Seed Beetle Callosobruchus Maculatus Research Articles

Isolation and Identification of Fungal Species from the Insect Pest Callosobruchus maculatus (F.)

Cowpea seed beetle Callosobruchus maculatus (F.) (Coleoptera: Bruchidae) is one of the most common and economically important pests of stored cereal products worldwide. Furthermore, these beetles can act as vectors for several fungal post-harvest diseases. The current research aimed to isolate the fungi associated with adults of C. maculatus (F.) (Coleoptera: Bruchidae). The present study aimed to isolate and identify fungi associated with adult insects and evaluate their potential as biocontrol agents against the cowpea beetle, C. maculatus. In this study, we collected C. maculatus adults from the Babylon local market and five regions (Hilah, Mahaweel, Al-Mashrou', Al-Haswa and Al-Musayyab) with no history of insecticide exposure. A potato dextrose agar medium was used to isolate the fungi attached to the surfaces of adult beetles. By Morphological and microscopic examination, Molecular identification and Sequencing analysis, Twenty-seven genera of fungi were isolated and identified from adult C. maculatus, including Aspergillus, Penicillium, Candida spp, white mycelium, Curvularia, Cladosporium, Chaetomium, Stachybotrys, Rhizopus, Drechslera, Scopulariopsis, Paecilomyces, Mucor, Geotrichum candidum, Streptomyces, Sarocladium, Beauveria bassiana, Talaromyces varians, Sporothrix flocculasa, Pseudozyma flocculasa, and Isaria fumosorosea. The molecular weights of the PCR products for the fungi isolates ranged from 650-700 bp, and the amplified ITS1-5.8S-ITS4 rDNA region of indigenous entomopathogenic fungal isolates showed a high sequence similarity (99-100%) with B. bassiana and M. anisopliae deposited in the NCBIGenebank. The phylogenetic tree analysis of the ITS region sequences showed a high degree of similarity between the isolates under study, ranging from 96.5-100. However, there were differences in the lines among clades, indicating genetic variation possibly due to mating or mutations in different environments. Our study suggests that the storage pest, C. maculatus, would be essential in spreading fungal contaminants and consequently increasing mycotoxin contamination in stored Cowpea. Keywords: Callosobruchus maculatus, Isolation, Fungi

Isolation and Identification of Fungal Species from the Insect Pest Callosobruchus maculatus (F.)

Cowpea seed beetle Callosobruchus maculatus (F.) (Coleoptera: Bruchidae) is one of the most common and economically important pests of stored cereal products worldwide. Furthermore, these beetles can act as vectors for several fungal post-harvest diseases. The current research aimed to isolate the fungi associated with adults of C. maculatus (F.) (Coleoptera: Bruchidae); the present study aimed to isolate and identify fungi associated with adult insects and evaluate their potential as biocontrol agents against the cowpea beetle, C. maculatus. In this study, we collected C. maculatus adults from the Babylon local market and five regions (Hilah, Mahaweel, Al-Mashrou’, Al-Haswa and Al-Musayyab) with no history of insecticide exposure. A potato dextrose agar medium was used to isolate the fungi attached to the surfaces of adult beetles. By Morphological and microscopic examination, Molecular identification and Sequencing analysis, Twenty-seven genera of fungi were isolated and identified from adult C. maculatus, including Aspergillus, Penicillium, Candida spp, white mycelium, Curvularia, Cladosporium, Chaetomium, Stachybotrys, Rhizopus, Drechslera, Scopulariopsis, Paecilomyces, Mucor, Geotrichum candidum, Streptomyces, Sarocladium, Beauveria bassiana, Talaromyces varians, Sporothrix flocculasa, Pseudozyma flocculasa, and Isaria fumosorosea. The molecular weights of the PCR products for the fungi isolates ranged from 650-700 bp, and the amplified ITS1-5.8S-ITS4 rDNA region of indigenous entomopathogenic fungal isolates showed a high sequence similarity (99-100%) with B. bassiana and M. anisopliae deposited in the NCBIGenebank. The phylogenetic tree analysis of the ITS region sequences showed a high degree of similarity between the isolates under study, ranging from 96.5-100. However, there were differences in the sequences among clades, indicating genetic variation possibly due to mating or mutations in different environments. Our study suggests that the storage pest, C. maculatus, would be essential in spreading fungal contaminants and consequently increasing mycotoxin contamination in stored cowpeas. Keywords: Callosobruchus maculatus, Isolation, Fungi.

