Phylogenetic distribution of a male pheromone that may exploit a nonsexual preference in lampreys

Pheromones are among the most important sexual signals used by organisms throughout the animal kingdom. However, few are identified in vertebrates, leaving the evolutionary mechanisms underlying vertebrate pheromones poorly understood. Pre‐existing biases in receivers' perceptual systems shape visual and auditory signalling systems, but studies on how receiver biases influence the evolution of pheromone communication remain sparse. The lamprey Petromyzon marinus uses a relatively well‐understood suite of pheromones and offers a unique opportunity to study the evolution of vertebrate pheromone communication. Previous studies indicate that male signalling with the mating pheromone 3‐keto petromyzonol sulphate (3kPZS) may exploit a nonsexual attraction to juvenile‐released 3kPZS that guides migration into productive rearing habitat. Here, we infer the distribution of male signalling with 3kPZS using a phylogenetic comparison comprising six of 10 genera and two of three families. Our results indicate that only P. marinus and Ichthyomyzon castaneus release 3kPZS at high rates. Olfactory and behavioural assays with P. marinus, I. castaneus and a subset of three other species that do not use 3kPZS as a sexual signal indicate that male signalling might have driven the evolution of female adaptations to detect 3kPZS with specific olfactory mechanisms and respond to 3kPZS with targeted attraction relevant during mate search. We postulate that 3kPZS communication evolved independently in I. castaneus and P. marinus, but cannot eliminate the alternative that other species lost 3kPZS communication. Regardless, our results represent a rare macroevolutionary investigation of a vertebrate pheromone and provide insight into the evolutionary mechanisms underlying pheromone communication.     

Cultural consonance and psychological distress: examining the associations in multiple cultural domains

Cultural consonance is the degree to which individuals, in their own beliefs and behaviors, approximate widely shared cultural models. In previous research in Brazil and the United States we found that higher cultural consonance in the cultural domains of lifestyle and social support was associated with lower psychological distress. The aim of this paper is to expand on these results in two ways. First, the measurement of cultural consonance has been improved through a closer link of cultural domain analyses and survey research. Second, the number of domains in which cultural consonance has been examined has been expanded to include—along with lifestyle and social support—family life, national identity, and food. We found that cultural consonance in these five domains can be conceptualized as two latent variables of generalized cultural consonance, and that this generalized cultural consonance is associated with lower psychological distress. These results continue to support the usefulness of cultural consonance as a theoretical construct in the explanation of human social suffering.     

Female preference function related to precedence effect in an amphibian anuran (Alytes cisternasii): tests with non-overlapping calls

We quantified precedence effect (measured as female preferencefor the leading calls in an acoustic interaction between twomales) with non-overlapping, simulated male calls presentedwith various phase relationships to female Iberian midwifetoads (Alytes cisternasii) in two-speaker phonotaxis playbacktests. The resulting information determines the shape of thefemale preference function for intercall delays. Females preferentiallyapproached leading callers for most tested phase angles. We found a gradation in the degree to which females selected theleader. They tended to exert a strong preference for the leaderin 30° test, and at higher phase angles, the overall preferencewas weaker and graded (the higher the phase angle, the lowerthe preference). Other parameters of female preference (latencyand repeatability) also had a graded relationship with phaseangle value. The sharp difference in probability of approachbetween 30° and 60° is consistent with a mechanismof male calling inhibition immediately after hearing a competitor'scall previously described in other taxa. In natural interactions,male A. cisternasii adjust the timing of their calls to a phaseangle that provides a slight but significant advantage to theleading caller.     

Female preference for multi-modal courtship: multiple signals are important for male mating success in peacock spiders

A long-standing goal for biologists has been to understand how female preferences operate in systems where males have evolved numerous sexually selected traits. Jumping spiders of the Maratus genus are exceptionally sexually dimorphic in appearance and signalling behaviour. Presumably, strong sexual selection by females has played an important role in the evolution of complex signals displayed by males of this group; however, this has not yet been demonstrated. In fact, despite apparent widespread examples of sexual selection in nature, empirical evidence is relatively sparse, especially for species employing multiple modalities for intersexual communication. In order to elucidate whether female preference can explain the evolution of multi-modal signalling traits, we ran a series of mating trials using Maratus volans. We used video recordings and laser vibrometry to characterize, quantify and examine which male courtship traits predict various metrics of mating success. We found evidence for strong sexual selection on males in this system, with success contingent upon a combination of visual and vibratory displays. Additionally, independently produced, yet correlated suites of multi-modal male signals are linked to other aspects of female peacock spider behaviour. Lastly, our data provide some support for both the redundant signal and multiple messages hypotheses for the evolution of multi-modal signalling.     

