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31.
SYNOPSIS. The life cycles of 2 strains of Allogromia laticollaris (CSH and TPA) raised on experimentally restricted diets have been studied. Cloned cultures of the strains differed in nutritional requirements for continuous reproduction. The TPA strain was more fecund. Both strains have a basically apogamic (asexual) life cycle; only occasionally were gamonts (sexually reproducing individuals) produced. They were autogamous (self-fertilizing) and fusion of the gametes took place within the parental test.
We found in CSH clones a regular alternation of vesicularly nucleated and compactly multinucleated diploid generations. The details of the life cycle of either strain are not known well enough to be able to construct life cycle diagrams more meaningful than that of Arnold. The 2 strains studied differ in cytologic and nuclear detail from each other and from the strain studied by Arnold. 相似文献
We found in CSH clones a regular alternation of vesicularly nucleated and compactly multinucleated diploid generations. The details of the life cycle of either strain are not known well enough to be able to construct life cycle diagrams more meaningful than that of Arnold. The 2 strains studied differ in cytologic and nuclear detail from each other and from the strain studied by Arnold. 相似文献
32.
FEDERICA TRONA DANIEL CASADO MIRYAN CORACINI MARIE BENGTSSON CLAUDIO IORIATTI PETER WITZGALL 《Physiological Entomology》2010,35(3):249-254
Upwind orientation flights of codling moth males Cydia pomonella L. to a single source of sex pheromone (E,E)‐8,10‐dodecadienol (codlemone) are significantly reduced when blending it with pheromone antagonists, either with codlemone acetate, (E,E)‐8,10‐dodecadienyl acetate, or with the codlemone isomer (E,Z)‐8,10‐dodecadienol. However, once activated by a pheromone stimulus, males no longer distinguish between a pheromone source and these antagonistic blend sources. This shows that the pheromone stimulus required for the initiation of an upwind flight response differs from the stimulus for maintaining upwind flight and landing at the source. In contrast to pheromone antagonists, males discriminate between pheromone alone and a blend source of pheromone and the plant volatile pear ester, ethyl (2E,4Z)‐2,4‐decadienoate. This indicates a difference in the detection and neural integration of pheromone and plant volatile stimuli. 相似文献
33.
JEAN‐MARIE SACHET BÉNÉDICTE PONCET ALAIN ROQUES LAURENCE DESPRÉS 《Ecological Entomology》2009,34(1):81-89
Abstract 1. Phenological shift in oviposition in seed predators may be a key factor for adaptive radiation if temporal differences lead to less intense competition. 2. This hypothesis was tested at two sites in the French Alps in three sympatric species of larch cone flies grouped into two phenological groups (early and late) differing in adult emergence and oviposition timing by approximately 2 weeks. The present study assessed the intensity of competition within and between groups by measuring four larval traits. Cone traits were measured, and the impact of early species parasitism on cone development was assessed. 3. The occupation of the central axis of a developing cone by one early larva has a strong detrimental effect on cone growth and seed production. However, there was almost no correlation between the variables measured on the cones and on the larvae, suggesting that the resources available were not limiting. 4. Inter‐group competition had no significant effect on early larvae. In contrast, both inter‐ and intra‐group competition had a significant negative effect on late larvae length (–11% and –16% respectively), dry mass (–8% and –23%), and lipid mass (–15% and –26%). The intensity of competition was stronger among larvae in the same phenological group, which is consistent with the hypothesis that shifts in oviposition promote adaptive radiation in larch cone flies by reducing competition among larvae. 相似文献
34.
