Kin recognition and incest avoidance in a group-living insect

International audienceMate choice theories predict that animals evolved strategies to mate with optimally genetically dissimilar partners, providing fitness benefits. In group-living species, when adults do not disperse, assessment of relatedness between conspecifics can be a key factor for choosing mates. Here, we report for the first time, kin recognition abilities and their implication in mate choice in the gregarious cockroach, Blattella germanica (L.). Binary choice tests showed that females mated preferentially with nonsibling rather than with sibling males, thus avoiding incest. In addition, inbreeding induced an important decrease of their reproductive success. Contrary to what could be expected when females had the choice between a nonsibling strain member and a nonstrain member, they did not avoid mating with distantly related nonstrain members, and extreme outbreeding induced an increase of their reproductive success. Furthermore, our mate choice experiments disentangled the influences of familiarity from those of relatedness and evidenced that kin discrimination was based on genetic cues independently of familiarity. Phenotype matching was a plausible mechanism for kin recognition. Contrary to many insect species, body size was not a salient criterion for mate choice and had no consequences on reproductive success

Local Enhancement Promotes Cockroach Feeding Aggregations

Communication and learning from each other are part of the success of animal societies. Social insects invest considerable effort into signalling to their nestmates the locations of the most profitable resources in their environment. Growing evidence also indicates that insects glean such information through cues inadvertently provided by their conspecifics. Here, we investigate social information use in the foraging decisions by gregarious cockroaches (Blattella germanica L.). Individual cockroaches given a simultaneous choice in a Y-olfactometer between the odour of feeding conspecifics and the mixed odour of food plus non-feeding conspecifics showed a preference for the arm scented with the odour of feeding conspecifics. Social information (the presence of feeding conspecifics) was produced by cockroaches of all age classes and perceived at short distance in the olfactometer arms, suggesting the use of inadvertently provided cues rather than signals. We discuss the nature of these cues and the role of local enhancement (the selection of a location based on cues associated with the presence of conspecifics) in the formation of feeding aggregations in B. germanica. Similar cue-mediated recruitments could underpin a wide range of collective behaviours in group-living insects

Mutual Mate Choice: When it Pays Both Sexes to Avoid Inbreeding

Theoretical models of sexual selection predict that both males and females of many species should benefit by selecting their mating partners. However, empirical evidence testing and validating this prediction is scarce. In particular, whereas inbreeding avoidance is expected to induce sexual conflicts, in some cases both partners could benefit by acting in concert and exerting mutual mate choice for non-assortative pairings. We tested this prediction with the gregarious cockroach Blattella germanica (L.). We demonstrated that males and females base their mate choice on different criteria and that choice occurs at different steps during the mating sequence. Males assess their relatedness to females through antennal contacts before deciding to court preferentially non-siblings. Conversely, females biased their choice towards the most vigorously courting males that happened to be non-siblings. This study is the first to demonstrate mutual mate choice leading to close inbreeding avoidance. The fact that outbred pairs were more fertile than inbred pairs strongly supports the adaptive value of this mating system, which includes no “best phenotype” as the quality of two mating partners is primarily linked to their relatedness. We discuss the implications of our results in the light of inbreeding conflict models

