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1.
Ecol Evol ; 13(9): e10501, 2023 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-37706164

RESUMO

Previous genetic studies of pollinator wasps associated with a community of strangler figs (Ficus subgenus Urostigma, section Americana) in Central Panama suggest that the wasp species exhibit a range in host specificity across their host figs. To better understand factors that might contribute to this observed range of specificity, we used sticky traps to capture fig-pollinating wasp individuals at 13 Ficus species, sampling at different phases of the reproductive cycle of the host figs (e.g., trees with receptive inflorescences, or vegetative trees, bearing only leaves). We also sampled at other tree species, using them as non-Ficus controls. DNA barcoding allowed us to identify the wasps to species and therefore assign their presence and abundance to host fig species and the developmental phase of that individual tree. We found: (1) wasps were only very rarely captured at non-Ficus trees; (2) nonetheless, pollinators were captured often at vegetative individuals of some host species; (3) overwhelmingly, wasp individuals were captured at receptive host fig trees representing the fig species from which they usually emerge. Our results indicate that wasp occurrence is not random either spatially or temporally within the forest and across these hosts, and that wasp specificity is generally high, both at receptive and vegetative host trees. Therefore, in addition to studies that show chemicals produced by receptive fig inflorescences attract pollinator wasps, we suggest that other cues (e.g., chemicals produced by the leaves) can also play a role in host recognition. We discuss our results in the context of recent findings on the role of host shifts in diversification processes in the Ficus genus.

2.
Zoological Lett ; 6: 10, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32549998

RESUMO

[This corrects the article DOI: 10.1186/s40851-020-00158-4.].

3.
Zoological Lett ; 6: 6, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32467772

RESUMO

We examine evidence for natural selection resulting in Apis mellifera becoming tolerant or resistant to Varroa mites in different bee populations. We discuss traits implicated in Varroa resistance and how they can be measured. We show that some of the measurements used are ambiguous, as they measure a combination of traits. In addition to behavioural traits, such as removal of infested pupae, grooming to remove mites from bees or larval odours, small colony size, frequent swarming, and smaller brood cell size may also help to reduce reproductive rates of Varroa. Finally, bees may be tolerant of high Varroa infections when they are resistant or tolerant to viruses implicated in colony collapse. We provide evidence that honeybees are an extremely outbreeding species. Mating structure is important for how natural selection operates. Evidence for successful natural selection of resistance traits against Varroa comes from South Africa and from Africanized honeybees in South America. Initially, Varroa was present in high densities and killed about 30% of the colonies, but soon after its spread, numbers per hive decreased and colonies survived without treatment. This shows that natural selection can result in resistance in large panmictic populations when a large proportion of the population survives the initial Varroa invasion. Natural selection in Europe and North America has not resulted in large-scale resistance. Upon arrival of Varroa, the frequency of traits to counter mites and associated viruses in European honey bees was low. This forced beekeepers to protect bees by chemical treatment, hampering natural selection. In a Swedish experiment on natural selection in an isolated mating population, only 7% of the colonies survived, resulting in strong inbreeding. Other experiments with untreated, surviving colonies failed because outbreeding counteracted the effects of selection. If loss of genetic variation is prevented, colony level selection in closed mating populations can proceed more easily, as natural selection is not counteracted by the dispersal of resistance genes. In large panmictic populations, selective breeding can be used to increase the level of resistance to a threshold level at which natural selection can be expected to take over.

