Courtship Behavior Research Articles

Dissecting the role of pheromone-binding protein 2 in courtship behavior of male Grapholita molesta moths.

For fruit-boring pests like Grapholita molesta, the courtship behavior of male moths is a crucial aspect that can be utilized for developing control methods. This study investigates the role of pheromone-binding proteins (PBPs) in the courtship behavior of male G. molesta moths, particularly how sex pheromone components affect PBP expression. We found that three GmolPBPs genes were mainly expressed in the antennae of adult males, with no expression in larvae or pupae. Notably, GmolPBP2 expression was significantly higher in males, while GmolPBP1 was more pronounced in females. Unmated males exposed to females or the sex pheromone component Z8-12:Ac showed marked upregulation of GmolPBPs expression. Using affinity chromatography, we purified GmolPBPs and confirmed their binding affinities. Especially for GmolPBP2, this protein had a high affinity for Z8-12:Ac and E8-12:Ac. RNA interference targeting GmolPBPs revealed that silencing GmolPBP2 significantly reduced male responses to sex pheromone components and courtship behavior towards females, while silencing GmolPBP1 and GmolPBP3 had no significant effects. These findings highlight the crucial role of GmolPBP2 in mediating male courtship behavior, emphasizing the importance of PBPs in pheromone communication and mating success in G. molesta.

Disruption of the odorant receptor co-receptor (Orco) reveals its critical role in multiple olfactory behaviors of a cosmopolitan pest.

The olfactory system of insects plays a pivotal role in multiple, essential activities including feeding, mating, egg laying, and host localization. The capacity of odorant receptors to recognize odor molecules relies on odorant receptor co-receptors forming heterodimers. Here we report the successful engineering a homozygous mutant strain of diamondback moth (Plutella xylostella) in which the odorant receptor co-receptor PxOrco was silenced using CRISPR/Cas9. This insect is a globally important crop pest for which novel control methods are urgently required. Behavioral assays demonstrated that PxOrco knockout males exhibited abolished courtship behaviors, inability to mate, and loss of selective preference for P. xylostella's key sex pheromone components. Whilst female mating behavior and fecundity remained unaffected by PxOrco knockout, oviposition response to leaf alcohol, a key cue for normal oviposition behaviour, was lost. Electroantennography revealed drastically reduced responses to sex pheromones and plant volatiles in PxOrco-deficient adults but food location by larvae was unaffected. Moreover, expression analysis of PxOrco-deficient pheromone receptors (PRs) indicated varied regulation patterns, with down-regulation observed in several PRs in both sexes. These findings underscore the critical role of PxOrco in regulating multiple olfactory aspects in P. xylostella, including feeding, mating, and host location. Our study identifies the potential of disrupting the Orco gene in this and other pest species to provide novel avenues for future pest control.

Four Neurotoxic Insecticides Impair Partner and Host Finding in the Parasitoid Leptopilina heterotoma and Bioactive Doses Can Be Taken up Via the Host

In modern agriculture, control of insect pests is achieved by using insecticides that can also have lethal and sublethal effects on beneficial non-target organisms. Here, we investigate acute toxicity and sublethal effects of four insecticides on the males’ sex pheromone response and the female host finding ability of the Drosophila parasitoid Leptopilina heterotoma. The nicotinic acetylcholine receptor antagonists acetamiprid, flupyradifurone and sulfoxaflor, as well as the acetylcholinesterase inhibitor dimethoate were applied topically as acetone solutions. Males treated with all four insecticides no longer preferred the female sex pheromone in a T-olfactometer. Duration of wing fanning, an element of the pheromone-mediated male courtship behavior, was also reduced by all four insecticides. The ability of females to orientate towards host-infested feeding substrate was not affected by acetamiprid in the tested dose range. However, treatment with dimethoate, flupyradifurone and sulfoxaflor resulted in the loss of the females’ preference for host odor. At the lowest doses interfering with olfactory abilities of L. heterotoma in this study (acetamiprid: 0.21 ng, dimethoate: 0.105 ng, flupyradifurone: 2.1 ng and sulfoxaflor: 0.21 ng), ≥ 90% of the wasps survive insecticide treatment. Male pheromone responses and female host finding were also disturbed in those L. heterotoma that had developed in D. melanogaster larvae reared on dimethoate-treated feeding medium at sublethal levels. Hence, doses of this insecticide sufficient to interfere with chemical orientation of L. heterotoma can be taken up by the parasitoid via the food chain.

