In species with uniparental care, the non-caring sex is expected to pursue mating opportunities throughout the breeding season to maximize reproductive success. Accordingly, males in some socially polygynous species have been observed to visit multiple potential breeding sites within a breeding season, often covering large distances. In socially polyandrous species, females typically search for additional mating opportunities after having laid a clutch for a male, but whether they move between breeding areas remains largely unknown. We tracked the movements of 21 female Eurasian dotterels, a sex-role reversed shorebird in which parental care is typically performed by the male alone, although females contribute to incubation at some nests. We found that females visited up to five sites (median: three) and travelled up to 1000 km between consecutive sites (median: 71 km). Movements during the early breeding season were primarily northwards, but females remained at a similar latitude later in the season. Females stayed longer at their final site (median: 41 days) than at other sites (median: 6 days), suggesting that they may switch to investing in parental care when mating opportunities are no longer available. Our findings support the hypothesis that females of socially polyandrous species may pursue mating opportunities and potentially lay clutches across multiple breeding sites within a single season.
Extinction debt and colonization credit describe the delayed impacts of environmental change on biodiversity, yet their significance largely remains unrecognized by those shaping conservation efforts. To address this gap, we conducted a systematic review of 127 empirical studies quantifying these biological lags across taxa, habitats and anthropogenic drivers. Our synthesis revealed geographic biases, with research concentrated in Northern Hemisphere terrestrial ecosystems, alongside taxonomic and habitat biases that continue to limit our understanding of these dynamics. Evaluation of anthropogenic drivers revealed a similarly skewed research effort, with habitat fragmentation dominating extinction debt studies and land-use change leading colonization credit research. By synthesizing proposed conservation strategies, we identified pathways for integrating time-lagged ecological responses into conservation frameworks. Despite the conceptual importance of these lags, most empirical efforts remain focused on isolated taxonomic groups, with limited consideration of how debts and credits propagate through communities or influence ecosystem services. This narrow focus restricts the utility of current findings for broad-scale conservation. We recommend that future research prioritizes the mechanisms driving lags across understudied ecosystems and environmental contexts. Crucially, conservation interventions must move beyond static biodiversity snapshots and explicitly account for extinction debt and colonization credit to ensure long-term ecosystem resilience.
The adaptive nature of basal metabolic rate (BMR) variation and its link to sustained metabolic performance, for example during reproduction, is one of the most important problems in physiological ecology. Different hypotheses are considered: one claims that low BMR (L-BMR) is adaptive under conditions favouring energy conservation, and natural selection should reduce BMR so that energy can be allocated to other functions; the second links high energy-expenditure capacity to high BMR (H-BMR) through larger guts and the capacity to acquire energy. Here, we examine this relationship by analysing reproductive outcome across multiple generations in two lines of laboratory mice subjected to long-term artificial selection for high or L-BMR. Our results link high energy-expenditure capacity to H-BMR, reflecting greater energy-acquisition abilities. Mice with H-BMR wean larger litters than females with L-BMR. However, the between-line difference is driven mainly by a progressive decrease in litter size in the L-BMR line and is less pronounced than the between-line type divergence in BMR. Our results emphasize that life-history models based exclusively on energy allocation typically overlook potential physiological constraints associated with traits as complex as BMR and cannot provide a single definitive explanation for the link between BMR and sustained performance.
Group living can make animals more resilient or more susceptible to human-induced rapid environmental change. Freshwater and coastal habitats are becoming increasingly turbid because of human activity, which limits the availability of visual information and hence responses to critical stimuli such as food and predators. Using shoals of three-spined sticklebacks (Gasterosteus aculeatus) responding to an unpredictable food stimulus, we confirm that fish were slower to attack in turbid water and were faster in larger groups. Turbidity and group size also modulated the effect of the shoals' collective behaviour: if small groups were in turbid water, the latency to attack was faster when they were more cohesive and more polarized, but in clear water, cohesion and polarization slowed the response of larger groups. These varying effects of collective state corresponded with differences before the food stimulus appeared, with fish increasing cohesion and coordination by being more polarized in direction, and being quicker to respond to one another's changes in speed in turbid water, especially in small groups. As the visibility of neighbours decreases in turbid water and should constrain collective behaviour, enhanced collective behaviour is instead consistent with an adaptive, plastic response that improves responses to stimuli when visual information is limited.
