Biology subjects

Moreira, X.

Publications and source records attributed to Moreira, X..

5 recordsLinked to original sources

bioRxiv2025

From leaves to defenders: how amount and dispersion of leaf damage affect extrafloral nectar production and ant-mediated protection in wild cotton (Gossypium hirsutum)

O_LIExtrafloral nectar (EFN) drives mutualistic interactions between plants and ants. However, EFN production is costly, and its induction is predicted to vary with herbivore-related factors. We examine how the amount and within-plant damage spatial uniformity (i.e., dispersed and concentrated damage) affect EFN production and ant-mediated defence in wild cotton (Gossypium hirsutum). Previous work suggests that severe and concentrated damage is costliest to plants, leading us to hypothesise that such damage would induce greater EFN production and, consequently, stronger ant attraction and protection. C_LIO_LIWe conducted a greenhouse experiment in which plants were subjected to one of the following mechanical damage treatments: control (no damage), low damage (two damaged leaves, 30% of area removed each), high concentrated damage (two damaged leaves, 60% each), and high dispersed damage (four damaged leaves, 30% each; i.e., same total area than concentrated damage). The day after treatments, we measured EFN volume and sugar content from one nectary per plant (a per-nectary EFN response), and the number of secreting nectaries per plant (a proxy for whole-plant level EFN response). Subsequently, we performed a field experiment using the same treatments to evaluate EFN-mediated ant recruitment and ant-provided protection by placing caterpillars on plants. C_LIO_LIBoth high-damage treatments increased EFN volume per nectary, whereas low damage did not. However, against our prediction, dispersed damage was the only treatment that increased the number of secreting nectaries. Consistently, once placed in the field, plants with dispersed damage recruited more ants and caterpillars on them were more likely to be attacked by ants. C_LIO_LIContrary to expectations, plants subjected to dispersed damage exhibited a greater total investment in EFN, presumably via local induction of more nectaries per plant, and thereby enhancing ant-mediated defence. This study highlights the importance of herbivory intensity and within-plant spatial uniformity in shaping ant-plant interactions. C_LI

ecology↗

bioRxiv2025

Effects of variability in the amount and dispersion of within-plant herbivory on resistance- and tolerance-related responses in wild cotton

Herbivory triggers complex induced defensive responses in plants that may vary depending on the amount and dispersion of damage, the latter has received much less attention. We examined how wild cotton (Gossypium hirsutum) responds to different amounts of herbivory and how it is dispersed among the leaves (concentrated versus dispersed) using the specialist caterpillar Alabama argillacea. In a greenhouse experiment, plants underwent different herbivory treatments: no damage, low herbivory (two caterpillars, one on each of two leaves), high concentrated herbivory (four caterpillars, two on each of two leaves), and high dispersed herbivory (four caterpillars, each on one of four leaves). We measured extrafloral nectar (EFN), an indirect defense trait, and phenolic production, a direct chemical defense, as well as regrowth capacity (new leaf biomass two months after herbivory) as a tolerance proxy. To distinguish between local and systemic defense induction, we measured resistance-related responses on damaged and undamaged leaves. EFN was significantly and more consistently induced in damaged leaves (i.e., stronger local induction) in response to high dispersed damage. Phenolic compounds were not affected by any of the damage treatments. Additionally, wild cotton fully compensated for damage in terms of new leaf biomass under all herbivory treatments, except after high concentrated damage, suggesting higher costs incurred by this type of herbivory. These results highlight the importance of studying plant-induced defenses under varying herbivory conditions and suggest opposing effects on resistance-related (EFN, indirect) versus tolerance-related induced responses, which are known to affect tri-trophic interactions associated with wild cotton. Main ConclusionVariability in caterpillar damage to wild cotton leaves differentially shapes resistance- and tolerance-related responses; dispersed damage induces more extrafloral nectar production, and concentrated damage more strongly drives reductions in regrowth.

ecology↗

bioRxiv2020

Search for top-down and bottom-up drivers of latitudinal trends in insect herbivory in oak trees in Europe