Sexual selection buffers the negative consequences of population fragmentation on adaptive plastic responses to increasing temperatures.

Whether sexual selection facilitates or hampers the ability to plastically respond to novel environments might depend on population structure, via its effects on sexual interactions and associated fitness payoffs. Using experimentally evolved lines of the seed beetle Callosobruchus maculatus, we tested whether individuals evolving under different sexual selection (monogamy vs. polygamy) and population spatial structure (metapopulation vs. undivided populations) treatments differed in their response across developmental thermal conditions (control, hot, or stressful) in a range of fitness and fitness-associated traits. We found that individuals from subdivided populations had lower lifetime reproductive success at hot temperatures, but only in lines evolving under relaxed sexual selection, revealing a complex interaction between sexual selection, population structure, and thermal environmental stress on fitness. We also found an effect of population structure on several traits, including fertility and adult emergence success, under exposure to high thermal conditions. Finally, we found a strong negative effect of hot and stressful temperatures on fitness and associated traits. Our results show that population structure can exacerbate the impact of a warming climate, potentially leading to declines in population viability, but that sexual selection can buffer the negative influence of population subdivision on adaptation to warm temperatures.

Increased male investment in sperm competition results in reduced maintenance of gametes.

Male animals often show higher mutation rates than their female conspecifics. A hypothesis for this male bias is that competition over fertilization of female gametes leads to increased male investment into reproduction at the expense of maintenance and repair, resulting in a trade-off between male success in sperm competition and offspring quality. Here, we provide evidence for this hypothesis by harnessing the power of experimental evolution to study effects of sexual selection on the male germline in the seed beetle Callosobruchus maculatus. We first show that 50 generations of evolution under strong sexual selection, coupled with experimental removal of natural selection, resulted in males that are more successful in sperm competition. We then show that these males produce progeny of lower quality if engaging in sociosexual interactions prior to being challenged to surveil and repair experimentally induced damage in their germline and that the presence of male competitors alone can be enough to elicit this response. We identify 18 candidate genes that showed differential expression in response to the induced germline damage, with several of these previously implicated in processes associated with DNA repair and cellular maintenance. These genes also showed significant expression changes across sociosexual treatments of fathers and predicted the reduction in quality of their offspring, with expression of one gene also being strongly correlated to male sperm competition success. Sex differences in expression of the same 18 genes indicate a substantially higher female investment in germline maintenance. While more work is needed to detail the exact molecular underpinnings of our results, our findings provide rare experimental evidence for a trade-off between male success in sperm competition and germline maintenance. This suggests that sex differences in the relative strengths of sexual and natural selection are causally linked to male mutation bias. The tenet advocated here, that the allocation decisions of an individual can affect plasticity of its germline and the resulting genetic quality of subsequent generations, has several interesting implications for mate choice processes.

Sexually antagonistic selection maintains genetic variance when sexual dimorphism evolves.

Genetic variance (VG) in fitness related traits is often unexpectedly high, evoking the question how VG can be maintained in the face of selection. Sexually antagonistic (SA) selection favouring alternative alleles in the sexes is common and predicted to maintain VG, while directional selection should erode it. Both SA and sex-limited directional selection can lead to sex-specific adaptations but how each affect VG when sexual dimorphism evolves remain experimentally untested. Using replicated artificial selection on the seed beetle Callosobruchus maculatus body size we recently demonstrated an increase in size dimorphism under SA and male-limited (ML) selection by 50% and 32%, respectively. Here we test their consequences on genetic variation. We show that SA selection maintained significantly more ancestral, autosomal additive genetic variance than ML selection, while both eroded sex-linked additive variation equally. Ancestral female-specific dominance variance was completely lost under ML, while SA selection consistently sustained it. Further, both forms of selection preserved a high genetic correlation between the sexes (rm,f). These results demonstrate the potential for sexual antagonism to maintain more genetic variance while fuelling sex-specific adaptation in a short evolutionary time scale, and are in line with predicted importance of sex-specific dominance reducing sexual conflict over alternative alleles.

