Ecological Entomology

O_LIPhenological shifts are a major ecological consequence of climate change, yet studies often focus on single life stages meaning that the potential for carryover effects between life stages remains poorly understood. Failing to account for these effects may lead to inaccurate estimates of phenological shifts, with consequences for predicted synchrony among interacting species. This is especially relevant for temperate systems where climate warming is occurring unevenly across the year. C_LIO_LIHere, we investigated how temperature experienced the previous autumn and winter (during the pupal and egg stage) influences spring phenology in the winter moth (Operophtera brumata), a herbivorous insect with distinct life stages. Using 50 years of local climate data to create five experimental temperature regimes, we first quantified phenotypic plasticity in the duration and temporal variability of pupal and egg development. We then examined how timing of adult moth emergence affects timing of offspring hatching. C_LIO_LIWe found divergent effects of temperature on different life stages; pupal development time was shortest at intermediate temperatures while egg development time decreased linearly with increasing temperature. Furthermore, phenological shifts due to the conditions experienced by the mother were carried over to influence the phenology of her offspring. While this carryover effect was partially compensated during subsequent stages, compensation decreased under warming conditions. C_LIO_LIThese results refine our understanding of the sensitivity of the annual cycle of winter moth phenology to variation in temperature with potential implications for population dynamics and interspecific interactions. Overall, our findings highlight the need to consider the impacts of warming across multiple life stages so that carryover effects can be properly accounted for. Doing so will improve predictions of phenological shifts under future climates. C_LI

Understanding how fruit fly species partition resources along environmental gradients is important for predicting pest pressure under changing climatic conditions. The population ecology of Dacus bivittatus (Bigot) and Dacus punctatifrons (Karsch) (Diptera: Tephritidae) was examined across six sites spanning 526-1,650 m above sea level in the Uluguru Mountains, Tanzania, over eight years (2004-2012). A total of 2,200 weekly trap records were aggregated into 292 site-month observations and standardised as flies per trap per day (FTD). Dacus bivittatus showed strong seasonal structuring (H = 43.03, p < 0.001), with abundance peaking during the cool dry season (June-August), whereas D. punctatifrons showed no clear seasonal pattern. Both species declined significantly with increasing altitude ({rho} = -0.308 and -0.769, respectively; p < 0.001), but the decline was steeper for D. punctatifrons. Species dominance shifted along the gradient: D. punctatifrons dominated warm lowland conditions (>24 {degrees}C), whereas D. bivittatus prevailed at elevations above approximately 569 m. Seasonal niche overlap declined markedly with altitude, indicating increasing temporal segregation between the species in cooler environments. These findings demonstrate that altitude structures ecological divergence between two closely related fruit fly pests and provide a basis for site-specific monitoring and climate-sensitive pest forecasting in tropical mountain agroecosystems.

The connection between female host plant preference and offspring performance is important for understanding how relationships between plants and phytophagous insects have evolved. According to the preference-performance hypothesis, female insects should evolve to oviposit on host plants on which offspring performance is the highest. Here, we examined the preference-performance hypothesis in the northern brown argus (Aricia artaxerxes) butterfly in the province of Uppland, Sweden, by comparing female host plant preference and larval growth between the host plant species wood cranesbill (Geranium sylvaticum) and bloody cranesbill (G. sanguineum). We also investigated if host plant preference in A. artaxerxes was related to the geographic distribution of A. artaxerxes and its host plants in the province Uppland. We found that the A. artaxerxes females, contrary to the preference-performance hypothesis, preferred ovipositing on G. sylvaticum, even though larvae feeding on G. sylvaticum were slightly smaller than those feeding on G. sanguineum. Since G. sylvaticum is more abundant and probably more utilized than G. sanguineum in Uppland, an explanation for this negative preference-performance connection may be that there are advantages associated with utilizing a more common host plant species, even though larvae feeding on this plant show reduced growth rates. Overall, the results show that factors other than offspring performance, such as geographic distribution, may influence female host plant preference in A. artaxerxes.

