Larval pupation site preference on fruit in different species of Drosophila

Larval pupation site preference (PSP) of different species of Drosophila was analyzed on fruit in the laboratory. The larvae of D. melanogaster, D. ananassae, D. virilis, D. novamexicana and D. hydei pupated on the surface of glass vials; D. simulans, D. yakuba, D. mauritiana and D. malerkotliana pupated in/on fruit; and D. rajasekari pupated on cotton plugs in all experiments. D. bipectinata larvae changed their preference from fruit in the control to glass surface for all of the fruits tested. The statistical analysis of PSP (glass and fruit) found a significant result in that compared to other species, D. mauritiana and D. ananassae preferred to pupate on cotton compared to the control.     

The utilization of naturally occurring yeasts by Drosophila species, using chemically defined substrates

The ability of three Drosophila species; Drosophila obscura, D. subobscura and D. phalerata, to utilize a range of naturally occurring yeasts as food sources was determined. The yeasts used were the dominant species of two commonly used breeding sites, Sorbus aucuparia fruits and the fruiting bodies of the fungus Phallus impudicus. The range of yeast species used was found to reflect the degree ot substrate specialization exhibited by these three species, with D. subobscura being broader niched than the other two species. There was an indication that D. phalerata was adapted to those yeasts normally found on its natural breeding site, Phallus impudicus. Many factors were found to affect the nutritional adequacy of the yeasts, including their growth period, the larval density, the presence of competitors and particularly the chemical composition of the basal growth medium.     

A field study of the association between the stinkhorn Phallus impudicus Pers. and the British fungal-breeding Drosophila

Emergence records for three species of Drosophila breeding in the stinkhorn ( Phallus impudicus ) are presented. These are D. phalerata, D. subobscura and D. cameraria . The numbers of stinkhorn present in one woodland (0.114 km²) have been estimated for a two-year period. In 1976, the total number of these fungal breeding sites during the summer was approximately 8000 and in 1977 it was 5300. Utilizing the estimates of breeding site numbers, Drosophila emergence data and estimates of adult survival from laboratory populations, density estimates for D. phalerata and D. subobscura are calculated.     

果蝇Drosophila nasuta亚群系统发育问题的探讨

果蝇Ｄｒｏｓｏｐｈｉｌａｎａｓｕｔａ亚群由在１４个处于不同物种分化阶段的种,亚种和分类元组成,这个亚群的物种有许多进化上的独特之处,使得它在物种分化研究方面倍受关注,然而,在形态学,生殖隔离,染色体和同工酶多态,线粒体ＤＮＡＲＦＬＰ,求偶歌特征惟及线粒体和核基因序列分析等方面的研究都未能清楚地阐明这一亚群的系统进化关系,本文综合分析了关于这一亚群的进化遗传学的研究结果,并提出了有待进一步的一些问题     

Proximate and ultimate factors influencing oviposition site selection by endoparasites on conifer seed cones: two sympatric dipteran species on larch

The taxonomically controversial Galerucella nymphaeae species complex (Coleoptera, Chrysomelidae) contains at least two distinct species in northern Europe, G. nymphaeae (L.) consuming Nuphar luteum, and G. sagittariae (Gyll.), living mainly on Comarum palustre in southern Finland and on Rubus chamaemorus in northern Finland. By analyzing chromosomal polymorphisms in sympatric populations of G. nymphaeae and G. sagittariae, it was shown that the two species do not hybridize in nature. Chorion polypeptide analysis revealed fixed genetic differences between the two species. However, differences between species must be small, since hybridization is easily induced in the laboratory and F1 hybrids are fertile. Larvae of G. sagittariae cannot survive on Nuphar, and those of G. nymphaeae survive very poorly on Comarum and Rubus. Adults of G. sagittariae from Comarum or Rubus do not choose between these two food plants in laboratory conditions regarding dwelling, egg laying or feeding, but their avoidance of Nuphar is complete. Galerucella nymphaeae clearly prefers Nuphar, but may occasionally also sit, lay eggs or feed on terrestrial plants. It is suggested that G. nymphaeae and G. sagittariae represent sibling species and that the two forms of G. sagittariae, one feeding on Comarum and the other one on Rubus, are habitat races adapted to semiaquatic and terrestrial habitats, respectively. Adaptation to different habitats has created an effective premating barrier to gene flow, supporting the possibility that a sympatric mode of divergence has been involved in habitat race formation and speciation in the species complex.     

