Conspicuous sexual signals are frequently under selection from conflicting sources, such as natural versus sexual selection and precopulatory versus postcopulatory sexual selection, which may act in the same or different directions. The Pacific field cricket (Teleogryllus oceanicus) is undergoing rapid evolutionary trait loss: mutations that render males obligately silent (the "flatwing phenotype") have become established on several islands of Hawai'i. Females strongly discriminate against silent males, yet flatwings do gain matings. In this study, we take advantage of this natural system to understand how investment in ejaculate quality under high and low perceived sperm competition risk (manipulated using acoustic cues) differs between wild type males and flatwings, which obligately adopt alternative reproductive tactics (ARTs). We replicated our study in two islands with different flatwing frequencies because female mating rate and therefore sperm competition risk is likely higher in O'ahu than Kaua'i. We measured testes mass and gene expression for three seminal fluid proteins (SFPs) that affect paternity success, sperm viability, and female propensity to remate. Compared to Kaua'i males, O'ahu males showed higher residual testes mass and expression of ToSfp011, which increases male sperm viability and paternity success, and reduces mate searching behaviour by females. We found no effect of immediate sperm competition risk or wing morph on any of the SFPs or testes mass. Differential SFP expression and residual testes mass in Hawaiian populations that likely differ in mating rate are compatible with the predictions of sperm competition theory.

In the early 1970s, Geoff Parker recognised that because females frequently mate with multiple males, competition for fertilizations will impose significant sexual selection on males and their ejaculates. Post-mating sexual selection has since developed into a significant evolutionary paradigm, in no small part fostered by the biennial meeting of the Biology of Spermatozoa (BoS) community. BoS celebrated its thirtieth anniversary in 2025, prompting reflection on the development of the discipline and its future. The paradigm has shifted from one focused predominantly on competition among males for fertilizations to a holistic appreciation of the role of females and ova in determining fertilisation success, and the interacting effects of males and females on fertilisation outcomes. The field has transitioned from a phenotypic focus to one in which omics are yielding unprecedented insight into the biology of sperm, ova and male and female reproductive fluids that affect fertilisation dynamics. Understanding sperm biology has become a strongly interdisciplinary venture, fostered by the BoS meetings. Key discoveries over the last 30 years are highlighted and areas for future development identified. The history of this field highlights the critical role played by small, focused meetings and workshops.

Among invertebrates, spiders are regarded as a model group for sexual selection studies. However, our understanding of their mating behaviour is highly biased towards species in the infraorder Araneomorphae. Knowledge of the mating systems of mygalomorph spiders (infraorder Mygalomorphae) remains rudimentary at best. Here, we report on the mating behaviour of a recently described Australian wishbone spider (Anamidae: Aname inexpecta) from south-western Western Australia. In doing so, we present the first detailed observations of mating behaviour of a member of the family Anamidae and describe a remarkable, novel male sexual behaviour for mygalomorph spiders ('burrow plugging'). This behaviour involves the male collecting soil with his chelicerae and placing it over the entrance to the female's burrow, sealing the entrance before actively guarding the plugged retreat. We provide some of the first insights into post-copulatory mate guarding in burrowing mygalomorph spiders, contributing to our understanding of mating systems in a group where such studies are rare.

Interactions between natural and sexual selection have been integral to the development of sexual selection theory, yet the role of natural selection in sexual trait evolution has received far less empirical attention than the role of sexual selection, and the extent to which natural and sexual selection are aligned remains an important empirical question. Insect cuticular hydrocarbons (CHCs) provide a good model for exploring interactions between natural and sexual selection because of their dual roles in sexual signalling and desiccation resistance. We used the geometric framework for nutrition to explore the potential for, and magnitude of trade-offs between male attractiveness, desiccation resistance and the abundance and blend of CHCs in the cricket Teleogryllus oceanicus. Attractiveness and desiccation resistance were both maximized on a diet that was rich in carbohydrate relative to protein. Although maximum expressions occurred at significantly different locations in nutritional space, the difference in angles between maximum attractiveness and desiccation resistance were small. Attractiveness and desiccation resistance were both associated with CHCs of moderate, rather than maximum, abundance and with a blend that was rich in two shorter chained alkenes relative to a single longer chained alkane. Partial correlations between fitness traits suggested that CHCs contribute indirectly to male attractiveness via their role in desiccation resistance. Our findings are consistent with the idea that natural and sexual selection on CHCs can be broadly aligned, facilitating rapid adaptation to ecological conditions and promoting speciation.

