RESUMO
Plants are able to sense their environment and respond appropriately to different stimuli. Vibrational signals (VS) are one of the most widespread yet understudied ways of communication between organisms. Recent research into the perception of VS by plants showed that they are ecologically meaningful signals involved in different interactions of plants with biotic and abiotic agents. We studied changes in the concentration of alkaloids in tobacco plants induced by VS produced by Phthorimaea operculella (Lepidoptera: Gelechiidae), a generalist caterpillar that naturally feeds on the plant. We measured the concentration of nicotine, nornicotine, anabasine and anatabine in four treatments applied to 11-weeks old tobacco plant: a) Co = undamaged plants, b) Eq = Playback equipment attached to the plant without VS, c) Ca = Plants attacked by P. operculella herbivory and d) Pl = playback of VS of P. operculella feeding on tobacco. We found that nicotine, the most abundant alkaloid, increased more than 2.6 times in the Ca and Pl treatments as compared with the Co and Eq treatments, which were similar between them. Nornicotine, anabasine and anatabine were mutually correlated and showed similar concentration patterns, being higher in the Eq treatment. Results are discussed in terms of the adaptive significance of plant responses to ecologically important VS stimuli.
Assuntos
Alcaloides/análise , Lepidópteros/fisiologia , Nicotiana/química , Alcaloides/metabolismo , Anabasina/análise , Animais , Cromatografia Gasosa-Espectrometria de Massas , Herbivoria , Interações Hospedeiro-Parasita , Larva/fisiologia , Modelos Lineares , Nicotina/análogos & derivados , Nicotina/análise , Análise de Componente Principal , Piridinas/análise , Nicotiana/metabolismo , Nicotiana/parasitologia , VibraçãoRESUMO
Samples of corbicular and stored pollen gathered by Tetragonisca angustula (Latreille, 1811) in an Amazon-Chiquitano transitional forest during the dry season were analyzed. The pollen spectrum was established as well as the dynamics of the relationship between the stingless bee and the surrounding flora. Pollen samples obtained from three rational hives were subjected to acetolysis and 55 pollen types were identified, the most frequent being from Anadenanthera (Fabaceae), Chenopodiaceae, and Dydimopanax (Araliaceae). Significant differences in pollen families used between hives along the months of collection were found in stored pollen and non-significant differences in corbicular pollen. Mean values of alpha diversity (H') showed T. angustula as a generalist while beta diversity qualitatively showed that pollen composition was similar between two hives both of which differed from the third hive. Pollen types in corbicular and stored pollen were in general related with richness of flowering plants in the foraging area; the pollen offer was less diverse than the pollen collected, and a trend to prefer the collection of pollen from the most abundant flowering species could be discerned. T. angustula showed polylectic feeding habits and a capacity to adapt to food availability.
Assuntos
Abelhas , Comportamento Alimentar , Florestas , Pólen/classificação , Animais , Bolívia , Estações do AnoRESUMO
Parasitoid fitness depends on the ability of females to locate a host. In some species of Ichneumonoidea, female parasitoids detect potential hosts through vibratory cues emanating from them or through vibrational sounding produced by antennal tapping on the substrate. In this study, we (1) describe host location behaviors in Grotea gayi Spinola (Hymenoptera: Ichneumonidae) and Labena sp. on nests of Manuelia postica Spinola (Hymenoptera: Apidae), (2) compare nest dimensions between parasitized and unparasitized nests, (3) correlate the length of M. postica nests with the number of immature individuals developing, and (4) establish the relative proportion of parasitized nests along the breeding period of M. postica. Based on our results, we propose that these parasitoids use vibrational sounding as a host location mechanism and that they are able to assess host nest dimensions and choose those which may provide them with a higher fitness. Finally, we discuss an ancestral host-parasitoid relationship between Manuelia and ichneumonid species.