中国黑腹果蝇种组40种果蝇的核型多样性研究

通过传统的敲片、Giemsa染色的方法制片对中国黑腹果蝇种组(Drosophilamelanogasterspeciesgroup)8个种亚组40种果蝇的染色体进行了分析,共发现18种核型,即A、A′′、C、C′、C′′、C′′′、C′′′′、D、D′、D′′、E、E′、E′′、F、F′、G、H和I,其中A、A′′、C′′′、C′′′′、D′′和F′为新发现的核型。8个种亚组的基本核型分别是:嗜凤梨果蝇种亚组(D.ananassaesubgroup)的核型为F、F′、G和H型;牵牛花果蝇种亚组(D.eleganssubgroup)的核型为A和A′′型;细针果蝇种亚组(D.eugracilissubgroup)的核型为C型;嗜榕果蝇种亚组(D.ficusphilasubgroup)的核型为C′型;黑腹果蝇种亚组(D.melanogastersubgroup)的核型为C和C′型;山果蝇种亚组(D.montiumsubgroup)的核型为C、C′、C′′、D、D′、D′′、E、E′、E′′和I型;铃木氏果蝇种亚组(D.suzukiisubgroup)的核型为C′′′和C′′′′型;高桥氏果蝇种亚组(D.takahashiisubgroup)的核型为C、C′′′和C′′′′型。透明翅果蝇(D.lucipennis)雌性核型2n=8,雄性核型2n=7,雄性Ⅳ号染色体为染色体单体。此外还发现,吉川氏果蝇(D.kikkawai)、林氏果蝇(D.lini)、奥尼氏果蝇(D.ogumai)、拟嗜凤梨果蝇(D.pseudoananassae)和叔白颜果蝇(D.triauraria)5种果蝇有B染色体。本文确定了D.sp.likeelegans、D.sp.likenyinyii、D.sp.liketrapezifrons1、D.sp.liketakahashii、D.sp.liketrapezifrons2和D.sp.likeauraria等6个未描述种的核型和1个新记录种吉里果蝇(D.giriensis)的核型。本研究证明了在黑腹果蝇种组内、亚组内、种内和单雌系内的核型多样性,为果蝇遗传和进化提供了进一步的细胞学证据。     

Comparative connectomics and escape behavior in larvae of closely related Drosophila species

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Drosophila subpulchrella, a new species of the Drosophila suzukii species subgroup from Japan and China (Diptera: Drosophilidae)

Drosophila (Sophophora) subpulchrella Takamori and Watabe, sp. nov., of the D. suzukii subgroup in the D. melanogaster species group, is described from Japan and southern China, and compared with its sibling species, D. pulchrella Tan et al. distributed in the Yun‐Gui Highland, south‐western China. The results of cross‐experiments show a complete pre‐mating isolation between D. subpulchrella and D. pulchrella.     

Revisiting the link between breeding effort and oxidative balance through field evaluation of two sympatric sibling insect species