The wishbone spiders of the genus Aname L. Koch, 1873 are highly diverse mygalomorph spiders with an extremely widespread distribution across continental mainland Australia. In this study we use an integrative approach, providing morphological and molecular data combined with natural history information, to address a taxonomic knowledge shortfall in the Northern Jarrah Forest subregion of south-western Western Australia. We here report the presence of at least two different clades in the area: the pulchella group and the mainae group. We describe six new species for the region, belonging to the newly defined 'A. spicata-complex' of the pulchella group: A. crassitibia sp. nov., A. inexpecta sp. nov., A. minuta sp. nov., A. reliquia sp. nov., A. spicata sp. nov. and A. trapezoidalis sp. nov. We also designate A. fuscocincta Rainbow & Pulleine, 1918 as a nomen dubium, the holotype being an unidentifiable juvenile. These findings expand our understanding of the diversity and distribution of Aname in the south-western Australian biodiversity hotspot and serve as a foundation for future, more comprehensive studies in the region. Given the ongoing resource extraction activities in the area, this work will also be important for environmental monitoring and conservation purposes. ZooBank: urn:lsid:zoobank.org:pub:961BFB99-5FCA-4ADA-B55F-7AAB947BBEAA.

The Australian wishbone spider genus Aname is perhaps the most diverse mygalomorph spider genus in the world, with an estimated 300 species distributed across the Australian mainland. In this study, we use extensive morphological and molecular datasets to revise the 'mellosa-complex', a clade of Western Australian species that are recognisable due to their distinctive morphology and characteristic 'hooded' burrow entrances. We delimit 25 species, including the nominal species A. mellosa Harvey, Framenau, Wojcieszek, Rix & Harvey, 2012, and 24 newly described species: A. amabilis sp. nov., A. arenicosta sp. nov., A. auromellosa sp. nov., A. boreoarca sp. nov., A. charlesdarwini sp. nov., A. cowani sp. nov., A. dimissa sp. nov., A. eowilsoni sp. nov., A. eurarca sp. nov., A. geminata sp. nov., A. isabelae sp. nov., A. jillae sp. nov., A. kaii sp. nov., A. nacta sp. nov., A. primarena sp. nov., A. prospecta sp. nov., A. sangeri sp. nov., A. senticosa sp. nov., A. simplex sp. nov., A. tacenda sp. nov., A. taracta sp. nov., A. terminata sp. nov., A. wanjarri sp. nov. and A. zephyrarca sp. nov. The mellosa-complex is endemic to xeric habitats north of the mulga-eucalypt line in Western Australia and comprises three distinct clades with largely non-overlapping distributions: the amabilis species-group, the charlesdarwini species-group and the mellosa species-group. Species in this complex, particularly those in the mellosa species-group, are morphologically cryptic. To ensure accurate identification, we provide molecular diagnoses and sequence data for all 23 species for which nucleotide data are available, totalling 429 sequenced specimens across the entire complex. These findings expand our understanding of the diversity and distributions of Aname species in Western Australia and, given the occurrence of many taxa in the resource-rich Pilbara bioregion, will be important for accurate Environmental Impact Assessments (EIAs). ZooBank: urn:lsid:zoobank.org:pub:B06C4B97-BC71-46B4-840D-A7D78C393F99.

Social interactions during development can have a significant and lasting impact on adult phenotypes and fitness. Indeed, a growing body of evidence suggests the early social environment plays an important role in cognitive development. However, existing studies largely focus on the impact of social group size, which does not necessarily capture all the cognitive demands associated with group living. Social network analysis can provide detailed insight into variation in social interactions between group members, and thus the information-processing challenges associated with group living at the individual level. Here, we explore whether social interactions during development are related to cognitive performance in juvenile Western Australian magpies (Gymnorhina tibicen dorsalis). Specifically, we investigated the relationship between social network measures of connectedness (physical proximity, play, agonistic and vocal interactions) and individual cognitive performance, tested at three developmentally sensitive time points during the first year of life. We found that social measures were related to cognitive performance: individuals in larger groups solve an associative learning task in fewer trials at 300 days post-fledging. Additionally, individuals that responded to vocalisations from more conspecifics and those that received aggressive interactions from more conspecifics perform better at an associative learning task at 300 days post-fledging. Our study highlights the value of considering individual-based social network measures, which capture the differences in specific social connections between individuals within groups, when investigating the relationship between the social environment and cognitive development.