Without it no music: cognition,biology and evolution of musicality

Musicality can be defined as a natural, spontaneously developing trait based on and constrained by biology and cognition. Music, by contrast, can be defined as a social and cultural construct based on that very musicality. One critical challenge is to delineate the constituent elements of musicality. What biological and cognitive mechanisms are essential for perceiving, appreciating and making music? Progress in understanding the evolution of music cognition depends upon adequate characterization of the constituent mechanisms of musicality and the extent to which they are present in non-human species. We argue for the importance of identifying these mechanisms and delineating their functions and developmental course, as well as suggesting effective means of studying them in human and non-human animals. It is virtually impossible to underpin the evolutionary role of musicality as a whole, but a multicomponent perspective on musicality that emphasizes its constituent capacities, development and neural cognitive specificity is an excellent starting point for a research programme aimed at illuminating the origins and evolution of musical behaviour as an autonomous trait.     

Evolutionary novelty in communication between the sexes

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.     

Real estate ads in Emei music frog vocalizations: female preference for calls emanating from burrows

During female mate choice, both the male's phenotype and resources (e.g. his nest) contribute to the chooser's fitness. Animals other than humans are not known to advertise resource characteristics to potential mates through vocal communication; although in some species of anurans and birds, females do evaluate male qualities through vocal communication. Here, we demonstrate that calls of the male Emei music frog (Babina dauchina), vocalizing from male-built nests, reflect nest structure information that can be recognized by females. Inside-nest calls consisted of notes with energy concentrated at lower frequency ranges and longer note durations when compared with outside-nest calls. Centre frequencies and note durations of the inside calls positively correlate with the area of the burrow entrance and the depth of the burrow, respectively. When given a choice between outside and inside calls played back alternately, more than 70 per cent of the females (33/47) chose inside calls. These results demonstrate that males of this species faithfully advertise whether or not they possess a nest to potential mates by vocal communication, which probably facilitates optimal mate selection by females. These results revealed a novel function of advertisement calls, which is consistent with the wide variation in both call complexity and social behaviour within amphibians.     

Leader preference in Neoconocephalus ensiger katydids: a female preference for a nonheritable male trait

Female preferences for males producing their calls just ahead of their neighbours, leader preferences, are common in acoustically communicating insects and anurans. While these preferences have been well studied, their evolutionary origins remain unclear. We tested whether females gain a fitness benefit by mating with leading males in Neoconocephalus ensiger katydids. We mated leading and following males with random females and measured the number and quality of F₁, the number of F₂ and the heritability of the preferred male trait. We found that females mating with leaders and followers did not differ in the number of F₁ or F₂ offspring. Females mating with leading males had offspring that were in better condition than those mating with following males suggesting a benefit in the form of higher quality offspring. We found no evidence that the male trait, the production of leading calls, was heritable. This suggests that there is no genetic correlate for the production of leading calls and that the fitness benefit gained by females must be a direct benefit, potentially mediated by seminal proteins. The presence of benefits indicates that leader preference is adaptive in N. ensiger, which may explain the evolutionary origin of leader preference; further tests are required to determine whether fitness benefits can explain the phylogenetic distribution of leader preference in Neoconocephalus. The absence of heritability will prevent leader preference from becoming coupled with or exaggerating the male trait and prevent females from gaining a ‘sexy‐sons’ benefit, weakening the overall selection for leader preference.     

Behavioural response evoked by conspecific distress calls in two neotropical treefrogs

Anurans emit distress calls when attacked by predators as a defensive mechanism. As distress calls may trigger antipredator behaviour even in individuals that are not under attack, we tested whether this defensive behaviour induced behavioural changes in neighbouring conspecifics. We compared the behavioural responses of two species of Neotropical hylid frogs (genus Boana) to conspecific distress calls and white noise. Individuals of both species interrupted their vocal activity and decreased call rate after hearing the distress call. Natural variation on signal intensity calibrated among the nearest neighbours did not influence the response and we did not observe negative phonotaxis after any acoustic stimulus. Despite the fact that many predators are acoustically oriented, we could not determine if such response (reduced call rate) was induced by risk assessment or by the masking effect on advertisement calls. Boana faber responded similarly to white noise and distress calls, while B. bischoffi responded more intensely to distress calls. Duration of silence after playbacks in B. faber was longer than B. bischoffi. We suggest that, if the signals are interpreted as a risk cue by neighbouring conspecifics, each species may be preyed upon by different predators, as they may have led to distinct defensive strategies and different responses to distress calls. If risk assessment information is included in distress calls, it triggers behavioural responses only in the nearest neighbours, as we did not observe responses on the vocal activity of the interspecific chorus. Our results add relevant data about acoustic communication and interpretations by anurans, highlighting the importance of considering cues within common and widespread signals.     

