highly recommended. Among the advantages of employing different traits for species classification, one of the most remarkable is that at the same time we obtain information about which traits have been involved in the diversification of species. In this study I investigated the variation observed in the ant species Ectatomma ruidum as an evidence of different taxa. E. ruidum is a widely distributed ant from the Neotropics and in previous studies based on mitochondrial sequences the species was proposed to include at least four different taxa. The geographic distribution patterns of the putative species shows that some of them are restricted to small areas, without any apparent geographic barrier separating populations, which raised the question about which mechanisms separated them. By analyzing recognition cues, acoustic signals, morphological acoustic traits and DNA sequences (mitochondrial DNA COI gene, 3RAD and UCE) I provide evidence supporting the separation for most of the previously proposed species. Additionally, the combination of phenotypic and genetic information unveiled that recognition cues may have had a very important role in the diversification of the species complex. Overall, this study adds evidence in favor of the use of a multi trait approach for the delimitation of closely related specie
... Many animals -monkeys, mice, bats, birds, frogs, crickets, grasshoppers, katydids, fruit flies -produce species-specific songs to attract and woo conspecifics of the other sex (Baker et al., 2019;Bradbury and Vehrencamp, 2011;Kostarakos and Hedwig, 2014;Neunuebel et al., 2015). The structure of song as well as the behavioral preference for it can evolve rapidly during speciation events (Blankers et al., 2015;Mendelson and Shaw, 2005), giving rise to the large diversity of species-specific songs. While genes linked to song pattern generation have been identified (Ding et al., 2016;Turner et al., 2013;Xu and Shaw, 2019), it is unclear how song pattern recognition adapts to drive speciation. ...
... Our modelling study of the song recognition network in the cricket brain provides first evidence that the underlying neuronal network is computationally flexible: by adapting physiological parameters it can produce all preference types described in crickets ( Fig. 4B-E). The computational flexibility of the recognition mechanism may explain the species richness as well as the speed of evolution in a particular taxon like crickets (Alexander, 1962;Blankers et al., 2015;Desutter-Grandcolas, 2003;Oh and Shaw, 2013;Otte, 1992). However, computational flexibility also needs evolvability -the ability to generate specific phenotypes during evolution (Blankers et al., 2015). ...
... The computational flexibility of the recognition mechanism may explain the species richness as well as the speed of evolution in a particular taxon like crickets (Alexander, 1962;Blankers et al., 2015;Desutter-Grandcolas, 2003;Oh and Shaw, 2013;Otte, 1992). However, computational flexibility also needs evolvability -the ability to generate specific phenotypes during evolution (Blankers et al., 2015). The "mechanistic degeneracy" of computation in biological neural networks -the fact that specific network outputs can be obtained by tuning disparate parameters -is thought to be a prerequisite for evolvability ((Wagner, 2011), see also (Hasson et al., 2020;Leonardo, 2005)). ...
How neural networks evolve to recognize species-specific communication signals is unknown. One hypothesis is that novel recognition phenotypes are produced by parameter variation in a computationally flexible "mother network". We test this hypothesis in crickets, where males produce and females recognize mating songs with a species-specific pulse pattern. Whether the song recognition network in crickets is computationally flexible to recognize the diversity of pulse patterns and what network properties support and constrain this flexibility is unknown. Using electrophysiological recordings from the cricket Gryllus bimaculatus, we built a model of the song recognition network that reproduces the network dynamics as well as the neuronal and behavioral tuning for that species. An analysis of the model's parameter space reveals that the network can produce all recognition phenotypes known in crickets and even other insects. Biases in phenotypic diversity produced by the model are consistent with the existing behavioral diversity in crickets, and arise from computations that likely evolved to increase energy efficiency and robustness of song recognition. The model's parameter to phenotype mapping is degenerate - different network parameters can create similar changes in the phenotype - which is thought to support evolutionary plasticity. Our study suggest that a computationally flexible mother network could underlie the diversity of song recognition phenotypes in crickets and we reveal network properties that constrain and support behavioral diversity.
... This is because only individuals in good condition can expend the energy required for conspicuous calling (Zahavi, 1975). Indeed, females of some cricket species prefer calling songs with longer pulse durations and shorter inter-pulse intervals or chirp intervals, which are characterized by their high chirp/trill duty cycle (Blankers et al., 2015;Hennig et al., 2016). 2.07.5 ...
Synopsis
Acoustic communication and hearing of insects under natural outdoor conditions is constrained by unpredictable changes on the structure of the acoustic signal propagated from sender to receiver, and background noise further decreases the probability of its detection, discrimination and localization. Behavioral solutions in various insect taxa allow coping with these problems. Furthermore, the chapter describes properties of the sensory system of receivers which evolved to extract behaviorally relevant information from the complex signaling and hearing conditions present in natural environments.
