Biology subjects

Guenard, B.

Publications and source records attributed to Guenard, B..

11 recordsLinked to original sources

bioRxiv2025

High-throughput phenomics of global ant biodiversity

The big data era in biology is underway, but the study of organismal form has been slow to capitalize on advances in imaging and computation. Modern imaging can digitize whole organisms, but low throughput has limited the effort to document morphological diversity. Within the open science initiative Antscan, we applied high-throughput synchrotron X-ray microtomography to capture phenotypes across a diverse and ecologically dominant insect group -- ants. We provide 2193 whole-body 3D ant datasets from 792 species to broadly cover the ant phylogeny with a global scope, also pairing phenomic data with genome sequencing projects. Scans acquired with standardized parameters facilitate automated analysis and free access to data can broaden the audience and incentivize methods development. Antscan presents a scalable approach to create libraries of diverse anatomies, heralding a new era of studies on the evolution, structure, and function of organismal phenotypes.

zoology↗

bioRxiv2023

Generalized mutualisms promote range expansion in both plant and ant partners

Mutualism improves organismal fitness, but strong dependence on another species can also limit a species ability to thrive in a new range if its partner is absent. We assembled a large, global dataset on mutualistic traits and species ranges to investigate how multiple plant-animal and plant-microbe mutualisms affect the spread of legumes and ants to novel ranges. We found that generalized mutualisms increase the likelihood that a species establishes and thrives beyond its native range, whereas specialized mutualisms either do not affect or reduce non-native spread. This pattern held in both legumes and ants, indicating that specificity between mutualistic partners is a key determinant of ecological success in a new habitat. Our global analysis shows that mutualism plays an important, if often overlooked, role in plant and insect invasions.

ecology↗

bioRxiv2022

New distribution data and phylogenetic approach reveal bioregionalization of the western Palearctic ants

AimBiogeographic regionalization has fascinated biogeographers and ecologists for centuries and is endued with new vitality by evolutionary perspectives. However, progress is scant for most insect groups due to shortfalls in distribution and phylogenetic information, namely Wallacean and Darwinian shortfalls respectively. Here, we used the western Palearctic ants as the case to tackle these shortfalls and test their biogeographic structure through novel distribution data and phylogenetic approaches. LocationWestern Palearctic realm. TaxonAnts (Formicidae). MethodsFirstly, we developed a refined database integrating the occurrences of 747 ant species across 207 regions of the western Palearctic realm, based on newly expert-validated records derived from the existing global ant biodiversity informatics. Using range estimates for these species derived from polygons and species distribution modelling, we produced species assemblages in 50 x 50 km grid cells. We calculated taxonomic and phylogenetic turnover of ant assemblages, performing hierarchical clustering analysis using the Simpson dissimilarity index to delineate biogeographic structure. ResultsAt both the regional list- and grid assemblage-levels, the Mediterranean has higher turnover and more biogeographic regions than northern Europe, both taxonomically and phylogenetically. Delineations based on grid assemblages detected more detailed biogeographic transitions, while those based on regional lists showed stronger insularity in biogeographic structure. The phylogenetic regionalization suggested closer but varied affinities between assemblages in comparison to the taxonomic approach. Main conclusionsHere, we integrated expert-validated regional lists, species distribution modelling, and a recent phylogeny to tackle Wallacean and Darwinian shortfalls for an important insect group by developing a next-generation map of biogeographic regionalization for the western Palearctic ants. The results of this study suggest strong constraints from geographic barriers and potential effects of climatic history on ant distributions and evolutionary history, and also provide baseline spatial information for future investigations of regional insect distributions.

