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1. Phylogenomics of peacock spiders and their kin (Salticidae: Maratus), with implications for the evolution of male courtship displays.

   https://doi.org/https://doi.org/10.1093/biolinnean/blaa165  

   Girard, M. B.; Elias, D. O.; Azevedo, G.; Bi, K.; Kasumovic, M; M., Waldock; Hedin, M. (January 2021, Biological journal of the Linnean Society)

   null (Ed.)

   Understanding diversity has been a pursuit in evolutionary biology since its inception. A challenge arises when sexual selection has played a role in diversification. Questions of what constitutes a ‘species’, homoplasy vs. synapomorphy, and whether sexually selected traits show phylogenetic signal have hampered work on many systems. Peacock spiders are famous for sexually selected male courtship dances and peacock-like abdominal ornamentation. This lineage of jumping spiders currently includes over 90 species classified into two genera, Maratus and Saratus. Most Maratus species have been placed into groups based on secondary sexual characters, but evolutionary relationships remain unresolved. Here we assess relationships in peacock spiders using phylogenomic data (ultraconserved elements and RAD-sequencing). Analyses reveal that Maratus and the related genus Saitis are paraphyletic. Many, but not all, morphological groups within a ‘core Maratus’ clade are recovered as genetic clades but we find evidence for undocumented speciation. Based on original observations of male courtship, our comparative analyses suggest that courtship behaviour and peacock-like abdominal ornamentation have evolved sequentially, with some traits inherited from ancestors and others evolving repeatedly and independently from ‘simple’ forms. Our results have important implications for the taxonomy of these spiders, and provide a much-needed evolutionary framework for comparative studies of the evolution of sexual signal characters. 

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2. Functional Allometry of Sexually Selected Traits in Tetraopes tetrophthalmus Red Milkweed Beetles (Coleoptera: Cerambycidae)

   https://doi.org/10.1002/jmor.70075  

   Cirino, Lauren A; Lindemann, Kirsten J; Hagey, Travis J; Rodríguez, Rafael L (August 2025, Journal of Morphology)

   ABSTRACT The allometry of sexually selected traits is highly variable. Some traits scale steeply in relation to body size while other traits scale more shallowly. Still others scale proportionately to body size. One explanation for this variability is trait function. Sexually selected traits should scale differently according to the function that they perform—the functional allometry hypothesis. Here, we investigate the functional allometry hypothesis in red milkweed beetles,Tetraopes tetrophthalmus(Coleoptera: Cerambycidae), a species that possesses multifunctional sexually selected traits. Males use their mandibles to eat and as weapons to fight rivals. Their antennae act as sensory organs and as tactile signals during copulatory courtship. We measured these sexually selected traits along with body size in both males and females. We also measured thorax and leg size, traits presumably not under sexual selection, as control traits. We found that tactile signal traits used in courtship were negatively allometric, while weapons, traits supporting the weapon, and control traits were isometric. Although male mandible weapons were isometric, we found that female mandibles were negatively allometric. Finally, weapon shape was also examined as this trait is important to fighting outcomes. We found that male mandible weapons have a rugose medial curve with a midpoint ledge that female mandibles lack. These results support the functional allometry hypothesis for variation in trait allometry. We discuss how interactions between the functions that these traits perform may influence the evolution of morphology. 

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3. Sex and design in our evolutionary cousins: The perception of beauty in nature

   https://doi.org/10.7203/metode.13.24202  

   Mendelson, Tamra C.; Ryan, Michael J. (April 2022, Mètode Revista de difusió de la investigació)

   Taking an evolutionary approach to the question of beauty, we discuss the expression and perception of sexual beauty across the animal kingdom. Animals experience beauty in their brains, and animal brains are tuned to features of the environment most relevant to their survival. Over evolutionary time, sexually reproducing animals have exploited that tuning to maximize their attractiveness to the opposite sex, often leading to extreme courtship traits and behaviors. These are the traits of sexual beauty. Combining modern principles of neuroscience and neuroaesthetics with established principles of evolutionary biology, we aim to understand the biological basis and evolution of beauty in all animals, including ourselves. 

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4. The role of cuticular hydrocarbon sexual dimorphism on Drosophila courtship

   Cong, Haosu; Luo, Mei; Chowdanayaka, Rajanikanth; Sbisa, Nadia; Wang, Zinan; Pu, Jian; Chung, Henry (September 2025, Animal behaviour)

   The evolution of mating signals is shaped by divergent roles and selective forces, which allow these signals to become multifunctional. Sexual dimorphism in mating signals can reflect this multifunctionality, where such dimorphism could contribute to both mate recognition and mate choice. Sexual dimorphism in mating signals is thought to arise due to divergent sex roles, driven by the interactions of several selective pressures. It has been suggested that, across taxa, both sexes can be choosy and result in sexual selection. However, whether sexual dimorphism in mating signals can predict its role in male courtship behaviour is still unclear. In this study, we used cuticular hydrocarbons (CHCs) in Drosophila species as a model to investigate the question, with CHCs serving as key chemical cues during courtship. This study investigates the relationship between CHC sexual dimorphism and its role in male courtship behaviour across 10 Drosophila species. Our results reveal variations in the degree of CHC sexual dimorphism across the test species. In addition, CHC detection was found to contribute to courtship initiation in most of the test species, but CHC sexual dimorphism did not predict male courtship behaviour. Notably, a longer courtship latency was observed following the loss of CHC detection, indicating that CHCs may convey information on mate quality. Our study suggests that sexual dimorphism in CHCs is not directly linked to its role in mating signal recognition and highlights the species-specific evolution of chemical signals in Drosophila courtship. 

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5. 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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