Understanding cognitive development is fundamental for explaining variation in adult cognitive phenotypes, and thus the processes driving cognitive evolution. The ontogeny of cognitive traits is likely influenced by both population-wide pressures, such as ecological demands, and individual-specific factors, including early life experiences. To properly investigate cognitive variation, we must therefore identify species-level developmental trajectories and individual variation from normative ontogeny. We studied the ontogeny of three cognitive traits-inhibition control, spatial cognition and physical problem-solving skills-in 41 wild meerkats (Suricata suricatta) from 12 litters (10 groups). Our longitudinal study followed individuals from early life to nutritional independence and into sub-adulthood. We found that rates of development (learning curves) varied among traits. Performance of cognitive traits did not correlate over ontogeny nor at specific time points, suggesting independent processes underlying each measured trait. While inhibitory control showed little individual variation in its development, spatial cognition and physical problem-solving showed substantive individual differences. Furthermore, physical problem-solving showed consistency in performance over time, a pattern that emerged near nutritional independence, reflecting its ecological importance early in life. Future research should determine the drivers of individual developmental variation and how such differences translate into fitness consequences.
The primate visual system is thought to have evolved under selective pressures favouring rapid detection of snakes, ancestral predators that shaped perceptual and attentional mechanisms. Yet, the transition from visual detection to subjective fear remains poorly understood and may depend on specific morphological cues. Here, we examined how snake morphology modulates human emotional and aesthetic responses across ecological and cultural contexts. A total of 377 participants from Portugal (low snake biodiversity) and Brazil (high snake biodiversity) rated images of 92 snake species on fear, disgust, beauty, valence, arousal and perceived size. Cluster analyses revealed three consistent emotional profiles across populations: a High-Fear cluster (mainly viperids, boids and mimics with threatening traits), a High-Valence cluster (mostly harmless colubrids and dipsadids), and a smaller High-Disgust cluster (fossorial or limbless reptiles). Cluster membership was unaffected by country, indicating cross-cultural consistency in emotional evaluations of snake morphology. Species in the High-Fear cluster exhibited higher edge density. By contrast, greater exposure to snakes, particularly in natural environments, was associated with lower Snake Fear Questionnaire scores. These results support the view that humans rely on evolutionarily conserved morphological heuristics (e.g. triangular heads, keeled scales and disruptive patterns) to assess potential threats, while individual predispositions and experience modulate response intensity.
Language and fire are hallmarks of the human condition, but most scholars treat them as independent traits. We develop a theory for the origin of language that links both touchstones of human evolution. First, we show that precursors to language were probably rooted in the gestural systems of living apes. Next, we show that attempts to explain the evolution of spoken language in utilitarian terms (a) are undermined by evidence of these abilities in other species and (b) overestimate the need for language to sustain daily practicalities of early small-scale social groups. Instead, we draw attention to the fireside niche as the likely site for the origin of language during oral storytelling. Fireside storytelling could: (i) resolve the conundrum of why load-bearing aspects of meaning shifted from gesture to speech, and (ii) promote hierarchical structure and a shift away from embodied gesture into arbitrary generative speech, enabling communication outside of direct experience and into social imagination: from our distant past and future, to other places and peoples. We examine visual properties of firelight to consider how it could enhance the effectiveness of storytelling. We generate testable predictions to address how firelight propelled the characteristically human expression of language.
