1,721,054 research outputs found
A quantitative threshold for nestmate recognition in a paper social wasp
No full textNest-mate recognition is fundamental for protecting social insect colonies from intrusion threats such as predators or social parasites. The aggression of resident females towards intruders is mediated by their cuticular semiochemicals. A positive relation between the amount of cues and responses has been widely assumed and often taken for granted, even though direct tests have not been carried out. This hypothesis has important consequences, since it is the basis for the chemical insignificance strategy, the most common
explanation for the reduction in the amount of semiochemicals occurring in many social parasites. Here we used the social wasp Polistes dominulus, a model species in animal communication studies and host of three social parasites, to test this hypothesis. We discovered that different
amounts of cuticular hydrocarbons (CHC) of a foreign female evoke quantitatively different behavioural reactions in the resident foundress.
The relation between CHCquantity and the elicited response supports the idea that a threshold exists in the chemical recognition systemof this species. The chemical insignificance hypothesis thus holds in a host–parasite system of Polistes wasps, even though other explanations should not be discarded
Ovarian indexes as indicators of reproductive investment and egg laying activity in social insects: a comparison among methods
No full textOvarian indexes as indicators of reproductive investment and egg laying activity in social insects: a comparison among methods
A network of sex and competition: the promiscuous mating system of an invasive weevil.
Full text linkInvasive alien pest insect species represent a major threat for agriculture and biodiversity. Because chemical treatments
employed to contrast such pests elicit serious environmental and human health problems, a great effort is currently directed
to develop long term and environmentally friendly biological control strategies. However, the successful application of some
promising techniques, such as the Sterile Insect Technique (SIT), requires a deep knowledge of the pest basic biology. Here, we
argue that understanding pest sexual biology using a social network approach can significantly improve the performance of control
strategies. For example, SIT may benefit from understanding how individuals interact and how males accede to reproduction,
in order to target the most reproductively active and polygamic males. In this paper we studied the socio-sexual networks of the
Asian red palm weevil (RPW) Rhynchophorus ferrugineus, a worldwide invader which is causing heavy economic impacts on
several palm species. We found that the RPW has a highly promiscuous mating system, characterized by forced interruptions of
pair copulations by additional males. The social network is highly non-random nor regular: few males almost monopolize reproduction,
behaving as key-players in the network of matings. Additionally, males have a stable pattern of sexual behaviour over
time. We use RPW social network as a case study to direct the development of management techniques such as SIT strateg
Visual recognition in social wasps
No full textSocial recognition, i.e. the ability to recognize and assign individual membership to a particular and relevant class, such as caste, dominance status, gender or colony, shapes the amazing organization of insect societies. Traditionally, it has been assumed that social recognition in social insects is mainly governed by chemicals. However, social insects also share information via many other sensory channels, and it has been recently demonstrated that visual signals can mediate several types of social recognition in some species of social wasps. Primitively social wasps, such as paper wasps of Polistes genus, are suitable models to investigate visual communication because their combs lack of envelops allowing light to produce visual cues, their colonies are small, they have a good vision, they show a remarkable individual within-colony colour variation and, finally, they show an intense social life based on social recognition. In this chapter we reviewed the role of visual cues in social recognition inside and outside social wasp colonies focusing both on the intraspecific and interspecific recognition contexts
Facial markings in the social cuckoo wasp Polistes sulcifer: no support for the visual deception and the assessment hypothesis
No full textInsect social parasites have to conquer a host colony by overcoming its defensive barriers. In additionto increased fighting abilities, many social parasites evolved sophisticated sensory deception mecha-nisms to elude host colonies defenses by exploiting host communication channels. Recently, it has beenshown that the conspicuous facial markings of a paper wasp social parasite, Polistes sulcifer, decrease theaggressiveness of host foundresses. Two main hypotheses stand as explanations of this phenomenon:visual sensory deception (i.e. the black patterning reduces host aggression by exploiting the host visualcommunication system) and visual quality assessment (i.e. facial markings reduce aggressiveness as theysignal the increased fighting ability of parasites). Through behavioral assays and morphological measure-ments we tested three predictions resulting from these hypotheses and found no support either for thevisual sensory deception or for the quality assessment to explain the reduction in host aggressivenesstowards the parasite. Our results suggest that other discrimination processes may explain the observedphenomenon
