Biological Journal of the Linnean Society

Although ants are conceived of as paragons of social complexity, it may be their locomotory capacity that truly sets them apart from other Hymenoptera. Based on our comparative kinematic analysis of Formicidae for level, straight-line locomotion in a broad phylogenetic context, we observe that ants are distinctly capable runners. No sampled hymenopteran paralleled the body-scaled speed of ants. Relative stride lengths for ants were longer than other sampled taxa despite short ground contact durations relative to swing durations. With respect to spatial gait patterns, ants had relatively narrow hindleg and broad midleg step-widths on average, possibly enhancing speed and turning ability. Ants were able to extend their propulsive pair of legs, those of the metathorax, extremely far posterad relative to other sampled taxa, and had a distinct locomotory posture, with a high ground clearance and the femorotibial joints raised above their backs. Despite the unique modifications of their coxotrochanteral articulations, ant forelimbs were largely unremarkable with respect to our quantified variables. Sawflies, in contrast, had extremely wide and perhaps inefficient foreleg stances, and were observed for the first time to have what appears to be a dominant tetrapodal gait pattern, which raises unexpected questions about the early evolution of the Hymenoptera. Finally, we observed variability in attachment abilities and no consistent pattern of leg liftoff sequence across the sampled taxa. Our results establish locomotory evolution in the Hymenoptera as a functionally and structurally variable system with numerous directions of future research, particularly for phylogenetic comparison across wing-monomorphic and wing-polymorphic lineages. Summary statementThis work establishes a comparative phylogenetic approach to hymenopteran kinematics, demonstrating that ant locomotory capacity is derived and observes, unexpectedly, that the sampled sawflies (symphyta) never used a tripod gait.

The evolution of conspicuous ornamentation is often thought to be the consequence of sexual selection, but this might not always be the case. One such candidate is contrasting pale-dark facial color patterns in front of eyes in insectivorous birds and other animals (lore-forehead borderlines, hereafter). A sight-line hypothesis suggested that the contrasting color between lore and forehead assists in tracking and capturing a fast-moving prey. However, this classic hypothesis have been criticized (and thus ignored) for several reasons including lack of formal statistical test controlling for phylogenetic inertia and confounding effect of dark facial color markings that are beneficial by reducing glare. Here, using a phylogenetic comparative approach, we tested the sight-line hypothesis and a widespread alternative explanation, the sexual selection hypothesis, in hirundines (Aves: Hirundinidae). We found no support for the sexual function of lore-forehead borderline in hirundines, because lore-forehead borderline was not positively related to indices of sexual selection (sexual plumage dimorphism and extrapair mating opportunity). In contrast, we found consistent support for the sight-line hypothesis. Species foraging on large prey items (i.e., fast prey) had higher degrees of lore-forehead borderline than others in this clade. Furthermore, an analysis of evolutionary pathways suggested inter-dependent evolution of lore-forehead borderline and prey size; transitions to the state with large prey and no lore-forehead borderline were less likely to occur than transitions from that state. These results remained significant when excluding species that lack dark lore, and thus, not mere presence of dark lores, but contrasting color patterns would be important. To my knowledge, the current study is the first macroevolutionary support for the sight-line hypothesis.

Turtles and tortoises (Order Testudines) possess a unique bony shell that varies in shape across ecological niches. Previous studies have linked turtle shell abnormalities to the presence of environmental stress, leading to asymmetry in shell shape. Here we present the first large-scale geometric morphometric analysis of shell asymmetry in preserved museum specimens from 92 turtle species, using high-resolution 3D scans and (semi)landmark-based methods. We quantified fluctuating asymmetry (FA) and directional asymmetry (DA) in the whole shell, carapace, and plastron, and tested for ecological and phylogenetic influences on shell shape. Our results reveal significant ecological effects on both symmetric and asymmetric components of shell morphology, with aquatic and marine species exhibiting higher FA than their terrestrial counterparts. The carapace showed higher asymmetry and integration than the plastron, suggesting different developmental constraints. Phylogenetic signal was present but weak, indicating convergence in shell shape among ecologically similar but distantly related species. Partial least squares analysis revealed strong covariation between symmetric and asymmetric components, supporting the shell as an integrated morphological unit. These findings highlight the utility of FA as a non-invasive indicator of developmental instability, with implications for conservation monitoring using preserved and living specimens.

