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Sexual selection is thought to shape phylogenetic diversity by affecting speciation or extinction rates. However, the net effect of sexual selection on diversification is hard to predict because many of the hypothesized effects on speciation or extinction have opposing signs and uncertain magnitudes. Theoretical work also suggests that the net effect of sexual selection on diversification should depend strongly on ecological factors, though this prediction has seldom been tested. Here, we test whether variation in sexual selection can predict speciation and extinction rates across passerine birds (up to 5812 species, covering most genera) and whether this relationship is mediated by environmental factors. Male-biased sexual selection, and specifically sexual size dimorphism, predicted two of the three measures of speciation rates that we examined. The link we observed between sexual selection and speciation was independent of environmental variability, though species with smaller ranges had higher speciation rates. There was no association between any proxies of sexual selection and extinction rate. Our findings support the view that male-biased sexual selection, as measured by frequent predictors of male-male competition, has shaped diversification in the largest radiation of birds.

Red sensitivity is the exception rather than the norm in most animal groups. Among species with red sensitivity, there is substantial variation in the peak wavelength sensitivity (λmax) of the long wavelength sensitive (LWS) photoreceptor. It is unclear whether this variation can be explained by visual tuning to the light environment or to visual tasks such as signalling or foraging. Here, we examine long wavelength sensitivity across a broad range of taxa showing diversity in LWS photoreceptor λmax: insects, crustaceans, arachnids, amphibians, reptiles, fish, sharks and rays. We collated a list of 161 species with physiological evidence for a photoreceptor sensitive to red wavelengths (i.e. λmax ≥ 550 nm) and for each species documented abiotic and biotic factors that may be associated with peak sensitivity of the LWS photoreceptor. We found evidence supporting visual tuning to the light environment: terrestrial species had longer λmax than aquatic species, and of these, species from turbid shallow waters had longer λmax than those from clear or deep waters. Of the terrestrial species, diurnal species had longer λmax than nocturnal species, but we did not detect any differences across terrestrial habitats (closed, intermediate or open). We found no association with proxies for visual tasks such as having red morphological features or utilising flowers or coral reefs. These results support the emerging consensus that, in general, visual systems are broadly adapted to the lighting environment and diverse visual tasks. Links between visual systems and specific visual tasks are commonly reported, but these likely vary among species and do not lead to general patterns across species. We conduct a comprehensive assessment of ecological drivers of red vision, across a broad range of taxa. Our results support the emerging consensus that, in general, visual systems are broadly adapted to the lighting environment and diverse visual tasks.

Sexual size dimorphism (SSD) is pervasive across taxa and reflects differences in the effects of sexual and natural selection on body size between the sexes. However, disentangling the complex eco‐evolutionary interactions between these two mechanisms remains a major challenge for biologists. Here, we combine macro‐evolutionary (between‐species), local evolutionary (between‐population) and fine‐scale evolutionary (within‐population) patterns of SSD to explore how sexual and natural selection interact and shape the evolution of SSD in Australian agamid lizards. Australian agamid lizards show substantial variation in SSD, ecological traits and species density making them an ideal study system to address this question. At the between‐species level, population density, ecological generalism and mean species size significantly predict SSD variation; however, only ecological generalism was found to significantly explain variation in larger‐than‐average male‐biased SSD. At the population level, density positively correlated with SSD in native habitats, but not city park habitats. Last, agonistic behaviour acted as the primary driver of SSD at the within‐population level. Our results indicate how sexual and natural selection can interact at different evolutionary scales, and show the importance of considering both selective mechanisms when investigating patterns of SSD. A plain language summary is available for this article. Plain Language Summary

Women comprise a minority of the Science, Technology, Engineering, Mathematics, and Medicine (STEMM) workforce. Quantifying the gender gap may identify fields that will not reach parity without intervention, reveal underappreciated biases, and inform benchmarks for gender balance among conference speakers, editors, and hiring committees. Using the PubMed and arXiv databases, we estimated the gender of 36 million authors from >100 countries publishing in >6000 journals, covering most STEMM disciplines over the last 15 years, and made a web app allowing easy access to the data (https://lukeholman.github.io/genderGap/). Despite recent progress, the gender gap appears likely to persist for generations, particularly in surgery, computer science, physics, and maths. The gap is especially large in authorship positions associated with seniority, and prestigious journals have fewer women authors. Additionally, we estimate that men are invited by journals to submit papers at approximately double the rate of women. Wealthy countries, notably Japan, Germany, and Switzerland, had fewer women authors than poorer ones. We conclude that the STEMM gender gap will not close without further reforms in education, mentoring, and academic publishing.