... Finally, the amount by which a male can differ from the most preferred trait value and still attract a female is measured by the tolerance, typically calculated as the width of the preference function at 67% of the maximum response. However, G. rubens and G. texensis differ strongly in peak preference, but only marginally in preference strength (Blankers et al. 2015b) and tolerance (unpublished results); only peak preference is sufficiently divergent for QTL mapping; In an alternative approach, we quantified preference functions more broadly by projecting individual responses of all backcrosses to all eight stimuli onto a linear discriminant function (obtained using "lda" in the R-package "MASS") (Venables and Ripley 2002), which had been trained on parental data (N = 73 G. rubens and N = 44 G. texensis females). This linear discriminant score will be referred to as pulse rate preference function from hereon, because it describes multiple aspects of interspecific variation in female preference through the variable correlation of all test patterns with the linear discriminant function (Table S2). ...
... We showed strong, positive genetic covariance between two male song traits, pulse rate and carrier frequency, that are known to be strongly correlated phenotypically (Blankers et al. 2015b(Blankers et al. , 2017. The strong covariance observed here would allow for a correlated response to selection. ...
Behavioral isolation is a potent barrier to gene flow and a source of striking diversity in the animal kingdom. However, it remains unclear if the linkage disequilibrium (LD) between sex‐specific traits required for behavioral isolation results mostly from physical linkage between signal and preference loci or from directional mate preferences. Here, we test this in the field crickets Gryllus rubens and G. texensis. These closely related species diverged with gene flow and have strongly diverged songs and preference functions for the mate calling song rhythm. We map quantitative trait loci for signal and preference traits (pQTL) as well as for gene expression associated with these traits (eQTL). We find strong, positive genetic covariance between song traits and between song and preference. Our results show that this is in part explained by incomplete physical linkage: although both linked pQTL and eQTL couple male and female traits, major effect loci for different traits were never on the same chromosome. We suggest that the finely‐tuned, highly divergent preference functions are likely an additional source of LD between male and female traits in this system. Furthermore, pleiotropy of gene expression presents an underappreciated mechanism to link sexually dimorphic phenotypes.
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... We showed strong, positive genetic covariance between two male song traits, pulse rate and 443 carrier frequency, that are known to be strongly correlated phenotypically (Blankers et al. 2015b(Blankers et al. , 444 2017). The strong covariance observed here would allow for a correlated response to selection 445 ...
Behavioral isolation is a potent barrier to gene flow and a source of striking diversity in the animal kingdom. However, it remains unclear if the linkage disequilibrium (LD) between sex-specific traits required for behavioral isolation results mostly from physical linkage between signal and preference loci or from directional mate preferences. Here, we test this in the field crickets Gryllus rubens and G. texensis . These closely related species diverged with gene flow and have strongly diverged songs and preference functions for the mate calling song rhythm. We map quantitative trait loci for signal and preference traits (pQTL) as well as for gene expression associated with these traits (eQTL). We find strong, positive genetic covariance between song traits and between song and preference. Our results show that this is in part explained by incomplete physical linkage: although both linked pQTL and eQTL couple male and female traits, major effect loci for different traits were never on the same chromosome. We suggest that the finely-tuned, highly divergent preference functions are likely an additional source of LD between male and female traits in this system. Furthermore, pleiotropy of gene expression presents an underappreciated mechanism to link sexually dimorphic phenotypes.
... The theoretical support for speciation with gene flow driven by divergence in secondary sexual characters is very thin at best (van Doorn et al. 2004;Weissing et al. 2011;Servedio 2015). Here we provide exciting and rare evidence for speciation with primary gene flow while both phenotypic (Gray and Cade 2000), quantitative genetic (Blankers et al. 2015b(Blankers et al. , 2017, and genomic analyses (this study) highlight a role for selection on (acoustic) mating behavior in driving reproductive isolation. A compelling alternative interpretation of the findings here is that the peripatric origin of G. rubens has allowed for an initial phase of reduced gene flow; during this phase mating signals and preferences may have diverged sufficiently (aided by a founder effect following a population bottleneck) to maintain reproductive isolation during a subsequent phase of range expansion culminating into the contemporary, widespread, and largely overlapping species' ...
Gene flow, demography, and selection can result in similar patterns of genomic variation and disentangling their effects is key to understanding speciation. Here, we assess transcriptomic variation to unravel the evolutionary history of Gryllus rubens and Gryllus texensis, cryptic field cricket species with highly divergent mating behavior. We infer their demographic history and screen their transcriptomes for footprints of selection in the context of the inferred demography. We find strong support for a long history of bidirectional gene flow, which ceased during the late Pleistocene, and a bottleneck in G. rubens consistent with a peripatric origin of this species. Importantly, the demographic history has likely strongly shaped patterns of neutral genetic differentiation (empirical FST distribution). Concordantly, FST based selection detection uncovers a large number of outliers, likely comprising many false positives, echoing recent theoretical insights. Alternative genetic signatures of positive selection, informed by the demographic history of the sibling species, highlighted a smaller set of loci; many of these are candidates for controlling variation in mating behavior. Our results underscore the importance of demography in shaping overall patterns of genetic divergence and highlight that examining both demography and selection facilitates a more complete understanding of genetic divergence during speciation. This article is protected by copyright. All rights reserved
... Phenotypic integration is a well-established tool in ecology and commonly is applied in morphological studies to infer functional adaptations and physiological constraints from patterns of covariation among traits in complex phenotypes (Pigliucci & Preston, 2004). Likewise, covariation and phenotypic integration in communication displays composed of several traits such as deer antlers, fruit color and morphology, and acoustic signals have been considered in order to evaluate, for example, their suitability to honestly signal physiological conditions or reward quality (Badyaev, 2004;Valido et al., 2011;Blankers et al., 2015). Correlations between quantitative traits (resulting in high phenotypic integration) may indicate functional modules which require a specific configuration to optimally perform or convey information, and thus are composed of traits that covary more strongly within than across modules (Wilkins et al., 2015). ...