We describe the antipredator armor of a unique population of threespine stickleback (Gasterosteus aculeatus) from Narrows Pond in western Newfoundland and compare traits for this population to nearby populations from marine and freshwater systems. After standardizing for length, Narrows Pond stickleback are shallower bodied and have shorter dorsal spines than stickleback from the other populations. Also, though the number of armor plates for Narrows Pond stickleback is greater than for typical low-plate morphs, the size of the lateral plates for Narrows Pond stickleback is much smaller. Finally, most (nearly 75% of sampled individuals) Narrows Pond stickleback do not have a pelvic structure (bilateral pelvic plate, ascending process, and ventral spine) and the remaining individuals have greatly reduced pelvic girdle whereas all individuals from the other populations possessed complete pelvic structures.

The proportion of adult males to females in the adult population, the adult sex ratio (ASR), is an important demographic parameter that has implications in sexual selection, ecology and conservation. ASR variation can be multifactorial but specific variables including sex roles - sex differences in courtship, mate competition, social pair-bonds and parental care- and sex-specific mortality have been suggested as important ASR determinants in birds. However, these relationships have not yet been comprehensively tested in specific avian groups. Here, we used phylogenetic comparative methods to study drivers of ASR variation across shorebirds (Charadrii and Scolopaci; n = 205 species), a charismatic bird group characterised by displaying extreme variations in ecology, sex roles and sexual selection traits. We found that ASR variation is associated with most sex role components but not with their sex-specific mortality. Although sex role and life history variables showed no significant sex bias, we found a trend towards reversed size dimorphism and sex role reversal across shorebirds. Sex roles components also showed correlations among each other that were surprisingly strong and in unexpected directions. Our results confirm that sex roles are important drivers of ASR variation and suggest that shorebirds may have alternative means of sex-specific mortality, possibly linked to their ecology.

Following an investigation into the hypothesis that the iconic Berlin specimen of Archaeopteryx fossilized in nesting position, which led to the discovery not only of its association with soft eggs and several hatchlings, but also similar findings in a second Archaeopteryx specimen, an attempt to characterize the entire Berlin specimen nest and estimate its number of eggs is reported here. The Berlin specimen arranged and brooded its eggs on the ground. Its clutch size appears to have exceeded one hundred eggs. Egg littering found not only in its fossil bed but also in the sediment layer immediately above it, inclusively with evidence that a subsequent generation nested over the specimen, is consistent with repeated usage of a ground nesting site. All Archaeopteryx specimens fossilized in different views of a similar pose that is compatible with a nesting posture, and evidence of eggs of consistent size with the 2D outlines of 3D flattened eggs is present not only in the Berlin, Teylers, Thermopolis and Maxberg specimens, but also in the isolated Archaeopteryx feather fossil. In addition, egg and hatchling littering are present in the Berlin, Teylers and isolated Archaeopteryx feather fossils. Taken together, these findings are indicative of colonial ground nesting behavior by Archaeopteryx in Solnhofen. Egg littering, eggs dorsal to the Berlin specimen torso and limb rotations in the London and Thermopolis Archaeopteryx specimens can all be explained by nesting in reentrances located at the margins or in sand banks of marine lagoons in Solnhofen, which would have been flooded, causing the subsequent collapse of the nest and the still-life preservation of its content. The discovery of colonial ground nesting in a winged Jurassic bird relative favors the evolution of birds from the ground up and suggests that wings and their elongated feathers were primarily associated with ground nest protection and only secondarily with flight.

The Vitelline Warbler (Setophaga vitellina) is an understudied species endemic to a few small islands in the western Caribbean. Little is known beyond its phylogenetic relationship to other New World warblers. We used island-wide surveys and bioacoustic recordings to investigate the distribution, vocalizations, and ecology of S. vitellina across a significant portion of the species range on Little Cayman Island. We recorded 417 songs from 91 individuals and analyzed the length, frequency, and shape of various song components. We observed and characterized high variation in the composition and character of songs. We also describe the call of the species, document an association with gumbo limbo (Bursera simaruba) trees, and report interactions with other bird species. Improved knowledge of Vitelline Warblers has value for evaluating conservation threats to an island endemic and for understanding the evolution of vocalization behavior in Neotropical songbirds.