Stingless bees are key pollinators in tropical ecosystems, yet their ecological dynamics remain poorly understood in highly seasonal environments such as the seasonally dry tropical forests of Ecuador. These ecosystems experience pronounced climatic seasonality, with sharp transitions between dry and wet periods that strongly affect floral resource availability. Understanding interspecific competition and niche partitioning in such systems is critical, particularly given the global decline of pollinators. We investigated resource use and niche dynamics in two native stingless bees, Melipona mimetica and Scaptotrigona sp., by quantifying pollen, nectar, and resin collection across seasons. Log-linear models were used to test the effects of species, season, and their interaction on resource use, while non-metric multidimensional scaling (NMDS) assessed niche overlap. Contrary to the expectation that niche overlap increases under resource scarcity, we found greater overlap during the wet season, when resources are more abundant. This suggests that both species converge on high-quality floral resources during peak availability, reflecting an adaptive response to strong environmental seasonality. Pollen use remained stable across seasons, consistent with generalist foraging behavior. In contrast, nectar collection increased significantly during the wet season, while resin exhibited a shared seasonal peak, likely associated with synchronized nest construction or maintenance. These findings reveal context-dependent competition dynamics and highlight the role of environmental seasonality in shaping pollinator interactions. Our study provides new insights into the ecology of threatened stingless bees and contributes to their conservation in tropical dry forest ecosystems.

O_LISaproxylic community assembly is structured both by deadwood and forest habitat gradients, as well as biotic interactions such as competition, predation, and parasitism. However, covariation between abiotic and biotic conditions in natural systems have limited our ability to disentangle these mechanisms. Furthermore, focus towards beetles and fungi in temperate or boreal forests has led to important taxonomic and geographic knowledge gaps. C_LIO_LIHere, we tested how experimentally-manipulated tree diversity, deadwood position (lying vs. standing), and biotic interactions with a dominant antagonist (ant exclusion) structure the community assembly of deadwood-cavity-nesting bees, wasps, and their parasitoids in a subtropical forest. C_LIO_LIOur findings reveal that lying deadwood supports a nested subset of the communities occurring in standing deadwood, with less diversity and abundance of hosts and parasitoids. We found that increased moisture, rather than ant activity, was the primary mechanism filtering Hymenoptera communities, as deadwood in contact with the forest floor retained twice as much moisture as standing substrate. Moreover, moisture gradients within each substrate type further reduced host abundance - likely due to reduced brood cell production and survival. In contrast, forest habitat (tree species richness, canopy cover, and coarse woody debris) had comparatively minor roles in shaping cavity-nesting community assembly. C_LIO_LIOur results provide a mechanism for the positive association between cavity-nesting Hymenoptera and standing deadwood in forests. Because standing deadwood is typically scarce in many managed forests, these findings support the retention and enhancement of such substrates to promote these ecologically-important insects. C_LI

Life-history traits play an important role in insect population dynamics and ecological processes. The azuki bean beetle Callosobruchus chinensis is a common pest of stored legumes and is also widely used as a model species in ecological and evolutionary research. In this study, we tested whether machine learning models could be used to estimate several traits of C. chinensis, including elytral length, development time and adult lifespan. Experimental data were obtained from laboratory populations. The dataset included biological and environmental variables such as strain, treatment condition, developmental day, sex, temperature, and CO2. Six different machine learning models were tested, including linear regression, random forest, support vector machine (SVM), neural network, gradient boosting and AdaBoost. Model performance was evaluated using cross-validation. The coefficient of determination (R2) and root mean square error (RMSE) were used to measure prediction accuracy. Prediction accuracy differed among traits. Elytral length showed relatively higher predictability than the other traits, while development time was difficult to estimate in most models. Lifespan was easier to predict than the other traits, and the neural network produced one of the highest prediction accuracies among the tested models. Feature importance analysis also showed that factors such as sex and treatment condition contributed to variation in several traits. Machine learning models therefore helped reveal relationships among biological variables and life-history traits in C. chinensis. Combining ecological experiments with machine learning analysis may help improve our understanding of insect traits and may support future studies in insect ecology and pest management.