Sexual selection has manifold ecological and evolutionary consequences, making its net effect on population fitness difficult to predict. A powerful empirical test is to experimentally manipulate sexual selection and then determine how population fitness evolves. Here, we synthesise 459 effect sizes from 65 experimental evolution studies using meta-analysis. We find that sexual selection on males tends to elevate the mean and reduce the variance for many fitness traits, especially in females and in populations evolving under stressful conditions. Sexual selection had weaker effects on direct measures of population fitness such as extinction rate and proportion of viable offspring, relative to traits that are less closely linked to population fitness. Overall, we conclude that the beneficial population-level consequences of sexual selection typically outweigh the harmful ones and that the effects of sexual selection can differ between sexes and environments. We discuss the implications of these results for conservation and evolutionary biology. Sexual selection has the potential to either increase or decrease absolute fitness. Here, Cally et al. perform a meta-analysis of 65 experimental evolution studies and find that sexual selection on males tends to increase fitness, especially in females evolving under stressful conditions.

Many animals improve their foraging success by producing signals that exploit the sensory biases of potential prey, but the specific properties that make these sensory traps effective remain unclear. We combine field experiments with phylogenetic comparative analyses to investigate the visual luring properties of different signal designs in web‐building spiders. Our field experiments used cardboard spider models to examine the effects of area of colour patches, colour and pattern on the foraging success of the colourful giant wood spider, Nephila pilipes. These experiments revealed that both the colour (yellow) and pattern (yellow and black mosaic) are essential for luring prey in a high ambient light environment. We subsequently used phylogenetic comparative analyses to demonstrate an evolutionary association between prey viewing environment and spider ventral signal among 63 species of orb‐weavers from 53 genera. Combined, our data show that (a) the colour of the bright body parts of orb‐weavers is essential for both diurnal and nocturnal prey attraction, whereas the pattern and area of colour patches are important for diurnal foraging and (b) the evolution of these visual lures is associated with the viewing environment, specifically ambient light intensity. We conclude that the effectiveness of colour luring might be a major driver of the convergent evolution of yellow mosaic patterns in phylogenetically divergent orb‐weavers. Our discoveries indicate that prey colour preferences and signal efficacy play a significant role in the evolution of visually mediated prey‐luring systems. A free Plain Language Summary can be found within the Supporting Information of this article. 摘要 許多動物可藉由體色傳遞誘引訊號, 利用獵物的感官偏好, 增加自身的捕食成功率。然而, 是哪些具體特質使此一欺騙訊號得以有效, 至今尚未明瞭。 本研究結合田野實驗與親緣比較方法, 探討結網性蜘蛛的視覺誘引特徵。在田野實驗中, 我們製作人面蜘蛛的色紙模型, 探討色斑的面積, 和顏色與排列形式, 對捕食成功率的影響。結果顯示, 在高光源環境下, 訊號的顏色 (黃色), 和排列形式 (黃色與黑色交錯之斑紋), 是誘引昆蟲獵物的關鍵因子。 使用親緣比較方法, 我們分析53屬63種結網性蜘蛛的自然史資料, 證實蜘蛛腹部體色的演化, 與獵物視覺環境相關。 整合田野實驗與親緣比較方法之結果, 我們得知 (一) 結網性蜘蛛體表斑紋的顏色, 為誘引日行和夜行性獵物的必要因素, 而排列形式和面積對於日間捕食活動極其重要； (二) 黃色與黑色交錯之斑紋, 此項表徵能有效誘引昆蟲, 且其演化歷程與視覺環境相關, 尤其是環境光源強度。 我們推論, 誘引獵物之效果, 是驅使親緣關係歧異的結網性蜘蛛, 演化出黃色與黑色交錯斑紋的主要因子。 我們的研究結果指出, 獵物的視覺偏好和誘引獵物之功效, 在欺騙訊號的演化中扮演重要角色。 A free Plain Language Summary can be found within the Supporting Information of this article.

Many animals undergo complete metamorphosis, where larval forms change abruptly in adulthood. Color change during ontogeny is common, but there is little understanding of evolutionary patterns in these changes. Here, we use data on larval and adult color for 246 butterfly species (61% of all species in Australia) to test whether the evolution of color is coupled between life stages. We show that adults are more variable in color across species than caterpillars and that male adult color has lower phylogenetic signal. These results suggest that sexual selection is driving color diversity in male adult butterflies at a broad scale. Moreover, color similarities between species at the larval stage do not predict color similarities at the adult stage, indicating that color evolution is decoupled between young and adult forms. Most species transition from cryptic coloration as caterpillars to conspicuous coloration as adults, but even species with conspicuous caterpillars change to different conspicuous colors as adults. The use of high‐contrast coloration is correlated with body size in caterpillars but not adults. Taken together, our results suggest a change in the relative importance of different selective pressures at different life stages, resulting in the evolutionary decoupling of coloration through ontogeny.

