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• Herbivore population dynamics are strongly influenced by the interactions established through their shared host. Such plant-mediated interactions can occur between different herbivore species and different life developmental stages of the same herbivore. However, whether these interactions occur between leaf-feeding herbivores and their soil-dwelling pupae is unknown. • We studied whether tomato (Solanum lycopersicum) leaf herbivory by the American serpentine leafminer Liriomyza trifolii affects the performance of conspecific pupae exposed to the soil headspace of the plant. To gain mechanistic insights, we performed insect bioassays with the jasmonate-deficient tomato mutant def-1 and its wild-type, along with phytohormones, gene expression and root volatiles analyses. • Belowground volatiles accelerated leafminer metamorphosis when wild-type plants were attacked aboveground by conspecifics. The opposite pattern was observed for def-1 plants, in which aboveground herbivory slowed metamorphosis. Leafminer attack induced jasmonate and abscisic acid accumulation and modulated volatile production in tomato roots in a def-1-dependent manner. • Our results demonstrate that aboveground herbivory triggers changes in root defence signalling and expression, which can directly or indirectly via changes in soil or microbial volatiles, alter pupal development time. This finding expands the repertoire of plant–herbivore interactions to herbivory-induced modulation of metamorphosis, with potential consequences for plant and herbivore community dynamics.

• Insect herbivore damage and abundance are often reduced in diverse plant stands. However, few studies have explored whether this phenomenon is a result of plant diversity effects on host plant traits. • We explored indirect effects of tree species diversity on herbivory via changes in leaf traits in a long-term forest diversity experiment in Finland. We measured 16 leaf traits and leaf damage by four insect guilds (chewers, gall formers, leaf miners and rollers) on silver birch (Betula pendula) trees growing in one-, two-, three- and five-species mixtures. • A decline in the frequency of birch in mixed stands resulted in reduced leaf area. This, in turn, mediated the reduction in chewing damage in mixed stands. In contrast, associational resistance of birch to leaf miners was not trait-mediated but driven directly by concurrent declines in birch frequency as tree species richness increased. • Our results show that leaf trait variation across the diversity gradient might promote associational resistance, but these patterns are driven by an increase in the relative abundance of heterospecifics rather than by tree species richness per se. Therefore, accounting for concurrent changes in stand structure and key foliar traits is important for the interpretation of plant diversity effects and predictions of associational patterns.

Climate change may alter the dynamics of outbreak species by changing the phenological synchrony between herbivores and their host plants. As host plant phenology has a genotypic component that may interact with climate, infestation levels among genotypes might change accordingly. When the outbreaking herbivore is active early in the season, its infestation levels may also leave a detectable imprint on herbivores colonizing the plant later in the season. In this study, we first investigated how the spring phenology and genotype of Quercus robur influenced the density of the spring‐active, outbreaking leaf miner Acrocercops brongniardellus. We then assessed how intraspecific density affected the performance of A. brongniardellus and how oak genotype and density of A. brongniardellus affected the insect herbivore community. We found that Q. robur individuals of late spring phenology were more strongly infested by A. brongniardellus. Conspecific pupae on heavily infested oaks tended to be lighter, and fewer heterospecific insect herbivores colonized the oak later in the season. Beyond its effects through phenology, plant genotype left an imprint on herbivore species richness and on two insect herbivores. Our results suggest a chain of knock‐on effects from plant phenology, through the outbreaking species to the insect herbivore community. Given the finding of how phenological synchrony between the outbreak species and its host plant influences infestation levels, a shift in synchrony may then change outbreak dynamics and cause cascading effects on the insect community. This study demonstrates how phenological synchrony between a leaf mining, outbreaking herbivore and its host plant influences outbreak densities, the performance of the herbivore itself and the presence of other insect herbivores.

