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Exploring the role of vibrational cues in a parasitoid-host interaction
No full textThe green peach aphid, Myzus persicae Sulzer (Aphididae, Hemiptera), is a major agricultural pest worldwide, and an efficient vector of several plant viruses, whose control still majorly relies on pesticides. However, the need to reduce pesticide use, given their side effects on non-target organisms and human health, and their inefficacy for containing the spread of aphid-borne viruses, call for research on alternative tools for pest control, such as biological control. Aphidius colemani Viereck (Braconidae, Hymenoptera) is a parasitoid that is commonly used as a biological control agent of M. persicae, but little is known about the behavioral interaction with its host.
The potentiality of Biotremology for pest control has already been highlighted by several studies. However, the role of substrate-borne vibrations in inter- and intra-specific communication in some insect taxa, including aphids and parasitoids, has never been addressed, and further studies may pave the way for the sustainable control of species currently representing major threats for food safety and security.
Therefore, the aim of this study is to characterize the role of substrate-borne vibrations in: i) the inter-specific communication between M. persicae and its parasitoid A. colemani; ii) the intra-specific communication between an “attacked” aphid and its conspecifics. Thereafter, the impact of previously recorded vibrational cues or signals on the aphid feeding behavior will be assessed using the Electrical Penetration Graph (EPG) technique, with a particular focus on the patterns conducive to viruses’ acquisition and inoculation.
Two are the major outcomes expected from the present study: i) insights into the role of substrate-borne vibrations in aphids intra-specific communication and parasitoid foraging behavior; ii) a proof of concept of the applicability of semiophysicals as an alternative to pesticides for aphids and aphid-borne viruses control
The Effect of the Sterile Insect Technique on Vibrational Communication: the case of Bagrada hilaris (Hemiptera: Pentatomidae)
No full textThe painted bug, Bagrada hilaris, is an agricultural pest in its original areas (Africa, South Asia, and the Middle East), and it has recently been recorded as an invasive species in southwestern part of the US, Chile, Mexico, and two islands in the Mediterranean basin. Its polyphagous diet causes severe damage to economically important crops. The control of this pest is primarily achieved by means of synthetic pesticides, which are often expensive, ineffective, and harmful to the ecosystem. Recent physiological bioassays to assess its potential control through the sterile insect technique demonstrated that mating between untreated females and males irradiated at doses of 64 and 100 Gy, respectively, resulted in 90% and 100% sterility of the eggs produced by the females. In this study, the mating abilities of virgin males irradiated at 60 and 100 Gy with virgin females were measured through a study of short-range courtship mediated by vibrational communication. The results indicate that males irradiated at 100 Gy emit signals with lower peak frequencies, mate significantly less than unirradiated males do, and do not surpass the early stages of courtship. Conversely, males irradiated at 60 Gy present vibrational signal frequencies that are comparable to those of the control and successfully mated males. Our findings suggest that B. hilaris individuals irradiated at 60 Gy are good candidates for the control of this species, given that they retain sexual competitiveness regardless of their sterility, through an area-wide program that incorporates the sterile insect technique
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Insect vibrational communication: description, decoding, and manipulation
Full text linkVibrations are extremely widespread and ancient among animals’ communication modalities; nevertheless, their importance has been neglected for many years. During my PhD I wanted to increase the knowledge about the role of vibrational signals in insects. Therefore, I conducted behavioral bioassays and laser vibrometer recordings to describe and decipher vibrations produced by four species belonging to two different orders. The role of vibrational signals in intraspecific communication varies widely among different groups of insects. For this reason I chose to study two model groups, Hemiptera and Hymenoptera. Hemiptera, in particular leafhoppers, rely almost exclusively on vibrations for intraspecific communication. Their reproductive strategy is based on the production of vibrational calling and courtship signals, which are necessary for identification and location of the mating partner. Similarly, male-male competition for mating is regulated by means of specific vibrational signals, which in many cases are used to interfere with an ongoing mating duet. The emission of specific disruptive noise gives the rival male a chance to access mating by replacing the calling male in the duet. Recent studies showed that disruptive signals can be played back into plants to effectively disrupt the mating behavior of the grapevine leafhopper, Scaphoideus titanus. These findings inspired my research, its aims and the experimental approach. First, I described and decoded the reproductive strategy and associated vibrational signals of two grapevine leafhoppers species, the green leafhopper, Empoasca vitis and the glassy-winged sharpshooter, Homalodisca vitripennis. Secondly, I used the acquired knowledge to select potential synthetic ‘disruptive signals’ and test their efficacy in disrupting the mating process of E. vitis in laboratory conditions. Hymenoptera, on the other hand, such as paper wasps of the genus Polistes, use mainly semiochemicals to coordinate colony activities (e. g., to discriminate among individuals and their roles). However, the “mechanical switch hypothesis” suggested that vibrations produced by body oscillation movements of foundresses can bias larvae development towards a worker phenotype. That is, when a larva is subjected to low frequency vibrations it will develop into a worker. The social parasite - host system, Polistes sulcifer – P. dominula, was a very good model to investigate the potential caste determination function of body oscillation movements in paper wasps. P. sulcifer, the parasite, does not have a worker caste and its reproductive success rely exclusively on the brood cares provided by the host workers that emerge from usurped colonies. For this reason, I described and compared the vibrations transmitted to the nest by both species in usurped and not-usurped colonies. Moreover, the “mechanical switch hypothesis” predicts that vibrations manipulate larval development by modulating the “nutritional effect” (i.e. larvae that are fed more should develop into reproductive individuals and viceversa). Therefore, I tested the P. dominula foundress ability to modulate the vibration emission in association or not with the feeding activity. This research unveiled remarkable information in both model groups. Several original aspects in the leafhopper mating behavior have been discovered. Main peculiarities have been found in the daily activity and the potential role of visual stimuli in E. vitis, and in the complex structure of signals and male-male rivalry interactions in H. vitripennis. These results showed that multimodal communication (i.e. vision plus vibrations) and ecological adaptations still need to be studied in leafhoppers to fully understand how vibrational signals evolved and adapted to ecological constraints. From an applied point of view, we identified one disruptive signal that, in laboratory conditions, was highly effective in disrupting E. vitis mating process. On the other hand, I described, for the first time in detail, the spectral properties of induced vibrations into a paper wasps nest produced by P. dominula and its social parasite P. sulcifer. By comparing the vibrations produced by P. dominula, in different larval nutritional conditions, and the parasite we found several significant differences. For example, the foundress varies the spectral and temporal properties when she is feeding the larvae; while the parasite produces vibrational events with some exaggerated features compared to the host (i.e. each event is composed of a higher number of pulses). Results have been discussed from an adaptive point of view considering the putative role of vibrations in leading larvae caste determination. Overall, this thesis provides novel insights on the great variability of functions and adaptations of vibrational signals. The acquired knowledge can be used as a basis to perform further experiments on biological and applied aspects of biotremology
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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