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Predicting the spread of populations across fragmented habitats is vital if we are to manage their persistence in the long term. We applied network theory with a model and an experiment to show that spread rate is jointly defined by the configuration of habitat networks (i.e., the arrangement and length of connections between habitat fragments) and the movement behavior of individuals. We found that population spread rate in the model was well predicted by algebraic connectivity of the habitat network. A multigeneration experiment with the microarthropod Folsomia candida validated this model prediction. The realized habitat connectivity and spread rate were determined by the interaction between dispersal behavior and habitat configuration, such that the network configurations that facilitated the fastest spread changed depending on the shape of the species’ dispersal kernel. Predicting the spread rate of populations in fragmented landscapes requires combining knowledge of species-specific dispersal kernels and the spatial configuration of habitat networks. This information can be used to design landscapes to manage the spread and persistence of species in fragmented habitats.

Background Folsomia candida is a model in soil biology, belonging to the family of Isotomidae, subclass Collembola. It reproduces parthenogenetically in the presence of Wolbachia , and exhibits remarkable physiological adaptations to stress. To better understand these features and adaptations to life in the soil, we studied its genome in the context of its parthenogenetic lifestyle. Results We applied Pacific Bioscience sequencing and assembly to generate a reference genome for F. candida of 221.7 Mbp, comprising only 162 scaffolds. The complete genome of its endosymbiont Wolbachia , was also assembled and turned out to be the largest strain identified so far. Substantial gene family expansions and lineage-specific gene clusters were linked to stress response. A large number of genes (809) were acquired by horizontal gene transfer. A substantial fraction of these genes are involved in lignocellulose degradation. Also, the presence of genes involved in antibiotic biosynthesis was confirmed. Intra-genomic rearrangements of collinear gene clusters were observed, of which 11 were organized as palindromes. The Hox gene cluster of F. candida showed major rearrangements compared to arthropod consensus cluster, resulting in a disorganized cluster. Conclusions The expansion of stress response gene families suggests that stress defense was important to facilitate colonization of soils. The large number of HGT genes related to lignocellulose degradation could be beneficial to unlock carbohydrate sources in soil, especially those contained in decaying plant and fungal organic matter. Intra- as well as inter-scaffold duplications of gene clusters may be a consequence of its parthenogenetic lifestyle. This high quality genome will be instrumental for evolutionary biologists investigating deep phylogenetic lineages among arthropods and will provide the basis for a more mechanistic understanding in soil ecology and ecotoxicology.

The scientific community remains divided on the most effective way to design landscapes for biodiversity conservation or restoration. Although there is a consensus that habitat loss is the main cause of biodiversity decline worldwide, the extent to which fragmentation (i.e. the division of remaining habitats into smaller areas) contributes to this decline is a subject of ongoing debate. The spatial arrangement of remaining patches and the nature and permeability of the intermediate matrix (i.e. how easily animals can move through it) are other elements related to habitat loss that are little considered. A better understanding of the effects of these factors on populations could help the community move forward. Here, we conducted a multigenerational, landscape‐scale experiment with the microarthropod Folsomia candida and quantified the respective effects of matrix resistance and inter‐patch distance on colonization rate, population size and extinction, at fixed habitat amount. We found that the amount of reachable habitat in the landscape, encompassing both the quantity of habitat and the matrix resistance, is a good predictor of population size and extinction rate. Survival of individuals while crossing different matrix types was the key underlying mechanism, as it determined both colonization rate and demography, preventing individuals from reaching and using remote or difficult‐to‐access patches. Our study shows that an explicit consideration of matrix resistance considerably improves both our understanding and our predictive ability of populations fate at landscape‐scale. It also opens new avenues for landscape ecology theory as well as long‐awaited perspectives for applied conservation.

Effects on soil Collembola of Cu, Zn, Pb, and Cd pollution from Cu smelters over 40 years were investigated in paddy fields from an area of Eastern China. We compared the field effects to those observed in single-species laboratory tests employing the hemiedaphic collembolan Folsomia candida and the epedaphic Sinella curviseta obtained from laboratory cultures and exposed to field-collected polluted soil. The results indicated that different collembolan species responded differently to the pollution in the fields and could be divided into sensitive, indifferent, and tolerant types accordingly. The abundance of sensitive species decreased as the pollution increased, but this was not the same for indifferent and tolerant species. The dominant species changed from sensitive to tolerant species as the pollution increased. The reproduction of F. candida and S. curviseta was most sensitive to the contaminated soil compared to growth and survival; the sensitivity of the two species was similar. The growth was more sensitive than the survival for F. candida but not for S. curviseta . The growth and survival of F. candida were much more sensitive than those of S. curviseta . Sensitivity of field populations of F. candida (EC 10 31 [15–46]) and hemiedaphic species Folsomia quadrioculata (EC 10 52 [0.7–102]) were comparable with sensitivity of the reproduction of F. candida in the single-species tests (EC 10 21 [14–27]), suggesting that single-species test based on laboratory cultures and field soil could be used to link laboratory and field data and then reflect the field situation. S. curviseta could be used as an epedaphic species in single-species tests and F. quadrioculata as an indicator species for assessment of field effect.

