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Introduction: The enemy hypothesis postulates that gall traits protect galling insects against natural enemies. Galls show a huge range of sizes, colors and ornaments, which vary even intraspecifically. However, galling insects are targets of various organisms that attack them directly or indirectly. In this context, to consider only one gall trait to investigate gall structure acting against only one guild of enemies can conceal an understanding of the community-level interactions. Objective: Herein, we take these ideas into consideration to investigate the conspicuous galls induced by Palaeomystella oligophaga Becker and Adamski 2008 (Lepidoptera) on Macairea radula (Bonpl.) (Melastomataceae) as a model system. We characterize this system through categorization of the different enemy guilds present in the community. We identified them to the lowest taxonomic level possible and determined the kind of interaction responsible for galling insects’ deaths. Considering the enemy hypothesis and the selection of secondary characteristics, we also aimed to determine which of the multiple gall traits influence the survival success of galling insects in a multi-enemy context. Methods: We inspected galls and characterized the enemy guilds affecting the galling insect and the mortality rates produced by each one of them. Next, we tested whether the distinct gall traits measured (parenchyma thickness, color, projections) promote galling insect survival with respect to each enemy. Results: The mortality induced by indirect enemies (organisms that interact with gall tissues and can interact secondarily with galling insect) was 47.3 %, being higher than that caused by parasitoids and predators (31.5 %). Despite the gall’s structural complexity, live galling insects showed the smallest occurrence (21.2 %). Parenchyma thickness was negatively related to Calliephialtes parasitoids, Gelechiidae cecidophages and predation signals. Conclusions: We demonstrated that the attacks to gall tissues by the cecidophages represented the highest threat to P. oligophaga survival, being higher than the mortality caused by direct enemies. That is, the gall traits were not as efficient as supposed to protect the galling insect from the attack of natural enemies. Nevertheless, we also demonstrated that parenchyma thickness can be negatively related to some organisms, especially direct enemies. Other traits hypothesized as defensive (e.g. projections, coloration) may simply play no role.
Introduction: The enemy hypothesis postulates that gall traits protect galling insects against natural enemies. Galls show a huge range of sizes, colors and ornaments, which vary even intraspecifically. However, galling insects are targets of various organisms that attack them directly or indirectly. In this context, to consider only one gall trait to investigate gall structure acting against only one guild of enemies can conceal an understanding of the community-level interactions. Objective: Herein, we take these ideas into consideration to investigate the conspicuous galls induced by Palaeomystella oligophaga Becker and Adamski 2008 (Lepidoptera) on Macairea radula (Bonpl.) (Melastomataceae) as a model system. We characterize this system through categorization of the different enemy guilds present in the community. We identified them to the lowest taxonomic level possible and determined the kind of interaction responsible for galling insects’ deaths. Considering the enemy hypothesis and the selection of secondary characteristics, we also aimed to determine which of the multiple gall traits influence the survival success of galling insects in a multi-enemy context. Methods: We inspected galls and characterized the enemy guilds affecting the galling insect and the mortality rates produced by each one of them. Next, we tested whether the distinct gall traits measured (parenchyma thickness, color, projections) promote galling insect survival with respect to each enemy. Results: The mortality induced by indirect enemies (organisms that interact with gall tissues and can interact secondarily with galling insect) was 47.3 %, being higher than that caused by parasitoids and predators (31.5 %). Despite the gall’s structural complexity, live galling insects showed the smallest occurrence (21.2 %). Parenchyma thickness was negatively related to Calliephialtes parasitoids, Gelechiidae cecidophages and predation signals. Conclusions: We demonstrated that the attacks to gall tissues by the cecidophages represented the highest threat to P. oligophaga survival, being higher than the mortality caused by direct enemies. That is, the gall traits were not as efficient as supposed to protect the galling insect from the attack of natural enemies. Nevertheless, we also demonstrated that parenchyma thickness can be negatively related to some organisms, especially direct enemies. Other traits hypothesized as defensive (e.g. projections, coloration) may simply play no role.
A B S T R A C TGalls are characterized by inducing cellular differentiation (hyperplasia or hypertrophy) resultant of the action of some organisms, mainly insects, on structures/organs of their host plants. The galls cause physiological changes in host plants, altering host traits, and their growth and survival. The early abscission of galled plant organs can be a form of plant defense. Therefore, the galls decayed more slowly than the healthy leaves, or the surrounding healthy leaf tissue in some abscised galled leaves, forming "green island galls". This study reported an instance where the host plant Miconia cinnamomifolia (Melastomataceae) abscises leaves galled by an unidentified coleopteran's gall on the soil of a fragment of Atlantic Forests, Brazil. Once on the forest soil galls were exposed to a new set of potential natural enemies, as pathogens and predators. Consequently, larval survival decrease of 79% to 36% in four months and fungal infestation increase of 2% to 21%. Neither size nor the weight of the galls differed between categories of mortality factors and larval survival. It was discussed the adaptive nature of the "Green Island Effect" as a counter-response of gallers to leaf abscission, which is a known plant defense strategy. Keywords: Atlantic Forest, beetle, Coleoptera, gall-inducing insects, insect gall, insect-plant interactions, natural enemies. IntroductionGalls are produced by induced cellular hypertrophy and/or hyperplasia on plant meristematic tissues, and result in the formation of symmetrical structures on one or more organs (see Raman et al., 2005;Fernandes & Santos, 2014). Because a galling inducer's development depends strictly on gall's tissues, the effects of galls on their host plants might continue while the gall's metabolism is active (Fay et al., 1996). Galling inducers manipulate their host plant's physiology by channeling nutrients into the gall tissues (e.g. Price et al., 1987;Hartley & Lawton, 1992;Florentine et al., 2005). Therefore, galled leaves, even when they are matured, may behave as a sink organ rather than a source of nutrients for the plant. That redirection of resources can be so strong that may lead galls to work against not only healthy organs but also even all others galled organs on the same plant (Sacchi et al., 1988; Larson & Whitham, 1997). In many cases, the negative effect of galls on their host plant is so intense that these herbivores are used as biological control agents of invasive plant species (e.g. Dennill, 1985;Harris & Shorthouse, 1996;Raman & Dhileepan, 1999, Badenes-Perez & Johnson, 2007.Having nutrients lost heavily by galls, and not invested in development and growth, made plants to evolve through time some mechanisms to protect themselves against gall induction Journal of Environmental Analysis and Progress V. 02 N. 01 (2017) Fernandes, 1988;Fernandes, 1990;Fernandes & Negreiros, 2001). One of these mechanisms consists of prematurely abscising galled leaves to protect the host plant against a high-intensity herbivory (Craig et al.,...
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