How can a small group of committed cooperators shape collective outcomes in social dilemmas? Previous studies have shown that zealots-individuals who always cooperate-can promote cooperation in prisoner's dilemmas. Yet real-world cooperation also involves multiplayer coordination problems, where their role remains less understood. Here, we examine the role of zealots in N-person stag-hunt games in both finite and infinite, well-mixed populations. We show that a minority of zealots facilitates the emergence of cooperation by lowering the barrier to coordination, but at the cost of reducing the equilibrium level of cooperation. More strikingly, zealots can create two new attractors in infinite populations-full cooperation and stable coexistence-that extend beyond the classical equilibrium of full defection or bistability between defection and cooperation (or coexistence). In finite populations, this dual effect largely persists as population size approaches infinity; otherwise, zealots either matter little or consistently enhance cooperation. Together, these findings revise the conventional view that zealots enhance cooperation in well-mixed populations, revealing instead their dual role in multiplayer coordination dilemmas. This nuanced influence may also shape broader collective problems, from collective-risk dilemmas to the emergence of social conventions.
Dehnel's phenomenon-a reversible seasonal reduction and regrowth of body size, skull, brain and visceral organs-is an extreme adaptive strategy, enabling small mammals to survive winter energetic constraints. First described in the common shrew Sorex araneus, similar seasonal remodelling has since been reported in other shrews and even in distantly related taxa, indicating convergent adaptation to cold environments. Here, we quantified year-round skull morphological changes in the long-clawed shrew (Sorex unguiculatus) from Hokkaido, Japan, using linear measurements and high-resolution two-dimensional geometric morphometrics. As classically described, braincase height decreased markedly in winter and regrew in spring. By contrast, we detected a previously unrecognized pattern: winter enlargement of the rostrum followed by reduction in early spring, which we term 'reverse Dehnel's phenomenon'. By integrating morphometric results with ecological and physiological evidence, we propose enhanced nasal thermoregulation as the most plausible explanation for this seasonal rostral enlargement. Our findings demonstrate that cranial remodelling in shrews is modular rather than uniformly reductive and introduce the reverse Dehnel's phenomenon as a novel winter adaptation. Our study provides one of the most temporally fine-resolved assessments of cranial remodelling to date, and highlights the evolutionary significance of seasonal skeletal plasticity in small mammals.
Apple snails (Ampullariidae) are freshwater gastropods of ecological and economic importance, but their digital representation remains uneven across taxa, regions and data types. Using a 171-species taxonomic reference, we integrated global occurrence and molecular data to assess repository coverage, spatial usability, threshold-based visibility and sampling completeness. The public occurrences comprised 13 349 spatially unique records representing 119 species. Observation-based records accounted for 70.4% of this total and were concentrated in regions where invasive lineages are well documented. Restricting spatial analyses to native-range scientific collections retained only 3614 records for 113 species. Although 154 species were detected in the Global Biodiversity Information Facility (GBIF) species-level records, only 119 had directly spatially usable records; 35 species were GBIF-present, but spatially non-usable, and 17 were not detected in GBIF. Genetic coverage exhibited similar limitations. Public molecular repositories yielded 8730 records across BOLD and GenBank before cross-repository de-duplication, representing 58 species and leaving 113 species without public molecular data. Macroecological visibility declined sharply as minimum occurrence thresholds increased. Sampling completeness remained uneven, with a median of zero in most region-by-resolution combinations, despite apparent improvements at coarser spatial grains. These combined shortfalls systematically leave the principal tropical centres of native diversity analytically under-represented.
Major radiations have given rise to huge swathes of life on Earth, and understanding their dynamics reveals the process of biodiversity generation itself. The rise of dinosaurs and other archosaurs during the Triassic was a spectacular example of such a radiation; it set the stage for Mesozoic faunas and gave rise to the largest land animals on Earth. Previous attempts to understand its dynamics have relied on phylogeny, necessitating the exclusion of much data. We use the Bayesian occurrence-based approach PyRate, allowing speciation and extinction dynamics to be estimated without recourse to phylogeny. We analyse stratigraphic range-based data for all archosauromorphs from the late Permian to the Early Jurassic, and test for association of body size with diversification using a body size proxy. We find an 'early burst' pattern of diversification, with initial high speciation giving way to increased extinction. Falling speciation is consistent with niche-filling following extinction, but increasing extinction may indicate a role for neutral dynamics during radiation. Cryptic diversification may be evidenced by a peak earlier than inferred using phylogenetic estimates. Body size is not statistically associated with diversification, but the positive direction of association potentially reflects the concurrent passive 'trend' of increasing size.