Reptiles have repeatedly invaded and thrived in aquatic environments throughout history, however fewer than 8% of the 6000 extant species are primarily aquatic. The Galapagos Marine Iguana (Amblyrhynchus cristatus), the worlds only marine lizard, may have had one of the most unique and challenging transitions to aquatic life. Curiously, previous studies have identified relatively few physiological adaptations in Marine Iguanas, however, little is known about the extent of morphological specialisation and performance trade-offs associated with the marine environment. By examining the morphology and locomotory performance of the Marine Iguana in comparison to their closely related mainland ancestors, the Black Spiny-tailed iguana (Ctenosaura similis) and Green Iguana (Iguana iguana), we found variation reflected specialisation to ecological niches. However, variation was more pronounced among subspecies of Marine Iguana, suggesting that little morphological or performance modification is required for iguanids to successfully invade aquatic environments, thus raising the question why there are so few extant aquatic reptilian lineages. We found that specialisation for the marine environment resulted in a trade-off in sprint speed in a terrestrial environment, similar to that seen in extant crocodilians. Reduced performance in a terrestrial environment likely poses little risk to large-bodied apex predators, whereas in iguanids, a performance trade-off would likely incur increased predation. As such, we suggest that this may explain why iguanids and other ancestral lineages have not undergone transitions to aquatic life. Additionally, we found that the magnitude of morphological and performance variation was more pronounced between subspecies of Marine Iguana than between iguanid species. Summary StatementThe Marine Iguana has undergone a unique evolutionary transition to aquatic behaviour, we explore the extent of morphological and performance specialisation required and why there are so few extant marine reptiles. O_FIG_DISPLAY_L [Figure 1] M_FIG_DISPLAY C_FIG_DISPLAY

Closely related sexual and parthenogenetic species often show distinct distribution patterns, known as geographical parthenogenesis. These patterns, characterized by a mosaic of separate sexual and parthenogenetic populations across their natural range, can also be found in facultative parthenogens - species in which every female is capable of both sexual and parthenogenetic reproduction. The underlying mechanisms driving this phenomenon in nature remain unclear. Features of the habitat, such as differences in host plant phenotypes or niche breadth, could favour sexual or asexual reproductive modes and thus help to explain geographical parthenogenesis in natural insect populations. Megacrania batesii is a facultatively parthenogenetic stick insect that displays geographical parthenogenesis in the wild. We aimed to explore whether sexual and parthenogenetic populations of M. batesii displayed niche differentiation or variations in niche breadth that could explain the separation of the two population types. To do this, we sampled host plants from across the range of M. batesii and quantified phenotypic traits that might affect palatability or accessibility for M. batesii, including leaf thickness, toughness, spike size and density, height, and chemical composition. We also quantified host plant density, which could affect M. batesii dispersal. We found little evidence of phenotypic differences between host plants supporting sexual versus asexual M. batesii populations, and no difference in host-plant density or niche breadth between the two population types. Our results suggest that habitat parameters do not play a substantial role in shaping patterns of geographical parthenogenesis in wild populations of M. batesii. Instead, population sex ratio variation could result from interactions between the sexes or dispersal dynamics.

The Jaera albifrons species complex comprises several closely related species of intertidal marine isopods that exhibit limited morphological differentiation and varying degrees of hybridization. In this pilot study, we analyzed regions of the nuclear rRNA genes (D1-D2 and ITS1) from populations of J. albifrons, J. praehirsuta, and J. ischiosetosa to assess their utility as diagnostic markers for species identification and phylogenetic inference. Despite the species morphological distinctness and ecological differences, rRNA variability was remarkably shallow across the complex, with only few variable sites in D1-D2 and ITS1. This contrasted sharply with high interspecific divergence observed in other Jaera species, indicating recent divergence and nascent speciation within the complex. J. ischiosetosa showed the lowest intra-individual variation and was most distinct from the two other species. Overlap between J. albifrons and J. praehirsuta genotypes, consistent with known introgressive hybridization, was considerable and likely stems from introgressive hybridization. Local hybridization patterns identifiable morphologically varied across settlements with of the settlements demonstrating unusually high hybridization rates. Different settlements were found to demonstrate a range of abiotic factors impacting spatial separation of the different species and varying degrees of similarity between the species in rRNA genotypes. Phylogenetic analysis of the genus revealed that the J. albifrons complex originates from among the species of the Mediterranean species group and represents a recent migration from the Mediterranean rather than an early-diverging lineage as previously suggested. These findings highlight the challenges of using rRNA markers for species delimitation in recently diverged and hybridizing taxa and underscore variable hybridization and spatial segregation as key factors shaping coexistence in mixed populations.