Just phoresy? Reduced lifespan in red palm weevils<i>Rhynchophorus ferrugineus</i>(Coleoptera: Curculionidae) infested by the mite<i>Centrouropoda almerodai</i>(Uroactiniinae: Uropodina)
No full textInvasive species usually act as carriers of their associated organisms like parasites and symbionts. This phenomenon has
also occurred with the recent colonization of the red palm weevil, Rhynchophorus ferrugineus, in the Mediterranean area: this
introduced pest is strictly associated with several species of mites (mainly belonging to the suborder Uropodina). In this
paper, we document the high rate of infestation of Central and Southern Italian red palm weevil populations by the mite
Centrouropoda almerodai. This mite species was found in all five investigated regions and infested the large majority of individuals
(from 57 to 95%) by settling preferentially under the first pair of wings. Although this mite–weevil association is
usually considered as a phoretic relationship, i.e. without impact on hosts, our study revealed that infested individuals have
a significantly reduced lifespan (by one-third) in comparison with those not infested. Our study provides evidences that
C. almerodai imposes a cost on its carrier host, at least under laboratory conditions, leading us to believe that the R. ferrugineus–
C. almerodai relationship is also not phoretic in the wild
Tracing outliers in the dataset of Drosophila suzukii records with the Isolation Forest method
Full text linkThe analysis of big data is a fundamental challenge for the current and future stream of data coming from many different sources. Geospatial data is one of the sources currently less investigated. A typical example of always increasing data set is that produced by the distribution data of invasive species on the concerned territories. The dataset of Drosophila suzuki invasion sites in Europe up to 2011 was used to test a possible method to pinpoint its outliers (anomalies). Our aim was to find a method of analysis that would be able to treat large amount of data in order to produce easily readable outputs to summarize and predict the status and, possibly, the future development of a biological invasion. To do that, we aimed to identify the so called anomalies of the dataset, identified with a Python script based on the machine learning algorithm “Isolation Forest”. We used also the K-Means clustering method to partition the dataset. In our test, based on a real dataset, the Silhouette method yielded a number of clusters of 10 as the best result. The clusters were drawn on the map with a Voronoi tessellation, showing that 8 clusters were centered on industrial harbours, while the last two were in the hinterland. This fact led us to guess that: (1) the main entrance mechanisms in Europe may be the wares import fluxes through ports, occurring apparently several times; (2) the spreading into the inland may be due to road transportation of wares; (3) the outliers (anomalies) found with the isolation forest method would identify individuals or populations that tend to detach from their original cluster and hence represent indications about the lines of further spreading of the invasion. This type of analysis aims hence to identify the future direction of an invasion, rather than the center of origin as in the case of geographic profiling. Isolation Forest provides therefore complimentary results with respect to PGP. The recent records of the invasive species, mainly localized close to the outliers position, are an indication that the isolation forest method can be considered predictive and proved to be a useful method to treat large datasets of geospatial data
Fight or fool? Physical strength, instead of sensory deception, matters in host nest invasion by a wasp social parasite
No full textInsect social parasites need to overcome host colonies’ defences to exploit their resources successfully.
Sophisticated sensory deception mechanisms to break the host’s barriers have been repeatedly reported
for many social parasites, possibly concealing the importance of open fighting, a more ancestral strategy.
Understanding the relative importance of fooling and fighting is primarily challenging when the two
strategies seem both available and advantageous. We focused on the paper wasp social parasiteehost
system Polistes sulcifereP. dominulus, where both fooling and fighting have been suggested to play a role
during usurpation contests. Host aggression is elicited by the chemical cues (hydrocarbons) that
intruders bear on their cuticle. Parasites would benefit from reducing the amount of these cues before
approaching the host colony. In addition, the parasites’ facial pattern has been shown to reduce the host’s
aggressive reaction, probably by amplifying the mandibular width. We tested the occurrence of chemical
and visual cheating through chemical analyses and laboratory usurpation trials, respectively. Usurping
parasites did not conceal their identity by reducing cuticular hydrocarbons, nor did their facial pattern
facilitate nest take-over. Contest outcome was instead predicted by the relative body size of the opponents.
Fighting, rather than fooling, is therefore the strategy used by P. sulcifer usurping females. The
importance of physical strength could thus explain why chemical or visual tricks do not play a role in
taking over the host colony despite their potential usefulness. Our findings suggest that the evolution of
sophisticated cheating mechanisms can be prevented by the ability to fight
IOBC-WPRS Working group "Biological control of fungal and bacterial plant pathogens" Proceedings of the meeting at Graz (Austria) 7-10 June 2010
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