Pollinator populations are facing worldwide declines, underscoring conservation needs. Yet, conservation assessments still mostly rely on occurrence data, often derived from heterogeneous and opportunistic observations. While such data can inform on species presence and distribution, they may overlook important markers of population declines. This is particularly problematic for social species such as bumble bees, which typically exhibit low effective population sizes despite high abundance of workers observed in the field. Despite these putative pitfalls, the relationship between occurrence-based and genetic-based estimates remains largely unexplored in social bees. We here investigated spatio-temporal genetic patterns in five Swiss Bombus species representing contrasting population trajectories over the last century: B. humilis and B. sylvarum (stable), B. ruderatus (increasing), B. pomorum (regionally extinct), and B. veteranus (declining). Museum specimens collected between 1929 and 2023 were genotyped at 11 microsatellite loci to compare spatio-temporal fluctuations in genetic diversity and population structure with occurrence data. Overall, multilocus heterozygosity and allelic richness remained stable in all species during the time period investigated, indicating that the diverging population trends did not result in substantial variation of genetic diversity. In contrast, strong and significant shifts in allelic frequencies between time periods were detected in three species, suggesting recent immigration events. Isolation by distance was detected in the cold-adapted B. veteranus, while the extant warm-adapted species (B. humilis, B. sylvarum, B. ruderatus) showed high levels of gene flow between locations. In B. pomorum, increasing genetic homogenization was observed before extinction. Altogether, these findings show that genetic diversity indexes are not the most adapted tools to monitor conservation status of social bee populations, and that estimates of population structure such as allelic shifts may be more informative. Moreover, these results highlight the importance of monitoring metapopulation dynamics and ensuring connectivity among populations to facilitate gene flow and enable demographic rescue processes.

Migration is widely recognized as a strategy for animals to track seasonally shifting resources. Yet, seasonal and spatial dynamics of migration are challenging to study, particularly for difficult-to-track insects. Among insects, monarch butterflies (Danaus plexippus) have a well-documented fall migration, but spring breeding recolonization remains poorly understood, particularly for the western population. We conducted multi-year surveys across six regions in the western United States to characterize monarch breeding phenology and evaluate three related hypotheses: (i) the successive broods model, with discrete generations shifting activity across the breeding range, (ii) a diffusion-like expansion model with overlapping breeding periods, and (iii) a mid-summer lull model with temporary summer declines in breeding for areas near the overwintering habitat. Monarch immature presence served as an indicator of local breeding activity. Our results do not support the successive broods or mid-summer lull hypotheses. Breeding onset occurred earlier near overwintering areas and gradually expanded north-and eastward, with sustained activity in many regions throughout the season. Termination of breeding also occurred earlier at more distant sites, resulting in longer breeding activity nearer to overwintering habitat. Immature monarch density declined with distance from overwintering areas at onset and termination, suggesting delayed colonization of peripheral regions. Together, these results support a diffusion-like expansion of breeding rather than sequential generational replacement. Western monarchs also do not initiate or terminate breeding in close synchrony with host plant availability, contrary to predictions from resource-tracking theory. These findings highlight fundamental differences between western monarch breeding dynamics and paradigms for eastern monarchs, demonstrating that a single species can employ fundamentally different spatial strategies for recolonizing its breeding range in different regions. More generally, these results distinguish insect migration from systems with direct movements between wintering and breeding habitats, and underscore the value of long-term, landscape-scale monitoring for resolving habitat use across heterogeneous environments.