The sweat bee Halictus rubicundus is an important pollinator with a large latitudinal range and many potential barriers to gene flow. Alongside typical physical barriers, including mountain ranges and oceans, the climate may also impose restrictions on gene flow in this species. The climate influences voltinism and sociality in H. rubicundus, which is bivoltine and can nest socially at lower latitudes but can be univoltine and solitary in the north of its range and at higher altitudes where the climate is cooler. Variation in voltinism due to the climate may result in differences in phenology between populations across this species geographical range. Differences in phenology could limit gene flow, rendering populations at extreme latitudes genetically isolated and potentially more vulnerable to environmental stressors. A previous study found that the Irish Sea restricts gene flow in this species, but there was no evidence that differences in phenology had a similar effect as there was no genetic differentiation between H. rubicundus populations on mainland Britain. Here we extend the previous study to consider populations of H. rubicundus at extreme northern and southern latitudes in the UK. Using 12 microsatellite markers for genotyping, we found that bees from a population in the far north of Scotland were genetically differentiated from bees collected in Cornwall in the south-west of England. In contrast, bees collected across the Irish Sea in Northern Ireland showed genetic overlap with both the Scottish and Cornish bees. Our results suggest that when populations at extreme latitudes are considered, phenology and the climate may act alongside physical barriers such as the Scottish Highlands and the Irish Sea to restrict gene flow in H. rubicundus. We discuss the implications of our results for local adaptation in the face of rapidly changing selection pressures which are likely under climate change.

The green-brown polymorphism among polyneopteran insects represents one of the most penetrant color polymorphisms in any group of organisms. Yet systematic overviews are lacking. I here present analyses of the phylogenetic, geographic and habitat distribution of the green-brown polymorphism across the complete European orthopteran fauna. Overall, 30% of European orthopterans are green-brown polymorphic. Polymorphic species are scattered across the entire phylogenetic tree, including roughly equal proportions of Ensifera and Caelifera. A few taxonomic groups, however, include only brown species. Polymorphic species occur more frequently in clades that contain monomorphic green species than in those without green species. The relative abundance of color morphs in polymorphic species is skewed towards green, and in particular rare/exceptional brown morphs are more common in predominantly green species than rare/exceptional green morphs in predominantly brown species. The patterns of abundances support the hypothesis that loss-of-function mutations play a role in creating polymorphic populations from green species. Polymorphic species are particularly common in moist to mesic grasslands, alpine and arboreal habitats. Dry, open, rocky and cave habitats as well as nocturnal lifestyles are dominated by monomorphic brown species. The proportion of polymorphic species increases from southern to northern latitudes. These marked habitat-dependencies also show that coloration is affected by natural selection and/or environmental filtering. Overall, the results illustrate that the occurrence of the polymorphism is phylogenetically, geographically and ecologically widespread and they suggest that polymorphism is thus potentially in mutation-selection balance across a large number of species.