The idea that oxidative stress could be a major force governing evolutionary trade‐offs has recently been challenged by experimental approaches in laboratory conditions, triggering extensive debates centered on theoretical and methodological issues. Here, we revisited the link between oxidative stress and reproduction by measuring multiple antioxidant and oxidative damages in wild‐caught females of two sibling weevil species (Curculio elephas, C. glandium). The strength of our study arised from (1) studied species that were sympatric and exploited similar resource, but displayed contrasting reproductive strategies and (2) individuals were sampled throughout adult life so as to relate oxidative status to breeding effort. We found that the short‐lived C. elephas sacrifices red‐ox homeostasis for immediate reproduction upon emergence as characterized by low antioxidant defenses and elevated oxidative damage. Comparatively, C. glandium massively invests in antioxidant and maintains low oxidative damage, which may contribute to their extended prereproductive period. Intriguingly, we also reveal, for the first time in a field study, an unexpected reactivation of antioxidant defenses with the onset of reproduction. Our results thus support the existence of a strong, but complex relationship between oxidative stress and life‐history evolution and highlight the need for a finer‐scale picture of antioxidant strategies.     

Early springs and breeding performance in two sympatric duck species with different migration strategies

The capacity of migratory species to adapt to climate change may depend on their migratory and reproductive strategies. For example, reproductive output is likely to be influenced by how well migration and nesting are timed to temporal patterns of food abundance, or by temperature variations during the brood rearing phase. Based on two decades (1988–2009) of waterfowl counts from a boreal catchment in southern Finland we assessed how variation in ice break‐up date affected nesting phenology and breeding success in two sympatric duck species, Mallard Anas platyrhynchos and Eurasian Teal Anas crecca. In Fennoscandia these species have similar breeding habitat requirements but differ in migration distance; Teal migrate roughly seven times as far as do Mallard. Annual ice break‐up date was used as a proxy of spring ‘earliness’ to test the potential effect of climate change on hatching timing and breeding performance. Both species were capable of adapting their nesting phenology, and bred earlier in years when spring was early. However, the interval from ice break‐up to hatching tended to be longer in early springs in both species, so that broods hatched relatively later than in late springs. Ice break‐up date did not appear to influence annual number of broods per pair or annual mean brood size in either species. Our study therefore does not suggest that breeding performance in Teal and Mallard is negatively affected by advancement of ice break‐up at the population level. However, both species showed a within‐season decline in brood size with increasing interval between ice break‐up and hatching. Our study therefore highlights a disparity between individuals in their capacity to adjust to ice break‐up date, late breeders having a lower breeding success than early breeders. We speculate that breeding success of both species may therefore decline should a consistent trend towards earlier springs occur.     

Comparison of the olfactory sensitivity of two sympatric steppe grasshopper species (Orthoptera: Acrididae) to plant volatile compounds

Two Oedipodinae grasshopper species Oedaleus decorus asiaticus B.-Bienko and Angaracris baraben-sis Pall. (Orthoptera: Acrididae) are important pests on the natural grasslands in Inner Mongolia and often require insecticide treatment during outbreaks[1]. They both prefer overgrazed steppes and xerophytous habi-tats, and have thus been suggested as indicator species for steppe deterioration in typical steppe zones of In-ner Mongolia[2]. The two species have a sympatric distribution and sync…     

The Effect of Resource pH on Pupation Height in Drosophila (Diptera: Drosophilidae)

This paper describes the effects of the pH of the larval resource on the pupation height of two cosmopolitan species of Drosophila: D. melanogaster and D. hydei. The pH levels of artificial media were modified using solutions of acids (hydrochloric, acetic, and citric) and a positive relationship was found between pupation height and resource pH; i. e., the more acidic the resource, the closer the larvae pupated to the resource surface. The clearest trends were between pupation height and the final pH of the resource, the larvae apparently responding to the pH they encountered just before pupation commenced. When using natural resources a difference in pupation height was found between the types of fruits used but there was no obvious trend linking pupation height with pH. This suggests that some other environmental factor(s) was (were) overriding the effects of pH, and consequently resource pH may play only a minor role in determining pupation behavior in nature.     