KATY MORGAN YVONNE‐MARIE LINTON PRADYA SOMBOON PRASANTA SAIKIA VAS DEV DUONG SOCHEAT CATHERINE WALTON 《Molecular ecology》2010,19(11):2269-2285
Tropical forests have undergone repeated fragmentation and expansion during Pleistocene glacial and interglacial periods, respectively. The effects of this repeated forest fragmentation in driving vicariance in tropical taxa have been well studied. However, relatively little is known about how often this process results in allopatric speciation, since it may be inhibited by recurrent gene flow during repeated secondary contact, or to what extent Pleistocene‐dated speciation results from ecological specialization in the face of gene flow. Here, divergence times and gene flow between three closely‐related mosquito species of the Anopheles dirus species complex endemic to the forests of Southeast Asia, are inferred using coalescent based Bayesian analysis. An Isolation with Migration model is applied to sequences of two mitochondrial and three nuclear genes, and 11 microsatellites. The divergence of An. scanloni has occurred despite unidirectional nuclear gene flow from this species into An. dirus. The inferred asymmetric gene flow may result from the unique evolutionary adaptation of An. scanloni to limestone karst habitat, and therefore the fitness advantage of this species over An. dirus in regions of sympatry. Mitochondrial introgression has led to the complete replacement of An. dirus haplotypes with those of An. baimaii through a recent (~62 kya) selective sweep. Speciation of An. baimaii and An. dirus is inferred to have involved allopatric divergence throughout much of the Pleistocene. Secondary contact and bidirectional gene flow has occurred only within the last 100 000 years, by which time the process of allopatric speciation seems to have been largely completed. 相似文献
35.
Abstract. 1. In haplodiploid organisms, virgin or sperm-depleted females can reproduce but are constrained to produce only male progeny. According to Godfray's constrained model, when p , the proportion of females constrained to produce only male progeny, is not null in a panmictic population, unconstrained females should bias their sex allocation towards females to compensate for the excess of males. These unconstrained females should be able to adjust the sex ratio in response to local variation of p .
2. In this paper an experimental approach is used to test the hypotheses of this model in the solitary endoparasitoid Venturia canescens under both field and laboratory conditions. Specifically, it is tested whether unconstrained females use their encounters with conspecifics (either male or female) to estimate p and then adjust their sex ratio accordingly.
3. As assumed by Godfray's model, constrained females actively search for host patches in the field and under laboratory conditions produce the same number of offspring during their lifetime as unconstrained females. As predicted by the model, unconstrained females produce a sex ratio biased towards females both in the laboratory and in the field.
4. The results show that this bias is not a response to encounters with conspecifics previous to oviposition. The hypothesis that the bias is due to differential mortality between sexes during ontogeny is also rejected. The proportions of constrained ovipositions estimated in two natural populations explain only a small fraction of the sex ratio bias observed in V. canescens. 相似文献
2. In this paper an experimental approach is used to test the hypotheses of this model in the solitary endoparasitoid Venturia canescens under both field and laboratory conditions. Specifically, it is tested whether unconstrained females use their encounters with conspecifics (either male or female) to estimate p and then adjust their sex ratio accordingly.
3. As assumed by Godfray's model, constrained females actively search for host patches in the field and under laboratory conditions produce the same number of offspring during their lifetime as unconstrained females. As predicted by the model, unconstrained females produce a sex ratio biased towards females both in the laboratory and in the field.
4. The results show that this bias is not a response to encounters with conspecifics previous to oviposition. The hypothesis that the bias is due to differential mortality between sexes during ontogeny is also rejected. The proportions of constrained ovipositions estimated in two natural populations explain only a small fraction of the sex ratio bias observed in V. canescens. 相似文献
36.
MANUEL SÁNCHEZ LÓPEZ-BERGES ANTONIO DI PIETRO MARIE-JOSÉE DABOUSSI HALA ABDEL WAHAB CHRISTELLE VASNIER M. ISABEL G. RONCERO MARIE DUFRESNE CONCEPCIÓN HERA 《Molecular Plant Pathology》2009,10(1):95-107
Forward genetic screens are efficient tools for the dissection of complex biological processes, such as fungal pathogenicity. A transposon tagging system was developed in the vascular wilt fungus Fusarium oxysporum f. sp. lycopersici by inserting the novel modified impala element imp160::gfp upstream of the Aspergillus nidulans niaD gene, followed by transactivation with a constitutively expressed transposase. A collection of 2072 Nia+ revertants was obtained from reporter strain T12 and screened for alterations in virulence, using a rapid assay for invasive growth on apple slices. Seven strains exhibited reduced virulence on both apple slices and intact tomato plants. Five of these were true revertants showing the re-insertion of imp160::gfp within or upstream of predicted coding regions, whereas the other two showed either excision without re-insertion or no excision. Linkage between imp160::gfp insertion and virulence phenotype was determined in four transposon-tagged loci using targeted deletion in the wild-type strain. Knockout mutants in one of the genes, FOXG_00016 , displayed significantly reduced virulence, and complementation of the original revertant with the wild-type FOXG_00016 allele fully restored virulence. FOXG_00016 has homology to the velvet gene family of A. nidulans . The high rate of untagged virulence mutations in the T12 reporter strain appears to be associated with increased genetic instability, possibly as a result of the transactivation of endogenous transposable elements by the constitutively expressed transposase. 相似文献
37.