O_LIAgricultural intensification can support the expansion of introduced species which are highly adapted to human-modified landscapes, but the mechanisms by which this occurs are often unclear. C_LIO_LIHere we investigate the spatial ecology of a rapidly expanding introduced bumble bee (Bombus impatiens) and a native congener (B. mixtus) in agricultural landscapes of southwestern British Columbia, Canada. We used microsatellite genotyping and spatially explicit capture-recapture models to compare the foraging distance of the two species, and fitted hierarchical models to compare their abundance, behaviour (nest searching vs foraging), and lineage survival as a function of landscape composition and configuration. C_LIO_LIWe found that B. impatiens had a broader foraging range than B. mixtus, and that its colony/worker abundance were positively associated with the surrounding area of residential gardens, but decreased relative to B. mixtus abundance in response to increasing seminatural area. In contrast, B. mixtus colony abundance decreased in landscapes with a greater area of intensively managed berry crops. C_LIO_LIWe observed fewer B. impatiens queens per survey in landscapes with more low-disturbance landcover, and hypothesize space use of this species could be shaped by concentration on potential nesting habitat. Consistent with this observation, nest searching behaviour was more common for B. impatiens queens, while B. mixtus queens were primarily observed foraging, suggesting these two species derive different value from agricultural landscapes during colony establishment. C_LIO_LIFinally, we found that the rate of lineage re-capture between 2022 colonies and 2023 spring queens was nearly 10-fold higher for B. impatiens than for B. mixtus, indicating a greater capacity of the introduced species to complete its life cycle in agro-natural landscape mosaics. C_LIO_LIOur results suggest that differences in spatial ecology may contribute to the differential success of these two species in human-modified landscapes, and provide insight into the mechanisms by which land-use change shapes community composition. C_LI O_FIG O_LINKSMALLFIG WIDTH=184 HEIGHT=200 SRC="FIGDIR/small/723627v1_ufig1.gif" ALT="Figure 1"> View larger version (62K): org.highwire.dtl.DTLVardef@1e72eacorg.highwire.dtl.DTLVardef@a958a0org.highwire.dtl.DTLVardef@1f970b6org.highwire.dtl.DTLVardef@156f522_HPS_FORMAT_FIGEXP M_FIG C_FIG Graphical abstract. Coloured diagrams of B. mixtus and B. impatiens are credited to Elaine Evans and the Xerces Society, with permission.

Honeypot ants represent an example of convergent evolution, where a group of workers specialized in storing liquid food in their crops (i.e., stomach) has independently evolved multiple times across different ant genera. While seasonal resource scarcity and arid conditions are thought to drive the evolution of repletism, the role of environmental variables in this process has not been tested. With this is mind, species ensemble models were computed to assess suitability and richness areas, and the importance of predictors. Predictor importance was compared between genera and groups occupying a similar geographical area. Niche overlap and similarity between honeypot ant species were also evaluated to determine whether they occupy similar environmental spaces. Similarity was mainly found within genera, and Leptomyrmex and Myrmecocystus showed striking niche differences. Overall, Leptomyrmex distribution was mainly influenced by atmospheric bioclimatic variables like precipitation and temperature, while Myrmecocystus had soil bioclimatic variables as the most important predictors for their current distribution. Our results indicate that honeypot ants species currently do not occupy the same environmental space, and are not experiencing the same contemporary environmental stressors. While our results suggest that contemporary environmental factors cannot explain the convergence of honeypot ants, future research will examine past climatic conditions along with investigations into the ant genomes to understand more about the causes and consequences of the convergence.

Over the past decade, the global rise in invasive species has accelerated at an unprecedented rate, intensifying threats to ecosystems, human health, and economies worldwide. Newly invasive taxa, such as Tropilaelaps mites, are of particular concern for apiculture and agroecosystems. Despite growing concern about the spread of Tropilaelaps mites and other arthropods, limited resources are available to assess their invasive potential. We characterized 118 invasive arthropod species using available literature to identify key biological and ecological traits associated with invasive potential. We developed predictive generalized linear mixed models (GLMMs) to determine the traits most important for predicting invasive potential (number of invaded regions), and the top-performing models were subsequently applied to Tropilaelaps mercedesae. Several traits were identified as significant predictors of invasiveness, including the degree of human association, resilience at small population sizes, diet breadth, maximum annual number of generations, altitude range, and the interaction between human association and temperature range. Notably, T. mercedesae was predicted to be capable of invading 160 regions, ranking it within the top 10% most invasive species among those evaluated (12th out of 119), ranked just below the cosmopolitan Varroa destructor mite. These findings position T. mercedesae as a high-risk, yet under-recognized, invasive threat. Collectively, this demonstrates the power of predictive trait-based modeling to inform invasion risk prior to widespread establishment and underscores the urgency of reallocating resources toward surveillance, research, and proactive management strategies rather than relying on costly, often ineffective post-establishment eradication.