4.
Evol Dev ; 22(1-2): 205-217, 2020 01.
Artigo em Inglês | MEDLINE | ID: mdl-31622546

RESUMO

The absence of a paternal contribution in an unfertilized ovum presents two developmental constraints against the evolution of parthenogenesis. We discuss the constraint caused by the absence of a centrosome and the one caused by the missing set of chromosomes and how they have been broken in specific taxa. They are examples of only a few well-underpinned examples of developmental constraints acting at macro-evolutionary scales in animals. Breaking of the constraint of the missing chromosomes is the best understood and generally involves rare occasions of drastic changes of meiosis. These drastic changes can be best explained by having been induced, or at least facilitated, by sudden cytological events (e.g., repeated rounds of hybridization, endosymbiont infections, and contagious infections). Once the genetic and developmental machinery is in place for regular or obligate parthenogenesis, shifts to other types of parthenogenesis can apparently rather easily evolve, for example, from facultative to obligate parthenogenesis, or from pseudoarrhenotoky to haplodiploidy. We argue that the combination of the two developmental constraints forms a near-absolute barrier against the gradual evolution from sporadic to obligate or regular facultative parthenogenesis, which can probably explain why the occurrence of the highly advantageous mode of regular facultative parthenogenesis is so rare and entirely absent in vertebrates.


Assuntos
Evolução Biológica , Invertebrados/crescimento & desenvolvimento , Partenogênese , Vertebrados/crescimento & desenvolvimento , Animais
5.
Insect Sci ; 27(6): 1334-1345, 2020 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-31599487

RESUMO

The majority of adult parasitoid wasps are unable to synthesize lipids and therefore face a trade-off between the investment of lipids in eggs or in the maintenance of soma. It has been shown that resource allocation should depend on body size in parasitoids. Given that smaller females have shorter expected life times, they should concentrate their reproductive effort into early life. To test this prediction, we investigated the relationship between body size and the timing of egg production in parasitoids. We measured body size, lipid reserves, and reproductive investment (number of eggs, ovigeny index equivalent [OIE] and egg size) at eclosion in five species of Asobara (Hymenoptera: Braconidae) originating from different geographic and climatic environments. Our results show significant interspecific variation in all these traits. A diagnostic test for phylogenetic independence revealed that closely related species did not resemble each other more closely than expected by chance for all traits measured. Lipid reserves scaled positively with body size both between and within species. In agreement with theory, OI correlated negatively with body size both between and within species. Total egg area at eclosion correlated negatively with lipid reserves both between and within species. This indicates the existence of a trade-off between allocation of lipids to current reproduction and survival/future reproduction. With the exception of the most extreme pro-ovigenic species, A. persimilis, we found that pro-ovigeny was compensated for by small egg size. Our results indicate the role of habitats in shaping interspecific variation in resource allocation strategies.


Assuntos
Vespas/fisiologia , Animais , Tamanho Corporal , Feminino , Reprodução , Especificidade da Espécie , Fatores de Tempo , Vespas/crescimento & desenvolvimento
6.
PeerJ ; 5: e3699, 2017.
Artigo em Inglês | MEDLINE | ID: mdl-28924495

RESUMO

BACKGROUND: Coexistence of sexual and asexual populations remains a key question in evolutionary ecology. We address the question how an asexual and a sexual form of the parasitoid Venturia canescens can coexist in southern Europe. We test the hypothesis that both forms are adapted to different habitats within their area of distribution. Sexuals inhabit natural environments that are highly unpredictable, and where density of wasps and their hosts is low and patchily distributed. Asexuals instead are common in anthropic environments (e.g., grain stores) where host outbreaks offer periods when egg-load is the main constraint on reproductive output. METHODS: We present a meta-analysis of known adaptations to these habitats. Differences in behavior, physiology and life-history traits between sexual and asexual wasps were standardized in term of effect size (Cohen's d value; Cohen, 1988). RESULTS: Seeking consilience from the differences between multiple traits, we found that sexuals invest more in longevity at the expense of egg-load, are more mobile, and display higher plasticity in response to thermal variability than asexual counterparts. DISCUSSION: Thus, each form has consistent multiple adaptations to the ecological circumstances in the contrasting environments.