OLIVIER MAURIN MARK W. CHASE MARIE JORDAAN MICHELLE VAN DER BANK 《Botanical journal of the Linnean Society. Linnean Society of London》2010,162(3):453-476
The putative complexity of Combretaceae and lack of information on phylogenetic relationships within the family led us to explore relationships between genera of Combretaceae by means of combined analyses of plastid and nuclear sequences. We collected DNA sequence data from the nuclear ribosomal internal transcribed spacer region and plastid rbcL, psaA‐ycf3 spacer and psbA‐trnH spacer for 14 of the 17 genera of Combretaceae. The current classification of the family into two subfamilies, Strephonematoideae and Combretoideae, is corroborated. Within Combretoideae, division into two tribes, Laguncularieae and Combreteae, is strongly supported. Within Combreteae subtribe Terminaliinae, relationships between genera are largely unresolved. Terminalia is not supported as monophyletic and two groups were identified, one containing mainly African species and another of mostly Asian species. Pteleopsis, Buchenavia and Anogeissus are embedded within Terminalia, and we suggest that all genera of Terminaliinae, with the exception of Conocarpus, should be included in an expanded circumscrition of Terminalia. Within subtribe Combretinae, a clade formed by the two monotypic genera Guiera and Calycopteris is sister to the rest of the subtribe. Groupings in Combretinae are consistent with recent results based on morphological data. Combretum is currently divided into three subgenera: Apethalanthum, Cacoucia and Combretum. The last two were included in this study and supported as monophyletic if Quisqualis is included within subgenus Cacoucia. Meiostemon is sister to subgenus Combretum. We recommend that subgenus Combretum should be expanded to include Meiostemon and subgenus Cacoucia to include Quisqualis. The sectional classification within Combretum proposed in earlier morphological studies is confirmed except for the exclusion of C. imberbe from section Hypocrateropsis in a separate and monotypic section and the inclusion of C. zeyheri (section Spathulipetala) in section Macrostigmatea. In order to accommodate C. imberbe, a new section is suggested. The reinstatement of previously recognized sections Grandiflora and Trichopetala, both of which had been sunk into subgenus Cacoucia section Poivrea, is proposed. © 2010 The Linnean Society of London, Botanical Journal of the Linnean Society, 2010, 162 , 453–476. 相似文献
38.
Plant species in fire‐prone environments possess specific traits which allow them to survive fire. Species are commonly classified according to whether they survive fire and resprout or whether they are killed by fire and regenerate from seed. However, different populations of the same species have been shown to vary in their responses. Therefore, the classification of a species into a single category based on fire‐response traits may not necessarily be representative of every population under every circumstance. This study examined the extent of within‐species variation in fire‐response traits of woody plants in south‐eastern Australia after the 2003 fires. Species were then classified using two approaches: (i) using data from a field survey of fire‐response traits, taking into account within‐species variation; and (ii) using species' fire responses listed in a pre‐existing fire‐response database compiled from a variety of primary sources. Field data showed that the majority of species in the study area resprouted after fire with around one in 10 species variable in their resprouting response. Almost half of all species varied from site to site according to whether they regenerated from seed, either solely or in addition to resprouting. The numbers of species classified as resprouters and seed regenerators varied according to the classification method used. Differences were also found between the classification method when calculating the mean proportion of resprouters and seed regenerators across sites. The fire‐response traits for some species from the database were found to differ from the observed field responses. This study demonstrated that the application of a fire‐response trait, reported in a trait database, to an entire species, may not adequately represent the actual fire responses of the populations of interest. Rather than considering the fire‐response traits of a species, accurate prediction may be better achieved by considering how different populations of plants will respond to fire. 相似文献
39.