Larger genomes show improved buffering of adult fitness against environmental stress in seed beetles.

Our general understanding of the evolution of genome size (GS) is incomplete, and it has long been clear that GS does not reflect organismal complexity. Here, we assess the hypothesis that larger genomes may allow organisms to better cope with environmental variation. It is, for example, possible that genome expansion due to proliferation of transposable elements or gene duplications may affect the ability to regulate and fine-tune transcriptional profiles. We used 18 populations of the seed beetle Callosobruchus maculatus, which differ in GS by up to 4.5%, and exposed adults and juveniles to environmental stress in a series of experiments where stage-specific fitness was assayed. We found that populations with larger genomes were indeed better buffered against environmental stress for adult, but not for juvenile, fitness. The genetic correlation across populations between GS and canalization of adult fitness is consistent with a role for natural selection in the evolution of GS.

Evolutionary consequences of pesticide exposure include transgenerational plasticity and potential terminal investment transgenerational effects.

Transgenerational plasticity, the influence of the environment experienced by parents on the phenotype and fitness of subsequent generations, is being increasingly recognized. Human-altered environments, such as those resulting from the increasing use of pesticides, may be major drivers of such cross-generational influences, which in turn may have profound evolutionary and ecological repercussions. Most of these consequences are, however, unknown. Whether transgenerational plasticity elicited by pesticide exposure is common, and the consequences of its potential carryover effects on fitness and population dynamics, remains to be determined. Here, we investigate whether exposure of parents to a common pesticide elicits intra-, inter-, and transgenerational responses (in F0, F1, and F2 generations) in life history (fecundity, longevity, and lifetime reproductive success), in an insect model system, the seed beetle Callosobruchus maculatus. We also assessed sex specificity of the effects. We found sex-specific and hormetic intergenerational and transgenerational effects on longevity and lifetime reproductive success, manifested both in the form of maternal and paternal effects. In addition, the transgenerational effects via mothers detected in this study are consistent with a new concept: terminal investment transgenerational effects. Such effects could underlie cross-generational responses to environmental perturbation. Our results indicate that pesticide exposure leads to unanticipated effects on population dynamics and have far-reaching ecological and evolutionary implications.

Does timing of post-stressor exposure mating matter for parental effect?

Stress and harsh environmental conditions affect an organism's life-history traits and may impact the following generation/s features and stress resistance by parental effect. However, it is unknown which time point after stressor exposure is better for mating and subsequent parental effect transfer to future generation/s. We assessed post-stressor exposure mating to evaluate whether early mating (an hour) or late mating (24 h) post stressors exposure would affect the parental effect. To address this issue, we used seed beetle Callosobruchus maculatus and mint and rosemary essential oils as environmental stressors to evaluate biological parameters, including immature development time, adult emergence, sex ratio, longevity, egg number, egg hatch, and copulatory behaviors. Results showed that the interval between stress exposure and mating affected parents' fitness. Thus, early-mated post-stressor-exposed females lived longer than late-mated females. However, mating timing did not influence male adult longevity. In the late-mated group, stress did not affect insects' mating behaviors, whereas adverse effects were recorded in early-mated beetles. Parents' stress exposure also did not alter biological parameters in the unexposed F1 generation. Then we let the F2 generation experience the same stressor as F0. Rosemary essential oil exposed late-mated grandparents produced grand offspring that laid more eggs with higher hatching rates than grand offspring of the control in response to rosemary essential oil. In other words, late-mated grandparents generated grand offspring who could better cope with the same stressor as F0. This study indicated that the interval between stress exposure and mating is important in the quality of parental effects. Parents having enough time for recovery could produce offspring and subsequently grand offspring more capable of coping with the same stressor.