Dynamic colour change is widespread in ectothermic animals, but has primarily been studied in the context of background matching. For most species, we lack quantitative data on the extent of colour change across different contexts. It is also unclear whether and how colour change varies across body regions, and how overall sexual dichromatism relates to the extent of individual colour change. In this study, we obtained reflectance measures in response to different stimuli for males and females of six species of agamid lizards (Agamidae, sister family to Chameleonidae) comprising three closely related species pairs. We computed the colour volume in a lizard‐vision colour space occupied by males and females of each species and estimated overall sexual dichromatism based on the area of non‐overlapping male and female colour volumes. As expected, males had larger colour volumes than females, but the extent of colour change in males differed between species and between body regions. Notably, species that were most sexually dichromatic were not necessarily those in which males showed the greatest individual colour change. Our results indicate that the extent of colour change is independent of the degree of sexual dichromatism and demonstrate that colour change on different body regions can vary substantially even between pairs of closely related species. We studied the extent of dynamic colour change in both sexes in six agamid species. This study indicates that the extent of colour change is independent of the degree of sexual dichromatism and demonstrates that colour change on different body regions can vary substantially even between pairs of closely related species.

In heterogeneous habitats, camouflage via background matching can be challenging because visual characteristics can vary dramatically across small spatial scales. Additionally, temporal variation in signaling functions of coloration can affect crypsis, especially when animals use coloration seasonally for intraspecific signaling (e.g., mate selection). We currently have a poor understanding of how wild prey optimize background matching within continuously heterogeneous habitats, and whether this is affected by requirements of intraspecific signaling across biological seasons. Here, we quantified color patterns of a wild population of shore skink (Oligosoma smithi), a variably colored lizard endemic to New Zealand, to (a) investigate whether background matching varies across a vegetation gradient; (b) assess potential signaling functions of color; and (c) to determine whether there is a trade-off between requirements for crypsis and intraspecific signaling in coloration across seasons. Although all pattern types occurred throughout the vegetation gradient, we found evidence for background matching in skinks across the vegetation gradient, where dorsal brightness and pattern complexity corresponded with the proportion of vegetation cover. There was also a significant disparity between ventral color (saturation) of juveniles and adults, and also between sexes, suggestive of sex recognition. However, there was little indication that color was condition-dependent in adults. Despite some evidence for a potential role in signaling, crypsis did not greatly differ across seasons. Our study suggests that selection favors a mix of generalist and specialist background matching strategies across continuously heterogeneous habitats.

Stress is an important potential factor mediating a broad range of cellular pathways, including those involved in condition‐dependent (i.e., honest) color signal expression. However, the cellular mechanisms underlying the relationship between stress and color expression are largely unknown. We artificially elevated circulating corticosterone levels in male tawny dragon lizards, Ctenophorus decresii, to assess the effect of stress on the throat color signal. Corticosterone treatment increased luminance (paler throat coloration) and decreased the proportion of gray, thereby influencing the gray reticulations that produce unique patterning. The magnitude of change in luminance for corticosterone‐treated individuals in our study was around 6 “just noticeable differences” to the tawny dragon visual system, suggesting that lizards are likely to be able to perceive the measured variation. Transmission electron microscopy (TEM) of iridophore cells indicated that luminance increased with increasing density of iridophore cells and increased spacing (and/or reduced size) of crystalline guanine platelets within them. Crystal spacing within iridophores also differed between skin colors, being greater in cream than either gray or yellow skin and greater in orange than yellow skin. Our results demonstrate that stress detectably impacts signal expression (luminance and patterning), which may provide information on individual condition. This effect is likely to be mediated, at least in part, by structural coloration produced by iridophore cells. Artificially elevated circulating corticosterone treatment increased luminance and decreased the proportion of grey reticulations that produce unique pattering on the throat color signal of male tawny dragon lizards, Ctenophorus decresii. Transmission electron microscopy (TEM) of iridophore cells indicated that luminance increased with increasing density of iridophore cells and increased spacing (and/or reduced size) of crystalline guanine platelets within them. Our results demonstrate that stress detectably impacts signal expression, which may provide information on individual condition and this effect is likely to be mediated, at least in part, by structural coloration produced by iridophore cells.