Abstract:Insect herbivory decreases plant fitness by constraining plant growth, survival and reproductive output. Most studies on the effects of herbivory in trees rely on correlational inter-individual comparisons and could, thus, be affected by confounding factors linked to both herbivory and plant performance. Using the Mediterranean Holm oak (Quercus ilex) as a study model, we followed an experimental approach in which leaf-feeding insects (mainly Lepidoptera caterpillars) were excluded from some shoots in all stud… Show more
“…In support of this hypothesis, in one past study, Quercus lobata individuals with earlier budburst suffered more leaf damage, which reduced their seed production (Pearse et al, 2015a). Past experiments in our study system indicated that insect herbivory can decrease Q. ilex seed set by half (Canelo et al, 2018). Early trees gain the advantage of reduced pollen limitation, but may suffer reduced seed set due to other factors, such as herbivory.…”
Section: Discussionsupporting
confidence: 79%
“…Past experiments in our study system indicated that insect herbivory can decrease Q . ilex seed set by half (Canelo et al ., 2018). Early trees gain the advantage of reduced pollen limitation, but may suffer reduced seed set due to other factors, such as herbivory.…”
Synchronised and quasi‐periodic production of seeds by plant populations, known as masting, is implicated in many ecological processes, but how it arises remains poorly understood. Flowering and pollination dynamics are hypothesised to provide the mechanistic link for the observed relationship between weather and population‐level seed production. We report the first experimental test of the phenological synchrony hypotheses as a driver of pollen limitation in mast seeding oaks (Quercus ilex). Higher flowering synchrony yielded greater pollination efficiency, which resulted in 2‐fold greater seed set in highly synchronised oaks compared to asynchronous individuals. Pollen addition removed the negative effect of asynchronous flowering on seed set. Because phenological synchrony operates through environmental variation, this result suggests that oak masting is synchronised by exogenous rather than endogenous factors. It also points to a mechanism by which changes in flowering phenology can affect plant reproduction of mast‐seeding plants, with subsequent implications for community dynamics.
“…In support of this hypothesis, in one past study, Quercus lobata individuals with earlier budburst suffered more leaf damage, which reduced their seed production (Pearse et al, 2015a). Past experiments in our study system indicated that insect herbivory can decrease Q. ilex seed set by half (Canelo et al, 2018). Early trees gain the advantage of reduced pollen limitation, but may suffer reduced seed set due to other factors, such as herbivory.…”
Section: Discussionsupporting
confidence: 79%
“…Past experiments in our study system indicated that insect herbivory can decrease Q . ilex seed set by half (Canelo et al ., 2018). Early trees gain the advantage of reduced pollen limitation, but may suffer reduced seed set due to other factors, such as herbivory.…”
Synchronised and quasi‐periodic production of seeds by plant populations, known as masting, is implicated in many ecological processes, but how it arises remains poorly understood. Flowering and pollination dynamics are hypothesised to provide the mechanistic link for the observed relationship between weather and population‐level seed production. We report the first experimental test of the phenological synchrony hypotheses as a driver of pollen limitation in mast seeding oaks (Quercus ilex). Higher flowering synchrony yielded greater pollination efficiency, which resulted in 2‐fold greater seed set in highly synchronised oaks compared to asynchronous individuals. Pollen addition removed the negative effect of asynchronous flowering on seed set. Because phenological synchrony operates through environmental variation, this result suggests that oak masting is synchronised by exogenous rather than endogenous factors. It also points to a mechanism by which changes in flowering phenology can affect plant reproduction of mast‐seeding plants, with subsequent implications for community dynamics.
“…They found that the strength of this scatterhoarder-tree mutualism is strongest for red oaks (Q. rubra), weakest for white oaks (Q. alba) and intermediate for chestnut oak (Castanea dentata) and hybrid chestnut (C. dentata x Castanea mollissima). Canelo et al (2018) employ a careful experimental approach to quantify the effects of herbivory by a leaf-feeding insect on the Mediterranean Holm oak's (Q. ilex) physiological responses in individual shoots that ultimately results in a drop in acorn production. Unlike other correlational studies, this study demonstrated the causal physiological links between herbivory and reproductive loss.…”
“…Most defoliation and herbivore exclusion experiments on temperate forest trees and fruit trees have shown a negative effect of defoliation on fruit set (Mehouachi et al 1995;Obeso 1998;Iglesias et al 2003;Frioni et al 2018) and on fruit size (Obeso 1998;Hoch 2005;Matsumoto et al 2017). In oaks, most studies concerned natural herbivory and showed also negative impact on fruit set and total fruit production (Crawley 1985;May and Killingbeck 1995;Hochwender et al 2003;Pearse et al 2015;Nakajima 2015;Canelo et al 2018). However, other studies have found no effect of herbivory on fruit set, fruit size or yield in other species (Obeso and Grubb 1993;Mehouachi et al 1995;Tamura and Hiura 1998;Ezzahouani and Williams 2003;Bañuelos and Obeso 2005;Frioni et al 2018;Pasqualotto et al 2019).…”
Background and Aims
In plants, high costs of reproduction during some years can induce trade-offs in resource allocation with other functions such as growth, survival and resistance against herbivores or extreme abiotic conditions, but also with subsequent reproduction. Such trade-offs might also occur following resource shortage at particular moments of the reproductive cycle. Because plants are modular organisms, resource allocation strategies to reproduction can also vary among hierarchical levels. Using a defoliation experiment, our aim was to test how allocation to reproduction was impacted by resource limitation.
Methods
We applied three levels of defoliation (control, moderate and intense) to branches of eight Quercus ilex trees shortly after fruit initiation and measured the effects of resource limitation induced by leaf removal on fruit development (survival, growth, and germination potential), and on the production of vegetative and reproductive organs the year following defoliation.
Key Results
We found that defoliation had little impact on fruit development. Fruit survival was not affected by the intense defoliation treatment, but reduced by moderate defoliation, and this result could not be explained by an upregulation of photosynthesis. Mature fruit mass was not affected by defoliation, nor was seed germination success. However, in the following spring, defoliated branches produced less shoots and compensated leaf loss by overproducing leaves at the expense of flowers. Therefore, resource shortage decreased resource allocation to reproduction the following season but did not affect sex ratio.
Conclusions
Our results support the idea of a regulation of resource allocation to reproduction beyond the shoot scale. Defoliation had larger legacy effects than immediate effects.
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