Experimental evolution reveals differential evolutionary trajectories in male and female activity levels in response to sexual selection and metapopulation structure.

Behavior is central to interactions with the environment and thus has significant consequences for individual fitness. Sexual selection and demographic processes have been shown to independently shape behavioral evolution. Although some studies have tested the simultaneous effects of these forces, no studies have investigated their interplay in behavioral evolution. We applied experimental evolution in the seed beetle Callosobruchus maculatus to investigate, for the first time, the interactive effects of sexual selection intensity (high [polygamy] vs. minimal [enforced monogamy]) and metapopulation structure (yes/no) on the evolution of movement activity, a crucial behavior involved in multiples functions (e.g., dispersal, predator avoidance, or resource acquisition) and thus, closely related to fitness. We found that the interactive effects of the selection regimes did not affect individual activity, which was assayed under two different environments (absence vs. presence of conspecific cues from both sexes). However, contrasting selection regimes led to sex‐ and context‐dependent divergence in activity. The relaxation of sexual selection favored an increase in female, but not male, movement activity that was consistent between environmental contexts. In contrast, selection associated with the presence/absence of metapopulation structure led to context‐dependent responses only in male activity. In environments containing cues from conspecifics, males from selection lines under population subdivision showed increased levels of activity compared to those assayed in an environment devoid of conspecifics cues, whereas the opposite was true for males from panmictic lines. These results underscore that both the effects of sexual selection and population spatial structure may be crucial in shaping sex‐specific behavioral evolution.

The mating system affects the temperature sensitivity of male and female fertility

Abstract To mitigate the effects of climate change, it is important to understand species' responses to increasing temperatures. This has often been done by studying survival or activity at temperature extremes. Before such extremes are reached, however, effects on fertility may already be apparent. Sex differences in the thermal sensitivity of fertility (TSF) could impact species persistence under climate warming because female fertility is typically more limiting to population growth than male fertility. However, little is known about sex differences in TSF. Here we first demonstrate that the mating system can strongly influence TSF using the seed beetle Callosobruchus maculatus. We exposed populations carrying artificially induced mutations to two generations of short‐term experimental evolution under alternative mating systems, manipulating the opportunity for natural and sexual selection on the mutations. We then measured TSF in males and females subjected to juvenile or adult heat stress. Populations kept under natural and sexual selection had higher fitness, but similar TSF, compared to control populations kept under relaxed selection. However, females had higher TSF than males, and strikingly, this sex difference had increased over only two generations in populations evolving under sexual selection. We hypothesized that an increase in male‐induced harm to females during mating had played a central role in driving this evolved sex difference, and indeed, remating under conditions limiting male harassment of females reduced both male and female TSF. Moreover, we show that manipulation of mating system parameters in C. maculatus generates intraspecific variation in the sex difference in TSF equal to that found among a diverse set of studies on insects. Our study provides a causal link between the mating system and TSF. Sexual conflict, (re)mating rates and genetic responses to sexual selection differ among ecological settings, mating systems and species. Our study therefore also provides mechanistic understanding for the variability in previously reported TSFs which can inform future experimental assays and predictions of species responses to climate warming. A free Plain Language Summary can be found within the Supporting Information of this article.

Metapopulation structure modulates sexual antagonism.

Despite the far‐reaching evolutionary implications of sexual conflict, the effects of metapopulation structure, when populations are subdivided into several demes connected to some degree by migration, on sexual conflict dynamics are unknown. Here, we used experimental evolution in an insect model system, the seed beetle Callosobruchus maculatus, to assess the independent and interacting effects of selection histories associated with mating system (monogamy vs. polygamy) and population subdivision on sexual conflict evolution. We confirm traditional predictions from sexual conflict theory by revealing increased resistance to male harm in females from populations with a history of intense sexual selection (polygamous populations) compared to females from populations with a history of relaxed sexual selection (monogamous populations). However, selection arising from metapopulation structure reversed the classic pattern of sexually antagonistic coevolution and led to reduced resistance in females from polygamous populations. These results underscore that population spatial structure moderates sexual selection and sexual conflict, and more broadly, that the evolution of sexual conflict is contingent on ecological context. The findings also have implications for population dynamics, conservation biology, and biological control.

