Human uses of birds may contribute to extinction risk, but it remains unclear whether different uses have variable impacts on bird conservation status. We analysed use and trade data from 3523 bird species accounts in the International Union for Conservation of Nature Red List to compare the impacts of use for food (hunted primarily for human consumption) and sport (hunted primarily for recreation) on bird conservation status. We found that species hunted for food were more likely to be listed as threatened and have declining populations compared with those not hunted for food. Sport-hunted species were not more likely to have declining populations compared with non-sport-hunted species, and there were no differences in threatened status. Species experiencing habitat loss and those with smaller geographic ranges had poorer conservation status, whereas body mass and diet had inconsistent effects. These results emphasize the negative effects of hunting for food on bird species and reiterate the need for effective management to mitigate these impacts.
The ecological effects of large herbivores are shaped by their spatial and temporal patterns of activity (i.e. where, when and how intensely they use specific locations). When large herbivores' ecological influences are perceived to be undesirable, the traditional approach has been to reduce their population size. This numbers-first logic assumes that ecological effects scale primarily with abundance. We argue that this framing provides an incomplete understanding of large herbivores' ecological impacts. Using African elephants (Loxodonta africana) as a well-documented case study, we show that ecological effects on plants, animals and ecosystem processes correlate more with spatio-temporal patterns of activity than with population size. In large, open systems characterized by strong gradients of water availability, forage quality, shade and risk, elephants concentrate into predictable hotspots while relaxing activity elsewhere, generating localized impacts and opportunities for recovery. By contrast, in small, fenced or fragmented landscapes, where movements are constrained, and gradients are weak, spatial self-regulation breaks down, producing homogenized use and widespread ecological effects. We contend that understanding where, when and under what constraints herbivores use space provides a more general and mechanistic basis for interpreting ecological influence than abundance alone, with implications that extend beyond elephants to large herbivores globally.
Soil degradation threatens food security, climate regulation, biodiversity and human wellbeing worldwide. Up to 75% of the world's soils are degraded, prompting rapid upscaling of global restoration efforts to meet international targets. Moreover, many soil management practices (e.g. conservation agriculture, cover cropping and reforestation) create litter/mulch habitats that support soil-surface-dwelling microbial and invertebrate functions. However, monitoring soil and leaf-litter biodiversity remains a major barrier to tracking restoration success, particularly for invertebrates that underpin key processes such as nutrient cycling and soil aggregation. Traditional sampling methods are labour-intensive, destructive and poorly suited to long-term or landscape-scale monitoring. Soil ecoacoustics is emerging as a promising non-destructive tool for monitoring soil biodiversity. However, its capacity for taxonomic resolution of invertebrate groups remains untested. Here, we present a proof-of-concept study demonstrating the potential of a soil-surface-dwelling invertebrate acoustic classifier. Using a low-cost, sound-attenuated recording system, we quantified 19 spectral and temporal audio features from six morphologically and behaviourally distinct invertebrate species under controlled conditions. Acoustic profiles differed among taxa and generally clustered into podous and apodous groups, suggesting that acoustic signatures capture taxon-specific traits. This work provides a foundation for developing automated acoustic classifiers that could enable scalable, non-destructive monitoring of soil biodiversity.
Innovation underpins adaptation to environmental challenges, yet its link to fitness remains unclear. This may reflect context-dependent effects, with fitness benefits emerging primarily under poor environmental conditions or among individuals in poorer condition. However, empirical tests linking innovation to fitness across environments in continuously monitored individuals remain rare. Here, we manipulated environmental quality in young wild house mice by providing either a high- or a comparatively lower quality diet. We quantified innovation propensity and latency early in life, using standardized tasks, and subsequently released individuals into semi-natural environments that matched their developmental diet. We then tracked body mass (as a proxy for fitness) and survival over six months. We tested whether the effects of innovation propensity and latency on fitness were more pronounced among individuals living in lower-quality conditions, as predicted by the necessity drives innovation hypothesis. Mice on the high-quality diet were more innovative. Moreover, while innovation propensity did not predict body mass trajectories, survival depended on an interaction between innovation latency and environmental quality, indicating environment-dependent fitness trade-offs. Our findings demonstrate that the fitness consequences of innovation are contingent on environmental variation, which may help explain inconsistent patterns reported across studies.