Chemical communication is ubiquitous. The identification of conserved structural elements in visual and acoustic communication is well established, but comparable information on chemical communication displays (CCDs) is lacking.
We assessed the phenotypic integration of CCDs in a meta‐analysis to characterize patterns of covariation in CCDs and identified functional or biosynthetically constrained modules.
Poorly integrated plant CCDs (i.e. low covariation between scent compounds) support the notion that plants often utilize one or few key compounds to repel antagonists or to attract pollinators and enemies of herbivores. Animal CCDs (mostly insect pheromones) were usually more integrated than those of plants (i.e. stronger covariation), suggesting that animals communicate via fixed proportions among compounds. Both plant and animal CCDs were composed of modules, which are groups of strongly covarying compounds. Biosynthetic similarity of compounds revealed biosynthetic constraints in the covariation patterns of plant CCDs.
We provide a novel perspective on chemical communication and a basis for future investigations on structural properties of CCDs. This will facilitate identifying modules and biosynthetic constraints that may affect the outcome of selection and thus provide a predictive framework for evolutionary trajectories of CCDs in plants and animals.
... In general, signal composition is determined by static traits, while measures of signalling effort are more dynamic [18]. This holds true in Texas field crickets, as carrier frequency, sound pressure level (amplitude), and pulse components (duration, pause, period, rate, and duty cycle) all have low coefficients of variation (CV<18; Table 1; sensu [11]), whereas trilling components (duration, pause, period, rate, and duty cycle) and calling effort all have high coefficients of variation CV>25; Table 1; sensu [11]). ...
... Given this, we asked whether any of our G. texensis males could have been misidentified. Two males had low pulse rates for G. texensis (<56 pulses per second) suggesting they might be misidentified (sensu [18] , Fig 1a). However, both males called at carrier frequencies above 5.5 kHz, with trill durations about 400 ms, and trill rates above 1.2 trills/second, suggesting they are G. texensis (sensu [18] , Fig 1c and 1d, respectively). ...
... Two males had low pulse rates for G. texensis (<56 pulses per second) suggesting they might be misidentified (sensu [18] , Fig 1a). However, both males called at carrier frequencies above 5.5 kHz, with trill durations about 400 ms, and trill rates above 1.2 trills/second, suggesting they are G. texensis (sensu [18] , Fig 1c and 1d, respectively). Further, given our study site was located about 100km west of the most western end of the range of G. rubens, we opted to include these males in our analyses. ...
The evolution of multiple sexual signals presents a dilemma since individuals selecting a mate should pay attention to the most honest signal and ignore the rest; however, multiple signals may evolve if, together, they provide more information to the receiver than either one would alone. Static and dynamic signals, for instance, can act as multiple messages, providing information on different aspects of signaller quality that reflect condition at different time scales. While the nature of static signals makes them difficult or impossible for individuals to augment, dynamic signals are much more susceptible to temporary fluctuations in effort. We investigated whether male Texas field crickets, Gryllus texensis, that produce unattractive static signals compensate by dynamically increasing their calling effort. Our findings lend partial support to the compensation hypothesis, as males that called at unattractive carrier frequencies (a static trait) spent more time calling each night (a dynamic trait). Interestingly, this finding was most pronounced in males that called with attractive pulse characteristics (static traits) but did not occur in males that called with unattractive pulse characteristics. Males that signalled with unattractive pulse characteristics (duration and pause) spent less time calling through the night. Our correlative findings on wild caught males suggest that only males that signal with attractive pulse characteristics may be able to afford to pay the costs of both trait exaggeration and increased calling effort to compensate for poor carrier frequencies.
... Could males evolve to exploit the female bias and evolve long trills? This would require sufficient phenotypic and genetic variation, often observed in crickets [36,37], and available acoustic niche space. Both G. firmus and G#13 are sympatric with other Gryllus that produce long trills, which in theory could limit the sound space available to them. ...
The question of why males of many species produce elaborate mating displays has now been largely resolved: females prefer to mate with males that produce such displays. However, the question of why females prefer such displays has been controversial, with an emerging consensus that such displays often provide information to females about the direct fitness benefits that males provide to females and/or the indirect fitness benefits provided to offspring. Alternative explanations, such as production of arbitrarily attractive sons or innate pre-existing female sensory or perceptual bias, have also received support in certain taxa. Here, we describe multivariate female preference functions for male acoustic traits in two chirping species of field crickets with slow pulse rates; our data reveal cryptic female preferences for long trills that have not previously been observed in other chirping species. The trill preferences are evolutionarily pre-existing in the sense that males have not (yet?) exploited the