Multispecies comparisons support a startle response origin for a novel vibrational signal in the cricket tribe Lebinthini.

Many animals communicate using call and response signals, but the evolutionary origins of this type of communication are largely unknown. In most cricket species, males sing and females walk or fly to calling males. In the tribe Lebinthini, however, males produce calls that trigger a vibrational reply from females, and males use the substrate vibrations to find the responding female. Here we assess two hypotheses regarding the behavioral origin of this multimodal duet in the Lebinthini. We conducted playback experiments and measured behavioral and neuronal responses in multiple related cricket species to assess whether the precursor to the lebinthine duet was 1) a startle response to high-frequency sound, or 2) elaboration of a preexisting courtship behavior. We found behavioral similarities between the vibrational response of Lebinthini females and the acoustic startle behavior in other gryllid crickets. Specifically, the amplitude of the vibrational reply increases with male song amplitude in Lebinthini, and the magnitude of vibrations produced by two gryllid species when startled with ultrasound also correlates with the stimulus amplitude. Like in-flight startle behavior, the startle vibrations produced by perched crickets are suppressed when low-frequency sound is played simultaneously. We also observed courtship behavior in four gryllid species and found few instances of female vibration. Vibrational signals observed in Gryllus pennsylvanicus females were not correlated with male calls and occurred more frequently in pairs that did not mate after courtship. Combined, accumulating evidence supports the hypothesis that the lebinthine duet more likely evolved from a startle precursor than courtship behavior.

Is Drosophila Larval Competition Involved in Incipient Speciation?

Geographical, ethological, temporal and ecological barriers can affect interbreeding between populations deriving from an ancestral population, this progressively leading to speciation. A rare case of incipient speciation currently occurs between Drosophila melanogaster populations sampled in Zimbabwe (Z) and all other populations (M). This phenomenon was initially characterized by Z females refusing to mate with M males. Despite the fact that Z and M flies produce different amounts of cuticular pheromones, their manipulation and that of other sensory signals exchanged during courtship behavior only marginally rescued the behavioral isolation. To further explore the putative mechanisms involved in this phenomenon, we first assessed the fecundity in matings between Z and M flies. Then, we measured the reproduction and survival in adults resulting of co-cultured Z and M larvae. In these two experiments, Z flies rarely emerged. Z and M larvae produced different amounts of food-derived metabolites which were altered in co-culture condition. This maybe related to the different bacteria composition in the gut and body of Z and M flies. However, the mating behavior of co-cultured flies did not change and their cuticular pheromone profile was slightly altered. Thus, the Z/M larval competition could reinforce the barriers induced by gametic and behavioral isolation processes on this incipient speciation phenomenon.

Bowerbird courtship-inspired feature selection for efficient high-dimensional data analysis using a novel meta-heuristic

The challenge of feature selection in high-dimensional datasets is critical in enhancing machine learning model performance and interpretability while reducing computational costs. This paper introduces a novel feature selection method inspired by the unique courtship behaviors of bowerbirds, termed Bowerbird Courtship-Inspired Feature Selection (BBFS). Mimicking the decorative strategies and selective adaptation of bowerbirds, BBFS optimizes the selection of feature subsets through a meta-heuristic approach that efficiently balances exploration and exploitation. We compare the effectiveness of BBFS with established algorithms like Binary Cuckoo Search Optimization (BCSO) and Binary Grey Wolf Optimization (BGWO) across seven diverse datasets. Our results demonstrate that BBFS consistently selects fewer features and maintains or enhances classification accuracy using Decision Trees and Naive Bayes classifiers. This study underscores the potential of BBFS as a scalable and robust tool for high-dimensional data analysis, offering significant improvements over traditional and contemporary feature selection methods.Graphical

Role of the ventral portion of intermediate arcopallium in stability of female Bengalese finch song preferences.