Noise affects the shape of female preference functions for acoustic signals

The shape of female mate preference functions influences the speed and direction of sexual signal evolution. However, the expression of female preferences is modulated by interactions between environmental conditions and the female's sensory processing system. Noise is an especially relevant environmental condition because it interferes directly with the neural processing of signals. Although noise is therefore likely a significant force in the evolution of communication systems, little is known about its effects on preference function shape. In the grasshopper Chorthippus biguttulus, female preferences for male calling song characteristics are likely to be affected by noise because its auditory system is sensitive to fine temporal details of songs. We measured female preference functions for variation in male song characteristics in several levels of masking noise and found strong effects of noise on preference function shape. The overall responsiveness to signals in noise generally decreased. Preference strength increased for some signal characteristics and decreased for others, largely corresponding to expectations based on neurophysiological studies of acoustic signal processing. These results suggest that different signal characteristics will be favored under different noise conditions, and thus that signal evolution may proceed differently depending on the extent and temporal patterning of environmental noise.     

Fenestration: a window of opportunity for carnivorous plants

A long-standing but controversial hypothesis assumes that carnivorous plants employ aggressive mimicry to increase their prey capture success. A possible mechanism is that pitcher plants use aggressive mimicry to deceive prey about the location of the pitcher''s exit. Specifically, species from unrelated families sport fenestration, i.e. transparent windows on the upper surfaces of pitchers which might function to mimic the exit of the pitcher. This hypothesis has not been evaluated against alternative hypotheses predicting that fenestration functions to attract insects from afar. By manipulating fenestration, we show that it does not increase the number of Drosophila flies or of two ant species entering pitchers in Sarracenia minor nor their retention time or a pitcher''s capture success. However, fenestration increased the number of Drosophila flies alighting on the pitcher compared with pitchers of the same plant without fenestration. We thus suggest that fenestration in S. minor is not an example of aggressive mimicry but rather functions in long-range attraction of prey. We highlight the need to evaluate aggressive mimicry relative to alternative concepts of plant–animal communication.     

Variability in the mating calls of the Lusitanian toadfish Halobatrachus didactylus: cues for potential individual recognition

The mating sounds (boatwhistles) of nesting batrachoidid Halobatrachus didactylus males were recorded in the Tagus Estuary from piers. Thirteen males with 16 boatwhistles per fish were analysed for 20 acoustic features. All variables showed larger between‐male than within‐male variation and differed significantly among individuals. Discriminant function analyses (DFA) considering seven of these variables assigned 90–100% of boatwhistles to the correct individual, depending on the number of males and number of sounds per male included in the model. The acoustic features that consistently best discriminated individuals were the dominant frequency of the middle tonal segment of the boatwhistle (P₂) and dominant frequency modulation, followed by P₂ pulse period, amplitude modulation and sound duration. These results suggest the possibility of individual recognition based on acoustic cues.     

Evidence for a receiver bias underlying female preference for a male mating pheromone in sea lamprey

Receiver bias models suggest that a male sexual signal became exaggerated to match a pre-existing sensory, perceptual or cognitive disposition of the female. Accordingly, these models predict that females of related taxa possessing the ancestral state of signalling evolved preference for the male trait in a non-sexual context. We postulated that female preference for the male-released bile alcohol mating pheromone, 3 keto petromyzonol sulfate (3kPZS), of the sea lamprey (Petromyzon marinus) evolved as a result of a receiver bias. In particular, we propose that migratory silver lamprey (Ichthyomyzon unicuspis), a basal member of the Petromyzontidae, evolved a preference for 3kPZS released by stream-resident larvae as a means of identifying productive habitat for offspring. Larval silver lamprey released 3kPZS at rates sufficient to be detected by migratory lampreys. Females responded to 3kPZS by exhibiting upstream movement behaviours relevant in a migratory context, but did not exhibit proximate behaviours important to mate search and spawning. Male silver lamprey did not release 3kPZS at rates sufficient to be detected by females in natural high-volume stream environments. We infer that female silver lamprey cue onto 3kPZS excreted by stream-resident larvae as a mechanism to locate habitat conducive to offspring survival and that males do not signal with 3kPZS. We suggest that this female preference for a male signal in a non-sexual context represents a bias leading to the sexual signalling observed in sea lamprey.