With 75 known species, the freshwater-fish genus Sinocyclocheilus is the largest cavefish radiation in the world, emerging as a model system for evolutionary studies. They show multiple adaptations for cave dwelling (stygomorphic adaptations), which include a range of traits such as eye degeneration (Normal-eyed, Micro-eyed and Eyeless), depigmentation of skin, and in some species, the presence of "horns". Their behavioural adaptations to subterranean environments, however, are poorly understood. Wall-following (WF) behaviour, where an organism remains in close contact with the boundary demarcating its habitat when in the dark, is a peculiar behaviour observed in a wide range of animals and is enhanced in some cave dwellers. Hence, we hypothesize wall-following to be present also in Sinocyclocheilus, possibly enhanced in Eyeless species compared to species with visual cues (Normal / Micro-eyed species). Using 13 species representative of Sinocyclocheilus radiation and eye-morphs, we designed a series of assays, based on pre-existing methods for Astyanax mexicanus behavioural experiments, to examine wall-following behaviour under three stimulation conditions. Our results indicate that eyeless species exhibit significantly enhanced levels of WF compared to Normal-eyed species, with Micro-eyed forms demonstrating intermediate levels. Using a mtDNA based dated phylogeny (chronogram with four clades A - D), we traced the degree of WF of these forms to outline common patterns. We show that intensity of WF behaviour is high in the subterranean clades (B & C) compared to clades with free-living species (A & D). Experiments on WF behaviour revealed that eyeless species are highly sensitive to vibrations, whereas normal-eyed species are the least sensitive. Since WF behaviour is present to some degree in all Sinocyclocheilus species, and given that these fishes evolved in the late Miocene, we identify this behaviour as being ancestral with WF enhancement related to cave occupation. Our results from this diversification-scale study of cavefish behaviour suggest that enhanced wall-following behaviour may be a convergent trait across all stygomorphic cavefish lineages. Significance statementSinocyclocheilus, a genus of 75 species of freshwater cavefish, is an emerging model system in evolutionary studies. Their adaptations for subterranean life, including eye degeneration, skin depigmentation, and horn-like structures, are well-known, but their behavioural adaptations remain understudied. Here we focus on a phenomenon, called "wall-following," where fish stay close to the cave walls in absence of light. We hypothesized that this behaviour would be more pronounced in eyeless species. We selected 13 species, representative of the diversity of the genus and eye types, and observed their wall-following behaviour under different conditions. Results were intriguing; eyeless species exhibited heightened wall-following behaviour compared to their sighted counterparts, with small-eyed species falling in between. Researchers also mapped this behaviour on a phylogenetic tree, discovering a pattern: cave-dwelling clades showed stronger wall-following than free-living ones. Wall-following is prevalent in all Sinocyclocheilus species and, given the evolutionary history of the genus, is considered an ancestral behaviour that intensified with cave adaptation. These findings contribute to our understanding of convergent evolution, suggesting that enhanced wall-following may be a shared trait among diverse cavefish lineages.

Hawksbill sea turtles (Eretmochelys imbricata) from the Hawaiian archipelago form a small, genetically isolated, population consisting of only a few tens of individuals breeding annually. Most females nest on the island of Hawaii, but little is known about the demographics of this rookery. This study used genetic relatedness, inferred from 135 microhaplotype markers, to determine breeding sex-ratios, estimate female nesting frequency, and assess relationships between individuals nesting on different beaches. Samples were collected during the 2017 nesting season and final data included 13 nesting females and 1,002 unhatched embryos, salvaged from 41 nests, 13 of which had no observed mother. Results show that most females used a single nesting beach laying 1-5 nests each. From female and offspring alleles the paternal genotypes of 12 breeding males were reconstructed and many showed high relatedness to their mates. Pairwise relatedness of offspring revealed one instance of polygyny but otherwise suggest a 1:1 breeding-sex ratio. Relatedness analysis and spatial-autocorrelation of genotypes indicate non-random mating among complexes of nesting beaches, for both sexes, suggesting strong natal philopatry. Nesting complexes also showed unique patterns of inbreeding and outbreeding across loci, further indicating that Hawaiian hawksbill turtles have demographically discontinuous nesting populations at a fine spatial scale.

How song repertoires vary within species and change over time is well studied in male songbirds. However, variation in female song repertoires remains largely unstudied despite female song being much more common and complex than once assumed. We investigated the song syllable repertoire of the New Zealand bellbird (Anthornis melanura), a species where both sexes have complex but sexually dimorphic song. We compared songs at individual and population levels to investigate sex and temporal variation of syllable repertoires. We detected 96 syllable types in the population over four years, of which 58% were unique to males, 32% unique to females and 9% were shared between the sexes. The population syllable repertoire of both sexes changed substantially across years with similar turnover rates (Jaccards similarity coefficients; female 52.9-69.0%; male 58.6-73.7%). Furthermore, many syllable types, unique to each sex, varied in prevalence within the population across years. The syllable repertoire sizes of individuals were higher for males than females (13-32, n = 7 and 6-16, n = 8, respectively). Although these sample sizes were low, the temporal variation in syllable prevalence and turnover for individuals were similar to patterns at the population level. Overall, male and female bellbirds exhibited similarities in temporal patterns of yearly repertoire composition, with rapid changes in syllable prevalence, but females had fewer syllable types than males. We suggest that these similarities and differences are consistent with male and female song repertoires being driven by similar but not identical selection pressures.

