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Animal choruses emerge from receiver psychology

View Article: PubMed Central - PubMed

ABSTRACT

Synchrony and alternation in large animal choruses are often viewed as adaptations by which cooperating males increase their attractiveness to females or evade predators. Alternatively, these seemingly composed productions may simply emerge by default from the receiver psychology of mate choice. This second, emergent property hypothesis has been inferred from findings that females in various acoustic species ignore male calls that follow a neighbor’s by a brief interval, that males often adjust the timing of their call rhythm and reduce the incidence of ineffective, following calls, and from simulations modeling the collective outcome of male adjustments. However, the purported connection between male song timing and female preference has never been tested experimentally, and the emergent property hypothesis has remained speculative. Studying a distinctive katydid species genetically structured as isolated populations, we conducted a comparative phylogenetic analysis of the correlation between male call timing and female preference. We report that across 17 sampled populations male adjustments match the interval over which females prefer leading calls; moreover, this correlation holds after correction for phylogenetic signal. Our study is the first demonstration that male adjustments coevolved with female preferences and thereby confirms the critical link in the emergent property model of chorus evolution.

No MeSH data available.


Clustering of genetically similar E. diurnus populations.(A) Mean and standard deviation of ln (probability of data) for each inferred number of clusters (K = 1–14) as estimated from Bayesian STRUCTURE analysis. Values are computed over 20 runs per K. (B) Bayesian STRUCTURE plots representing distinct clusters inferred from the 17 E. diurnus populations sampled (Fig. 4A). Each of the 14 horizontal panels represents a STRUCTURE plot based on a given number of inferred clusters (K = 1–14); in each plot distinct clusters are coded by a different color. The 335 individuals sampled from all 17 populations are each represented by a narrow vertical line, and the probability (q = 0 to 1) of an individual’s assignment to a distinct cluster is indicated by the height of the line segment bearing the color of that distinct cluster. Thus, individuals represented by lines composed of 2 or more segments of different colors may belong to the several distinct clusters whereas those represented by lines composed of a single color are likely to be pure. Fig. 5C depicts the distinct clusters inferred with K = 7.
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f6: Clustering of genetically similar E. diurnus populations.(A) Mean and standard deviation of ln (probability of data) for each inferred number of clusters (K = 1–14) as estimated from Bayesian STRUCTURE analysis. Values are computed over 20 runs per K. (B) Bayesian STRUCTURE plots representing distinct clusters inferred from the 17 E. diurnus populations sampled (Fig. 4A). Each of the 14 horizontal panels represents a STRUCTURE plot based on a given number of inferred clusters (K = 1–14); in each plot distinct clusters are coded by a different color. The 335 individuals sampled from all 17 populations are each represented by a narrow vertical line, and the probability (q = 0 to 1) of an individual’s assignment to a distinct cluster is indicated by the height of the line segment bearing the color of that distinct cluster. Thus, individuals represented by lines composed of 2 or more segments of different colors may belong to the several distinct clusters whereas those represented by lines composed of a single color are likely to be pure. Fig. 5C depicts the distinct clusters inferred with K = 7.

Mentions: In further analyses we dealt with several factors that potentially generated the matching of male and female timing parameters as an artifact. First, we applied the method of independent contrasts (PIC) to our NJ tree of populations to remove any phylogenetic signal from the m-f correlation27. Under most circumstances inter-population gene flow would invalidate the use of PIC to treat intra-specific relationships2829, but the negligible migration in E. diurnus, which are flightless, and the distinctive population genetic structure fully justify its application here. Our NJ tree (Fig. 5A) clearly reveals a branching topology that is consistent, in its details, with another tree based on COI30, indicating that our working phylogeny is most probably an accurate depiction of the true one. To be conservative, we also analyzed our microsatellite data with a Bayesian clustering protocol to identify genetically distinct population clusters and assign individuals to these entities (Fig. 6). We then created a NJ tree for the 7 strongly differentiated clusters identified (Fig. 5C) and again applied the PIC correction. We found that the m-f correlation remained highly significant following PIC correction whether applied to the tree of all 17 populations sampled or to the revised tree of 7 genetically distinct clusters (Fig. 5B,D). Thus, the observed matching of male and female timing parameters is not a phylogenetic artifact of our sampled populations.


