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Abstract When different alleles are favored in different environments, dominance reversal where alternate alleles are dominant in the environment in which they are favored can generate net balancing selection. The sexes represent two distinct genetic environments and sexually antagonistic (SA) selection can maintain genetic variation, especially when the alleles involved show sex-specific dominance. Sexual dimorphism in gene expression is pervasive and has been suggested to result from SA selection. Yet, whether gene-regulatory variation shows sex-specific dominance is poorly understood. We tested for sex-specific dominance in gene expression using three crosses between homozygous lines derived from a population of a seed beetle, where a previous study documented a signal of dominance reversal for fitness between the sexes. Overall, we found that the dominance effects of variants affecting gene expression were positively correlated between the sexes (r = 0.33 to 0.44). Yet, 586 transcripts showed significant differences in dominance between the sexes. Sex-specific dominance was significantly more common in transcripts with more sex-biased expression, in two of three of our crosses. Among transcripts showing sex-specific dominance, lesser sexual dimorphism in gene expression among heterozygotes was somewhat more common than greater. Gene ontology enrichment analyses showed that functional categories associated with known SA phenotypes in Callosobruchus maculatus were overrepresented among transcripts with sex-specific dominance, including genes involved in metabolic processes and the target-of-rapamycin pathway. Our results support the suggestion that sex-specific dominance of regulatory variants contributes to the maintenance of genetic variation in fitness mediated by SA selection in this species.

Abstract The Brazilian Cerrado is considered one of the world's biodiversity hotspots due to both its levels of endemism and threat. The biotic and abiotic limitations on the production of non-cultivated forest seeds in this environment are poorly studied; Plathymenia reticulata, popularly known as “vinhático” is a typical forest species of the Brazilian Cerrado. This study aimed to identify insect predators of seeds of this plant before their dispersal, quantify injuries caused by these boring insects and, after dispersal, evaluate the impact of controlled burning of vegetation on seed germination. Dry seed of P. reticulata, collected pre-dispersal, contained only the boring insect Acanthoscelides clitellarius (Fahraeus) (Chrysomelidae: Bruchinae). In general, a larva of this insect consumes around 37.7% of the dry mass of a seed. This, as a rule, makes the attacked seed unviable. Insect larvae destroyed 17.4% of the seed lots sampled. In addition to insects, post-dispersal, seed germination of this plant is significantly compromised by the action of controlled fire. Considering that this forest species is widely distributed in the Brazilian Cerrado landscape, identifying biotic and abiotic agents that compromise its seeds is of fundamental importance for conservation and recovery programs of this landscape. Resumo O Cerrado brasileiro é considerado um dos hotspots de biodiversidade do mundo devido aos seus níveis de endemismo e ameaça. As limitações bióticas e abióticas na produção de sementes florestais não cultivadas neste ambiente são pouco estudadas; Plathymenia reticulata, popularmente conhecida como “vinhático”, é uma espécie florestal típica do Cerrado brasileiro. Este estudo teve como objetivo identificar insetos predadores de sementes desta planta antes de sua dispersão, quantificar os danos causados por esses insetos perfuradores e, após a dispersão, avaliar o impacto da queima controlada da vegetação na germinação das sementes. Sementes secas de P. reticulata, coletadas antes da dispersão, continham apenas o inseto perfurador Acanthoscelides clitellarius (Fahraeus) (Chrysomelidae: Bruchinae). Em geral, uma larva deste inseto consome cerca de 37,7% da massa seca de uma semente. Isso, em regra, torna a semente atacada inviável. As larvas do inseto destruíram 17,4% dos lotes de sementes amostrados. Além dos insetos, a germinação das sementes desta planta, após a dispersão, é significativamente comprometida pela ação do fogo controlado. Considerando que esta espécie florestal possui ampla d istribuição na paisagem do Cerrado brasileiro, a identificação de agentes bióticos e abióticos que comprometem suas sementes é de fundamental importância para programas de conservação e recuperação desta paisagem.

The seed-beetle Amblycerus Thunberg, 1815 the second most diverse genus of Bruchinae (Chrysomelidae) in the Western Hemisphere, is organized into groups of species, as many others in the subfamily. The main objective of this work is to delimit the group sclerolobii , here established as composed by five described species, A. sclerolobii Ribeiro-Costa, 2000, A. kingsolveri Ribeiro-Costa, 1993, A. marinonii Ribeiro-Costa, 1993, A. manauara Ribeiro-Costa, 2000, A. tachigaliae Kingsolver, 1976 and four new species: A. biacutus Ribeiro-Costa, sp. nov. , A. falcorostrus Ribeiro-Costa & Morse, sp. nov ., A. morsei Ribeiro-Costa, sp. nov. (type localities: Brazil: Amazonas, Manaus) and A. truncatus Ribeiro-Costa, sp. nov. (type locality Brazil: Mato Grosso, Sinop). Therefore, including these new species 70 Brazilian species of Amblycerus were recorded. Amblycerus bicolor (Pic, 1927) previously considered to belong to this group is excluded and placed as incertae sedis. The sclerolobii group is distributed mainly in the Brazilian Amazonia biome, consuming Tachigali Aubl., Dinizia Ducke, and Stryphnodendron Mart. seeds (Fabaceae). Diagnoses are presented for this group and for ten species (including A. bicolor ), and descriptions for the four new ones, an identification key for the nine species, colored photographs of external morphology, and detailed male genitalia illustrations for all the species studied. Due mainly to previously broad contributions on the taxonomy of Amblycerus that resulted in many species groups, we also present a revised study of this intrageneric taxonomic level. From 37 species groups now we update to 32 groups with a total of 96 species assigned to them. Finally, a detailed systematic study of some specific groups is also suggested before mergence.