Effects of elevated CO2 on the interspecific competition between two sympatric species of Aphis gossypii and Bemisia tabaci fed on transgenic Bt cotton

Abstract Effects of elevated CO₂ (twice ambient vs. ambient) and Bt Cry1Ac transgene (Bt cotton cv. 33^B vs. its nontransgenic parental line cv. DP5415) on the interspecific competition between two ecologically similar species of cotton aphid Aphis gossypii and whitefly biotype‐Q Bemisia tabaci were studied in open‐top chambers. The results indicated that elevated CO₂ and Bt cotton both affected the population abundances of A. gossypii and biotype‐Q B. tabaci when introduced solely (i.e., without interspecific competition) or two species coexisted (i.e., with interspecific competition). Compared with ambient CO₂, elevated CO₂ increased the population abundances of A. gossypii and biotype‐Q B. tabaci as fed on Bt and nontransgenic cotton on 45 (i.e., seedling stage) and 60 (i.e., flowering stage) days after planting (DAP), but only significantly enhanced aphid abundance without interspecific competition on the 45‐DAP nontransgenic cotton and 60‐DAP Bt cotton, and significantly increased whitefly abundance with interspecific competition on the 45‐DAP Bt cotton and 60‐DAP nontransgenic cotton. In addition, compared with nontransgenic cotton at elevated CO₂, Bt cotton significantly reduced biotype‐Q B. tabaci abundances without and with interspecific competition during seedling and flowering stage, while only significantly decreasing A. gossypii abundances without interspecific competition during the seedling stage. When the two insect species coexisted, the proportions of biotype‐Q B. tabaci were significantly higher than those of A. gossypii on Bt and nontransgenic cotton at the same CO₂ levels, and elevated CO₂ only significantly increased the percentages of biotype‐Q B. tabaci and significantly reduced the proportions of A. gossypii on seedling and flowering nontransgenic cotton. Therefore, the effects of elevated CO₂ were favorable for biotype‐Q B. tabaci to out‐compete A. gossypii under the predicted global climate change.     

Population genetics of accessory gland proteins and sexual behavior in Drosophila melanogaster populations from Evolution Canyon

Evolution Canyon in Lower Nahal Oren, Mount Carmel, Israel has been identified as a location promoting sympatric speciation. Several previous studies on Drosophila melanogaster populations from the two disparate slopes of the canyon suggest that these two populations are experiencing incipient speciation. However, recent microsatellite data did not reveal the expected level of population differentiation. Given the importance of this system for studying speciation, we set out to test two predictions of the incipient speciation hypothesis--genetic differentiation and sexual isolation. We sequenced six different Acp genes from isofemale lines from the south-facing slope (11 lines) and north-facing slope (nine lines) of Evolution Canyon. We found no evidence of genetic differentiation between the two slopes (F(ST) = -0.03). We also conducted mate choice tests, using intraslope F1 hybrids between different isofemale lines. There was no significant departure from random mating in mixtures of flies from the two slopes. Our results provide further indication that it is unlikely these two populations are experiencing incipient speciation. We discuss our results in light of the discrepancies that have been published on this enigmatic D. melanogaster system from Evolution Canyon.     

Sexual isolation in Drosophila. II. Intraspecific variation in mate recognition systems

A simple behavioral model is used to investigate whether differences in the specific-mate-recognition system (SMRS), occur within species of the Drosophila genus. This model takes into account, and overcomes, the distorting effect of vigor differences on experimental results. Analysis shows significant deviations from the expected values under the assumption of identical SMRSs in around one fifth of the multiple-choice experiments performed with natural strains of twelve different Drosophila species. Different selection procedures raise the number of significant assortative mating results between strains of D. melanogaster and D. pseudoobscura from 3.0% to 32.8%. Finally, sub- or semispecific taxa show variations in their SMRS even more frequently (74.5%). Differences in male vigor and female receptivity are also found. These results show that a classification of Drosophila species based on SMRS stability, as proposed by the “Recognition concept of species”, is virtually impossible.     