7.
Oecologia ; 174(3): 967-77, 2014 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-24169941

RESUMO

Coexistence of species sharing the same resources is often possible if species are phylogenetically divergent in resource acquisition and allocation traits, decreasing competition between them. Developmental and life-history traits related to resource use are influenced by environmental conditions such as temperature, but thermal trait responses may differ among species. An increase in ambient temperature may, therefore, affect trait divergence within a community, and potentially species coexistence. Parasitoids are interesting models to test this hypothesis, because multiple species commonly attack the same host, and employ divergent larval and adult host use strategies. In particular, development mode (arrested or continued host growth following parasitism) has been recognized as a major organiser of parasitoid life histories. Here, we used a comparative trait-based approach to determine thermal responses of development time, body mass, egg load, metabolic rate and energy use of the coexisting Drosophila parasitoids Asobara tabida, Leptopilina heterotoma, Trichopria drosophilae and Spalangia erythromera. We compared trait values between species and development modes, and calculated trait divergence in response to temperature, using functional diversity indices. Parasitoids differed in their thermal response for dry mass, metabolic rate and lipid use throughout adult life, but only teneral lipid reserves and egg load were affected by developmental mode. Species-specific trait responses to temperature were probably determined by their adaptations in resource use (e.g. lipogenesis or ectoparasitism). Overall, trait values of parasitoid species converged at the higher temperature. Our results suggest that local effects of warming could affect host resource partitioning by reducing trait diversity in communities.


Assuntos
Drosophila melanogaster/parasitologia , Himenópteros/crescimento & desenvolvimento , Temperatura , Animais , Metabolismo Basal , Tamanho Corporal , Feminino , Aquecimento Global , Interações Hospedeiro-Parasita , Himenópteros/metabolismo , Larva , Metabolismo dos Lipídeos , Oviparidade , Óvulo , Fenótipo , Filogenia , Especificidade da Espécie
8.
Mol Ecol ; 22(17): 4433-44, 2013 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-23879258

RESUMO

Wolbachia are endosymbiotic bacteria known to manipulate the reproduction of their hosts. These manipulations are expected to have consequences on the population genetics of the host, such as heterozygosity levels, genetic diversity and gene flow. The parasitoid wasp Tetrastichus coeruleus has populations that are infected with parthenogenesis-inducing Wolbachia and populations that are not infected. We studied the population genetics of T. coeruleus between and within Wolbachia-infected and uninfected populations, using nuclear microsatellites and mitochondrial DNA. We expected reduced genetic diversity in both DNA types in infected populations. However, migration and gene flow could introduce new DNA variants into populations. We therefore paid special attention to individuals with unexpected (genetic) characteristics. Based on nuclear and mitochondrial DNA, two genetic clusters were evident: a thelytokous cluster containing all Wolbachia-infected, parthenogenetic populations and an arrhenotokous cluster containing all uninfected, sexual populations. Nuclear and mitochondrial DNA did not exhibit concordant patterns of variation, although there was reduced genetic diversity in infected populations for both DNA types. Within the thelytokous cluster, there was nuclear DNA variation, but no mitochondrial DNA variation. This nuclear DNA variation may be explained by occasional sex between infected females and males, by horizontal transmission of Wolbachia, and/or by novel mutations. Several females from thelytokous populations were uninfected and/or heterozygous for microsatellite loci. These unexpected characteristics may be explained by migration, by inefficient transmission of Wolbachia, by horizontal transmission of Wolbachia, and/or by novel mutations. However, migration has not prevented the build-up of considerable genetic differentiation between thelytokous and arrhenotokous populations.


Assuntos
Variação Genética , Genética Populacional , Vespas/genética , Vespas/microbiologia , Wolbachia/fisiologia , Animais , Bélgica , Núcleo Celular/genética , Análise por Conglomerados , DNA Mitocondrial/genética , Feminino , Genes de Insetos , Haplótipos , Masculino , Repetições de Microssatélites , Modelos Genéticos , Dados de Sequência Molecular , Países Baixos , Partenogênese , Simbiose
9.
Ned Tijdschr Geneeskd ; 157(4): A5687, 2013.
Artigo em Holandês | MEDLINE | ID: mdl-23343740