Dynamique d'une population de Blattella germanica en milieu urbain

WOS:A1990EG13000010International audienceA population of Blattella germanica L. (Dictyoptcra) cockroaches was studied in a swimming-bath. Trapped adults were marked and released in their capture area.The overall recapture rate was 15%, but it varied according to the capture area. This rate was higher in the toilets than around the pool borders. Distances between capture and recapture points also varied. Recaptures were more frequent in the capture area than in other areas; only 15% of the animals left their initial area. Movements occurred mainly between neighbouring areas. Recaptures in the capture area were lower around the large pool than around the shallow pool and in the toilets.In conclusion, there were three types of areas which were differently occupied. This could be explained by variations of resources like shelter and food. The complexity of the environmental structure favoured development of cockroach populations although they were able to modify their behavior in relation to the environmental features.Une population de Blattes (Blattella germanica) a été étudiée dans l'enceinte d'une piscine par des piégeages hebdomadaires. Les animaux adultes sont marqués et relâchés dans leur zone de capture initiale.Le taux de recapture total est de 15%; mais on observe des differences en fonction de la zone de capture. Le taux de recapture est plus élevé dans les toilettes qu'en bordure des bassins. Par contre les distances entre capture et recapture y sont plus faibles.D'autre part, le taux de recapture est plus élevé dans la zone de capture initiale: seulement 15% des animaux changent de zone. Les déplacements ont lieu principalement entre deux zones voisines. Les recaptures dans la zone d'origine sont meilleures autour du petit bassin et dans les toilettes qu'autour du grand bassin.D'après ces résultats, il est possible de distinguer trois types de zone qui présentent un taux d'occupation plus ou moins élevé. Le taux d'occupation dans ces trois zones pourrait être lié à l'abondance des ressources telles que la nourriture et les abris. L'augmentation de la complexité de la structure du milieu qui augmente le nombre d'abris potentiels semble favoriser le développement des populations de Blattes. Celles-ci sont cependant capables d'adapter leur comportement avec les caractéristiques du milieu et de l'exploiter au mieux

Rôle Des Facteurs Sociaux Sur L'Expression De La Rythmicité Circadienne Dans Un Groupe Chez Periplaneta Americana (Dictyopt.)

WOS:A1981LV57000002International audienceL'étude d'un groupe de Periplaneta americana a permis de préciser l'impact des facteurs sociaux sur l'expression de la rythmisation circadienne des activités. En LD: 12-12, les individus du groupe modifient dans le temps leur activité locomotrice, en relation avec leur statut social (time territoriality). En LL, on mesure pour chaque individu une période de Free-running pour l'activité locomotrice, l'activité alimentaire et les parades sexuelles. La valeur de cette période de F.R. n'est pas corrélée avec le statut social. Par contre, les relations de phase entre ces trois comportements ne sont maintenues que chez les individus dominants. La rupture des relations temporelles entre ces trois comportements que nous observons chez les subordonnés, indique que le couplage entre ces trois oscillations n'est pas de même intensité sans que l'on puisse savoir s'il s'agit d'un système multioscillateur. Des animaux arythmiques ne se synchronisent pas sur l'activité d'un groupe d'animaux en Free-running, car il n'y a pas de période de F.R. commune au niveau du groupe qui permette aux individus arythmiques d'avoir un repère circadien

Utilisation de l'espace dans un groupe de Periplaneta americana

International audienceThe spacing pattern in a bisexual group of Periplaneta americana is related to species and its social organization. Over a 24 h period, females spend 60% of their time in shelters which are on top of the experimental cage. Males spend 80 to 85% of their time outside, on top of the cage and particularly around females' shelters. Females spend some time (7%) at the bottom of the cage where they deposit oothecae. The spacing patterns revealed to be very similar in LD: 12-12 and LL. It was also interesting to notice that dominant males spend more time than subordinates in the highly attractive parts of the cage, around females' shelters and spend less time in shelters at the bottom of the cage. This spacing pattern is related to a precise knowledge of the cage topography and other individuals in the group.L'utilisation de l'espace dans un groupe bisexué de Periplaneta americana présente des caractéristiques particulières liées à l'espèce et à son organisation sociale. Sur une période de 24 h., les femelles passent 60% de leur temps dans les abris situés en haut du terrarium. Les mâles passent 80 à 85% sur les parois libres en haut du terrarium, notamment les zones bordant les abris occupés par les femelles. Les femelles passent un temps relativement long sur le plancher (7%) lors du dépôt des oothèques. La répartition dans l'espace est sensiblement la même en LD: 12-12 et LL. On constate d'autre part, que les mâles dominants passent davantage de temps que les dominés dans les zones à fort indice d'attraction, autour des abris des femelles et restent moins de temps dans les abris en bas du terrarium. Cette utilisation de l'espace est liée à une connaissance précise du milieu et des autres individus du groupe

How and why to disperse or not?

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