Vocal traits are often essential for distinguishing phenotypically cryptic taxa. The hummingbird genus Patagona comprises two species, near identical in plumage and morphology, that differ in almost every aspect of their ecology and evolution: The Northern Giant Hummingbird (Patagona peruviana) and Southern Giant Hummingbird (Patagona gigas). Here, we characterized the songs of both giant hummingbird species and assessed whether song can be used to distinguish the two in the field. We recorded both species in Peru, Bolivia, and Chile in 2023 and 2025 and used public data to analyze song variation of 217 individuals recorded across the Andes. Sampling spanned 49 years, >36{degrees} of latitude, and >4,300 meters in elevation. We first quantified species-level song differences in allopatric breeding populations and trained a linear discriminant model to identify individuals to species. The trained model had 100% classification accuracy. We then used our trained model to identify individuals recorded during co-occurring, non- breeding periods of overlap, and subsequently analyzed range-wide song variation; this model had 98.72% classification accuracy (1.28% error rate; one individual misidentified). We found striking song divergence between the two species, uncovering that Northern and Southern Giant Hummingbirds can be reliably and easily identified by song across their ranges and during any month of the year. We provide new data on the range limits of both species in northern Bolivia, highlighting a previously unknown zone of overlap around Lake Titicaca. Unlike other phenotypic traits, song provides a robust method for identifying the giant hummingbird species, opening doors to future research on ecology, trait evolution, hybrid zone dynamics, and conservation of the worlds largest hummingbirds.

The link between skull shape and dietary ecology in birds at macroevolutionary scales has recently been called into question by analyses of 3D shape that reveal that cranial anatomy is mainly influenced by other factors such as allometry. It is still unknown whether this form-function disconnect also exists at smaller evolutionary scales, for example within specialized ecological guilds. Vultures are a diverse guild of 23 extant species in two families (Accipitridae and Cathartidae) that exhibit phenotypic convergence as a result of highly-specialized feeding ecology. Vultures are the only known obligate scavengers among vertebrates and are usually grouped together under this single dietary category, but within this specialized diet there are three distinct, species-specific feeding strategies termed ripper, gulper, and scrapper. We use three-dimensional geometric morphometrics to quantify the relative contributions of feeding ecology, allometry, and phylogeny on vulture skull shape, along with several non-vulture raptors of similar size, range and ecology. Families show clear separation in shape, but phylogenetic signal is comparatively weak (Kmult = 0.33). Taking into account the influence of phylogeny, skull shape is not significantly correlated with either skull size or feeding type, but there are examples of strong, significant convergence and parallel shape evolution across feeding groups. Furthermore, skull shape performs strongly in predicting feeding ecology in a phylogenetic discriminant function analysis. These findings highlight the importance of detailed assessment of feeding behavior in studies of ecomorphology, rather than broader dietary categories alone, and reveal that ecology can be readily inferred from form given appropriate information.

BackgroundThe ruff sandpiper Calidris pugnax is a Palearctic lekking shorebird with three genetic morphs determined by an autosomal inversion. Male morphs differ strikingly in body size, ornaments, endocrinology and mating behavior. Aggressive Independents represent the ancestral haplotype, while female-mimicking Faeders and semi-cooperative Satellites are the inverted haplotypes. Because one inversion breakpoint is homozygous lethal, the inverted haplotypes cannot recombine and are expected to accumulate deleterious mutations. The inversion regions also harbor genes involved in spermatogenesis. However, it remains unknown whether the genetic differences between the morphs also translate into differences in sperm traits. Here, we use a captive-bred population of ruffs to compare sperm swimming speed and morphology among the morphs. ResultsRuff sperm morphologically resembled those of passerines, but moved differently, vibrating from side to side while slowly moving forward, rather than rotating while moving forward. Faeder sperm moved the slowest, which is consistent with the prediction of genetic deterioration over time. However, against expectation, sperm of Independents did not seem to be of the highest quality, i.e., their sperm were not the fastest nor the least variable, and they had sperm with the shortest tail and midpiece. Although the midpiece contains the energy-producing mitochondria, sperm midpiece length was not associated with sperm swimming speed. Instead, two of three velocity metrics weakly positively correlated with head length (absolute and relative). ConclusionsThe three genetically determined ruff morphs showed subtle differences in swimming speed and in the length of some sperm components. However, the between-morph differences in sperm swimming speed were not linked to the differences in morphology. We conclude that there is at best limited evidence for lower-quality sperm in the morphs that carry the inversion, and suggest that the potential for the evolution of morph-specific sperm adaptations may be limited in this system. Lay SummaryThe ruff sandpiper is a shorebird that exhibits three genetically distinct types of males, which differ markedly in body size, ornaments, hormones, and mating behavior. Aggressive Independents represent the type that evolved first. Semi-cooperative Satellites and female-mimicking Faeders evolved later through a specific type of genetic rearrangement called an inversion, in which a segment of a chromosome reversed in orientation. Due to the nature of this inversion, Satellite and Faeder chromosomes are expected to deteriorate over time. However, it remains unclear whether the genetic differences between these morphs, which affect physiological and behavioral traits, also translate into differences in sperm traits. We used a captive population of ruffs to compare sperm swimming speed and length measurements between the three types of males. Faeder sperm was the slowest, which is consistent with expectations based on genetic deterioration over time. However, against our expectations, the sperm of Independents does not appear to have better performance characteristics. Although the midpiece of a sperm is responsible for energy production, the length of the midpiece did not relate to sperm swimming speed.