RESUMO

Medications and radiographic contrast dyes are sometimes detected in surface waters, ground water and drinking water; these have proven detrimental effects on organisms living in such waters The concentration of medications found in drinking water is at least a thousand times below their minimum therapeutic dosages. In humans, the long-term effects of daily exposure to low dosages of medications and 'mixture toxicity' is not known; based on the concentrations and substance toxicity, it is presumed that the risk is nil.. Physicians can play their part in controlling the problem of medications becoming part of the water cycle by taking this into account when prescribing medications. Users can make a difference by handling their medications with care and by returning all unused portions to the pharmacy. The pharmaceutical industry can also do its part by taking degradability, options for removal and the environmental effects of medications into account during their stages of development.


Assuntos
Água Potável , Resíduos de Drogas/efeitos adversos , Resíduos de Drogas/análise , Poluição Química da Água/efeitos adversos , Poluição Química da Água/análise , Água Potável/administração & dosagem , Água Potável/efeitos adversos , Água Potável/análise , Água Potável/química , Monitoramento Ambiental , Humanos , Medição de Risco
10.
J Theor Biol ; 309: 67-77, 2012 Sep 21.
Artigo em Inglês | MEDLINE | ID: mdl-22728675

RESUMO

Temperature increase can affect physiological and behavioural constraints. Here, we use a stochastic dynamic modelling approach to predict changes in physiological adaptations and behaviour in response to temperature increase of pro-ovigenic parasitoids (i.e., parasitoids that mature all of their eggs before emergence). Adults of most species of parasitoids, are not capable of de novo lipogenesis. The allocation of lipids accumulated during the larval stage determines adult lifespan and fecundity. In females, lipids can be allocated either to egg production or to adult lipid reserves leading to a trade-off between fecundity and lifespan. Our results show that selection by an increase in ambient temperature, favours a smaller initial egg load and a larger amount of lipids for maintenance. The cost of habitat exploitation increases with temperature because the rate of lipid consumption increases. Hence, lifetime reproductive success decreases. When the optimal activity rate shifts to match the higher ambient temperature, these effects become less pronounced.


Assuntos
Adaptação Fisiológica , Mudança Climática , Óvulo/fisiologia , Parasitos/fisiologia , Animais , Metabolismo Basal , Ecossistema , Modelos Biológicos , Oviposição/fisiologia , Parasitos/metabolismo , Análise de Regressão , Reprodução/fisiologia , Temperatura
11.
Mol Ecol ; 21(16): 3898-906, 2012 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-22548357

RESUMO

The widespread occurrence of sex is one of the most elusive problems in evolutionary biology. Theory predicts that asexual lineages can be driven to extinction by uncontrolled proliferation of vertically transmitted transposable elements (TEs), which accumulate because of the inefficiency of purifying selection in the absence of sex and recombination. To test this prediction, we compared genome-wide TE load between a sexual lineage of the parasitoid wasp Leptopilina clavipes and a lineage of the same species that is rendered asexual by Wolbachia-induced parthenogenesis. We obtained draft genome sequences at 15-20× coverage of both the sexual and the asexual lineages using next-generation sequencing. We identified transposons of most major classes in both lineages. Quantification of TE abundance using coverage depth showed that copy numbers in the asexual lineage exceeded those in the sexual lineage for DNA transposons, but not LTR and LINE-like elements. However, one or a small number of gypsy-like LTR elements exhibited a fourfold higher coverage in the asexual lineage. Quantitative PCR showed that high loads of this gypsy-like TE were characteristic for 11 genetically distinct asexual wasp lineages when compared to sexual lineages. We found no evidence for an overall increase in copy number for all TE types in asexuals as predicted by theory. Instead, we suggest that the expansions of specific TEs are best explained as side effects of (epi)genetic manipulations of the host genome by Wolbachia. Asexuality is achieved in a myriad of ways in nature, many of which could similarly result in TE proliferation.