Development time and pupation behavior in theDrosophila melanogaster subgroup (Diptera: Drosophilidae)

This study is an in-depth analysis of intersexual, intraspecific, and interspecific variability in larvopupal developmental time, pupation site preference, and larval and pupal survival of a number of isofemale lines of the speciesDrosophila mauritiana, D. melanogaster, D. sechellia, D. simulans, D. teissieri, andD. yakuba. There was no significant sex differences in pupation height, but females eclosed significantly earlier than males in all species. In addition, the suggestion of a strong negative correlation between larval developmental time and pupation height could not be confirmed in this study. The hypothesis that differences in pupation height provide a basis for niche partitioning between closely related species with overlapping distributions was tested by three planned orthogonal contrast analyses of variance. First, the two speciesD. teissieri andD. yakuba, with largely overlapping distribution, were significantly different in pupation height. Second, the two allopatric, nonoverlapping island speciesD. mauritiana andD. sechellia did not significantly differ in pupation height. However, the absence of a significant difference in the final contrast between the two cosmopolitan speciesD. melanogaster andD. simulans, which are often found together, makes us cautious to accept the hypothesis.     

Ovarian defects in hybrids of the species pair Drosophila virilis and Drosophila texana

In interspecific matings between Drosophila virilis and Drosophila texana female sterility is observed in F₂ hybrid females. A previous study has shown that no vitellogenin synthesis occurs in the fat body of sterile hybrid females. The results presented in this paper show that hybrid ovaries of sterile females transplanted into the abdomens of females of the parental species are not able to develop upon maturity. With few exceptions, the hybrid ovaries remained alive in the host environment, but their oocytes failed to develop to vitellogenic stages. Thus, in hybrid females between Drosophila virilis and Drosophila texana sterility is the result of defects in both the two main developmental processes of egg maturation, the synthesis of vitellogenins in the fat body and the uptake of vitellogenins by the ovary. Dev Genet 20:47–52, 1997. © 1997 Wiley-Liss, Inc.     

Life cycles and challenges for fish species that breed in South African estuaries

The literature currently recognizes four guilds of estuarine resident fish species, namely solely estuarine, estuarine and marine, estuarine and freshwater, and estuarine migrant. In this review the life cycles of actual representatives from these four guilds are assessed to determine whether the current definitions, which have never been formally tested, are appropriate to fish species resident in South African estuaries. Detailed information and diagrammatic life cycles are provided for the selected species covered by this review. A potential new estuarine resident guild category is also identified, namely, those taxa that are primarily estuarine but also have subpopulations recorded in both adjacent marine and freshwater habitats. The full range of reproductive characteristics employed by estuary resident species is examined, ranging from live bearers, pouch and nest brooders, to a suite of oviparous taxa that attach their ova to estuarine rocks, shells, and submerged vegetation, all of which assists with larval retention within the estuarine environment. The small size and early reproductive maturity of most estuarine resident species is highlighted, with reduced vulnerability to predation in shallow, sheltered, often turbid estuary waters offering considerable protection during spawning events when compared to the open ocean. In addition, these small fish would not have to move considerable distances at any stage of their life cycle, since egg, larval, juvenile, and adult stages all occur in the same place. The existence of contingent subpopulations within many estuarine resident species is noted, physico-chemical stresses on these species are highlighted, and the eurytopic nature of these small fish taxa emphasized.     

Vitellogenetic defects in hybrids of the species pair Drosophila virilis and Drosophila texana

In interspecific matings between the species Drosophila virilis and Drosophila texana, female sterility can be observed in F₂ backcross females and in F₂ hybrid females. The results presented in this report show that the female sterility, whenever it exists, is due to prevention of vitellogenin synthesis in the fat body, but other abnormalities such as defects with the hybrid ovaries are not excluded. The observation that sterility appears among females from backcrosses suggests that incompatibilities between interspecific genes may cause female sterility even in the presence of a complete habloid genome from one or the other species. Yet, the parallel observation that female sterility appears only in hybrid females with recombinant chromosomes indicates that sterility results when conspecific combinations of genes on the same chromosome are broken by interspecific recombination. © 1996 Wiley-Liss, Inc.