The process of decision making is a complex procedure influenced by both external and internal conditions. Songbirds provide an excellent model to investigate the neural mechanisms of decision making, because females rely on acoustic signals called songs as important stimuli in directing their mate choice. Previous experiments by our group and others have implicated secondary auditory brain sites in female evaluation of song quality, including the caudal portions of the nidopallium (NC) and mesopallium (CM). Recent pathway tracing experiments reveal a convergence of those sites onto a third region, the ventral portion of the intermediate arcopallium (AIV), suggesting that AIV may also play an important role in song evaluation and mate choice. Here we combined behavioral testing with lesion inactivation to investigate the role of AIV in song preference of female Bengalese finches (Lonchura striata domestica). Inactivation of AIV was associated with destabilization of rank ordering of song preferences. These data suggest a model in which the convergence of auditory activity in AIV plays an important role in female perception of song quality and production of courtship behaviors. Together with previous results that also demonstrate a role for the auditory areas that converge onto AIV, these findings extend the experimental tractability of this emerging animal model of sensory perception and decision making.

Neurological confirmation of periplanone-D exploitation as a primary sex pheromone and counteractions of other components in the smoky brown cockroach Periplaneta fuliginosa.

The smoky brown cockroach, Periplaneta fuliginosa, is a peridomestic pest inhabiting broad regions of the world from temperate to subtropical zones. In common with other related species such as the American cockroach, Periplaneta americana, female-emitted sex pheromone components, named periplanones, are known to be key volatiles that elicit long-range attraction and courtship rituals in males. How periplanones are processed in the nervous system has been entirely unexplored in P. fuliginosa. By using pheromone compounds, periplanones A, B, C, and D, as stimulants to the antenna, we identified four distinct types of interneurons (projection neurons) that relay pheromonal signals from a single olfactory glomerulus of the first-order olfactory center (antennal lobe) to higher-order centers in the ipsilateral hemibrain. All glomeruli innervated by pheromone-responsive projection neurons clustered near the antennal nerve entrance of the antennal lobe. The projection neuron with dendrites in the largest glomerulus was tuned specifically to periplanone-D, and adding other components to periplanone-D counteracted the excitation elicited by periplanone-D alone. Likewise, the projection neuron with dendrites in the second largest glomerulus and that with dendrites in a medium-sized glomerulus were tuned to periplanone-A and periplanone-B, respectively. Our results are, therefore, consistent with behavioral findings that periplanone-D alone acts as a primary sex attractant and that other components act as potential behavioral antagonists. Moreover, a comparison of the glomeruli in P. fuliginosa and P. americana suggested that there are differences in the sizes of homologous glomeruli, as well as in the ligands they process.

Characterization of a Novel Male Pheromone Compound in Leucoptera sinuella (Lepidoptera: Lyonetiidae) and Its Role in Courtship Behavior.