Urban pollinator gardens can provide refugia and support diverse populations of native bees amid threats from habitat destruction, pesticides, and potential ecological pressures from the introduced honey bee (Apis mellifera (Linnaeus, 1748)). The University of California, Berkeley, maintained a native bee garden at the Oxford Tract research facility to study the biodiversity, phenology, and foraging habits of urban bees from 2003 to 2009. That garden was decommissioned, and a new garden was re-established in 2019. Using diversity observations from the early 2000s garden and non-lethal sampling techniques, we characterized plant-pollinator interactions between flowers and urban bees in the newer bee garden with a bipartite interaction network. Across 12 flower species, we observed two non-native pollinators, the honey bee (A. mellifera) and the alfalfa leafcutter (Megachile rotundata (Fabricius, 1793)), along with at least ten native bee species across three families (Apidae, Halictidae, Megachilidae). We found that, despite the garden being created for native bees, honey bees accounted for 84% of all pollination interactions. The most abundant native bees were sweat bees (Family: Halictidae). Generalist interactions dominated the network, as both honey and sweat bees foraged on most available flowers. Honey bees showed a significant positive correlation with floral abundance, visiting flowers with the highest number of inflorescences, whereas native bees did not show this preference. These results indicate that native bee garden stewardship could benefit from greater floral diversity, while avoiding the dominance of any single species with high floral abundance, thereby reducing the likelihood of direct competition with honey bees.

Rapid changes to weather caused by climate change have a negative effect on much of the worlds animal populations and species. Some populations are more vulnerable than others to the effects of climate change, and individuals are particularly vulnerable during early development. Good embryonic development is important for vertebrate species because this can dictate their breeding success and survival rates, and disruptions to this phase can have far reaching fitness effects that can last into adulthood and beyond. We looked at the impact of weather (ambient temperature, rainfall and wind speed) on the embryonic development of thorn-tailed Rayadito (Aphrastura spinicauda) at two different latitudes in Patagonia, Chile. We measured the heart rate of embryos just before hatching using an egg buddy machine to determine embryonic development. Optimum development of nestlings is important for fledging, so it is essential that embryonic development is successful. We studied two populations. One is situated in a temperate rainforest on the northern border of Patagonia called Pucon which we studied in 2018 and 2019, with mild temperatures (12 degrees Celsius), high rainfall (636ml) and low wind speeds (6.3km/h). The other is in a sub-Antarctic old growth forest in southern Patagonia called Navarino island which we studied in 2018, 2019 and 2023, which is comparatively drier (138ml), colder (8.3 degrees Celsius) and has higher average wind speeds (16.6km/h). We found that embryonic development was better in the south compared to the north, indicated by higher embryo heart rates near hatching in the south. Development of embryos in the northern site was slower when conditions were cold and windy. Development of embryos in the southern site was unaffected by temperature, rainfall or wind speeds. In northern Patagonia, when minimum temperatures were low and wind speeds high during the period encompassing clutch completion, initiation of full incubation and during incubation, have a negative impact on embryonic development. In contrast, when Rayaditos in the southern population experience slow embryonic development, they extend the incubation period allowing embryos more time to develop before hatching. Our study shows that in the north of Patagonia embryonic development declines over years and that Rayaditos seem not to have adapted to dealing with climate change. On the other hand, in the south of Patagonia, embryonic development is unaffected by climatic factors, suggesting that Rayaditos are adapting to climate change through extending their incubation periods, allowing embryos to fully develop before hatching. It appears that Rayaditos in the northern population are not extending their incubation periods and are not adapting to the threats posed by climate change. To our knowledge, this is the first study of its kind to examine embryonic development in the field and to associate this to changing weather patterns whilst highlighting specific days on which development is influenced.