Neonicotinoid insecticides have come under increasing scrutiny for their impact on non-target organisms, especially pollinators. The current scientific literature is mainly focused on the impact of these insecticides on pollinators and some aquatic insects, leaving a knowledge gap concerning soil invertebrates. This study aimed at filling this gap, by determining the toxicity of imidacloprid and thiacloprid to five species of soil invertebrates: earthworms ( Eisenia andrei ), enchytraeids ( Enchytraeus crypticus ), Collembola ( Folsomia candida ), oribatid mites ( Oppia nitens ) and isopods ( Porcellio scaber ). Tests focused on survival and reproduction or growth, after 3–5 weeks exposure in natural LUFA 2.2 standard soil. Imidacloprid was more toxic than thiacloprid for all species tested. F. candida and E. andrei were the most sensitive species, with LC 50 s of 0.20–0.62 and 0.77 mg/kg dry soil for imidacloprid and 2.7–3.9 and 7.1 mg/kg dry soil for thiacloprid. EC 50 s for effects on the reproduction of F. candida and E. andrei were 0.097–0.30 and 0.39 mg/kg dry soil for imidacloprid and 1.7–2.4 and 0.44 mg/kg dry soil for thiacloprid. The least sensitive species were O. nitens and P. scaber . Enchytraeids were a factor of 5–40 less sensitive than the taxonomically related earthworm, depending on the endpoint considered. Although not all the species showed high sensitivity to the neonicotinoids tested, these results raise awareness about the effects these insecticides can have on non-target soil invertebrates.

Most ectotherms follow the temperature‐size rule (TSR): in cold environments individuals grow slowly but reach a large asymptotic length. Intraspecific competition can induce plastic changes of growth rate and asymptotic length and competition may itself be modulated by temperature. Our aim was to disentangle the joint effects of temperature and intraspecific competition on growth rate and asymptotic length. We used two distinct clonal lineages of the Collembola Folsomia candida, to describe thermal reaction norms of growth rate, asymptotic length and reproduction over six temperatures between 6 and 29°C. In parallel, we measured the long‐term size structure and dynamics of springtail populations reared under the same temperatures to measure growth rates and asymptotic lengths in populations and to quantify the joint effects of competition and temperature on these traits. We show that intraspecific competition modulates the temperature‐size rule. In dense populations there is a direct negative effect of temperature on asymptotic length, but there is no temperature dependence of the growth rate, the dominant factor regulating growth being competition. The two lineages responded differently to the joint effects of temperature and competition on growth and asymptotic size and these genetic differences have marked effects on population structure along our temperature gradient. Our results reinforce the idea that the TSR of ectotherms can be modulated by biotic and abiotic stressors when studied in non‐optimal laboratory experiments. Untangling complex interactions between the environment and demography will help to understand how growth trajectories respond to environmental change and how climate change may influence population size structure. A free Plain Language Summary can be found within the Supporting Information of this article. Résumé 1La plupart des ectothermes suivent la règle de la taille‐température (temperature‐size rule, TSR): dans les environnements froids, les individus grandissent lentement mais atteignent une grande longueur asymptotique. La compétition intraspécifique peut, elle aussi, affecter les taux de croissance et la longueur asymptotique. Et l'intensité de la compétition peut elle‐même être modulée par la température. Notre objectif ici est de démêler les effets conjoints de la température et de la compétition intraspécifique sur les taux de croissance et la longueur asymptotique. Nous avons utilisé deux lignées clonales du collembole Folsomia candida, pour décrire les normes de réaction thermiques du taux de croissance, de la longueur asymptotique et de la reproduction sur six températures entre 6° et 29°C. En parallèle, nous avons mesuré la structure en taille et la dynamique à long terme des populations de collemboles élevés aux mêmes six températures pour mesurer les taux de croissance, les longueurs asymptotiques et l'intensité de la compétition dans les populations afin de pouvoir quantifier les effets conjoints de la compétition et de la température sur ces deux traits (croissance et taille). Nous montrons que la compétition intraspécifique module la règle température‐taille : dans les populations denses, il y a un effet négatif direct de l'augmentation de température sur la longueur asymptotique, mais il n'y a pas de dépendance directe du taux de croissance à la température, le facteur dominant régulant la croissance étant la compétition. Les deux lignées ont répondu différemment aux effets conjoints de la température et de la compétition sur la croissance et la taille asymptotique et ces différences génétiques ont des effets marqués sur la structure des populations le long de notre gradient de température. Nos résultats renforcent l'idée que la réponse des ectothermes à la température peut être modulée par des facteurs de stress biotiques et abiotiques. Démêler les interactions complexes entre l'environnement (température) et la démographie (compétition) peut permettre de mieux comprendre comment les trajectoires de croissance peuvent répondre à des changements environnementaux et comment le changement climatique peut influencer la structure en taille des populations. A free Plain Language Summary can be found within the Supporting Information of this article.

