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1. Chemical cues in the mating behavior of a highly polygynous bird

   https://doi.org/10.1007/s00265-024-03477-0  

   Rivers, Pearl R; DuVal, Emily H (June 2024, Behavioral Ecology and Sociobiology)

   Visual and auditory signals are well-established components of avian courtship, but the role of chemical signaling remains poorly understood, particularly in mating systems with elaborate courtship displays. To test how chemical cues influence mating behavior we conducted two experiments in the lance-tailed manakin (Chiroxiphia lanceolata). First, in a field experiment, we tested the response of free-living males and females to manipulation of chemical cues at male display perches by cleaning the perches with ethanol or a dry cloth (control) and quantified a potential chemical signaling behavior (bill-wiping) in response to experimental manipulation. During bouts of dance perch maintenance and displays with a female present (i.e., activity relevant to female mate choice) males increased bill-wiping behavior during initial ethanol treatment periods. We also detected carryover effects of the ethanol treatment; in later treatment periods males bill-wiped more when the prior treatment was ethanol. The likelihood of a female either revisiting a display area or copulating with a male was unrelated to experimental treatment. Next, in captive trials, we assessed female preference for olfactory cues from males that differed in their genetic diversity, a trait previously identified as relevant to female mate choice. In contrast to similar trials in other bird species, females showed no clear preference. Together, these results provide some evidence for chemical signaling by males at display perches, but it remains unclear what information chemical cues convey. 

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2. Acoustic and postural displays in a miniature and transparent teleost fish, Danionella dracula

   https://doi.org/10.1242/jeb.244585  

   Tatarsky, Rose L.; Guo, Zilin; Campbell, Sarah C.; Kim, Helena; Fang, Wenxuan; Perelmuter, Jonathan T.; Schuppe, Eric R.; Conway, Kevin W.; Reeve, Hudson K.; Bass, Andrew H. (August 2022, Journal of Experimental Biology)

   ABSTRACT Acoustic behavior is widespread across vertebrates, including fishes. We report robust acoustic displays during aggressive interactions for a laboratory colony of Danionella dracula, a miniature and transparent species of teleost fish closely related to zebrafish (Danio rerio), which are hypothesized to be sonic based on the presence of a hypertrophied muscle associated with the male swim bladder. Males produce bursts of pulsatile sounds and a distinct postural display – extension of a hypertrophied lower jaw, a morphological trait not present in other Danionella species – during aggressive but not courtship interactions. Females show no evidence of sound production or jaw extension in such contexts. Novel pairs of size-matched or -mismatched males were combined in resident–intruder assays where sound production and jaw extension could be linked to individuals. In both dyad contexts, resident males produced significantly more sound pulses than intruders. During heightened sonic activity, the majority of the highest sound producers also showed increased jaw extension. Residents extended their jaw more than intruders in size-matched but not -mismatched contexts. Larger males in size-mismatched dyads produced more sounds and jaw extensions compared with their smaller counterparts, and sounds and jaw extensions increased with increasing absolute body size. These studies establish D. dracula as a sonic species that modulates putatively acoustic and postural displays during aggressive interactions based on residency and body size, providing a foundation for further investigating the role of multimodal displays in a new model clade for neurogenomic and neuroimaging studies of aggression, courtship and other social interactions. 

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3. Varied female and male courtship behavior facilitated the evolution of a novel sexual signal

   https://doi.org/10.1093/beheco/arac049  

   Fitzgerald, Sophia L; Anner, Sophia C; Tinghitella, Robin M (June 2022, Behavioral Ecology)

   Jennions, Michael D (Ed.)