Methods for estimating and modeling the long-term and short-term adult flight dynamics of the conifer silk moth Dendrolimus superans (Lepidoptera: Lasiocampidae) are examined. The analysis uses light trap adult catch data collected over 21 years, from 2005 to 2025. Three models of adult flight are considered: a flight-initiation model driven by weather factors, an autoregressive model of long-term catch dynamics, and a binary model of seasonal catch. For the flight-initiation model, we propose estimating the accumulated temperature sum ST from the date when the first derivative of the remote sensing vegetation index NDVI becomes positive until the date of the first adult capture of the season. ST is shown to be sufficiently stable across all years of observation, with flight each year beginning after this temperature sum is reached. The second model demonstrates that the long-term light trap catch time series is well described by a second-order autoregressive model AR(2), in which the catch of the current year depends on catches from the two preceding years. This long-term series is compared with a previously studied larval population density series of the Siberian silk moth; both are shown to be AR(2) series with similar coefficient values, which suggesting that adult catch data may serve as a proxy for absolute larval population density. In the third model, we describe the transition from absolute-scale seasonal catch dynamics (number of adults per day) to a binary scale (0, 1), where 0 denotes days on which no adults were attracted to the trap, and 1 denotes days on which at least one individual was captured. The seasonal absolute catch series is thereby transformed into a binary series of zeros and ones, and relationships between adjacent values in such a binary series are examined. A linear relationship between the absolute and binary seasonal dynamics series is demonstrated, making it possible to estimate absolute catches from binary catch values and to analyze seasonal flight in sparse pest populations. This potentially opens new avenues for understanding how outbreak populations function at chronically low density. Author summaryForest pests can cause catastrophic damage, yet predicting their outbreaks remains challenging. During periods of low population density, standard monitoring methods become labor-intensive and uninformative, while the transition to an outbreak often occurs unexpectedly. Using a 21-year dataset of adult Siberian silk moth (Dendrolimus superans) captures from light traps, we developed an approach combining three complementary models. First, we showed that moth flight begins upon reaching a specific temperature sum, with the starting point determined by NDVI vegetation index dynamics rather than a calendar date--making the forecast more ecologically relevant. Second, long-term adult population dynamics follow a second-order autoregressive model AR(2), matching the dynamics previously observed for larval populations. This establishes light trap data as a reliable proxy for absolute population density when ground surveys are impractical. Third, we introduced a method to analyze seasonal flight using binary data (presence/absence of moths per day), which we showed is linearly related to absolute abundance. This enables studying population dynamics during periods of extremely low density, when traditional methods fail. Our approach opens new possibilities for early warning systems to detect when a population risks transitioning from a latent state to an outbreak phase.

Venom is an important functional trait that helps predatory animals capture prey. Centipede predatory venoms are complex cocktails of multiple proteins, such as neurotoxins (scoloptoxins), cytotoxins, {beta}-pore-forming toxins, and enzymes. We examined venom phenotypes in two closely related and co-occurring centipede species, Scolopendra morsitans (n=28) and S. hardwickei (n=11), in peninsular India to determine whether their venoms are similar or dissimilar. An integrated proteo-transcriptomic approach was used to characterise the venom phenotypes of the two species across multiple individuals in peninsular India. We used species occurrence records and species distribution models to assess the distributional overlap among these species within the peninsular Indian region. The species showed significant overlap in their current and projected geographical ranges, corresponding with their co-occurrence. We characterised the venom profiles of both species and found that the venoms were cocktails of enzymes, {beta}-pore-forming toxins, and neurotoxins comprising 110 and 84 proteins in S. morsitans and S. hardwickei, respectively. However, the venom composition of both species differed significantly in toxin abundance and species-specific protein repertoires. This indicates trait divergence in venom phenotypes, suggesting that distinct venom compositions may facilitate coexistence among ecologically similar predatory centipedes. The observed variation in venom phenotypes among co-distributed species opens up important avenues for future research into their ecological roles and functional significance. In this study, we provided a detailed account of venom composition across multiple individuals from the species geographic range and highlighted the importance of investigating the role of venom as a trait that could influence species interactions and shape communities in these diverse tropical forests.