Individual feeding success can change with the size of a social group through competition, cooperation, recruitment and other processes. Female sperm whales (Physeter macrocephalus) live in long-term social units that themselves can form larger, temporary groups, but the individual-level impacts of group formation are unknown. We measured feeding success on 88 days following groups off the Galápagos Islands and Chile using defecation rates. Feeding success increased about fourfold as group sizes rose from one social unit (about 10 animals) to 4-5 units. Our data did not suggest recruitment into successful groups, and the whales' prey are generally relatively small and slow, arguing against cooperative capture. Instead, it seems most plausible that individuals receive valuable information about patchy prey distributions from foraging group members over scales of 100 to 1000 m. Feeding success fell for the largest groups, suggesting a foraging optimum of about 40-50 animals off the Galápagos Islands and 30-40 animals off Chile. These are close to the mean typical group sizes in these areas, which indicates that efficient foraging on patchy prey may largely drive group size. Considerable differences between oceans in the group sizes of female sperm whales are probably linked to variation in the patchiness of resource availability.
Mathematical models are central to understanding disease transmission for host-pathogen systems across the biosphere. However, most existing frameworks do not explicitly treat host population heterogeneity as a formal driver of variation in transmission dynamics. This gap is most visible in human disease, where social inequalities are well known to structure infectious disease risk, but applies broadly: ecological, behavioural and demographic structure shapes transmission in non-human host populations as well. Here, we introduce a new metric, structural causal influence, which uses causal analysis to quantify how subpopulations contribute to overall transmission through structural differences in exposure, susceptibility or recovery. Using a multi-population model, we show that even a population whose isolated reproduction number lies below one can be drawn into a sustained epidemic through minimal contact with a more affected group.
Chronically male-biased sex ratios are predicted to intensify sexual conflict and reduce female fitness. Yet empirical tests of female responses in natural settings are rare. We tested how female reproductive performance depends on social environment in the field using two closely related sympatric damselflies that differ strikingly in adult sex ratios: one experiences consistently male-biased sex ratios (Enallagma exsulans), whereas the other does not (E. traviatum). In field experiments, females from the chronically male-biased species were less sensitive to elevated male density, maintaining fertility despite increased harassment. By contrast, fertility declined under high male density in the species that naturally encounters more balanced sex ratios. Fecundity and survival remained largely unchanged, suggesting that fertility is the primary fitness component sensitive to variation in male density. Mixed-species trials showed that frequent heterospecific mating attempts imposed only modest additional costs to females. These results provide field-experimental evidence that closely related species can differ markedly in how female fertility responds to social environment under natural conditions. The correspondence between these differences and natural sex ratios is also consistent with a putative role for adaptation to persistent male bias.
Sexual cannibalism is among the most extreme outcomes of sexual conflict, and the Australian widow spider Latrodectus hasselti is well known for this behaviour. Curiously, males of L. hasselti actively facilitate cannibalism through self-sacrificial mating traits. During copulation, the male somersaults his abdomen onto the female's fangs and develops an abdominal constriction that prevents his premature death, allowing him to monopolize paternity. The closely related sister species L. katipo, however, lacks self-sacrificial mating traits. Given the close relatedness of the two species, the differences in mating traits must have evolved rapidly and are expected to have a rather simple genetic basis. We hypothesize that these two complex traits are tightly linked on the X chromosome and show a single-locus Mendelian inheritance. To test this hypothesis, we backcrossed the two species and scored F2 males for the presence of copulatory somersault and abdominal constriction during mating. Our results suggest that the two traits are not genetically linked, and that the self-sacrificial somersault follows a single-locus X-linked Mendelian inheritance pattern, while the abdominal constriction has a more complex genetic basis. Our work shows that even extremely complex mating traits can evolve rapidly and have a simple genetic basis.
Carnivoran mammals (cats, dogs, bears, seals, etc.) and their kin radiated during the Palaeogene, among other carnivorous clades (hyaenodonts, mesonychians, and oxyaenodonts). This radiation has often been framed as a competition ultimately won by carnivorans, but the data supporting this hypothesis largely originate from North America. We derive body mass (BM) from dental measurements in European hyaenodonts, mesonychians, oxyaenodonts, and carnivoramorphans ranging from the latest Palaeocene to the end of the Oligocene (MP 6-30; 57.2-23.3 Ma) and compare those with North American data. We show that European assemblages tell a different story, with a marked increase of the disparity of carnivoramorphan BMs at and after the Middle Eocene Climatic Optimum (MECO; 40 Ma), with no clear effect on hyaenodonts. The 'Grande Coupure' (Eocene-Oligocene transition, approx. 34-33.5 Ma) marks the onset of a progressive decrease in the mean BM of hyaenodonts, while carnivoramorphans continue their rise initiated around the MECO. The observed BM patterns therefore do not follow the expected double-wedge pattern of competitive replacement and are possibly best explained by climate change-induced biodiversity dynamics.