The poplar moth, Leucoptera sinuella (Lepidoptera: Lyonetiidae), is widely distributed across Europe, Asia, and parts of Africa. It was first identified in Chile in 2015 and has since become a significant pest in the agricultural sector. Additionally, economic losses are further aggravated by the presence of L. sinuella pupae in nearby fruit orchards. This study investigated the presence of a male-produced sex pheromone in L. sinuella, focusing on the hairpencil (HP) glands, which are known as dissemination structures for male pheromones in lepidopterans. Male HP glands were solvent-extracted and analyzed by gas chromatography-mass spectrometry. Chemical microderivatization and comparisons of mass spectra and retention indices of natural compounds with synthetic standards led to the identification of two compounds: (Z)-3-decenyl hexanoate (the major component) and (Z)-3-decen-1-ol (a minor component). Although electrophysiological assays did not show detectable antennal responses to (Z)-3-decenyl hexanoate, behavioral bioassays demonstrated its role as a short-range courtship signal in L. sinuella. Males with ablated hairpencils exhibited significantly reduced courtship success compared to controls; however, exposure of females to synthetic (Z)-3-decenyl hexanoate or HP extract restored male courtship success. To our knowledge, (Z)-3-decenyl hexanoate has not been previously reported as a sex pheromone component in any insect species, making this discovery an intriguing addition to the diversity of chemical communication in insects.

Understanding the genetics of sex determination in insects and its relevance to genetic pest management.

Sex determination pathways regulate male and female-specific development and differentiation and offer potential targets for genetic pest management methods. Insect sex determination pathways are comprised of primary signals, relay genes and terminal genes. Primary signals of coleopteran, dipteran, hymenopteran and lepidopteran species are highly diverse and regulate the sex-specific splicing of relay genes based on the primary signal dosage, amino acid composition or the interaction with paternally inherited genes. In coleopterans, hymenopterans and some dipterans, relay genes are Transformer orthologs from the serine-arginine protein family that regulate sex-specific splicing of the terminal genes. Alternative genes regulate the splicing of the terminal genes in dipterans that lack Transformer orthologs and lepidopterans. Doublesex and Fruitless orthologs are the terminal genes. Doublesex and Fruitless orthologs are highly conserved zinc-finger proteins that regulate the expression of downstream proteins influencing physical traits and courtship behaviours in a sex-specific manner. Genetic pest management methods can use different mechanisms to exploit or disrupt female-specific regions of different sex determination genes. Female-specific regions of sex determination genes can be exploited to produce a lethal gene only in females or disrupted to impede female development or fertility. Reducing the number of fertile females in pest populations creates a male-biased sex ratio and eventually leads to the local elimination of the pest population. Knowledge on the genetic basis of sex determination is important to enable these sex determination pathways to be exploited for genetic pest management.

Seven new species from Eocene Baltic amber reveal surprising diversity and suggest possible speciation scenarios in the relictual family Collohmanniidae (Acari: Oribatida)

This study provides a comprehensive morphological analysis of ten fossil specimens from the genus Collohmannia, found in Eocene Baltic amber, with nine representing different species. Collohmanniidae, a unique monogeneric family of oribatid mites are among the largest oribatids. They feed on leaf litter and present significant sexual dimorphism and courtship behavior, which includes the transfer of nuptial food from male to female. Extant Collohmannia species inhabit isolated mountain forest areas. A fragmentation hypothesis has been proposed to account for their highly disjunctive distribution, suggesting that climate change divided a large forest area previously occupied by a parent species, leading to the allopatric evolution of several species of Collohmannia. However, with the discovery of a significant number of fossil species in Eocene Baltic amber we propose an alternate hypothesis with the Baltic amber forest serving as an arena for speciation of Collohmanniidae. According to it, the driving force of speciation was dietary and was based on gut microbiome specificity, reinforced by the female choice during the courtship ritual. In this paper we describe seven new fossil species of Collohmannia (C. sellnicki sp. nov., C. albertii sp. nov., C. nortoni sp. nov., C. groehni sp. nov., C. kerneggeri sp. nov., C. weiterschani sp. nov., C. clavata sp. nov.), re-describe C. schusteri based on study of the holotype, synonymize Embolacarus with Collohmannia, propose and describe the neotype of C. pergrata comb. nov., and provide a key to all described Collohmanniidae. Together with the hypotheses of speciation we propose verification experiments to be performed on extant Collohmannia mites.