Sleeping and feeding are crucial for survival of any animal. In case of large predators, knowing where these activities occur can help us understand their behavioural adaptations for coexisting with people and could help mitigating human-carnivore conflicts. Leopard (Panthera pardus) is an elusive and highly adaptable large felid that mostly lives outside protected areas and can survive also in close proximity to humans. However, most leopard research in Africa has been conducted in protected areas and we poorly understand leopards habitat selection while resting and hunting. To shed light on their coexistence with humans, we investigated habitat features influencing leopard selection of resting and kill sites on farmlands in central Namibia, using generalized linear mixed models (GLMM) under a use-availability study design and blinded field-sampling. Leopards primarily selected resting sites that were located in mountainous, steep, rugged terrain and sites with good concealment while kill sites were selected in mountainous habitats. Human infrastructure did not affect leopard resting and kill site selection. Thus, the capacity of leopards to perform essential life-supporting behaviours while coexisting with people appears to be primarily driven by their ability to remain concealed, rather than spatially avoiding humans.

The ectoparasitic mite Varroa destructor is the most significant parasite of the Western honey bee (Apis mellifera) and a major driver of colony losses worldwide. Although extensive research has focused on behavioral and physiological mechanisms of host resistance, comparatively little attention has been paid to potential phenotypic responses of the parasite itself. Here we investigated body size variation in Varroa destructor associated with varroa-resistant and non-resistant honey bee colonies across four European countries. We quantified the dorsal shield area of adult female mites from multiple colonies differing in the honey bee colonies resistance status, using standardized digital image analysis. Across geographically distant non-resistant populations, mite body size was remarkably consistent, with a median dorsal shield area of 1.47 mm2. In contrast, mites originating from varroa-resistant colonies were consistently smaller, with a median dorsal shield area of 1.37 mm2, representing an approximately 6.8% reduction in body size. This pattern was reproducible across different geographical areas, honey bee genetic backgrounds and beekeeping practices. The striking stability of mite body size in non-resistant populations contrasted with the consistent reduction observed in mites associated with resistant hosts, suggesting a host associated shift in parasite phenotype. Because body size in arthropods integrates developmental conditions, nutritional availability and resource allocation, the observed pattern may reflect altered developmental environments and selective pressures imposed by resistant hosts. Our results show a consistent morphological shift in this globally important parasite associated with resistant hosts and suggest that dorsal shield size in Varroa could serve as a new selection marker for varroa-resistant honey bee colonies.