The tail of birds contributes substantially to flight aerodynamics through lift generation, reduction of pressure drag, and pitch stabilization. Hummingbirds are powerful flyers, able to sustain hovering in still air, generate lift in both the up- and downstroke, and takeoff due to substantial developmental investment in their wings and corresponding musculature. Given the abundance of wing power, it is possible that tails are less essential to the aerodynamics of hummingbird flight than they are in other birds, freeing them for non-locomotor functions. Hummingbird tails are well known for their morphological elaboration as sexually selected ornaments, including sound generation. Our observations, and brief descriptions in the literature, led us to hypothesize that tail flaring may serve as another form of sexual signaling, used by males during male-male fighting. To test this, we used high-speed video to record agonistic encounters among seven species of hummingbird the field and found 95% of inter- and intra-sexual and specific contests included tail flaring. We measured kinematics of this flaring during male-male fighting of calliope hummingbirds (Selasphorus calliope, n = 5) indoors. Consistent with our hypothesis, captive males exhibited greater angles of tail flare when engaged in a fight (26.9 {+/-} 42.9{degrees}, mean {+/-} sd) than when performing solitary landing (-12.7 {+/-} 8.6 {degrees}) and takeoff (-11.1 {+/-} 6.6 {degrees}) maneuvers. We evaluate these results in the context of signaling during animal contests and propose future tests of whether tail flaring is an honest signal of individual quality and Resource Holding Potential (RHP). Summary StatementMale-male fighting is common in hummingbirds with competition over food and mates. During these competitions, tail flaring and waggle maneuvers are used as a signal of aggressive intent.

Scoliid wasps comprise a clade of aculeate insects whose larvae are parasitoids of scarabaeid beetle grubs. While scoliids have been studied and used as biological control agents, research into the groups evolution, as well as the stability of scoliid taxonomy, has been limited by a lack of reliable phylogenies. We use ultraconserved element (UCE) data under concatenation and the multispecies coalescent to infer a phylogeny of the Scoliidae. In order to mitigate potential issues arising from model misspecification, we perform data filtering experiments using posterior predictive checks and matched-pairs tests of symmetry. Our analyses confirm the position of Proscolia as sister to all other extant scoliids. We also find strong support for a sister group relationship between the campsomerine genus Colpa and the Scoliini, rendering the Campsomerini non-monophyletic. Campsomerini excluding Colpa (hereafter Campsomerini sensu stricto) is inferred to be monophyletic, with the Australasian genus Trisciloa recovered as sister to the remaining members of the group. Out of nine genera in which more than one species was sampled, Campsomeriella, Dielis, Megascolia, and Scolia are inferred to be non-monophyletic. Analyses incorporating fossil data indicate an Early Cretaceous origin of the crown Scoliidae, with the split between Scoliini + Colpa and Campsomerini s.s. most probably occurring in the Late Cretaceous. Posterior means of Scoliini + Colpa and Campsomerini s.s. crown ages are estimated to be in the Paleogene, though age 95% HPD intervals extend slightly back past the K-Pg boundary, and analyses including fossils of less certain placement result in more posterior mass on older ages. Our estimates of the stem ages of Nearctic scoliid clades are consistent with dispersal across Beringia during the Oligocene or later Eocene. Our study provides a foundation for future research into scoliid wasp evolution and biogeography by being the first to leverage genome-scale data and model-based methods. However, the precision of our dating analyses is constrained by the paucity of well-preserved fossils reliably attributable to the scoliid crown group. Despite concluding that the higher-level taxonomy of the Scoliidae is in dire need of revision, we recommend that taxonomic changes be predicated on datasets that extend the geographic and taxonomic sampling of the current study.