Assuntos
Reprodução Assexuada/genética , Vespas/fisiologia , Wolbachia/fisiologia , Animais , Evolução Biológica , Metilação de DNA , Elementos de DNA Transponíveis , Feminino , Genoma de Inseto , Elementos Nucleotídeos Longos e Dispersos , Dados de Sequência Molecular , Partenogênese/genética , Sequências Repetidas Terminais , Vespas/microbiologia
12.
J Insect Physiol ; 58(7): 979-84, 2012 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-22579566

RESUMO

Metabolic rate, a physiological trait closely related to fitness traits, is expected to evolve in response to two main environmental variables: (1) climate, low metabolic rates being found in dry and hot regions when comparing populations originating from different climates in a common garden experiment and (2) resource limitations, low metabolic rates being selected when resources are limited. The main goal of this study was to investigate if differences in intrinsic resource limitations may have disrupted the expected evolution of metabolic rate in response to climate in a parasitic wasp. We compared CO(2) production of females from 4 populations of a Drosophila parasitoid, Leptopilina boulardi, as an estimate of their metabolic rate. Two populations from a hot and dry area able to synthesise lipids de novo at adult stage were compared with two populations originating from a mild and humid climate where no lipid accumulation during adult life was observed. These last females are thus more limited in lipids than the first ones. We observed that a high metabolic rate has been selected in hot and dry environments, contrarily to the results of a great majority of studies. We suggest that lipogenesis occurring there may have allowed the selection of a higher metabolic rate, as females are less limited in energetic resources than females from the mild environment. A high metabolic rate may have been selected there as it partly compensates for the long distances that females have to cross to find laying opportunities in distant orchards. We suggest that intrinsic resources should be integrated when investigating geographical variations in metabolism as this factor may disrupt evolution in response to climate.


Assuntos
Evolução Biológica , Vespas/química , Vespas/metabolismo , Animais , Clima , Ecossistema , Feminino , Cinética , Metabolismo dos Lipídeos , Fenótipo , Temperatura , Vespas/genética
13.
PLoS One ; 6(7): e20870, 2011.
Artigo em Inglês | MEDLINE | ID: mdl-21765889

RESUMO

Females of the larval parasitoid of Drosophila, Asobara citri, from sub-Saharan Africa, defend patches with hosts by fighting and chasing conspecific females upon encounter. Females of the closely related, palearctic species Asobara tabida do not defend patches and often search simultaneously in the same patch. The effect of patch defence by A. citri females on their distribution in a multi-patch environment was investigated, and their distributions were compared with those of A. tabida. For both species 20 females were released from two release-points in replicate experiments. Females of A. citri quickly reached a regular distribution across 16 patches, with a small variance/mean ratio per patch. Conversely, A. tabida females initially showed a clumped distribution, and after gradual dispersion, a more Poisson-like distribution across patches resulted (variance/mean ratio was closer to 1 and higher than for A. citri). The dispersion of A. tabida was most probably an effect of exploitation: these parasitoids increasingly made shorter visits to already exploited patches. We briefly discuss hypotheses on the adaptive significance of patch defence behaviour or its absence in the light of differences in the natural history of both parasitoid species, notably the spatial distribution of their hosts.


Assuntos
Envelhecimento/fisiologia , Drosophila/fisiologia , Drosophila/parasitologia , Meio Ambiente , Territorialidade , Clima Tropical , Vespas/fisiologia , Animais , Comportamento Animal , Simulação por Computador , Feminino , Modelos Biológicos , Fatores de Tempo
14.
Naturwissenschaften ; 98(8): 705-9, 2011 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-21681419

RESUMO

In holometabolous insects, pupation site selection behaviour has large consequences for survival. Here, we investigated the combined effects of temperature and parasitism by the parasitoid Asobara tabida on larval pupation behaviour in two of its main Drosophila sp. hosts differing in their climate origin. We found that larvae of Drosophila melanogaster--a species with a (sub)tropical origin--placed at 25°C pupated higher in rearing jars than those placed at 15°C. The opposite pattern was observed for Drosophila subobscura larvae--a species from temperate regions--which pupated lower, i.e. on or near the substrate at 25°C, than those placed at 15°C. When placed at 25°C, parasitized larvae of both species pupated closer to the substrate than unparasitized ones. Moreover, the Drosophila larvae that had been exposed and probably stung by A. tabida, but were not parasitized, pupated lower than the control unparasitized larvae. These results provide new insights of host behaviour manipulation by A. tabida larvae.