Inbreeding and cognitive impairment in animals

Abstract The physiological costs of inbreeding in wild animals are well-documented, but the potential cognitive costs of inbreeding have received far less attention. A growing body of evidence indicates that inbreeding is associated with impaired learning ability and aberrant innate behaviors in model systems, as well as intellectual disability and lower general intelligence in humans. As highlighted in this review, however, far less is known about inbreeding-linked cognitive impairments for wild populations and the potential behavioral and fitness implications of these impairments. Here, we review evidence indicating that, through its negative effects on song and other courtship behaviors, as well as its association with deficits in mating behavior and parental care, inbreeding is likely to have negative consequences for reproductive success in wild animals. The impairment of specific cognitive abilities, such as learning, innovation, and decision-making, may be particularly detrimental for inbred animals in changing environments, where individuals must adjust their behavior appropriately to deal with novel threats and resources.

Effects of ttk on development and courtship of male Nilaparvata lugens.

The transcription product of tramtrack (ttk) is an important transcription factor which plays many roles in the regulation of the development, differentiation and chromosome recombination of organisms. Few studies have been reported on the specific functions of ttk in other insects except Drosophila melanogaster. Our aims are to reveal the ttk effects on development and courtship of male rice pest brown planthopper (BPH), Nilaparvata lugens. In this study, we first assayed spatiotemporal expression of ttk in BPH, then treated the fourth nymphs of BPH with dsttk. We found most individuals died before emerging to adults, the adult eclosion rate was only 18.89%. No courtship behavior was found in individuals injected with dsttk. Further research showed that the main frequency of courtship vibration signal (CVS) 431.3 Hz in the individuals injected with dsttk was significantly higher than 223 Hz in the individuals injected with dsGFP, and female adults nearly had no response to the 431.3 Hz CVS. We found that about 81% of the 4-instar nymphs of BPH treated with dsttk died before they emerged as adults, the successfully emerged adults emitted the 431.3 Hz CVS to which female adults did not respond and lost the ability of courtship. This was first finding about the functions of ttk in rice planthopper and illustrated the potential of ttk as target for RNAi to control rice planthopper. © 2024 Society of Chemical Industry.

Through the eyes of the Andean bear: Camera collar insights into the life of a threatened South American Ursid.

Due to Andean bears' propensity for inhabiting challenging environments and terrain, their wild ecology remains poorly understood, especially when compared to other members of the Ursidae family. In one of the steepest, wettest regions of the Andes, the Kosñipata Valley of southeastern Peru, we attached and retrieved camera-borne collars on three wild free-ranging Andean bears. From just one longer term camera collar deployed on a single individual over a period of 4 months, we observed a variety of rare or previously undocumented natural history observations. These include courtship and mating behaviors, social interactions with conspecifics, novel dietary items of previously unrecorded fruit consumption, cannibalism, potential infanticide, the sole documented case of primate consumption, and evidence of geophagy. The wealth of novel natural history insights gained from just 4 months of camera collar data of this poorly studied species has elucidated numerous avenues warranting further investigation.

More than stridulation: signal interaction and constraint in the complex vibroacoustic courtship of a cricket

Field crickets (Gryllidae) produce sounds by tegminal stridulation, well-studied for its role in female attraction and choice. However, understanding female preferences for their courtship song remains elusive, despite considering additional chemical, visual, and thermal signals. Beyond stridulation, crickets also display vibrational courtship behaviours that remain largely unexplored. Using Acheta domesticus as a model, we conduct the first comprehensive analysis of the entirety of vibroacoustic courtship signals in crickets, including their interaction. Employing audio recording, laser vibrometry, and videorecording, we unveil a complex signal involving simultaneous wing stridulation, body tremulation, and leg drumming against the substrate in a prolonged display, unique among insects. We identify robust correlations, coupling, and coordination between these signal components. We show the tightest coupling between the two types of stridulation pulses, and between tremulation and drumming signals, while drumming-stridulation coupling is less consistent, revealing a constraint on drumming performance. This constraint in the expression of one signal component, without a trade-off, represents a specific case within complex dynamic signalling. In addition, we find no correlation between drumming rate and its accuracy relative to stridulation, challenging common expectations. Our findings indicate that the information conveyed by the complex courtship display in A. domesticus is not simply proportional to that in the song, shedding light on previous ambiguities surrounding its function. Spectral-intensity analysis indicates the closest perceptual connection between stridulation and drumming signals, likely commonly influencing female choice, while proposing another function for tremulation. Further research should delve deeper into the function of this intricate signal.

