Biology subjects

Desouhant, E.

Publications and source records attributed to Desouhant, E..

6 recordsLinked to original sources

bioRxiv2025

Same-sex sexual behaviours in a wasp despite sex recognition cues: the broad mating filter hypothesis

Same-sex sexual behaviour (SSB) in animals, once considered an evolutionary dead end, is surprisingly widespread, particularly among male insects. These behaviours may arise from either adaptive or non-adaptive processes. Over shorter timescales, SSB can occur when courtship costs are low or when missing a mating opportunity is costly, leading to a reduced behavioural threshold for courtship--a "broad mating filter," as predicted by threshold acceptance theory. We investigated SSB in males of the parasitoid wasp Venturia canescens (Hymenoptera: Ichneumonidae), a species where encounters are infrequent and male courtship is energetically not costly. We hypothesised that males exhibit a broad mating filter, accepting conspecifics for courtship regardless of sex. First, behavioural assays assessed whether SSB correlated with higher reproductive success. Second, we compared cuticular hydrocarbon (CHC) profiles between sexes, as these compounds may serve as cues for sex recognition. Our chemical analyses revealed clear quantitative CHC differences between males and females, indicating potential for sex recognition. Nonetheless, 18% of males displayed SSB, and these behaviours had no detectable effect on either courting or mating success. Moreover, males receiving SSB did not experience any reproductive advantage. Our findings support the hypothesis of a broad mating filter in V. canescens males. In this species, where conspecific encounters are rare, SSB appears to arise from reduced discrimination rather than adaptive benefits, consistent with a low-cost courtship strategy and high opportunity costs of missed mating events.

animal behavior and cognition↗

bioRxiv2023

Foraging at night under artificial light: consequences on reproductive senescence and lifetime reproductive success for a diurnal insect

O_LIThe increasing use of artificial light at night (ALAN) is currently a major anthropogenic disturbance, with largely unappreciated eco-evolutionary consequences for nocturnal but also diurnal organisms. It has been hypothesized that light pollution could create new opportunities for the latter to forage and reproduce at night, which is called the night-light niche, with fitness consequences still scarcely explored. C_LIO_LIWe exposed diurnal parasitoid wasps (Venturia canescens) to one of three light-at-night conditions: control (0 lux), low intensity (0.7 lux) or high intensity (20 lux) throughout their lives. We then monitored changes in both behavioural and life-history traits, namely daytime and nighttime feeding and egg-laying activity, reproductive senescence, lifespan and lifetime reproductive success. C_LIO_LILight pollution influenced the nighttime activity of wasps. The proportion of wasps feeding and laying eggs at night increased, and we also detected a tendency for a higher nighttime reproductive success under a high intensity of light pollution. Surprisingly, high intensity of light pollution also increased the wasps lifespan. Such changes did not affect the lifetime reproductive success of the wasps, but influenced the distribution of ovipositions between day and night. C_LIO_LIReproductive senescence occurs in V. canescens, evidenced by the linear decline in daily reproductive success with age regardless of the light condition. ALAN conditions, in interaction with mother age, affected developmental time in offspring, highlighting an effect on reproductive senescence. C_LIO_LIWe demonstrated that light pollution induced the use of the night-light niche in a diurnal insect, with a shift in the distribution of egg-laying events between day and night. While we did not observe strong consequences on individual fitness, such changes in the dynamics of parasitism behaviour may nevertheless have major consequences for population dynamics, especially in natural conditions. C_LI

animal behavior and cognition↗

bioRxiv2022

Larval density in the invasive Drosophila suzukii: immediate and delayed effects on life-history traits

The immediate and delayed effects of density are key in determining population dynamics, since they can positively or negatively affect the fitness of individuals. These effects have great relevance for polyphagous insects for which immature stages develop within a single site of finite feeding resources. Drosophila suzukii is a crop pest that induces severe economic losses for agricultural production, however little is known about the effects of density on its life-history traits. In the present study, we (i) investigated the egg distribution resulting from females egg-laying strategy and (ii) tested the immediate and delayed effects of larval density on emergence rate, development time, sex ratio of offspring, fecundity and adult size (a range of 1 to 50 larvae was used). We showed that most of fruits contain several eggs and aggregate of eggs of high density can be found in some fruits. This high density has no immediate effects on the emergence rate, but has effect on larval developmental time. This trait was involved in a trade-off with adult life-history traits: the larval development was reduced as larval density increased, but smaller and less fertile adults were produced. Our results should help to better understand the population dynamics of this species and to develop more successful control programs.