Spiders of the genus Aname L. Koch, 1873, commonly referred to as wishbone spiders, are a ubiquitous and extremely diverse component of the Australian mygalomorph fauna. Distributed across most of mainland Australia, and with an estimated endemic fauna in excess of 300 species, it is perhaps the world’s most diverse mygalomorph spider genus. Unsurprisingly, this group presents an enormous taxonomic challenge, with 80% or more of the fauna still undescribed, and a large proportion of species occurring in arid, semi-arid or otherwise remote parts of inland Australia. To address these shortfalls, this study represents the first in a planned series of major revisions to rapidly advance our knowledge of the Australian wishbone spiders. Here, we revise the Aname fauna of subtropical and tropical eastern Australia, applying an integrative approach of unprecedented monographic scope for a taxonomic study on Australian Mygalomorphae, bringing together morphological monography, live habitus information, burrowing biology and molecular phylogenetics resulting from extensive field work. Our expanded molecular phylogeny is augmented with 131 new barcode (COI) sequences from eastern Australian Aname species, and we provide descriptions, natural history observations and distributional data for a total of 68 eastern species. Of these, 10 represent redescriptions of previously described and valid species: A. barrema Raven, 1985, A. blackdownensis Raven, 1985, A. camara Raven, 1985, A. carina Raven, 1985, A. distincta (Rainbow, 1914), A. longitheca Raven, 1985, A. inimica Raven, 1985, A. pallida L. Koch, 1873, A. robertsorum Raven, 1985, and A. warialda Raven, 1985. Three represent species previously considered junior synonyms that have now been revalidated: A. attenuata (Rainbow & Pulleine, 1918) stat. rev., A. giraulti (Rainbow, 1914) stat. rev., and A. villosa Rainbow & Pulleine, 1918 stat. rev. One species (Aname collinsorum Raven, 1985) is now considered a junior synonym of Aname giraulti (Rainbow, 1914) syn. nov. Finally, 55 species are newly described: Aname albicula sp. nov., A. ammolithica sp. nov., A. aurantella sp. nov., A. aurensis sp. nov., A. barakula sp. nov., A. bifaceta sp. nov., A. boreovillosa sp. nov., A. braemar sp. nov., A. briggsi sp. nov., A. broadwater sp. nov., A. calida sp. nov., A. callitra sp. nov., A. cassowariensis sp. nov., A. consuelo sp. nov., A. convoluta sp. nov., A. corundaria sp. nov., A. cudmore sp. nov., A. dingo sp. nov., A. distorta sp. nov., A. eddieorum sp. nov., A. ethabuka sp. nov., A. ferruginea sp. nov., A. flexicaudula sp. nov., A. fossoria sp. nov., A. fuscochelicera sp. nov., A. gilbertensis sp. nov., A. harmoniosa sp. nov., A. hughenden sp. nov., A. inglewood sp. nov., A. insolita sp. nov., A. intermedia sp. nov., A. lambkinae sp. nov., A. lawrenceae sp. nov., A. litoralis sp. nov., A. magnifica sp. nov., A. mariala sp. nov., A. mulgana sp. nov., A. namoi sp. nov., A. nigrochelicera sp. nov., A. nigrotarsa sp. nov., A. occivillosa sp. nov., A. olkola sp. nov., A. platensis sp. nov., A. pyroensis sp. nov., A. rubrochelicera sp. nov., A. rupicola sp. nov., A. savannella sp. nov., A. savannensis sp. nov., A. scutitheca sp. nov., A. serpentina sp. nov., A. tropicana sp. nov., A. truncata sp. nov., A. vigilata sp. nov., A. viridiensis sp. nov., and A. warrego sp. nov.