Antagonistic coevolution has long been predicted to leave a macroevolutionary signature of escalating defences in host species. Opposing this classic theory, we previously reported phylogenetic declines in the concentrations of cardenolide toxins among milkweed species in the genus Asclepias. Here we tested the hypothesis of a trade-off between toxin concentration and potency, such that species with lower investment in toxin abundance show higher potency per unit toxin. We tested leaf extracts from more than 50 Asclepias species in vitro against the monarch butterfly's neural Na+/K+-ATPase, the physiological target of cardenolides. Indeed, in phylogenetically controlled analyses, we found a macroevolutionary trade-off between cardenolide concentration and potency among Asclepias species. Machine learning identified metabolomic features associated with high potency, suggesting triterpenoids that may have a combinatory effect with cardenolides against the butterfly's highly adapted enzyme. Finally, metrics of toxin potency phylogenetically increased over the evolutionary history of Asclepias. This result supports the hypothesis that, in the face of costly defences and toxin-sequestering insect pests, milkweeds evolved low concentrations of more potent toxins, probably along with other plant metabolites that enhance chemical defence. Coevolution may generally drive discordant investment in concentration versus potency of plant chemistry, with defence evolving towards effective and economical strategies.
Local seasonal adaptation across latitudes is ubiquitous, but its fitness consequences are rarely estimated in the field. Using a common-garden field experiment at the northern range margin of the butterfly Lasiommata megera, we show that fitness consequences of among-population genetic differences in photoperiodism for diapause (dormancy) timing depend on when during the adult flight period eggs are laid. Among the earliest individuals, those from southern populations were more likely to avert diapause than locally adapted northern range margin populations, and natural selection acted strongly against this non-diapause development. However, for all populations, virtually all eggs laid only one week later resulted in larvae that entered diapause, limiting overall among-population phenotypic differences in diapause induction. This demonstrates how evolved genetic differences for a reaction norm interact with phenology to influence the developmental decisions of larvae in the wild. Rapid local adaptation of photoperiodism has likely occurred through natural selection acting on a limited part of each autumn generation, implying a smooth fitness landscape where mildly maladapted populations can establish and subsequently evolve towards the local fitness peak. Thus, latitudinal differences in day length are unlikely to restrict climate change-driven range expansions.
The marine plankton record offers a unique archive of deep-time ecological and evolutionary dynamics in the open ocean. With distinct biomineral compositions, trophic modes and other diverse ecological and geographic preferences, fossilized marine unicellular plankton groups (diatoms, calcareous nannofossils/coccolithophores, radiolarians, planktonic foraminifera and dinoflagellates) allow for the identification of traits affecting extinction risk over millions of years. Here, we demonstrate that over the Cenozoic era, trophic mode, classified as either autotrophic, mixotrophic or heterotrophic, is highly influential on the long-term biodiversity dynamics of marine plankton. This trophic distinction is associated with up to a 38% lower Cenozoic extinction rate in autotrophs than in other trophic groups. Correspondingly, autotrophs tend to persist longer and exhibit less volatile extinction dynamics. These patterns hold across multiple levels of comparison: between fully autotrophic and fully heterotrophic groups, within dinoflagellates that include both strategies, and in composite groupings based on trophic mode or biomineral composition. By identifying trophic mode as a key determinant of extinction risk, our results provide a deep-time context for predicting plankton responses to ongoing ocean change.
Genomic regions of reduced recombination can preserve linkage among co-adapted alleles, facilitating local adaptation despite high connectivity. Such regions-often generated by chromosomal inversions-may be especially important in highly dispersive marine taxa yet remain poorly documented in echinoderms. Here, we combined a chromosome-level reference genome with genome-wide ddRAD-seq from 296 Marthasterias glacialis individuals across 19 Atlantic-Mediterranean locations to quantify population structure and scan for recombination-suppressed haploblocks. Genome-wide neutral markers showed significant population differentiation together with evidence of high connectivity, revealed by the presence of inter-ecoregion migrants. Additionally, we identified 16 polymorphic haploblocks with patterns consistent with putative chromosomal inversions spanning 18.6% of the genome. Haploblock haplotypes were strongly environmentally and geographically structured and contained genes with key functions in stress response, osmoregulation and thermal tolerance. Haplotype distributions also paralleled previously described mitochondrial lineages despite nuclear gene flow, consistent with a model of ancient divergence followed by secondary contact. Overall, our results suggest a role for widespread structural polymorphism in adaptive differentiation in Echinodermata, providing a framework for linking echinoderm genome rearrangements to ecological divergence. Marthasterias glacialis thus emerges as a promising system to explore how structural variation contributes to adaptation and genome evolution in highly dispersive organisms.