Assuntos
Abelhas/parasitologia , Comportamento de Nidação , Animais , Feminino , Himenópteros/fisiologiaRESUMO
We, herein, report evidence that wing fanning by the aphid parasitoid Aphidius ervi Haliday (Hymenoptera: Braconidae) constitutes a courtship song. Complete removal of the forewings or only the distal half of them reduced male copulation success in comparison to intact males. Males that achieved copulation within the observation period produced wing fanning at a higher rate than males that did not copulate. Playback of wing fanning sound altered the behaviour of virgin females, increasing the time they devoted to grooming, as compared with subjects that were exposed to silence or white noise. Our findings contribute to the understanding of the acoustic dimension of the sensory modalities employed by this aphid parasitoid in sexual signalling.
Assuntos
Comportamento Sexual Animal , Vespas/fisiologia , Asas de Animais/fisiologia , Acústica , Animais , Afídeos/parasitologia , Feminino , Masculino , Som , Espectrografia do SomRESUMO
Transgenerational maternal effects on performance (rm) after host transfer were evaluated in the generalist aphid Myzus persicae s.s., and in its subspecies specialized on tobacco, M. persicae nicotianae Blackman. We tested whether the performance of these taxa, when reared separately on optimal and suboptimal hosts (as sources of different maternal background) and then transferred to optimal hosts, experienced variations along four successive generations. Additionally, to compare the tolerance of both taxa to stress following host transfers, developmental instability (fluctuating asymmetry and body abnormalities) along the four generations was assessed. Taxon, rearing host, and generation affected the performance after host transfer. In the generalist, there was a significant improvement of rm along generations when transferred from suboptimal to optimal host and a significant decrease when transferred from optimal to optimal host; in the specialist, no increase or decrease occurred in any host transfer treatment. Transfer from suboptimal to optimal hosts caused higher losses of remaining replicates along generations than transfers from optimal to optimal hosts, and the specialist showed higher losses than the generalist. The only significant effect detected in comparisons involving fluctuating asymmetry values was that of taxon on length of siphunculi. Frequency of body abnormalities was not affected by treatments. Collectively, these results show a transgenerational weakening of maternal effects in the generalist but not in the specialist aphid, and suggest that rearing the latter in a suboptimal host causes not easily reversible changes that further give rise to constraints in performance.
Assuntos
Afídeos/fisiologia , Interações Hospedeiro-Parasita/fisiologia , Adaptação Fisiológica , Animais , Afídeos/crescimento & desenvolvimento , Feminino , Preferências Alimentares , Especificidade da Espécie , Nicotiana/parasitologiaRESUMO
In Chile, the aphid Sitobion avenae is of recent introduction, lives on cultivated and wild Poaceae, and is thought to reproduce by permanent parthenogenesis. In order to study the genetic variability and population structure of this species, five microsatellite loci were typed from individual aphids collected from different cultivated and wild host plants, from different geographical zones, and years. Chilean populations showed a high degree of heterozygosity and a low genetic variability across regions and years, with four predominant genotypes representing nearly 90% of the sample. This pattern of low clonal diversity and high heterozygosity was interpreted as the result of recent founder events from a few asexually reproducing genotypes. Most geographical and temporal variation observed in the genetic composition resulted from fluctuations of a few predominant clones. In addition, comparisons of the genotypes found in Chile with those described in earlier surveys of S. avenae populations in Western Europe led us to identify 'superclones' with large geographical distribution and high ecological success, and to make a preliminary exploration of the putative origin(s) of S. avenae individuals introduced to Chile.
Assuntos
Afídeos/genética , Genética Populacional , Partenogênese , Agricultura , Animais , Chile , Células Clonais , Geografia , Repetições de Microssatélites , Controle de Pragas , Plantas Comestíveis , PoaceaeRESUMO
Decision-making during host selection by phytophagous insects has proved to be related to host range, with specialists taking faster decisions than generalists; however, this pattern fails to materialize in some host selection studies performed with aphids. Differences found in testing designs point to rearing effects on aphid host selection. To test whether specialization patterns derive from the nature of the aphid or as a consequence of rearing environment, host selection behaviours were compared between the generalist Myzus persicae (Sulzer) s.s. and its subspecies specialized on tobacco when reared on a common host and offered the choice of an alternative host and a non-host plant. Pre-alighting (host finding and attraction towards host volatiles) and post-alighting (leaf surface exploration and probing) behaviours did not differ between the generalist and the tobacco-specialist, except in the allocation of time to probing behaviour; furthermore, all specialists chose the host on which they performed best. Thus, although the specialist was not faster than the generalist, it showed a higher level of commitment to its preferred host plant.