Trade-offs should be ubiquitous in nature. Yet, direct trade-offs between traits essential for fitness are challenging to detect. Recent theory suggests that population-level variation in resource acquisition could play an important role in our ability to detect trade-offs. Here, we test experimentally the hypothesis that the detection of trade-offs depends on the underlying distribution of individuals with different resource acquisition in a population. Specifically, we resampled ecologically and experimentally relevant resource acquisition distributions from a population of male Australian field crickets (Teleogryllus oceanicus) subjected to a continuous range of diet manipulation. While we found evidence for trade-offs between different male fitness traits, the distribution of resource acquisition in the population had no systematic effect on the strength of these trade-offs. Interestingly, trade-offs were most pronounced between postcopulatory traits and immune function, but trade-offs involving precopulatory traits were relatively weak. Overall, our findings question the hypothesis that resource acquisition may influence our ability to detect trade-offs and instead suggest that other factors, like the hierarchical complexity of resource allocation, make detecting trade-offs so elusive.

Sexual conflict is widespread among sexually reproducing organisms. Phenotypic plasticity in female resistance traits has the potential to moderate the harm imposed by males during mating, yet female plasticity has rarely been explored. In this experiment, we investigated whether female seed beetles invest more in immunocompetence, measured as phenoloxidase (PO) capacity, when exposed to cues signalling a greater risk of sexual conflict. Risk perception was manipulated by housing focal individuals alone or with a companion as developing larvae, followed by exposure to a mating-free male- or female-biased social environment when adults. We predicted that females exposed to cues of increased sexual conflict would have increased PO capacity. However, PO capacity did not differ between either larval or adult social treatments. Our results suggest that females may not perceive a risk to their fitness on the basis of increased male presence or are unable to adjust this aspect of their phenotype in response to that risk.

Our understanding of microbial variation in male reproductive tissues is poorly understood, both regarding how it varies spatially across different tissues and its ability to affect male sperm and semen quality. To redress this gap, we explored the relationship between male sperm viability and male gut and reproductive tract microbiomes in the Pacific field cricket, Teleogryllus oceanicus. We selected cohorts of males within our populations with the highest and lowest natural sperm viability and characterized the bacterial microbiota present in the gut, testes, seminal vesicle, accessory glands and the spermatophore (ejaculate) using 16S ribosomal RNA gene metabarcoding. We identified bacterial taxa corresponding to sperm viability, highlighting for the first time an association between the host’s microbial communities and male competitive fertilization success. We also found significant spatial variation in bacterial community structure of reproductive tissue types. Our data demonstrate the importance of considering the microbial diversity of both the host gut and reproductive tract when investigating male fertility in wildlife and potentially human clinical settings.

Taxonomic studies have evolved greatly since their early stages and new techniques have been incorporated to improve species descriptions. Those involving the comparison of traits, either quantitatively or qualitatively, can be difficult because the identification of a species must rely on the experience of the observer and errors can occur when cryptic species are involved. Molecular methods have been used to fill these gaps, but morphological methods are still needed to match the recognized molecular species with an adequate taxonomic description. Focusing on the trapdoor spider genus Proshermacha Simon, 1908, we provide a case study using Geometric Morphometrics (GM) techniques to identify morphological divergence between species found in the south-western Australia region. We used GM to identify morphological divergence from museum-preserved specimens by examining shape variation of sexual characters from 39 male specimens from five different localities on a single mountain range. Variation in the shape of both the palpal bulb and tibia provided strong evidence to distinguish two morphotypes, while metatarsus shape showed fewer between-locality differences. Our results illustrate the utility of GM methods, when applied to a few taxonomically-informative structures, as a quantitative species delimitation tool for taxonomic studies.

ABSTRACTSpecies translocations are increasingly being used in conservation and for biological control. The success of a translocation can be strongly influenced by the evolutionary processes occurring during the early phase of the introduction and the subsequent spread to new regions. In this study, morphological variation and population genetic structure were assessed in the African dung beetle Digitonthophagus gazella, a species that was intentionally introduced to Australia for biological control in 1968 and subsequently spread widely across the northern part of the continent. A dataset based on 1594 neutral single nucleotide polymorphism (SNP) loci that were genotyped in 187 individuals from 12 sites revealed significant genetic divergences between sites (global FST = 0.118) and provides evidence of restricted gene flow among established populations at small to moderate spatial scales (74–500 km). Geometric morphometric analyses revealed significant divergence among populations in the shape of the foretibia, a trait ecologically important for tunnelling in soil and dung. Moreover, phenotypic divergence in this trait for both sexes was significantly higher than genetic differentiation at selectively neutral loci (PST > FST), suggesting that directional selection is contributing to the phenotypic divergences among populations. Our study shows how population structure can establish quickly in an introduced species and highlights the importance of considering local adaptation when performing translocations on established populations.