Vibrational signals differ between contests and copulatory courtship in the red milkweed beetle Tetraopes tetrophthalmus (Coleoptera: Cerambycidae)

Abstract Substrate-borne vibrational communication is commonly used by herbivorous insects to communicate intraspecific information. This form of communication is underexplored and many discoveries of the form and functional significance of these vibrations have yet to be made. Here, we add red milkweed beetles, Tetraopes tetrophthalmus (Coleoptera: Cerambycidae) to the record of arthropods that communicate with these plant-borne vibrations. Red milkweed beetles, like other cerambycids, commonly use stridulation to produce audible squeaks when in stressful situations and can also produce plant-borne vibrations when in contact with conspecifics. These beetles engage in fights for territory which ultimately results in mating opportunities (i.e., contests). We placed beetles into three sex-ratio treatments: male–male (contests), male–female (copulatory courtship), or male–male–female (contests and copulatory courtship). We first describe contests and copulatory courtship behaviours. We then used laser vibrometry and found that red milkweed beetles communicate by producing plant-borne vibrational signals composed of low-frequency rumbles and high-frequency clacks during male–male contests and copulatory courtship. We compared the spectral and temporal features of the vibrations between the two pre-copulatory contexts. We found that vibrational signals were shorter and had a higher fundamental and dominant frequencies when beetles engaged in contests compared to copulatory courtship behaviours. Our results show that these beetles use plant-borne vibrations as context-dependent signals that communicate different information under these two pre-copulatory scenarios. Our data suggests that these context-dependent signals may help beetles gain access to mates and prolong copulation.

Experimental Evolution Induced by Maternal Post-copulatory Factors in Drosophila.

Experimental evolution is a powerful approach to study the mechanisms underlying the adaptation of selected characters under the conditions chosen in the laboratory. Drosophila melanogaster is a species frequently used to investigate the experimental evolution of characters, especially those related to reproduction. Recent intra-generational studies showed that cis-vaccenyl acetate (cVa), a sex pheromone transferred with bacteria on eggs by females either 1day (D1) or 5days (D5) after copulation, differentially affected the behavior and pheromone release in adult males emerging from these eggs. Here, we extended this finding to determine whether this alternative egg exposure repeated over many generations could affect a larger set of reproduction-related characters in both sexes. To test the repetitive effects of maternal D1 or D5 post-copulatory factors, we carried out an experimental selection procedure consisting of exposing eggs during 40 successive generations to D1 or D5 maternal post-copulatory factors. We compared cVa and cuticular pheromones, courtship and mating behaviors, and fecundity at different generations in flies of D1 and D5 lines. Based on findings obtained at earlier generations, we also determined survival, bacterial composition and gene expression in adults. Some of these complex traits significantly diverged between D1 and D5 lines indicating that maternal post-copulatory factors transmitted to eggs can influence adult life history traits.

Active-matrix TFT driven GaN blue Micro-LED display realized with electroplated copper-tin-silver micro bumps-based bonding structure