zoology↗

bioRxiv2021

The global spread and invasion capacities of alien ants

The ecological and economic impacts of biological invasions are usually highly conspicuous, but these are the outcome of a global, multistage process that is obscured from view. For most taxa, we lack a large-scale picture of the movements of alien species, the biases and barriers that promote or inhibit their spread at each stage, and blind spots in our ability to detect species during their spread. For instance, countries rely heavily on customs interceptions to prevent new species introductions, but their efficacy for detecting invaders remains unclear. To address these gaps, we synthesize and provide data at unprecedented geographic resolution on the global diversity and distribution of alien ants, a pervasive group strongly impacting humans and ecosystems. From >145,000 records spanning 602 regions, we identify 522 ant species exhibiting human-mediated spread, doubling recent estimates of their diversity. We show that movements of alien ant species across regions globally are non-random and, moreover, that these flows differ by the extents to which species invade--ranging from arrival to indoor establishment, naturalization, and harmful status. Importantly, we find that almost two-thirds of the 309 species that naturalize globally--most of which are ground- and litter-dwelling--are absent from customs interceptions, which record disproportionately high numbers of arboreal species. Our results illustrate the vast, yet uneven extent of ant invasions globally, and suggest that most alien species bypass biosecurity controls while spreading successfully worldwide. This raises doubts on the efficacy of current customs interceptions procedures and highlights a need for radically new approaches. Significance statementBiological invasions impact humans and ecosystems tremendously. Invasions are difficult to address because little is known about large-scale patterns of spread, species capacities to invade ecosystems, and the efficacy of existing biosecurity measures. This paper tackles these issues for alien ants, one of the most damaging groups of invasive animals. An unprecedented dataset reveals that 522 ant species exhibit human-mediated spread, 270 more than previously known. Species are grouped under four levels of invasion capacity corresponding to different invasion barriers. Geographic sources and sinks for the groups differ globally. Two-thirds of species with naturalization capacity have never been recorded at customs interceptions, which fail to detect many litter-dwelling species. Novel detection and control strategies for inconspicuous alien organisms are needed.

ecology↗

bioRxiv2021

Opposing effects of competitive exclusion determine invasion outcomes and structure ant assemblages

Understanding how species phenotypic differences affect competition is key to explaining community assembly and predicting biodiversity responses. Many studies overlook the variable effects that species trait differences can have on the direction of competitive exclusion, which reverses depending on the specific mechanism at play. We performed a comprehensive trait-based study of an ant invasion integrating morphological, dietary, physiological and behavioral analyses. We found that trait differences between invasive and resident species were not only associated with niche differences which promoted the coexistence of dissimilar species, but also competitive ability differences which acted in the opposite fashion. Furthermore, competition along separate trait axes led to complex and contrasting patterns in the invaded assemblages, where species were at once similar (clustered) in some traits but also dissimilar (overdispersed) in others. Our results reveal that different aspects of phenotype may distinctly modulate the effect of competition in structuring ecological communities and functional diversity.

ecology↗

bioRxiv2020

Mangroves are an overlooked hotspot of insect diversity despite low plant diversity

We here compare the tropical arthropod fauna across a freshwater swamp and six different forest types (rain-, swamp, dry-coastal, urban, freshwater swamp, mangroves) based on 140,000 barcoded specimens belonging to ca. 8,500 species. Surprisingly, we find that mangroves, a globally imperiled habitat that had been expected to be species-poor for insects, are an overlooked hotspot for insect diversity despite having low plant diversity. Our study reveals a species-rich mangrove insect fauna (>3,000 species) that is distinct (>50% of species are mangrove-specific), and has high species turnover across Southeast and East Asia. For most habitats, plant diversity is a good predictor for insect diversity, but mangroves are an exception and compensate for a comparatively low number of phytophagous and fungivorous insect species by supporting an unusually rich community of predators whose larvae feed in the productive mudflats. For the remaining tropical habitats, the insect communities have diversity patterns that are largely congruent across guilds. The discovery of such a sizeable and distinct insect fauna in a globally threatened habitat underlines how little is known about global insect biodiversity.

ecology↗

bioRxiv2020

Critical Thermal maximum measurements and its biological relevance: the case of ants