Animal choruses emerge from receiver psychology
Clustering of genetically similar E. diurnus populations.(A) Mean and standard deviation of ln (probability of data) for each inferred number of clusters (K = 1–14) as estimated from Bayesian STRUCTURE analysis. Values are computed over 20 runs per K. (B) Bayesian STRUCTURE plots representing distinct clusters inferred from the 17 E. diurnus populations sampled (Fig. 4A). Each of the 14 horizontal panels represents a STRUCTURE plot based on a given number of inferred clusters (K = 1–14); in each plot distinct clusters are coded by a different color. The 335 individuals sampled from all 17 populations are each represented by a narrow vertical line, and the probability (q = 0 to 1) of an individual’s assignment to a distinct cluster is indicated by the height of the line segment bearing the color of that distinct cluster. Thus, individuals represented by lines composed of 2 or more segments of different colors may belong to the several distinct clusters whereas those represented by lines composed of a single color are likely to be pure. Fig. 5C depicts the distinct clusters inferred with K = 7.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5037466&req=5

f6: Clustering of genetically similar E. diurnus populations.(A) Mean and standard deviation of ln (probability of data) for each inferred number of clusters (K = 1–14) as estimated from Bayesian STRUCTURE analysis. Values are computed over 20 runs per K. (B) Bayesian STRUCTURE plots representing distinct clusters inferred from the 17 E. diurnus populations sampled (Fig. 4A). Each of the 14 horizontal panels represents a STRUCTURE plot based on a given number of inferred clusters (K = 1–14); in each plot distinct clusters are coded by a different color. The 335 individuals sampled from all 17 populations are each represented by a narrow vertical line, and the probability (q = 0 to 1) of an individual’s assignment to a distinct cluster is indicated by the height of the line segment bearing the color of that distinct cluster. Thus, individuals represented by lines composed of 2 or more segments of different colors may belong to the several distinct clusters whereas those represented by lines composed of a single color are likely to be pure. Fig. 5C depicts the distinct clusters inferred with K = 7.
Mentions: In further analyses we dealt with several factors that potentially generated the matching of male and female timing parameters as an artifact. First, we applied the method of independent contrasts (PIC) to our NJ tree of populations to remove any phylogenetic signal from the m-f correlation27. Under most circumstances inter-population gene flow would invalidate the use of PIC to treat intra-specific relationships2829, but the negligible migration in E. diurnus, which are flightless, and the distinctive population genetic structure fully justify its application here. Our NJ tree (Fig. 5A) clearly reveals a branching topology that is consistent, in its details, with another tree based on COI30, indicating that our working phylogeny is most probably an accurate depiction of the true one. To be conservative, we also analyzed our microsatellite data with a Bayesian clustering protocol to identify genetically distinct population clusters and assign individuals to these entities (Fig. 6). We then created a NJ tree for the 7 strongly differentiated clusters identified (Fig. 5C) and again applied the PIC correction. We found that the m-f correlation remained highly significant following PIC correction whether applied to the tree of all 17 populations sampled or to the revised tree of 7 genetically distinct clusters (Fig. 5B,D). Thus, the observed matching of male and female timing parameters is not a phylogenetic artifact of our sampled populations.

View Article: PubMed Central - PubMed

ABSTRACT

Synchrony and alternation in large animal choruses are often viewed as adaptations by which cooperating males increase their attractiveness to females or evade predators. Alternatively, these seemingly composed productions may simply emerge by default from the receiver psychology of mate choice. This second, emergent property hypothesis has been inferred from findings that females in various acoustic species ignore male calls that follow a neighbor’s by a brief interval, that males often adjust the timing of their call rhythm and reduce the incidence of ineffective, following calls, and from simulations modeling the collective outcome of male adjustments. However, the purported connection between male song timing and female preference has never been tested experimentally, and the emergent property hypothesis has remained speculative. Studying a distinctive katydid species genetically structured as isolated populations, we conducted a comparative phylogenetic analysis of the correlation between male call timing and female preference. We report that across 17 sampled populations male adjustments match the interval over which females prefer leading calls; moreover, this correlation holds after correction for phylogenetic signal. Our study is the first demonstration that male adjustments coevolved with female preferences and thereby confirms the critical link in the emergent property model of chorus evolution.

No MeSH data available.