In primates, most evidence linking sociality to fitness comes from studies of female-female bonds, whereas the consequences of heterosexual relationships remain understudied. This is particularly true in species such as mandrills (Mandrillus sphinx), where male group tenure is short, and interactions with females can range from affiliative to coercive. Using 13 years of behavioural and life-history data on 76 adult females, we show that grooming exchanged with all males has contrasting fitness consequences depending on its direction. Grooming given to males tended to improve female survival and was associated with higher juvenile offspring survival, whereas grooming received from males reduced female survival. These opposing effects suggest that heterosexual grooming interactions may entail both benefits and costs for females, depending on whether females provide or receive affiliation. Finally, agonistic interactions between females and males showed modest evidence of negative associations with juvenile survival, whereas male-female spatial proximity had no detectable effect overall. Our results show that even transient male-female associations can have lasting consequences for fitness and that these effects depend critically on the direction and timing of specific interactions rather than on global measures of sociality.
Obtaining host DNA from the blood meals of their invertebrate parasites (invertebrate-derived DNA, iDNA) has proven to be a powerful tool in terrestrial ecology for detecting vertebrates to answer questions relating to host community diversity. However, the use of iDNA in the marine environment is limited. Here, we assessed the efficacy of sampling parasites from the critically endangered flapper skate (Dipturus intermedius) to determine whether iDNA could (i) identify the host species and (ii) obtain host haplotype sequences. In total, 34 copepods (Trebius caudatus specimens, n = 30; Caligus elongatus specimens, n = 4) were processed from 20 flapper skates. Fin-clips were also taken from each flapper for comparison. iDNA identified the host species with 91% success. The host haplotype sequenced from multiple T. caudatus specimens sampled from the same host matched in all cases. A bias-reduced logistic regression found a positive but non-significant association between copepod gut length (z-score) and host-copepod haplotype match success (β = 0.67, p = 0.34). These findings demonstrate the utility of iDNA for confirming the identity and the haplotype of a cryptic conservation-listed batoid and its potential to transform community-led genetic sampling.
Abstract The faunas around methane seeps in the deep sea thrive on an in-situ food source and are thus expected to show no latitudinal gradients in their diversity. An analysis of 478 modern and 824 fossil (Cretaceous to Pleistocene) occurrences of seep molluscs shows that this is indeed the case. However, seep molluscs from 200 to 1000 m depth show a dip in diversity between 15 and 35° latitude, a pattern that has persisted at least since the Oligocene. This dip in diversity coincides with the distribution of oxygen minimum zones, suggesting oxygen limitation as a main driver of this pattern. The diversity dip is less severe in the Eocene, potentially due to weaker ocean stratification, and hence less distinct bathymetric gradients of oxygen concentration, before the Eocene–Oligocene climate transition. Given the role of oxygen in the diversity of seep faunas and their distribution in the geologic record, it is suggested that oxygen limitation could be responsible for the scarcity of seep faunas in the early Palaeozoic.
Courtship displays are remarkably complex in birds, especially in species under strong sexual selection. An overlooked aspect is the organization of gestural elements, where more temporarily coordinated and predictable movements may improve information transfer. We tested if display organization is influenced by the number of gestural elements in the displays, lek spatial structure, body size and habitat. We built a dataset of lekking bird gestural displays for males and females described in the literature and video recordings from online platforms. From recordings, we quantified display organization using information theory measures. For both sexes, species with larger repertoires showed more organized displays, indicating that increased complexity does not constrain syntax. Sex differences in display organization were higher in species with lower sexual size dimorphism, suggesting a trade-off between traits important for communication. By highlighting display organization of gestural displays, we offer an extensive investigation of an overlooked yet crucial aspect of bird courtship.
For any sensory system, the detection of relevant information is a challenging task. Natural habitats are full of sensory stimulation, of which only a fraction can be detected and processed. For visual animals, some features, like the movement of the target, are known to enhance signal saliency. However, less is known about the effect of other dynamic signal properties, such as flashing or flickering, that are known to improve saliency in human contexts. Here, we used mate-seeking butterflies in their natural habitat to test how flashing, lateral back-and-forth movement, and their interaction affect the detectability of a visual stimulus. We found that both lateral movement and flashing (resulting from an oscillation that simulated 'fluttering') of the stimulus contributed independently and additively to the likelihood of detection, with some evidence that movement made the stimulus more conspicuous from greater distances. These effects did not interact, meaning that flashing did not modify the influence of movement (and vice versa). Coupled with evidence in humans, this result supports the importance of flashing as a universal, potentially independent means of increasing visual signal saliency.
Marine taxa have repeatedly introduced diversity to continental freshwater fish faunas, yet their contribution to total morphological disparity remains poorly quantified. We analysed body shape disparity across 642 North American fish species using three-dimensional geometric morphometrics and kernel density hypervolumes to assess the extent to which transient marine species expand morphospace beyond that occupied by exclusively freshwater species. Marine-affiliated taxa account for 7.7× the hypervolume of freshwater species and expand the total morphospace by 144%, significantly exceeding chance expectations (p < 0.0001). Marine and freshwater morphospaces exhibited minimal overlap, with marine taxa extending the morphospace along multiple axes of body shape disparity. Despite comprising only 27% of the species, marine-affiliated taxa contribute disproportionately to morphological variance and exhibit greater within-group dispersion. These patterns support a 'museum effect', in which marine environments preserve the morphological diversity lost from more unstable freshwater systems. Our results demonstrate that regional freshwater morphological diversity depends partly on connectivity to marine source pools, with implications for understanding evolutionary constraints and conserving functional diversity in freshwater ecosystems.