Identification of the geographic origin of invasive species can be critical to effective management and amelioration of negative impacts in the introduced range. Liriomyza huidobrensis is a polyphagous leafmining fly that is a devastating pest of many vegetable and floriculture crops around the world. Considered native to South and possibly Central America, L. huidobrensis became invasive in the 1980s and has since spread to at least 30 countries on five continents. We used phylogeographic analysis of over 2 kb of mitochondrial cytochrome oxidase I and II sequence data from 403 field‐collected specimens from both native and introduced populations to investigate the geographic origins of invasive L. huidobrensis worldwide. Within South America, there was substantial genetic variation, as well as the strong phylogeographic structure typical of a native range. In contrast, leafminers from the introduced range and Central America all contained little genetic variation and shared the same small set of haplotypes. These haplotypes trace to Peru as the ultimate geographic origin of invasive populations. Central America is rejected as part of the original geographic range of L. huidobrensis. Within Peru, the primary export region of Lima shared an extremely similar pattern of reduced haplotype variation to the invasive populations. An additional 18 specimens collected at US ports of entry did not share the same haplotype profile as contemporary invasive populations, raising perplexing questions on global pathways and establishment success in this species.

1. Tree health declines can be caused by interactions between pests and pathogens and many studies have shown a reduction in their damage in mixed species forests compared to monocultures. Yet few authors have considered tree diversity effects on both groups simultaneously. Moreover, it is unclear whether diversity effects on tree pests and pathogens are robust to changes in abiotic conditions, such as drought. 2. We addressed tree diversity effects on foliar insect herbivory, oak powdery mildew and their interaction under contrasting water regimes in a large-scale tree diversity experiment in SW France. Using an irrigation treatment that alleviated drought conditions, we were able to experimentally assess the effects of tree diversity under contrasting abiotic environments. We surveyed plots along a richness gradient from one to four tree species, in which a focal study species of oak (Quercus robur) was mixed with other oak species (Q. pyrenaica and Q. ilex) and a taller, broadleaved species (Betula pendula). 3. Increasing tree species richness lowered leaf miner abundance, leaf chewer damage and oak powdery mildew infection, consistent with a protective effect of resource dilution. However, richness effects on leaf miners were stronger in irrigated compared to non-irrigated blocks, indicating that environmental conditions can modulate diversity effects. Separate from the effect of tree species richness, the presence of birch in a plot increased damage by leaf chewers and powdery mildew , but lowered leaf miner damage, suggesting additional tree neighbour identity effects potentially linked to modulation of microclimate. We found a negative association between leaf miner abundance and oak powdery mildew, consistent with antagonism between oak damage agents. 4. Synthesis. Overall, our study illustrates the importance of considering both tree diversity and composition (neighbour identity) in designing forests more resistant to pest and pathogen damage.

ABSTRACT There are few literature publications on the species of Cerodontha Rondani, 1861 that occur in Brazil. This contrasts with the situation in the Nearctic region and Europe, where the genus is well-studied. We analyzed specimens of Cerodontha from two important collections in Brazil: Instituto Nacional de Pesquisas da Amazônia and Museu Nacional, Universidade Federal do Rio de Janeiro. As a result, we found and describe two new species: Cerodontha (Poemyza) teresopoliensis sp. nov. and Cerodontha (Poemyza) rafaelii sp. nov., that both can be recognized for some specific character, as the darker body coloration and form of the male genitalia. We also provide new records and additional characters to diagnosis for the Cerodontha (Butomomyza) orcina Spencer, 1973 and Cerodontha (Butomomyza) obscurata Martinez, 1992. The descriptions are illustrated with images of the external morphology of the adult and male genitalia. A key to the Brazilian species of the subgenera Butomomyza and Poemyza are also provided.