Holometabolous polyphagous insects undergo complete metamorphosis and exploit multiple host plants, exposing them to highly variable ecological conditions across both life stages and host plants. Whether these species, like specialist ones, harbour a stable core microbiota, or whether life stages or host plants act as the primary drivers of microbiota assembly remain open questions. Here, we characterized the fungal and bacterial communities associated with Drosophila suzukii across life stages and host fruits using 16S and ITS metabarcoding. We tested the relative influence of life stage and host fruit on microbiota composition, using community and network-based analyses. We first identified that host fruit significantly structured fungal communities, but not bacterial ones. Yeast communities were rather fruit-specific: Hanseniaspora and Pichia mostly associated with cherries and strawberries, contrary to Metschnikowia with blackberries. In contrast, bacteria and filamentous fungi were shared across fruits, constituting for fruits a core microbiota dominated by Gluconobacter cerinus, Tatumella and Cladosporium. Second, we found that both bacterial and fungal D. suzukii communities were structured by life stage, and that fungal, but not bacterial communities, were also structured by host fruits. D. suzukii individuals harboured a core bacteria composed of G. cerinus and a niche-specific microbiota composed of yeasts: Hanseniaspora typical in individuals related to cherry and strawberry, and Metschnikowia to blackberry. Components of both core and niche-specific microbiota were most likely horizontally acquired by D. suzukii from host fruits. Taken together our results underline the importance of meta-community approaches to investigate tripartite interactions among insects, host plants and microbiota. IMPORTANCEThe role of gut microbiota in mediating interactions between phytophagous insects and their host plants has been well illustrated in specialist species. However, it has been less comprehensively studied in polyphagous species, which infest multiple host plants, and across life stages for holometabolous species experiencing separate ecological niches through development. We tested the existence of a core, a niche-specific and a stage-specific microbiota in a polyphagous holometabolous species, D. suzukii. We examined both fungal and bacterial communities in larvae, pupae and emerging flies infesting three host fruits. Our results showed first that the assembly of bacteria, filamentous fungi and yeasts on fruits is driven by different ecological processes. Second, that D. suzukii harbours a core bacterial microbiota, a niche-specific microbiota constituted by yeasts and no stage-specific microbiota. Our study emphasizes the importance of considering jointly the assembly of host plant and polyphagous insect microbial communities to better understand the ecology and evolution of insect-microbe interactions.

Natural history collections underpin our understanding of species distributions, yet some historical records remain embedded in modern avifaunal checklists despite limited documentation and no independent verification. One such case concerns the Dusky Parrot Pionus fuscus in Colombia: although reported from specimens collected by Melbourne A. Carriker Jr. in 1942 in the Serrania de Perija, the species has not been observed in the country for nearly eight decades yet continues to be included in national checklists and conservation assessments. We reassessed the validity of this record by applying a multi-evidence framework integrating historic archival reconstruction, specimen-based morphological comparisons, climatic niche analyses, biogeographic limit assessment and contemporary survey-effort data. Historical documentation and morphological evidence based on high-resolution specimen images and associated curatorial records demonstrate that the Carriker specimens correspond to Pionus chalcopterus, not P. fuscus. Climatic niche analyses reveal minimal environmental overlap between P. chalcopterus and P. fuscus, and place the Perija locality within the climatic niche of P. chalcopterus, while regional biogeography and extensive modern birdwatching coverage provide no support for the occurrence of P. fuscus in Perija. Together, these concordant lines of evidence demonstrate that P. fuscus does not occur in Colombia. Our findings support its removal from national bird lists and conservation assessments and highlight how integrated, multi-evidence reassessments of historical records strengthen ornithological baselines, improve biogeographic inference and ensure that conservation priorities rest on verifiable evidence.

Attracting specific pollinators can be favoured by natural selection to avoid reproductive interference between sympatric plant species. However, the ways in which fine differences in floral traits lead to the attraction of specific pollinators are diverse and unknown in many pollination interactions. We surveyed pollinators on three sympatric Aristolochia species (A. clematitis, A. pistolochia and A. rotunda) pollinated by Diptera to investigate if specific pollination occurs. To decipher if specific pollination may be mediated by different floral odours, we characterized the volatile organic compounds (VOCs) emitted by flowers and highlighted those VOCs electrophysiologically detected by pollinators in A. rotunda and A. pistolochia. Among the most abundant pollinators, Forcipomyia monilicornis was a specific pollinator of A. pistolochia while two Dasyhelea species were specific pollinators of A. clematitis. Forcipomyia aristolochiae and T. ruficeps were non-specific pollinators of A. rotunda, although they were more frequently found in A. rotunda flowers. The floral odours of A. rotunda and A. pistolochia differed significantly from each other and elicited specific electrophysiological responses in their respective pollinators. Although several pollinator species visit more than one Aristolochia species, those pollinators are preferentially found in one Aristolochia species. Selective attraction is likely mediated by specific VOCs.