The cat (Felis catus) is one of the worst invasive species, with well-documented impacts on biodiversity, especially on islands. Despite this, local administrations commonly implement trap-neuter-return (TNR) programmes to manage free-roaming cat populations. Here, we assess the effects of cat colonies on the endemic Tenerife lizard (Gallotia galloti). We used fruit-baited pitfall traps placed near and away from cat colonies to estimate lizard abundance and collect biometric data. Lizard abundance was lower near cat colonies compared with nearby control areas. Moreover, the individuals captured close to the colonies were smaller. Measurements of lizard carcasses found near colonies indicate that cats preferentially prey on larger individuals, explaining both their reduced abundance and their smaller body size. Interestingly, despite their smaller size, lizards near cat colonies presented higher scaled mass index values. Stable isotope analyses (δ13C and δ15N) of faecal samples suggest that these lizards partially rely on dried cat food available within colonies. Overall, cat colonies significantly altered lizard abundance, size structure and body condition. Given the ecological importance of G. galloti as both a seed disperser and prey, our findings highlight the need to limit the spread of free-roaming cat colonies, particularly in protected areas, to mitigate the effects on native biodiversity.
Elevational gradients are frequently linked to dramatic biodiversity shifts, but the drivers and dynamics of alpine adaptation often remain unclear. A Batesian mimicry polymorphism in Aotearoa New Zealand stoneflies provides an ideal system for assessing the role of elevational gradients in selecting for melanic (dark) versus non-melanic (light) colour phenotypes. Although previous studies have proposed that melanism should be favoured in alpine ecosystems, we find the opposite pattern, with consistently reduced frequencies of dark phenotypes detected in upland versus lowland habitats. Specifically, parallel alpine reductions in frequencies of melanic (mimic) Zelandoperla (approx. 1500 specimens genotyped across 7 independent stream populations) are linked to reduced abundance of the noxious model Austroperla above the alpine treeline. Our findings highlight that shifting ecological interactions across environmental gradients can drive rapid evolutionary change over fine spatial scales.
Larvae of leaf miners live within leaves and feed on internal tissues, making successful entry into the leaf essential for their endophagous lifestyle. In the leaf-mining moth Acrocercops transecta, females lay eggs on the surface of host-plant leaves. Immediately after hatching, larvae penetrate the leaf directly through the eggshell, representing the only opportunity to enter host leaves. Under laboratory conditions, we observed substantial mortality caused by failure of leaf entry. The nearly transparent eggshell of A. transecta enabled observation of embryonic development, revealing that correct dorsoventral orientation, ventral side facing the leaf epidermis, is essential for successful mining, whereas inverted orientation leads to failure. We developed a novel egg transplantation method and showed that correcting inverted embryos by flip transplantation restored mining success, while inverting normally oriented embryos prevented it. Notably, inverted embryos were also observed under natural conditions, causing mortality in first-instar larvae. Furthermore, under laboratory conditions, the mortality rates differed between the horticultural host Juglans regia and the natural host J. mandshurica. These results reveal a previously unrecognized source of mortality in leaf miners and demonstrate that precise dorsoventral orientation during oviposition is essential for offspring survival, highlighting a fine-scale egg-loading mechanism shaping successful host adaptation in insects.
Mating signals, such as songs or plumage ornamentation, are key prezygotic barriers that promote behavioral isolation by ensuring that individuals are able to mate with conspecifics and avoid the costs of hybridization. Previous family-level comparative studies in birds have revealed that song similarity is positively correlated with the incidence of hybridization, whereas genomic research in avian hybrid zones suggests that plumage divergence does not necessarily prevent gene flow. However, no study has jointly evaluated the relative contribution of both signalling modalities to hybridization incidence within a broad macroevolutionary framework. We combined a large-scale dataset on documented hybridization events across bird species with quantitative measures of acoustic and plumage divergence and tested their association using phylogenetically informed comparative models. We found that species-level acoustic divergence showed a strong negative association with the number of hybridization partners after accounting for sympatry. In contrast, male plumage divergence did not predict hybridization incidence, yet female plumage divergence showed a significant negative association. These results indicate that song represents a major reproductive barrier in birds, probably because it is a long-range and evolutionarily labile signal. Moreover, male plumage coloration may play a more limited role in reproductive isolation, potentially because male ornaments may introgress more readily across species boundaries.