Metabolic rate (MR) is a key functional trait simply because metabolism converts resources into population growth rate. Yet, our empirical understanding of the sources of within species variation in MR, as well as of its life history and ecological correlates, is rather limited. Here, we assess whether MR lies at the root of a syndrome of correlated rate‐dependent life‐history traits in an insect. Selection for early (E) or late (L) age‐at‐reproduction for >160 generations in the bean beetle Acanthoscelides obtectus has produced beetles that differ markedly in juvenile development, body size, fecundity schedules, ageing and life span. Here, we use micro‐respirometry to test whether this has been associated with the evolution of age‐ and sex‐specific metabolic phenotypes. We find that mass‐specific MR is 18% higher in E lines compared to L lines and that MR decreases more rapidly with chronological, but not biological, age in E lines. Males, under sexual selection to “live‐fast‐die‐young”, show 50% higher MR than females and MR decreased more rapidly with age in males. Our results are consistent with a central role for MR for the divergence in “pace‐of‐life” seen in these beetles, supporting the view that MR lies at the root of ecologically relevant life‐history trait variation within species. A plain language summary is available for this article. Plain Language Summary

The role of mitochondrial DNA for the evolution of life-history traits remains debated. We examined mitonuclear effects on the activity of the multisubunit complex of the electron transport chain (ETC) involved in oxidative phosphorylation (OXPHOS) across lines of the seed beetle Acanthoscelides obtectus selected for a short (E) or a long (L) life for more than > 160 generations. We constructed and phenotyped mitonuclear introgression lines, which allowed us to assess the independent effects of the evolutionary history of the nuclear and the mitochondrial genome. The nuclear genome was responsible for the largest share of divergence seen in ageing. However, the mitochondrial genome also had sizeable effects, which were sex-specific and expressed primarily as epistatic interactions with the nuclear genome. The effects of mitonuclear disruption were largely consistent with mitonuclear coadaptation. Variation in ETC activity explained a large proportion of variance in ageing and life-history traits and this multivariate relationship differed somewhat between the sexes. In conclusion, mitonuclear epistasis has played an important role in the laboratory evolution of ETC complex activity, ageing, and life histories and these are closely associated. The mitonuclear architecture of evolved differences in life-history traits and mitochondrial bioenergetics was sex-specific.

Genetic differentiation can be promoted allopatrically by geographic isolation of populations due to limited dispersal ability and diversification over time or sympatrically through, for example, host-race formation. In crop pests, the trading of crops across the world can lead to intermixing of genetically distinct pest populations. However, our understanding of the importance of allopatric and sympatric genetic differentiation in the face of anthropogenic genetic intermixing is limited. Here, we examined global sequence variation in two mitochondrial and one nuclear genes in the seed beetle Callosobruchus maculatus that uses different legumes as hosts. We analyzed 180 samples from 42 populations of this stored bean pest from tropical and subtropical continents and archipelagos: Africa, the Middle East, South and Southeast Asia, Oceania and South America. For the mitochondrial genes, there was weak but significant genetic differentiation across continents/archipelagos. Further, we found pronounced differentiation among subregions within continents/archipelagos both globally and within Africa but not within Asia. We suggest that multiple introductions into Asia and subsequent intermixing within Asia have generated this pattern. The isolation by distance hypothesis was supported globally (with or without continents controlled) but not when host species was restricted to cowpeas Vigna unguiculata, the ancestral host of C. maculatus. We also document significant among-host differentiation both globally and within Asia, but not within Africa. We failed to reject a scenario of a constant population size in the recent past combined with selective neutrality for the mitochondrial genes. We conclude that mitochondrial DNA differentiation is primarily due to geographic isolation within Africa and to multiple invasions by different alleles, followed by host shifts, within Asia. The weak inter-continental differentiation is most likely due to frequent inter-continental gene flow mediated by human crop trade.