Disparate genetic variants associated with distinct components of cowpea resistance to the seed beetle Callosobruchus maculatus.

Polygenic genome-wide association mapping identified two regions of the cowpea genome associated with different components of resistance to its major post-harvest pest, the seed beetle Callosobruchus maculatus. Cowpea (Vigna unguiculata) is an important grain and fodder crop in arid and semi-arid regions of Africa, Asia, and South America, where the cowpea seed beetle, Callosobruchus maculatus, is a serious post-harvest pest. Development of cultivars resistant to C. maculatus population growth in storage could increase grain yield and quality and reduce reliance on insecticides. Here, we use a MAGIC (multi-parent, advanced-generation intercross) population of cowpea consisting of 305 recombinant inbred lines (RILs) to identify genetic variants associated with resistance to seed beetles. Because inferences regarding the genetic basis of resistance may depend on the source of the pest or the assay protocol, we used two divergent geographic populations of C. maculatus and two complementary assays to measure several aspects of resistance. Using polygenic genome-wide association mapping models, we found that the cowpea RILs harbor substantial additive-genetic variation for most resistance measures. Variation in several components of resistance, including larval development time and survival, was largely explained by one or several linked loci on chromosome 5. A second region on chromosome 8 explained increased seed resistance via the induction of early-exiting larvae. Neither of these regions contained genes previously associated with resistance to insects that infest grain legumes. We found some evidence of gene-gene interactions affecting resistance, but epistasis did not contribute substantially to resistance variation in this mapping population. The combination of mostly high heritabilities and a relatively consistent and simple genetic architecture increases the feasibility of breeding for enhanced resistance to C. maculatus.

The role of maternal effects on offspring performance in familiar and novel environments.

Maternal effects are an important evolutionary force that may either facilitate adaptation to a new environment or buffer against unfavourable conditions. The degree of variation in traits expressed by siblings from different mothers is often sensitive to environmental conditions. This could generate a Maternal-by-Environment interaction (M × E) that inflates estimates of Genotype-by-Environment effects (G × E). We aimed to test for environment-specific maternal effects (M × E) using a paternal full-sib/half-sib breeding design in the seed beetle Callosobruchus maculatus, where we split and reared offspring from the same mother on two different bean host types-original and novel. Our quantitative genetic analysis indicated that maternal effects were very small on both host types for all the measured life-history traits. There was also little evidence that maternal oviposition preference for a particular host type predicted her offspring's performance on that host. Further, additive genetic variance for most traits was relatively high on both hosts. While there was higher heritability for offspring reared in the novel host, there was no evidence for G × Es, and most cross-host genetic correlations were positive. This suggests that offspring from the same family ranked similarly for performance on both host types. Our results point to a genetic basis of host adaptation in the seed beetle, rather than maternal effects. Even so, we encourage researchers to test for potential M × Es because, due to a lack of testing, it remains unclear how often they arise.

Thermal Preferences of Cowpea Seed Beetles (Callosobruchus maculatus): Effects of Sex and Nuptial Gift Transfers.