   Abstract Sexual selection can contribute to speciation when signals and preferences expressed during mate choice are coupled within groups, but come to differ across groups (generating assortative mating). When new sexual signals evolve, it is important to investigate their roles in both mate location and courtship contexts, as both signaling functions are critical in mate choice. In previous work, researchers identified two new male morphs (silent and purring) in Hawaiian populations of the Pacific field cricket, Teleogryllus oceanicus. These morphs likely evolved because they protect males from an acoustically orienting parasitoid, yet still obtain some reproductive success. But, it remains unknown how the purring morph functions in close courtship encounters. We compared the relative success of the very recently evolved purring morph to that of the ancestral and silent morphs during courtship encounters. Purring males produce a novel courtship song and were not as successful in courtship as the ancestral type, but were mounted by females as often and as quickly as the obligately silent morph that arose and spread ~20 years ago. Purring males initiate courtship more quickly than other morphs, and females from populations where purring is common exhibit higher overall mounting rates. Thus, differences in the behavior of purring males and of females from populations where purring is common may have facilitated the origin of this novel sexual signal. We found no assortative mating between males of a given morph and females from their own population, and so we hypothesize that multiple male types will be maintained within the species because each achieves fitness in different ways. 

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4. Proposing a neural framework for the evolution of elaborate courtship displays

   https://doi.org/10.7554/eLife.74860  

   Schwark, Ryan W; Fuxjager, Matthew J; Schmidt, Marc F (May 2022, eLife)

   In many vertebrates, courtship occurs through the performance of elaborate behavioral displays that are as spectacular as they are complex. The question of how sexual selection acts upon these animals’ neuromuscular systems to transform a repertoire of pre-existing movements into such remarkable (if not unusual) display routines has received relatively little research attention. This is a surprising gap in knowledge, given that unraveling this extraordinary process is central to understanding the evolution of behavioral diversity and its neural control. In many vertebrates, courtship displays often push the limits of neuromuscular performance, and often in a ritualized manner. These displays can range from songs that require rapid switching between two independently controlled ‘voice boxes’ to precisely choreographed acrobatics. Here, we propose a framework for thinking about how the brain might not only control these displays, but also shape their evolution. Our framework focuses specifically on a major midbrain area, which we view as a likely important node in the orchestration of the complex neural control of behavior used in the courtship process. This area is the periaqueductal grey (PAG), as studies suggest that it is both necessary and sufficient for the production of many instinctive survival behaviors, including courtship vocalizations. Thus, we speculate about why the PAG, as well as its key inputs, might serve as targets of sexual selection for display behavior. In doing so, we attempt to combine core ideas about the neural control of behavior with principles of display evolution. Our intent is to spur research in this area and bring together neurobiologists and behavioral ecologists to more fully understand the role that the brain might play in behavioral innovation and diversification. 

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5. Life-Long Experience with Male Mating Tactics Shapes Spatial Cognition and Coercion Evasion in Female Swordtails

   https://doi.org/10.3390/fishes8110562  

   Queller, Philip S; Adams, Elena_R M; Cummings, Molly E (November 2023, Fishes)

   Social experiences can shape adult behavior and cognition. Here, we use El Abra swordtails (Xiphophorus nigrensis) to assess how life-long experience with different male mating tactics shapes coercion evasion ability and female spatial cognition. We raised females from birth to adulthood in environments that varied by male mating tactic: coercers only, courtship displayers only, coercers and displayers together, mixed-strategists, and female only. In adulthood, we tested females’ behavioral responses to a coercive male and spatial cognition in a maze. Females reared with only displayers were significantly worse at distancing themselves from the coercive male than females raised with coercers and displayers and females raised with only coercers. Females raised with a single mating tactic (either courtship display or coercion) exhibited significantly higher accuracy in the spatial maze than females from other rearing groups, and showed significant reduction in total errors (courtship display group) or latency to reward (coercion group) over successive trials. These more predictable environments (one tactic), and not the more complex environments (two tactics), showed evidence for spatial learning. The results are discussed in light of the existing literature on two components of environmental change (environmental predictability and the certainty with which cues predict the best behavioral response) and their effect on the development of cognitive abilities. 

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