Climate change can alter predator–prey interactions when predators and prey have different thermal preferences as temperature change can exacerbate thermal mismatches (also called thermal asymmetry) with population-level consequences. We tested this using micro-arthropod predators (Stratiolaelaps scimitus) and prey (Folsomia candida) that differ in their temperature optima to examine predator–prey interactions across two temperature ranges, a cool (12 and 20 °C) and warm (20 and 26 °C) range. We predict that the lower thermal preference and optimum in F. candida will alter top-down control (i.e., interaction strength) by predators with interaction strength being strongest at intermediate temperatures, coinciding with F. candida thermal optimum. Predators and prey were placed in mesocosms, whereafter we measured population (predator and prey abundance), trait-based (average predator and prey body mass, and prey body length distribution), and predator–prey indices (predator–prey mass ratio (PPMR), Dynamic Index, and Log Response Ratio) to determine how temperature affected their interactions. Prey populations were the highest at intermediate temperatures (average temperature exposure: 16–23 °C) but declined at warmer temperatures (average temperature exposure: 24.5–26 °C). Predators consistently lowered prey abundances and average prey mass increased when predators were added. Top-down control was the greatest at intermediate temperatures (indicated by Log Response Ratio) when temperatures were near or below the thermal optimum for both species. Temperature-related prey declines negated top-down control under the warmest conditions suggesting that mismatches in thermal performance between predators and their prey will alter the strength and dominance of top-down or bottom-up forces of predator–prey interactions in a warmer world.

Climate warming can destabilize interactions between competitors as smaller organisms gain advantages in warmer environments. Whether and how warming-induced effects on competitive interactions are modified by predation remains unknown. We hypothesized that predation will offset the competitive advantage of smaller prey species in warmer environments because of their greater vulnerability to predation. To test this, we assembled a litter arthropod community with two Collembola species (Folsomia candida and Proisotoma minuta) of different body sizes across a temperature gradient (three thermal environments) and in the presence and absence of predatory mites. Predatory mites reduced Collembola coexistence with increasing temperatures. Contradicting our hypothesis, the larger prey species always outperformed the smaller prey species in warmer environments with predators. Larger prey probably benefited as they expressed a greater trait (body length) plasticity to warming. Warming can thus magnify predation effects and reduce the probability of prey coexistence.

Folsomia candida (Collembola: Isotomidae) is one of the most important indicator species for soil animal studies and is widely distributed worldwide. Here, we utilized PacBio HiFi long reads, Oxford Nanopore Technologies (ONT) ultralong reads, Hi-C, Illumina short reads, and ONT long-read transcriptome sequencing to assemble and annotate the genome of Folsomia candida . Two gapless, telomere-to-telomere, haplotype-resolved genomes (HapA and HapB) were successfully assembled, with genome sizes of 228.62 and 228.45 Mb, respectively. The scaffold N50 sizes are 41.45 Mb for both haplotypes. We manually curated and annotated each gene on HapA, providing comprehensive annotation information for this haplotype. Gene annotation revealed a total of 26,329 protein-coding genes in HapA and 26,768 in HapB. These haplotype-resolved Folsomia candida genomes provide a high-quality genomic resource that enables future studies on soil arthropods and springtail genomics.

RNA viruses of the genera Ambivirus, Mitovirus, Sclerotimonavirus, and Partitivirus were found in a single isolate of Fusarium graminearum. The genomes of the mitovirus, sclerotimonavirus, and partitivirus were assigned to previously described viruses, whereas the ambivirus genome putatively represents a new species, named Fusarium graminearum ambivirus 1 (FgAV1). To investigate the effect of mycoviruses on the fungal phenotype, the spontaneous loss of mycoviruses during meiosis and the transmission of mycoviruses into a new strain via anastomosis were used to obtain isogenic F. graminearum strains both with and without mycoviruses. Notable effects observed in mycovirus-harboring strains were (i) the suppression of the synthesis of trichothecene mycotoxins and their precursor trichodiene, (ii) the suppression of the synthesis of the defense compound aurofusarin, (iii) the stimulation of the emission of 2-methyl-1-butanol and 3-methyl-1-butanol, and (iv) the increased attractiveness of fungal mycelia for fungivorous collembolans. The increased attractiveness of mycovirus-infected filamentous fungi to animal predators opens new perspectives on the ecological implications of the infection of fungi with viruses.