1- Herbivore regulation is one of the services provided by plant diversity in terrestrial ecosystems. It has been suggested that tree diversity decreases insect herbivory in forests, but recent studies have reported opposite patterns, indicating that tree diversity can trigger associational resistance or susceptibility. The mechanisms underlying the tree diversity–resistance relationship thus remain a matter of debate. 2- We assessed insect herbivory on pedunculate oak saplings (Quercus robur) in a large-scale experiment in which we manipulated tree diversity and identity by mixing oaks, birch and pine species. 3- Tree diversity at the plot scale had no effect on damage due to leaf chewers, but abundance of leaf miners decreased with increasing tree diversity. The magnitude of this associational resistance increased with host dilution, consistent with the ‘resource concentration hypothesis’. 4- At a smaller scale, we estimated tree apparency as the difference in total height between focal oak saplings and their nearest neighbouring trees. Levels of oak infestation with leaf miners decreased significantly with decreasing tree apparency. As the probability of having taller neighbours increased with tree diversity, notably due to the increase in the proportion of faster growing nonhost trees, such as birches and pines, tree apparency may be seen as a ‘hidden’, sampling effect of tree diversity. 5- Synthesis. These findings suggest that greater host dilution and lower tree apparency contribute to associational resistance in young trees. They also highlight the importance of taking plant size into account as a covariate, to avoid misleading interpretations about the biodiversity–resistance relationship.

The genetic diversity of Coffea canephora Pierre ex A. Froehner present in old seminal crops must be characterized because it represents a source of genetic variability for breeding programs. In this study, the genetic diversity of 388 half‐sib families of C. canephora, collected from Espírito Santo, Brazil, were assessed for their phenotypic traits. The data were obtained in a trial planted in April 2018 with five commercial clones as controls. Vegetative development was evaluated based on plant height, stem diameter, and average height and diameter growth rates. Abiotic (drought) and biotic (rust, leaf miner, and mealybug) stresses were evaluated by a rating scale. The phenotypic variability of the population was detected for all traits, and divergent clusters of families were identified. Negative correlations indicated that adverse conditions hampered the early development of the coffee plants. Groups of families should be investigated for breeding programs according to adequate development even under stressful conditions. These results show the importance of preserving the germplasm of old crops in the south of Espírito Santo as a source of genetic resources for coffee breeding programs. This valuable resource should be maintained and conserved as a strategy to guarantee the sustainability of coffee production. Core Ideas This is a groundbreaking study of half‐sib families from old seminal crops. Old seminal matrices are valuable sources of Coffea canephora genetic resources. The characterization, study, and preservation of old seminal matricies are fundamental for breeding of coffee. Divergent families were identified with adequate initial vegetative development.

Density- and trait-mediated indirect interactions (DMIIs and TMIIs respectively) are important drivers of community dynamics but how plant nutrients (bottom-up effects) affect the magnitude of such indirect interactions has been scarcely addressed. To assess the impact of bottom-up forces on indirect interactions, we carried out laboratory and greenhouse experiments manipulating plant nutrient supplies in a four-species diamond food web consisting of a plant (tomato), two phytophagous insects (a leafminer and an aphid) and a predator (a mirid bug) attacking both herbivores. Multiple negative indirect effects of the leafminer occurred towards the aphid. The presence of its eggs negatively affected aphid population growth through increased predator abundance (DMIIs), and larval herbivory slowed down aphid development and negatively modulated aphid behaviours, for example they spent less time feeding (TMIIs), likely owing to enhanced plant chemical defences and/or decreased plant nutritional quality. Moreover, the low plant nutrient supply further magnified TMIIs. Synthesis. Abiotic factors modulated predator- and plant-mediated indirect interactions among herbivorous community members. Our study highlights the importance of using a holistic approach, from foliar chemistry to community dynamics, for disentangling interspecific interactions in a simple food web.

Main conclusionDissimilar patterns of variants affecting genes involved in response to herbivory, including those leading to difference in VOC production, were identified in tomato lines with contrasting response to Tuta absoluta. Tuta absoluta is one of the most destructive insect pest affecting tomato production, causing important yield losses both in open field and greenhouse. The selection of tolerant varieties to T. absoluta is one of the sustainable approaches to control this invasive leafminer. In this study, the genomic diversity of two tomato varieties, one tolerant and the other susceptible to T. absoluta infestation was explored, allowing us to identify chromosome regions with highly dissimilar pattern. Genes affected by potential functional variants were involved in several processes, including response to herbivory and secondary metabolism. A metabolic analysis for volatile organic compounds (VOCs) was also performed, highlighting a difference in several classes of chemicals in the two genotypes. Taken together, these findings can aid tomato breeding programs aiming to develop tolerant plants to T. absoluta.