Assuntos
Drosophila/fisiologia , Drosophila/parasitologia , Interações Hospedeiro-Parasita/fisiologia , Himenópteros/fisiologia , Temperatura , Animais , Drosophila melanogaster/parasitologia , Drosophila melanogaster/fisiologia , Larva/parasitologia , Pupa
15.
Mol Ecol ; 20(17): 3644-52, 2011 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-21668807

RESUMO

Wolbachia are endocellular bacteria known for manipulating the reproductive systems of many of their invertebrate hosts. Wolbachia are transmitted vertically from mother to offspring. In addition, new infections result from horizontal transmission between different host species. However, to what extent horizontal transmission plays a role in the spread of a new infection through the host population is unknown. Here, we investigate whether horizontal transmission of Wolbachia can explain clonal genetic variation in natural populations of Leptopilina clavipes, a parasitoid wasp infected with a parthenogenesis-inducing Wolbachia. We assessed variance of markers on the nuclear, mitochondrial and Wolbachia genomes. The nuclear and mitochondrial markers displayed significant and congruent variation among thelytokous wasp lineages, showing that multiple lineages have become infected with Wolbachia. The alternative hypothesis in which a single female became infected, the daughters of which mated with males (thus introducing nuclear genetic variance) cannot account for the presence of concordant variance in mtDNA. All Wolbachia markers, including the hypervariable wsp gene, were invariant, suggesting that only a single strain of Wolbachia is involved. These results show that Wolbachia has transferred horizontally to infect multiple female lineages during the early spread through L. clavipes. Remarkably, multiple thelytokous lineages have persisted side by side in the field for tens of thousands of generations.


Assuntos
Genes Bacterianos , Interações Hospedeiro-Patógeno , Vespas/genética , Wolbachia/genética , Wolbachia/patogenicidade , Animais , DNA Mitocondrial/genética , Transmissão de Doença Infecciosa , Feminino , Variação Genética , Haplótipos , Masculino , Repetições de Microssatélites , Dados de Sequência Molecular , Tipagem de Sequências Multilocus/métodos , Partenogênese/genética , Filogeografia , Análise de Sequência de DNA , Fatores Sexuais , Vespas/microbiologia
16.
BMC Ecol ; 11: 4, 2011 Jan 27.
Artigo em Inglês | MEDLINE | ID: mdl-21272293