ecology↗

bioRxiv2022

Diet as a major driver of endosymbiont proliferation in cereal weevils

Nutritional symbioses between insects and intracellular bacteria (endosymbionts) are a major force of adaptation, allowing animals to colonize nutrient-poor ecological niches. Many beetles feeding on tyrosine-poor substrates rely on a surplus of aromatic amino acids produced by bacterial endosymbionts. This surplus of aromatic amino acids is crucial for the biosynthesis of a thick exoskeleton, the cuticle, which is made of a matrix of chitin with proteins and pigments built from tyrosine-derived molecules, providing an important defensive barrier against biotic and abiotic stress. Other endosymbiont-related advantages for beetles include faster development and improved fecundity. The association between Sitophilus oryzae and Sodalis pierantonius endosymbiont represents a unique case study among beetles: endosymbionts undergo an exponential proliferation in young adults concomitant with the cuticle tanning, then they are fully eliminated. While endosymbiont clearance, as well as total endosymbiont titer, are host-controlled processes, the mechanism triggering endosymbiont exponential proliferation remains poorly understood. Here, we show that endosymbiont exponential proliferation relies on host carbohydrate intake, unlike the total endosymbiont titer or the endosymbiont clearance, which are under host genetic control. Remarkably, insect fecundity was preserved, and the cuticle tanning was achieved, even when endosymbiont exponential proliferation was experimentally blocked, except in the context of a severely unbalanced diet. Moreover, a high endosymbiont titer coupled with nutrient shortage, dramatically impacted host survival, revealing possible environment-dependent disadvantages for the host, likely due to the high energy cost of exponentially proliferating endosymbionts. Abstract ImportanceBeetles thriving on tyrosine-poor diet sources often develop mutualistic associations with endosymbionts able to synthesize aromatic amino acids. This surplus of aromatic amino acids is used to reinforce the insects protective cuticle. An exceptional feature of the Sitophilus oryzae / Sodalis pierantonius interaction is the exponential increase in endosymbiotic titer observed in young adult insects, in concomitance with cuticle biosynthesis. Here, we show that host carbohydrate intake triggers endosymbiont exponential proliferation, even in conditions that lead to the detriment of the host survival. In addition, when hosts thrive on a balanced diet, endosymbiont proliferation is dispensable for several host fitness traits. The endosymbiont exponential proliferation is therefore dependent on the nutritional status of the host, and its consequences on host cuticle biosynthesis and survival depend on food quality and availability.

evolutionary biology↗

bioRxiv2020

Experimental evolution of virulence and associated traits in a Drosophila melanogaster - Wolbachia symbiosis

AO_SCPLOWBSTRACTC_SCPLOWEvolutionary theory predicts that vertically transmitted symbionts are selected for low virulence, as their fitness is directly correlated to that of their host. In contrast with this prediction, the Wolbachia strain wMelPop drastically reduces its Drosophila melanogaster host lifespan at high rearing temperatures. It is generally assumed that this feature is maintained because the D. melanogaster-wMelPop symbiosis is usually not exposed to environmental conditions in which the symbiont is virulent. To test this hypothesis, we submitted wMelPop-infected D. melanogaster lines to 17 generations of experimental evolution at a high temperature, while enforcing late reproduction by artificial selection. The fly survival was measured at different time points, as well as two traits that have been proposed to be causally responsible for wMelPop virulence: its relative density and the mean number of copies of octomom, an 8-genes region of the Wolbachia genome. We hypothesised that these conditions (high temperature and late reproduction) would select for a reduced wMelPop virulence, a reduced wMelPop density, and a reduced octomom copy number. Our results indicate that density, octomom copy number and virulence are correlated to each other. However, contrary to our expectations, we could not detect any reduction in virulence during the course of evolution. We discuss the significance of our results with respect to the evolutionary causes of wMelPop virulence.

evolutionary biology↗

bioRxiv2017

Insects and incest: field evidence for dangerous liaisons in a parasitoid wasp

O_LISib mating avoidance is a pervasive behaviour, which likely evolves in species that sare subject to inbreeding depression. Laboratory studies have provided elegant demonstrations, but small-scale bioassays often minimize the costs associated with mate finding and mate-choice and may for this reason produce spurious findings.\nC_LIO_LIWe inferred the mating behaviour of the parasitoid wasp Venturia canescens from the genetic analyses of natural populations. We used V. canescens as a model organism because in this species, laboratory experiments have shown that sib mating yields a 25% decrease in fertile offspring, and congruently, sib mating is partially avoided.\nC_LIO_LIOur study consisted in genotyping 86 wild-caught males, 155 wild-caught-females and their 226 daughters at eighteen microsatellite loci. With these data, we were able to reconstruct the genotype of females mate and estimate the relatedness of each mating pairs.\nC_LIO_LIWe found that the effective rate of sib mating does not differ from the probability that sibs encounter one another at random, which suggest a sib mating tolerance in this species. However, complementary lab experiments confirmed that kin discrimination exist in this species, with related pairs having a lower mating latency.\nC_LIO_LIThese results suggest that V. canescens tolerate sib mating in the field despite kin discrimination, and therefore call into question the common beliefs on inbreeding depression in species with single-locus complementary sex determination. This inbreeding tolerance also opens up the question of the maintenance of the kin discrimination in this species.\nC_LI

animal behavior and cognition↗