The degradation of natural landscapes is a key driver of biodiversity loss and the erosion of ecosystem services, including disease regulation. Although linked to higher zoonotic disease risk, the mechanisms by which landscape structure shapes host-parasite eco-evolutionary dynamics remain poorly understood. Here, we combine a spatially explicit metacommunity and coevolutionary model with empirical host-parasite interactions to examine how landscape configuration shapes ecological and coevolutionary outcomes. We found that: (i) landscapes with more natural cover and lower fragmentation level dilute the distribution of parasites throughout the host community and lead to more homogeneous coevolutionary trajectories; (ii) highly degraded, fragmented landscapes constrain host-parasite dispersal, promoting smaller, more heterogeneous interaction networks with divergent coevolutionary dynamics, which raise the risk of new parasite variants emerging; and (iii) loss of habitat reduces diversity, reducing parasite host range. These results extend the dilution effect hypothesis by incorporating the structure of the interaction networks and the coevolutionary dynamics. Our findings suggest increased zoonotic transmission risk and stronger parasite-host interactions in degraded landscapes. Hence, conservation actions should focus on maintaining forest core integrity to mitigate the effects of landscape conversion on host-parasite dynamics and to promote the disease-regulation service of natural ecosystems.
Wildlife is increasingly forced to share space with humans, facing disturbances that operate across different spatial and temporal scales. The press-pulse framework, originally developed in the disturbance ecology literature, distinguishes between long-term sustained 'presses' and more acute 'pulses'. Because pulses occur during ongoing press conditions, their ecological effects depend on how they interact with that background, helping explain why certain disturbances result in transient, localized changes, while others lead to lasting, widespread impacts. Here, we expand this framework by applying it to regimes of human disturbances, and incorporating 'pauses' as a third category. Pulses and pauses (e.g. episodes of extreme weather, or drastic changes in human mobility) can substantially affect wildlife behaviour, yet their effects are often modulated by background 'press' conditions. We offer a conceptual framework for disentangling effects across space and time and highlight how plasticity in wildlife movement-particularly in terms of navigating risks and tracking resources-can lead to both adaptive and nonadaptive responses to human disturbances. This enables predictions about how shifts in animal movement can influence human wildlife interactions and conflict with humans under different scenarios. Applying the press-pulse-pause framework to movement ecology allows researchers to improve our understanding of how wildlife is affected by different disturbance regimes, advancing efforts to foster sustainable human-wildlife coexistence in an era of mounting pressures.
The biological traits associated with the origin of social behaviour remain a fundamental question in evolutionary biology. Among bees, the family Halictidae provides a particularly valuable system for addressing this question, as it represents the only bee family outside Apidae in which eusociality has evolved. Yet, the ecological and morphological factors underlying these transitions remain poorly understood. To investigate the evolutionary relationships among scopa type, floral breadth and eusociality, we conducted a comparative analysis using a multilocus phylogeny reconstructed from 207 species. Ancestral state reconstructions indicate that the posteriorly caged scopa evolved multiple times from an ancestral straight form, most prominently within Halictini and closely related tribes. Comparative analyses indicate a consistently positive but transformation- and clade-sensitive association between posteriorly caged scopa and recorded floral breadth, whereas eusocial taxa show a more robust association with broader recorded floral breadth. Together, these findings suggest non-random phylogenetic associations among pollen-transport morphology, floral breadth and sociality in Halictidae, while indicating that these relationships do not follow a single causal pathway.