AimThe strength of species interactions is traditionally expected to become stronger toward the Equator. However, recent studies have reported opposite or inconsistent latitudinal trends in the bottom-up (plant quality) and top-down (natural enemies) forces driving insect herbivory, possibly because these forces have rarely been studied concomitantly. This makes previous attempts to understand the effect of large scale climatic gradients on insect herbivory unsuccessful. LocationEurope Time period2018-2019 Major taxa studiedQuercus robur MethodsWe used scholar-based citizen science to simultaneously test for latitudinal variation in plant-herbivore-natural enemy interactions. We further investigated the underlying climatic factors associated with variation in herbivory, leaf chemistry and attack rates in Quercus robur across its complete latitudinal range in Europe. We quantified insect herbivory and the occurrence of specialist herbivores as well as leaf chemistry and bird attack rates on dummy caterpillars on 261 oak trees. ResultsClimatic factors rather than latitude per se were the best predictors of the large-scale (geographical) variation in the incidence of gall-inducers and leaf-miners as well as of leaf nutritional quality. However, insect herbivory, plant chemical defences (leaf phenolics) and bird attack rates were not influenced by latitude or climatic factors. The incidence of leaf-miners increased with increasing concentrations of hydrolysable tannins and decreased with those of condensed tannins, whereas the incidence of gall-inducers increased with increasing leaf soluble sugar concentration and decreased with increasing leaf C:N ratios. However, neither other traits nor bird attack rates varied with insect herbivory. Main conclusionsThese findings help to refine our understanding of the bottom-up and top-down mechanisms driving geographical variation in plant-herbivore interactions, and urge for further examination of the drivers of insect herbivory on trees.

ecology↗

bioRxiv2019

Leaf chemical defences and insect herbivory in oak: accounting for canopy position unravels marked genetic relatedness effects

Background and AimsHighly controlled experiments revealed that plant genetic diversity and relatedness can shape herbivore communities and patterns of herbivory. Evidence from the field is scarce and inconsistent. We assessed whether a genetic signal underlying herbivory can be detected in oak forest stands when accounting for variation at smaller (within-tree) and larger (among-stand) scales. MethodsWe tested relationships between tree genetic relatedness, leaf chemical defences and insect herbivory at different canopy layers in 240 trees from 15 Pedunculate oak (Quercus robur) forest stands and partitioned sources of variability in herbivory and defences among stands, individuals, and branches. Key ResultsLeaf defences, insect herbivory, and their relationship differed systematically between the upper and the lower tree canopy. When accounting for this canopy effect, the variation explained by tree genetic relatedness rose from 2.8 to 34.1 % for herbivory and from 7.1 to 13.8 % for leaf defences. The effect was driven by markedly stronger relationships in the upper canopy. ConclusionsOur findings illustrate that properly accounting for other sources of variation acting at different scales can reveal potentially relevant effects of the host plant genotype on patterns of leaf chemical defences and associated insect herbivory in natural tree populations.

ecology↗

bioRxiv2019

Growth and mortality of the oak processionary moth, Thaumetopoea processionea L., on two oak species: direct and trait-mediated effects of host and neighbour species identity

The presence of heterospecific neighbours can affect damage caused by pest insects on focal plants. However, how plant neighbours influence herbivore performance is poorly understood. We tested the independent and interactive effects of tree species identity and tree neighbour type (conspecific vs. heterospecific) on the performance of a major oak pest, the oak processionary moth larvae (OPM, Thaumetopoea processionea) fed on Quercus robur and Q. petraea. We performed a factorial greenhouse experiment in which we grew two oak saplings per pot, either from the same species or from both species. We quantified growth and mortality of OPM larvae, leaf phenolic compounds, C:N ratio and bud phenology. OPM larvae performed significantly better on Q. petraea than on Q. robur, regardless of plant neighbour type. Phenolic compounds and C:N, but not phenology, differed between oak species and neighbour species identity. Only bud phenology had a significant effect on OPM performance, which was better when young larvae had access to recently unfolded leaves, regardless of oak species and neighbour identity. Although oak neighbour identity altered the expression of leaf traits, this effect had no measurable consequences on OPM performance. However, further studies should consider the effect of oak species neighbour on OPM preferences for either Q. robur or Q. petraea, in pure and mixed stands, before translating current results into recommendations for forest management. Author ContributionTD and BC conceived the study and acquired the data. TD performed experiment and analysed the data. EV, TD and XM performed the chemical analyses. TD and BC drafted the first version of the manuscript and all authors wrote the final version of the manuscript. TD, BC conceived and designed research. TD performed experiment and analysed data. EV, TD, XM performed the chemical analyses. TD, BC wrote the manuscript. All authors read and approved the manuscript. AM and DB conceived and designed research. AM and BB conducted experiments. GR contributed new reagents or analytical tools. AM, BB and GR analysed data. AM wrote the manuscript. All authors read and approved the manuscript.

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