RESUMO

BACKGROUND: The genetic structure of populations can be influenced by geographic isolation (including physical distance) and ecology. We examined these effects in Leptopilina boulardi, a parasitoid of Drosophila of African origin and widely distributed over temperate and (sub) tropical climates. RESULTS: We sampled 11 populations of L. boulardi from five climatic zones in Iran and measured genetic differentiation at nuclear (Amplified Fragment Length Polymorphism; AFLP) and mitochondrial (Cytochrome Oxidase I; COI) loci. An Analysis of Molecular Variance (AMOVA) for the AFLP data revealed that 67.45% of variation resided between populations. No significant variation was observed between climatic zones. However, a significant difference was detected between populations from the central (dry) regions and those from the wetter north, which are separated by desert. A similarly clear cut genetic differentiation between populations from the central part of Iran and those from the north was observed by UPGMA cluster analysis and Principal Coordinates Analysis (PCO). Both UPGMA and PCO further separated two populations from the very humid western Caspian Sea coast (zone 3) from other northern populations from the temperate Caspian Sea coastal plain (zone 2), which are connected by forest. One population (Nour) was genetically intermediate between these two zones, indicating some gene flow between these two groups of populations. In all analyses a mountain population, Sorkhabad was found to be genetically identical to those from the nearby coastal plain (zone 2), which indicates high gene flow between these populations over a short geographical distance. One population from the Caspian coast (Astaneh) was genetically highly diverged from all other populations. A partial Mantel test showed a highly significant positive correlation between genetic and geographic distances, as well as separation by the deserts of central Iran. The COI sequences were highly conserved among all populations. CONCLUSION: The Iranian populations of L. boulardi showed clear genetic structure in AFLP profiles, but not in COI sequence data. The transfer of fruits containing Drosophila larvae parasitized by L. boulardi appears to have caused some unexpected gene flow and changed the genetic composition of populations, particularly in urban areas. Nevertheless, our results suggest that climate, geographic distance and physical barriers may all have contributed to the formation of genetically distinct populations of L. boulardi. Inevitably, there will be overlap between the portions of variance explained by these variables. Disentangling the relative contributions of climate and geography to the genetic structure of this species will require additional sampling.


Assuntos
Vespas/genética , Análise do Polimorfismo de Comprimento de Fragmentos Amplificados , Animais , Clima , Drosophila/parasitologia , Complexo IV da Cadeia de Transporte de Elétrons/genética , Fluxo Gênico , Variação Genética , Proteínas de Insetos/genética , Irã (Geográfico) , Melaço , Dados de Sequência Molecular , Filogenia , Vespas/classificação , Vespas/enzimologia , Vespas/fisiologia
17.
Naturwissenschaften ; 98(3): 175-80, 2011 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-21221516

RESUMO

Wolbachia is a maternally inherited bacterium that manipulates the reproduction of its host. Recent studies have shown that male-killing strains can induce cytoplasmic incompatibility (CI) when introgressed into a resistant host. Phylogenetic studies suggest that transitions between CI and other Wolbachia phenotypes have also occurred frequently, raising the possibility that latent CI may be widespread among Wolbachia. Here, we investigate whether a parthenogenesis-inducing Wolbachia strain can also induce CI. Parthenogenetic females of the parasitoid wasp Asobara japonica regularly produce a small number of males that may be either infected or not. Uninfected males were further obtained through removal of the Wolbachia using antibiotics and from a naturally uninfected strain. Uninfected females that had mated with infected males produced a slightly, but significantly more male-biased sex ratio than uninfected females that had mated with uninfected males. This effect was strongest in females that mated with males that had a relatively high Wolbachia titer. Quantitative PCR indicated that infected males did not show higher ratios of nuclear versus mitochondrial DNA content. Wolbachia therefore does not cause diploidization of cells in infected males. While these results are consistent with CI, other alternatives such as production of abnormal sperm by infected males cannot be completely ruled out. Overall, the effect was very small (9%), suggesting that if CI is involved it may have degenerated through the accumulation of mutations.


Assuntos
Citoplasma/fisiologia , Vespas/microbiologia , Wolbachia/fisiologia , Animais , Cruzamento , Feminino , Genes Bacterianos/genética , Masculino , Dados de Sequência Molecular , Razão de Masculinidade , Wolbachia/genética
18.
PLoS One ; 5(12): e14251, 2010 Dec 08.
Artigo em Inglês | MEDLINE | ID: mdl-21170378