With the rapid advancement of display and smart lighting technologies, micro-light-emitting diodes (Micro-LEDs) have garnered substantial attention due to their exceptional performance characteristics. However, a significant challenge persists in achieving reliable interconnections between Micro-LED chips and driver backplanes. This article proposes and implements the Double-Layer Photoresist Structure Electroplating (DPSE) technique for fabricating Cu-SnAg metal bumps, thereby facilitating the heterogeneous integration of oxide thin film transistors (TFTs) with GaN-based blue LEDs. The DPSE process was optimized by addressing several critical factors, including the correlation between bump height and electroplating time, the occurrence of cracks in the photoresist surface, and the removal of the conductive layer. Metal bumps were successfully fabricated on TFT backplanes with dimensions of 16.5 μm × 10 μm, an average height of 5.39 μm, and a uniformity of approximately 2.266 %. To demonstrate the efficacy of this approach, a 0.495-inch blue active-matrix Micro-LED display was designed and fabricated. This display features a mesa size of 15 µm × 30 µm, a pixel pitch of 222 µm, and a pixel density of 114 pixels per inch (PPI). The resultant blue Micro-LED display exhibits excellent optical characteristics, achieving a brightness of 1625 cd/m² (nits). It is anticipated that the methodology and findings presented in this study will contribute significantly to the advancement of Micro-LED display technology in consumer electronics. This research not only represents a significant advancement in the field of Micro-LED display technology but also paves the way for future innovations in high-resolution, energy-efficient display systems.

Vibrational noise disrupts Nezara viridula communication, irrespective of spectral overlap

Insects rely on substrate vibrations in numerous intra- and interspecific interactions. Yet, our knowledge of noise impact in this modality lags behind that in audition, limiting our understanding of how anthropogenic noise affects insect communities. Auditory research has linked impaired signal perception in noise (i.e., masking) to spectral overlap. We investigated the impact of noise with different spectral compositions on the vibrational communication of the stink bug Nezara viridula, examining courtship behaviour and signal representation by sensory neurons. We found negative effects of vibrational noise regardless of spectral overlap, challenging common expectations. Noise impaired the ability of males to recognize the female signal and localise its source: overlapping noise decreased sensitivity of receptor neurons to the signal and disrupted signal frequency encoding by phase-locking units, while non-overlapping noise only affected frequency encoding. Modelling neuronal spike triggering in sensory neurons linked disrupted frequency encoding to interference-induced alterations of the signal waveform. These alterations also affected time delays between signal arrivals to different legs, crucial for localisation. Our study thus unveils a new masking mechanism, potentially unique to insect vibrosensory systems. The findings highlight the higher vulnerability of vibration-mediated behaviour to noise, with implications for insect interactions in natural and anthropogenically altered environments.

Multimodal signalling in manakins: lack of correlated evolution between acoustic, visual and behavioural traits

Sexual traits, such as visual adornments, sound‐based cues and courtship dances, are frequently displayed in combination as multimodal signals. Some hypotheses propose that different signals trade‐off with each other, potentially due to resource limitations (‘trade‐off’ or transfer hypothesis) or that these develop simultaneously to enhance communication effectiveness (‘joint evolution’ hypothesis). Alternatively, multiple cues may evolve independently to serve distinct functions or convey different information (‘multiple messages’ hypothesis). Here, we explored the interdependence between different signal modalities in manakins (Pipridae), which are known for great interspecific diversity in the degree of elaboration in courtship dance, song and plumage coloration. We also used comparative methods to explore the mode of evolution and the degree of conservatism of these signals. We found that song, plumage coloration and courtship dance evolved independently as there was no correlation between these traits. Song evolution in manakins was attracted to a single optimum and exhibited a weak phylogenetic signal in comparison with those of colour and behavioural diversity. The high support found for the speciational and κ models when analysing the multivariate estimates of trait variability suggests that these signals (especially colour and behaviour attributes) may have evolved in a punctuated manner, with large evolutionary changes at speciation events and minimal subsequent changes along the branches. Our results show that song, colour and dance diversity are each associated (or marginally associated) with different ecological factors, indicating that sexual signals in manakins might convey different information and/or respond to different selection pressures. Larger species and those with lower dispersal capacity tend to exhibit higher colour richness, which in turn differed among lek categories, being higher in species with ‘classic’ leks and lower in non‐lekking species. Overall, the present study supports the idea that correlation between signal modalities does not constitute a widespread pattern in songbirds.