HERVE BOCHERENS ELSE MARIE FRIIS RÉ MARIOTTI KAJ RAUNSGAARD PEDERSEN 《Lethaia: An International Journal of Palaeontology and Stratigraphy》1993,26(4):347-358
Carbon isotopic abundances have been measured for more than one hundred samples of fossil plants ranging in age from middle Triassic to late Tertiary. Most of the plant fossils were identified at the specific or generic level and were selected as representing a variety of continental environments, including xeric and humid habitats. Material analysed included numerous fragments of flowers, seeds, fruits, leaves and wood, as well as a single amorphous lignite sample. The analyses performed for the plant fragments indicate relatively constant isotopic compositions during this time interval, with plant δ13C values ranging between -28 and -20%. These values are within the range for living terrestrial plants with C3, photosynthesis, although values more positive than -23% are rare in C3 plants and typically found in plants growing under environmental stress. Lower δ13C values might have been expected owing to the much higher CO2, levels of the Cretaceous atmosphere that have been inferred from marine carbonates. No fossils with values indicating C4, photosynthesis were discovered. Fossil plants from inferred mesic environments showed δ13C values ranging between -26.7 and -24.1%. Highest δ13C values in angiosperms (up to -20.1%) were measured for Late Cretaceous combretaceous flowers from Portugal. Some cheirolepidiaceous conifers from the Early Cretaceous also showed high δ13C values. Values measured for Pseudofrenelopsis varians and Glenrosa taxensis were -21.9%, and values of gymnosperm wood, probably of cheirolepidiaceous affinity, were -19.0%. These high values are in accordance with inferred ecological conditions for the fossil plants. They may suggest a tendency for C4,-like photosynthesis, although the data are equivocal. Higher values (-17.3%) clearly falling outside the C3, range were, however, obtained from a single lignite fragment of Late Cretaceous (Maastrichtian) age. The nature of this plant fragment is unknown, but the result suggests that C4-like photosynthesis was present at least in some latest Cretaceous vegetation. A hadrosaurian dinosaur with well-preserved collagen-like organic matter from the same deposit showed δ13C values around-16%, which also suggests the presence of CAM or even C4 plants in the latest Cretaceous. □Carbon isotopic abundances, δ13C values, dinosaurs, plants, photosynthetic pathways, Mesozoic. 相似文献
40.
MELANIE PEREZ RAPHAEL LEBLOIS BARBARA LIVOREIL ROGER BOUR JOSIE LAMBOURDIERE SARAH SAMADI MARIE‐CATHERINE BOISSELIER 《Biological journal of the Linnean Society. Linnean Society of London》2012,105(3):591-606
Testudo marginata, the largest European land tortoise, is suffering habitat degradation and destruction. Some populations, in markedly degraded habitats, are characterized by divergent morphotypes. However, the evolutionary significance of these morphotypes is of debate. Using 11 polymorphic microsatellites, we studied: (1) marginated tortoises from Sardinia that display a divergent morphotype – this population was potentially introduced from Greece; and (2) an area in the southern Peloponnese that includes a small and degraded zone in which marginated tortoises are dwarf. Genetic analyses run without any a priori assignment clearly acknowledge the specimens sampled in the territory of the dwarf form as a single group whilst Sardinian specimens are clustered with other specimens from the northern part of the area sampled in Greece. Demographic analyses suggest that Sardinian tortoises originated recently from some of the populations sampled in the northern part of the area sampled in Greece. Over locations sampled in Greece, a landscape‐genetic analysis allowed us to detect potential landscape features that may reduce gene flow between the dwarf form territory and surrounding areas. Our results suggest that the territory of the dwarf form is particularly propitious for marginated tortoises and that conservation regulations in Greece should be reinforced to protect this area from increasing impact of human activities changing from traditional agriculture to mechanization and extensive use of chemicals. © 2011 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, 105 , 591–606. 相似文献