O_LIUpper thermal limit (UTL) is a key trait in evaluating ectotherm fitness. Critical Thermal maximum CTmax, often used to characterize the UTL of an organism in laboratory setting, needs to be accurate to characterize this significant and field-relevant threshold. The lack of standardization in CTmax assays has, however, introduce methodological problems in its measurement and incorrect estimation of species upper thermal limit; with potential major implications on the use of CTmax in forecasting community dynamics under climate change. In this study we ask if a satisfactory ramping rate can be identified to produce accurate measures of CTmax for multiple species. C_LIO_LIWe first identified the most commonly used ramping rates (i.e. 0.2, 0.5 and 1.0 {degrees}Cmin-1) based on a literature review, and determined the ramping rate effects on CTmax value measurements in 27 ant species (7 arboreal, 16 ground, 4 subterranean species) from eight subfamilies using both dynamic and static assays. In addition, we used field observations on multiple species foraging activity in function of ground temperatures to identify the most biologically relevant CTmax value to ultimately develop a standardized methodological approach. C_LIO_LIIntegrating dynamic and static assays provided a powerful approach to identify a suitable ramping rate for the measurements of CTmax values in ants. Our results also showed that among the values tested the ramping rate of 1 {degrees}Cmin-1 is optimal, with convergent evidences from CTmax values measured in laboratory and from foraging thermal maximum measured in the field. Finally, we illustrate how methodological bias in terms of physiological trait measurements can also affect the detection of phylogenetic signal (Pagels{lambda} and Bloombergs K) in subsequent analyses. C_LIO_LIOverall, this study presents a methodological framework allowing the identification of suitable and standardized ramping rates for the measurement of ant CTmax, which may be used for other ectotherms. Particular attention should be given to CTmax values retrieved from less suitable ramping rate, and the potential biases that functional trait based research may induce on topics such as global warming, habitat conversion or their impacts on analytical interpretations on phylogenetic conservatism. C_LI

ecology↗

bioRxiv2020

Trait-similarity and trait-hierarchy jointly determine co-occurrences of resident and invasive ant species

Interspecific competition, a dominant process structuring ecological communities, acts on species phenotypic differences. Species with similar traits should compete intensely (trait-similarity), while those with traits that confer competitive ability should outcompete others (trait-hierarchy). Either or both of these mechanisms may drive competitive exclusion within a community, but their relative importance and interacting effects are rarely studied. We show empirically that spatial associations (pairwise co-occurrences) between an invasive ant Solenopsis invicta and 28 other ant species across a relatively homogenous landscape are explained largely by an interaction of trait-similarity and trait-hierarchy in one morphological trait. We find that increasing trait-hierarchy leads to more negative associations; however these effects are counteracted when species are sufficiently dissimilar (by 37-95%) in their trait ranges. We also show that a model of species co-occurrences integrating trait-similarity and trait-hierarchy consolidates predictions of different theoretical assembly rules. This highlights the explanatory potential of the trait-based co-occurrence approach.

ecology↗

bioRxiv2019

Genomic signature of shifts in selection in a sub-alpine ant and its physiological adaptations

Understanding how organisms adapt to extreme environments is fundamental and can provide insightful case studies for both evolutionary biology and climate-change biology. Here, we take advantage of the vast diversity of lifestyles in ants to identify genomic signatures of adaptation to extreme habitats such as high altitude. We hypothesised two parallel patterns would occur in a genome adapting to an extreme habitat: i) strong positive selection on genes related to adaptation and, ii) a relaxation of previous purifying selection. We tested this hypothesis by sequencing the high-elevation specialist Tetramorium alpestre and four other phylogenetic related species. In support of our hypothesis, we recorded a strong shift of selective forces in T. alpestre, in particular a stronger magnitude of diversifying and relaxed selection when compared to all other ants. We further disentangled candidate molecular adaptations in both gene expression and protein-coding sequence that were identified by our genome-wide analyses. In particular, we demonstrate that T. alpestre has i) a derived level of expression for stv and other heat-shock proteins in chill shock tests, and ii) enzymatic enhancement of Hex-T1, a rate-limiting regulatory enzyme that controls the entry of glucose into the glycolytic pathway. Together, our analyses highlight the adaptive molecular changes that support colonisation of high-altitude environments.