Simple SummaryThe thermal environment is crucial for organismal functioning, and many cold-blooded organisms, including insects, behaviorally regulate their body temperature. Why do insects inhabit given thermal conditions? We propose that access to water affects thermal preference and that insects with poor access to water inhabit colder environments, which reduces evaporation and preserves water. We studied the seed beetle Callosobruchus maculatus, which, as adults, do not drink or eat; however, males provide their mates with sperm, as well as nuptial gifts, including nutrients and water sources. We compared preferred temperatures between males and females that had access to mates or remained unmated and measured the sizes of the transferred gifts. We found that females preferred higher temperatures than males, but these preferences did not change due to mating or the transfer of larger or smaller gifts. It appears that males and females receive and lose certain amounts of water during mating, but they do not alter their thermal preferences according to the amount of water they receive or lose.The thermal environment influences insect performance, but the factors affecting insect thermal preferences are rarely studied. We studied Callosobruchus maculatus seed beetles and hypothesized that thermal preferences are influenced by water balance, with individuals with limited water reserves preferring cooler habitats to reduce evaporative water loss. Adult C. maculatus, in their flightless morph, do not consume food or water, but a copulating male provides a female with a nuptial gift of ejaculate containing nutrients and water. We hypothesized that gift recipients would prefer warmer habitats than gift donors and that both sexes would plastically adjust their thermal preferences according to the size of the transferred gift. We measured the thermal preference in each sex in individuals that were mated once or were unmated. In the mated group, we measured the sizes of the nuptial gifts and calculated proportional body mass changes in each mate during copulation. Supporting the role of water balance in thermal preference, females preferred warmer habitats than males. Nevertheless, thermal preferences in either sex were not affected by mating status or gift size. It is likely that high rates of mating and gift transfers in C. maculatus living under natural conditions promoted the evolution of constitutive sex-dependent thermal preferences.

Maternal Lethality and Paternal Rescue in the Apterous Mutant of a Seed Beetle, Callosobruchus analis (Fabricius) (Coleoptera: Chrysomelidae: Bruchinae)

Flight wings enable insects to find novel habitats, food and mates across wide geographic ranges. However, winged species sometimes produce apterous mutants that often have reduced fitness. Spread of the apterous mutation through the population can be restricted because of female sterility or the recessive inheritance of the mutation. In the seed beetle Callosobruchus maculatus (Fabricius) (Chrysomelidae: Bruchinae), an apterous trait was reported to be sex linked; the trait is not expressed in males. Apterous females in C. maculatus are usually sterile. This mutant in C. maculatus was lost a century ago, but recently I discovered apterous mutants in Callosobruchus analis (Fabricius), a sister species of C. maculatus. I examined the inheritance system of the mutant in C. analis. The mutation followed essentially the simple Mendelian inheritance that is presumed to be through a single autosomal locus with two alleles. Contrary to the case of C. maculatus, the apterous trait of C. analis was expressed in both females and males. I found that sterility was observed only in female mutants, but was rescued by a paternal gamete of a wild type. Since this characteristic can be used to investigate second male paternity, I conducted crossing experiments and found that C. analis exhibited non-zero second male paternity.

Individual and combined effects of insecticides, inert dusts and high temperatures on Callosobruchus maculatus (coleoptera: Chrysomelidae)

In this study individual and combined effects of some chemical and physical factors including cypermethrin, dichlorvos, ash, kaolin and high temperatures were assessed on adults of cowpea seed beetle Callosobruchus maculatus (F.) at laboratory conditions. The adults were exposed to the studied factors on concrete arenas prepared in plastic Petri dishes. Twenty up to 24 h old adults were released in each Petri dish, and their mortality was recorded 72 h after treatment. The LC25 values of the insecticides, LD25 values of the inert dusts and LTi25 values of high temperatures were estimated and used for determining combination effects of the two factors. To determine combination effects of three factors, LC15 values of insecticides, LD15 values of inert dusts and LTi15 values of high temperatures were estimated and used in the bioassays. The LC50 and LD50 values for cypermethrin, dichlorvos, ash and kaolin were 1286.96 mg a. i./L, 1350.55 mg a. i./L, 36.64 g/m2 and 45.18 g/m2, respectively. The LTi50 values at 45, 48, 50, 52 and 55 °C were 34, 29, 18, 11 and 8 min, respectively. The results indicated that the effect of simultaneous exposure to cypermethrin, high temperatures and ash or kaolin was significantly more than sum of individual effects of these factors. It means the effects of cypermethrin, high temperatures and inert dusts were synergized by each other. If similar treatments performed at larger scales give comparable results, it may be concluded that reduced dosage of cypermethrin, high temperatures and ash or kaolin combinations would be effective alternative control methods and can be used in cowpea seed beetle management programs.