Assuntos
Afídeos/fisiologia , Nicotiana/parasitologia , Adaptação Fisiológica , Animais , Comportamento Alimentar/fisiologia , Preferências Alimentares , Interações Hospedeiro-ParasitaRESUMO
Herbivorous insect species with narrow diet breadth are expected to be more prone to genetic differentiation than insect species with a wider diet breadth. However, a generalist can behave as a local specialist if a single host-plant species is locally available, while a specialist can eventually behave as a generalist if its preferred host is not available. These problems can be addressed by comparing closely related species differing in diet breadth with overlapping distributions of insect and host populations. In this work, diet breadth, genetic diversity and population differentiation of congeneric aphid species from southern beech forests in Chile were compared. While at the species level no major differences in genetic diversity were found, a general trend towards higher genetic diversity as diet breadth increased was apparent. The aphid species with wider diet breadth, Neuquenaphis edwardsi (Laing), showed the highest genetic diversity, while the specialist Neuquenaphis staryi Quednau & Remaudière showed the lowest. These differences were less distinct when the comparisons were made in the same locality and over the same host. Comparison of allopatric populations indicates that genetic differentiation was higher for the specialists, Neuquenaphis similis Hille Ris Lambers and N. staryi, than for the generalist N. edwardsi. Over the same host at different locations, genetic differentiation among populations of N. edwardsi was higher than among populations of N. similis. The results support the assumption that specialists should show more pronounced genetic structuring than generalists, although the geographical distribution of host plants may be playing an important role.
Assuntos
Afídeos/genética , Variação Genética , Animais , Afídeos/fisiologia , Chile , Dieta/veterinária , Feminino , Interações Hospedeiro-Parasita , Masculino , Dinâmica PopulacionalRESUMO
The tobacco-feeding race of Myzus persicae (Sulzer), formerly known as M. nicotianae Blackman, was introduced into Chile during the last decade. In order to evaluate the genetic diversity and insecticide resistance status of Chilean tobacco aphid populations, a field survey was conducted in 35 tobacco fields covering a 300 km latitudinal survey. The populations sampled were characterized using microsatellite markers and morphometric multivariate analysis. Insecticide resistance levels were assessed through a microplate esterase assay and the mutation status of the kdr gene. All samples collected corresponded to the same anholocyclic aphid genotype, and showed morphological variation within the range expected for the tobacco-feeding race of M. persicae. Esterase activity showed the level and variability expected for an R1 clone lacking mutations in the sodium channels (susceptible kdr), thus corresponding to a type slightly resistant to organophosphate and carbamate, and susceptible to pyrethroid insecticides.
Assuntos
Afídeos/genética , Variação Genética , Resistência a Inseticidas/genética , Nicotiana/parasitologia , Animais , Afídeos/efeitos dos fármacos , Chile , Feminino , Genótipo , Masculino , Repetições de MicrossatélitesRESUMO
Interspecific chemical variation of precloacal pore secretions of Liolaemus lizards was characterized in 20 species, and intraspecific chemical variation was characterized using nine individuals of L. bellii. The latitude (Chile, 18 degrees to 33 degrees South latitude) and altitude (100 to 4350 m.a.s.l.) of the capture sites were recorded, as well as the number of precloacal pores of each lizard. Secretions were analyzed by GC-MS. A total of 49 compounds were found distributed among the 20 species of Liolaemus. Different chemical patterns occurred at intra- and interspecific levels. Compounds belonged to three main families: n-alkanes, long chain carboxylic acids, and steroids. Cholesterol and five carboxylic acids (tetradecanoic, hexadecanoic, hexadecenoic, octadecanoic, and Z-9-octadecenoic) appeared in all species. The number of precloacal pores correlated positively with altitude and negatively with latitude, suggesting that lizards produce more secretions under harsh environments.