RESUMO

Behavioral ecologists assume that animals use a motivational mechanism for decisions such as action selection and time allocation, allowing the maximization of their fitness. They consider both the proximate and ultimate causes of behavior in order to understand this type of decision-making in animals. Experimental psychologists and neuroeconomists also study how agents make decisions but they consider the proximate causes of the behavior. In the case of patch-leaving, motivation-based decision-making remains simple speculation. In contrast to other animals, human beings can assess and evaluate their own motivation by an introspection process. It is then possible to study the declared motivation of humans during decision-making and discuss the mechanism used as well as its evolutionary significance. In this study, we combine both the proximate and ultimate causes of behavior for a better understanding of the human decision-making process. We show for the first time ever that human subjects use a motivational mechanism similar to small insects such as parasitoids and bumblebees to decide when to leave a patch. This result is relevant for behavioral ecologists as it supports the biological realism of this mechanism. Humans seem to use a motivational mechanism of decision making known to be adaptive to a heterogeneously distributed resource. As hypothesized by Hutchinson et al. and Wilke and Todd, our results are consistent with the evolutionary shaping of decision making because hominoids were hunters and gatherers on food patches for more than two million years. We discuss the plausibility of a neural basis for the motivation mechanism highlighted here, bridging the gap between behavioral ecology and neuroeconomy. Thus, both the motivational mechanism observed here and the neuroeconomy findings are most likely adaptations that were selected for during ancestral times.


Assuntos
Tomada de Decisões , Adolescente , Adulto , Animais , Comportamento de Escolha , Comunicação , Ecologia , Evolução Molecular , Feminino , Humanos , Aprendizagem , Masculino , Pessoa de Meia-Idade , Modelos Estatísticos , Motivação , Análise de Regressão , Software
19.
C R Biol ; 333(6-7): 554-65, 2010.
Artigo em Inglês | MEDLINE | ID: mdl-20541166

RESUMO

Many organisms, including entomopathogenous fungi, predators or parasites, use aphids as ressources. Parasites of aphids are mostly endoparasitoid insects, i.e. insects which lay eggs inside the body of an other insect which will die as a result of their development. In this article, we review the consequences of the numerous pecularities of aphid biology and ecology for their endoparasitoids, notably the Aphidiinae (Hymenoptera: Braconidae). We first examine the various mechanisms used by aphids for defence against these enemies. We then explore the strategies used by aphidiine parasitoids to exploit their aphid hosts. Finally, we consider the responses of both aphids and parasitoids to ecological constraints induced by seasonal cycles and to environmental variations linked to host plants and climate. The fundamental and applied interest of studying these organisms is discussed.


Assuntos
Afídeos/parasitologia , Evolução Biológica , Ecologia , Animais , Afídeos/fisiologia , Comportamento Animal/fisiologia , Biodiversidade , Interações Hospedeiro-Parasita , Reprodução
20.
Proc Natl Acad Sci U S A ; 107(19): 8677-82, 2010 May 11.
Artigo em Inglês | MEDLINE | ID: mdl-20421492

RESUMO

Evolutionary loss of traits can result from negative selection on a specific phenotype, or if the trait is selectively neutral, because the phenotype associated with the trait has become redundant. Even essential traits may be lost, however, if the resulting phenotypic deficiencies can be compensated for by the environment or a symbiotic partner. Here we demonstrate that loss of an essential me-tabolic trait in parasitic wasps has evolved through environmental compensation. We tested 24 species for the ability to synthesize lipids de novo and collected additional data from the literature. We found the majority of adult parasitoid species to be incapable of synthesizing lipids, and phylogenetic analyses showed that the evolution of lack of lipogenesis is concurrent with that of parasitism in insects. Exploitive host manipulation, in which the host is forced to synthesize lipids to the benefit of the parasitoid, presumably facilitates loss of lipogenesis through environmental compensation. Lipogenesis re-evolved in a small number of parasitoid species, particularly host generalists. The wide range of host species in which generalists are able to develop may impede effective host manipulation and could have resulted in regaining of lipogenic ability in generalist parasitoids. As trait loss through environmental compensation is unnoticed at the phenotypic level, it may be more common than currently anticipated, especially in species involved in intricate symbiotic relationships with other species.


Assuntos
Evolução Biológica , Lipídeos/biossíntese , Parasitos/fisiologia , Vespas/fisiologia , Animais , Comportamento Alimentar/fisiologia , Feminino , Lipogênese/fisiologia , Filogenia , Característica Quantitativa Herdável
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