Maladaptive plasticity facilitates evolution of thermal tolerance during an experimental range shift

BackgroundMany organisms are responding to climate change with dramatic range shifts, involving plastic and genetic changes to cope with novel climate regimes found at higher latitudes. Using experimental lineages of the seed beetle Callosobruchus maculatus, we simulated the initial phase of colonisation to progressively cooler and/or more variable conditions, to investigate how adaptation and phenotypic plasticity contribute to shifts in thermal tolerance during colonisation of novel climates.ResultsWe show that heat and cold tolerance rapidly evolve during the initial stages of adaptation to progressively cooler and more variable climates. The evolved shift in cold tolerance is, however, associated with maladaptive plasticity under the novel conditions, resulting in a pattern of countergradient variation between the ancestral and novel, fluctuating thermal environment. In contrast, lineages exposed to progressively cooler, but constant, temperatures over several generations expressed only beneficial plasticity in cold tolerances and no evolved response.ConclusionsWe propose that thermal adaptation during a range expansion to novel, more variable climates found at high latitudes and elevations may typically involve genetic compensation arising from maladaptive plasticity in the initial stages of adaptation, and that this form of (countergradient) thermal adaptation may represent an opportunity for more rapid and labile evolutionary change in thermal tolerances than via classic genetic assimilation models for thermal tolerance evolution (i.e., selection on existing reaction norms). Moreover, countergradient variation in thermal tolerances may typically mask cryptic genetic variability for these traits, resulting in apparent evolutionary stasis in thermal traits.

Combining Experimental Evolution and Genomics to Understand How Seed Beetles Adapt to a Marginal Host Plant.

Genes that affect adaptive traits have been identified, but our knowledge of the genetic basis of adaptation in a more general sense (across multiple traits) remains limited. We combined population-genomic analyses of evolve-and-resequence experiments, genome-wide association mapping of performance traits, and analyses of gene expression to fill this knowledge gap and shed light on the genomics of adaptation to a marginal host (lentil) by the seed beetle Callosobruchus maculatus. Using population-genomic approaches, we detected modest parallelism in allele frequency change across replicate lines during adaptation to lentil. Mapping populations derived from each lentil-adapted line revealed a polygenic basis for two host-specific performance traits (weight and development time), which had low to modest heritabilities. We found less evidence of parallelism in genotype-phenotype associations across these lines than in allele frequency changes during the experiments. Differential gene expression caused by differences in recent evolutionary history exceeded that caused by immediate rearing host. Together, the three genomic datasets suggest that genes affecting traits other than weight and development time are likely to be the main causes of parallel evolution and that detoxification genes (especially cytochrome P450s and beta-glucosidase) could be especially important for colonization of lentil by C. maculatus.

Efficiency of wood ashes of apples, grapes and olives against cowpea seed beetle Callosobruchus maculatus (F.) under laboratory conditions

Efficiency of wood ashes of apples, grapes and olives against cowpea seed beetle Callosobruchus maculatus (F.) under laboratory conditions

Sexual conflict and the environment: teasing apart effects arising via males and females

When males and females differ in their reproductive interests, each sex attempts to increase its own reproductive success, sometimes to the detriment of its mate. The environment that individuals experience has been shown to be fundamental in mediating this sexual conflict, since it can alter the balance between the costs and benefits that males and females obtain from mating. In the seed beetle Callosobruchus maculatus water availability is an important environmental factor that can alter this balance, with consequences for female mating strategies and the strength of sexual conflict. Whether the effect of water availability arises via effects on females or males, however, has not been explored. Here we manipulated access to water independently for adult males and females and explored how this environmental variation affected male and female mating behaviour, female fitness and offspring development. We found that access to water did not alter the size of ejaculates that males transferred, but that males with water available had longer copulation durations. We also found that females with access to water, despite living longer and laying a similar number of eggs during their lifetime, had offspring with longer development times and lower eclosion success than those of females with no access to water. Our results suggest that water availability has detrimental effects on female fitness, but despite changes in male mating behaviour these effects are not related to changes in the costliness of males as mates.