evolutionary biology↗

bioRxiv2019

The cryptic impacts of invasion: functional homogenization of tropical ant communities by invasive fire ants

Invasive insects represent major threats to ecosystems worldwide. Yet their effects on the functional dimension of biodiversity, measured as the diversity and distribution of traits, are overlooked. Such measures often determine the resilience of ecological communities and the ecosystem processes they modulate. The fire ant Solenopsis invicta is a highly problematic invasive species occurring on five continents. Its impacts on the taxonomic diversity of native ant communities have been studied but its impacts on their functional diversity are unknown. Comparing invaded and uninvaded plots in tropical grasslands of Hong Kong, we investigated how the presence of S. invicta affects the diversity and distribution of ant species and traits within and across communities, the functional identities of communities, and functionally unique species. We calculated the functional diversity of individual species, including the trait variation from intraspecific polymorphisms, and scaled up these values to calculate functional diversity at the community level. Invasion had only limited effects on species richness and functional richness, which were 13% and 8.5% lower in invaded communities respectively. In contrast, invasion had pronounced effects on taxonomic and functional composition due to turnover in species and trait values. Furthermore, invaded communities were functionally more homogeneous, displaying 23% less turnover and 56% more redundancy than uninvaded communities, as well as greater clustering and lower divergence in trait values. Invaded communities had fewer functionally-unique individuals and were characterized by ant species with narrower heads and bodies and shorter mandibles. Our results suggest that studies based only on taxonomic measures of diversity or indices describing trait variety risk underestimating the full ramifications of invasions. Investigating the diversity and distributions of traits at species, community and landscape levels can reveal the cryptic impacts of alien species which, despite causing little taxonomic change, may substantially modify the structure and functioning of ecological communities.

ecology↗

bioRxiv2018

Evolution of the latitudinal diversity gradient in the hyperdiverse ant genus Pheidole

AimThe latitudinal diversity gradient is the dominant pattern of life on Earth, but a consensus understanding of its origins has remained elusive. The analysis of recently diverged, hyper-rich invertebrate groups provides an opportunity to investigate latitudinal patterns with the statistical power of large trees while minimizing potentially confounding variation in ecology and history. Here, we synthesize global phylogenetic and macroecological data on a hyperdiverse (>1100 species) ant radiation, Pheidole, and evaluate the roles of three general explanations for the latitudinal gradient: variation in diversification rate, tropical conservatism, and ecological regulation.\n\nLocationGlobal.\n\nTime PeriodThe past 35 million years.\n\nMajor taxa studiedThe hyperdiverse ant genus Pheidole Westwood.\n\nMethodsWe assembled geographic data for 1499 species and morphospecies, and inferred a dated phylogeny of Pheidole of 449 species, including 150 species newly sequenced for this study. We tested correlations between diversification rate and latitude with BAMM, HiSSE, GeoSSE, and FiSSE, and examined patterns of diversification as Pheidole spread around the globe.\n\nResultsWe found that Pheidole diversification occurred in series of bursts when new continents were colonized, followed by a slowdown in each region. There was no evidence of systematic variation of net diversification rates with latitude across any of the methods. Additionally, we found latitudinal affinity is moderately conserved with a Neotropical ancestor and phylogenetic inertia alone is sufficient to produce the gradient pattern.\n\nMain ConclusionsOverall our results are consistent with tropical conservatism explaining the diversity gradient, while providing no evidence that diversification rate varies systematically with latitude. There is evidence of ecological regulation on continental scales through the pattern of diversification after colonization. These results shed light on the mechanisms underlying the diversity gradient, while contributing toward a much-needed invertebrate perspective on global biodiversity dynamics.

evolutionary biology↗