Aim: The seed beetle Callosobruchus maculatus is an important tropical and subtropical pest of legumes distributed world-wide. Archaeological evidence suggests an African origin with later world-wide invasion facilitated by the last centuries' legume trading and exchange. To date, no studies could identify the routes or timing of dispersal of the species. Here, we investigate the global phylogeography of this pest to shed light on the main inter-continental dispersal routes that led to it becoming a cosmopolitan pest. Location: World-wide. Methods: We sampled seed beetles over a large fraction of the species' range and sequenced one nuclear and three mitochondrial loci. Using this data, we estimated spatio-temporal phylogeographical reconstructions, and the demographic history of the species. We also used our dataset to evaluate the effect of panmixia on Bayesian demographic estimations. Results: Callosobruchus maculatus exhibited regional and continental genetic structure, with the highest genetic diversity found in Africa. Our discrete Bayesian phylogeographical approach indicated that the species first dispersed to Asia and then colonized the pantropical belt. The three methods used for inferring the demographic history of C. maculatus indicated a recent demographic expansion in the world-wide dataset, as well as in the subset restricted to African samples. Such a signal was, however, not observed in the subset composed of Asian specimens. This demographic expansion occurred in the Holocene and is likely explained by the spread of cowpea and other host legumes across and out of Africa. Main conclusions: The inferred dispersal routes support the idea that the evolutionary history of C. maculatus relates to the trade of its main host plant, Vigna unguiculata. Human-mediated processes appear to have shaped the global genetic structure of this pest. As a methodological implication, we demonstrate that coalescent-based demographic reconstructions can be erroneous if the dataset violates the assumption of panmixia.

Reproductive interference (RI) is a negative interspecific interaction caused by reproductive activities. Previous studies have implied that male-male competition increases RI capability, consisting of the male harm-inflicting capability of RI by males (RI infliction) and the female susceptibility to heterospecific male harm (RI resistance). Geographical populations show variations in the intensity of male-male competition and sexual conflict due to the influence of biotic/abiotic factors. We made two predictions: (1) RI capability would vary among conspecific populations, and (2) the degree of RI infliction by males would match that of female RI resistance in geographical strains. To test these predictions, we measured the fecundity of once-mated females in two scenarios: housed with heterospecific males and without males. We performed experiments using six strains from each of two bean weevil species, Callosobruchus maculatus and C. chinensis. The results demonstrated intraspecific variation in RI capability within both Callosobruchus species, but the RI infliction of males and RI resistance of females within a geographical strain did not consistently coincide. Our results suggest that RI varies depending on geographical strains, even within species, but we did not obtain evidence that sexual conflict molds RI capability, indicating traits driving RI do not follow the sexual conflict in both Callosobruchus species.

Allometric analysis provides an insight into the function and diversification mechanisms of body parts in organisms. The allometry and variability in size of various body parts of three hymenopteran species, Anisopteromalus calandrae (Howard), Anisopteromalus quinarius Gokhman & Baur, and Heterospilus prosopidis Viereck, which are solitary ectoparasitoids of stored-product insect pests, were studied. The relationship between many of the traits measured and body size is negatively allometric, others were isometric, and none were positively allometric. The two species of Anisopteromalus were less variable in size than H. prosopidis and there were intersexual differences in both species of Anisopteromalus. Although the patterns in these differences are complex and difficult to interpret from an ecological perspective, based on information on their behaviour it is hypothesized that stabilizing selection is associated with the negative allometry of two traits: ovipositor length in at least two species and male leg length in both species of Anisopteromalus. This hypothesis is supported by the lower variability in the size of these body parts compared to other body parts examined in this study, which is typical of traits subject to stabilizing selection.

Phytophagous beetles, particularly those within the superfamilies Chrysomeloidea and Curculionoidea, constitute one of the most diverse and ecologically significant groups of insect herbivores. Within this group, the subfamily Bruchinae is especially notable for its close association with leguminous plant seeds. As most Bruchinae species do not feed during the adult stage, the timing and regulation of vitellogenesis remain unclear. Previous studies suggest that vitellogenesis may be triggered by volatile organic compounds emitted by host seeds, which promote juvenile hormone (JH) synthesis. This increase in JH is hypothesized to stimulate vitellogenesis, enhance female attractiveness, and ultimately facilitate fertilization and oviposition. To explore this hypothesis, we investigated the external cues regulating reproductive physiology in the capital breeder Zabrotes subfasciatus. Specifically, we examined the effects of host seeds and male presence on oviposition dynamics, fecundity, ovary activation, and the expression of vitellogenic genes (vg and vgR) throughout adult life. Our results show that females initiate vitellogenesis during the final phases of adult development, enabling oviposition to begin as early as the first day after emergence. Oviposition remains at basal levels throughout adult life unless both host seeds and males are present (p < 0.0001). This oviposition pattern is consistent with ovary activation dynamics, which reveal that vitellogenesis peaks early in the oviposition period and is prolonged by the presence of seeds and males (p < 0.05). Notably, vg and vgR gene expression respond differentially to these cues (p < 0.05). We integrate our findings with previous literature to propose a working model for the regulation of oviposition in the Bruchinae beetle Z. subfasciatus.