Extensive research has investigated the relationship between the social environment and cognition, suggesting that social complexity may drive cognitive evolution and development. However, evidence for this relationship remains equivocal. Group size is often used as a measure of social complexity, but this may not capture intraspecific variation in social interactions. Social network analysis can provide insight into the cognitively demanding challenges associated with group living at the individual level. Here, we use social networks to investigate whether the cognitive performance of wild Western Australian magpies ( Gymnorhina tibicen dorsalis ) is related to group size and individual social connectedness. We quantified social connectedness using four interaction types: proximity, affiliative, agonistic and vocal. Consistent with previous research on this species, individuals in larger groups performed better on an associative learning task. However, social network position was also related to cognitive performance. Individuals receiving aggressive interactions performed better, while those involved in aggressive interactions with more group members performed worse. Overall, this suggests that cognitive performance is related to specific types of social interaction. The findings from this study highlight the value of considering fine-grained metrics of sociality that capture the challenges associated with social life when testing the relationship between the social environment and cognition.

Sexually selected weapons used to monopolize mating opportunities are predicted to trade-off with traits used in competition for fertilization. Yet, the limited size range typically found among adults of a species often precludes clear comparisons between population-level and individual-level relative trait investment. The jousting weevil, Brentus anchorago (Coleoptera: Brentidae), varies more than 26-fold in body mass, which is among the most extreme adult body size ranges of any solitary terrestrial species. We reveal a trade-off at a population level: hypermetric scaling in male weapons (slope = 1.59) and a closely mirrored reversal in allocation to postcopulatory traits (slope = 0.54). Yet, at the individual level, we find the opposite pattern; males that invest relatively more in weapons for their size class also invest more in postcopulatory traits. Across 36 dung beetle and 41 brentine weevil species, we find the allometric slope explains more trait variation at larger body size ranges; in brentines, population-level scaling patterns become more detectable in species with a larger range in adult body size. Our findings reveal that population-level allometries and individual-level trade-offs can both be important in shaping relative trait allocation; we highlight that the adult body size range is rarely examined but may be integral to gaining a deeper understanding of trade-offs in reproductive allocation.

Sperm competition is known to favor the evolution of male traits that confer an advantage in gaining fertilizations when females mate multiply. Ejaculate production can be costly and the strategic allocation of sperm in relation to the sperm competition environment is a taxonomically widespread phenomenon. However, variation among males in their ability to adjust ejaculate allocation has rarely been explored. Here, we manipulated the phenotypic condition of male seed beetles, Callosobruchus maculatus, via larval diet quality and measured ejaculate allocation across varying levels of sperm competition manipulated using olfactory cues. Furthermore, we asked how strategic ejaculation was impacted by previous ejaculation. We found no variation in ejaculate allocation in response to experimentally manipulated cues to sperm competition. Ejaculate allocation was reduced by a male's previous mating history but was unaffected by the larval diets on which males were reared. We suggest that either male seed beetles are unable to adjust ejaculate size to the immediate competitive environment, or that sperm displacement strategies employed by males favor maximal investment at all mating events, especially when unmated females are infrequently encountered. As our study is one of few to examine condition dependence in strategic ejaculation, emphasis should be placed on future studies investigating this possibility across a wider range of taxa and animal mating systems.

Individual differences in cognitive performance can have genetic, social and environmental components. Most research on the heritability of cognitive traits comes from humans or captive non-human animals, while less attention has been given to wild populations. Western Australian magpies (Gymnorhina tibicen dorsalis, hereafter magpies) show phenotypic variation in cognitive performance, which affects reproductive success. Despite high levels of individual repeatability, we do not know whether cognitive performance is heritable in this species. Here, we quantify the broad-sense heritability of associative learning ability in a wild population of Western Australian magpies. Specifically, we explore whether offspring associative learning performance is predicted by maternal associative learning performance or by the social environment (group size) when tested at three time points during the first year of life. We found little evidence that offspring associative learning performance is heritable, with an estimated broad-sense heritability of just -0.046 ± 0.084 (confidence interval: -0.234/0.140). However, complementing previous findings, we find that at 300 days post-fledging, individuals raised in larger groups passed the test in fewer trials compared with individuals from small groups. Our results highlight the pivotal influence of the social environment on cognitive development.