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1.
The genusCirsium comprises both gynodioecious and dioecious species. The observation of microsporogenesis in female plants ofC. montanum, C. oleraceum, C. palustre andC. spinosissimum shows that the male sterility is due to a degeneration of the tapetum. This degeneration occurs more or less early according to the species and, in the light of these results, a scheme of evolution in the male sterility mechanism is proposed. Furthermore, the male sterility mechanism inC. montanum is very similar to that previously found in female plants of the dioecious speciesC. arvense. This fact enhances the possibility of evolution of the dioecy ofC. arvense from the gynodioecy found in other species. According to these results, a general scheme of evolution of sexes in the genusCirsium is proposed.  相似文献   

2.
Dendrocacalia crepidifolia Nakai (Compositae, Senecioneae), the only species of this arboreal genus endemic to Haha Island in the Bonin Islands, was found to be dioecious. Male flowers differ from female ones in having a stunted style (style in female exserted from corolla and deeply bifurcating) and anthers filled with fertile pollen (anthers in the female lacking pollen). The size of the corolla and number of florets per head were similar between male and female flowers. The crown area of this arboreal species was also similar in male and female plants. The sex ratio was 0.55 male, not significantly different from 0.5. Both sexes produced nectar of similar sugar concentration (ca. 50%). The flowers are pollinated by feral honeybees (Apis mellifera), but they are thought to have been pollinated by small, lesshairy, endemic solitary bees before honeybees were introduced and subsequently became the dominant bee species on the island. The evolution of dioecy ofDendrocacalia on the island is thought to stem from the deleterious effects of inbreeding that are inherent in plants with geitonogamy. The increased geitonogamy on the island has resulted from increased woodiness (i.e., increased number of flowers per plant) and the original dependence on endemic bee pollinators, which are now endangered.  相似文献   

3.
Summary When the phoretic mite Poecilochirus carabi reproduces in the brood chamber of its carrier Necrophorus vespilloides, a beetle with biparental brood care, the first deuteronymphs of the new mite generation aggregate on the male beetle. They do not use sex-specific traits to discriminate between male and female beetles in the brood chamber, but traits that are related to the beetles' behaviour and may be displayed by both parent beetles. When the male beetle departs, it carries virtually all deuteronymphs then present in the brood chamber. Deuteronymphs that develop later congregate on the female, which leaves the crypt some days after the male. Only those deuteronymphs that miss the female's departure disperse on the beetle larvae, meaning they have to wait in their pupal chambers until the beetles have completed their development. On average, 86% of the deuteronymphs leave the brood chamber on the parent beetles, thereby gaining the advantage of an early departure. As soon as their carrier arrives at one of the beetles' meeting places, the deuteronymphs can transfer between the beetles present. Choice experiments revealed that the deuteronymphs tend to even out density differences between congregating carriers, and prefer sexually mature to immature beetles. Therefore, transferring between beetles results in a dispersion of deuteronymphs on the sexually mature beetles of the population.  相似文献   

4.
The genus Ischioscia Verhoeff, 1928 is reviewed. 26 species are considered valid. A key for their identification is given, as well as a map showing the geographic distribution. The known range of the genus covers a large area from the central Amazon region to the mountains of Guatemala. The species of Ischioscia have a typical “philosciid” habitus (“runner” type); they can be distinguished from other Neotropical species with similar habitus by the following apomorphies: (1) male pereiopod 1 carpus enlarged to a plate-like extension, (2) scale field on male pereiopod 1 covering entire frontal side of the carpus, (3) male pereiopod 7 ischium with a ventral scale field, (4) dactylus in both sexes with a long inner claw. The groundpattern of Ischioscia is reconstructed, and an analysis of the phylogenetic relations within the genus is made on the basis of morphological data. The species are very similar to each other, most differences are found in the male structures of sexually dimorphic features. Ischioscia sturmi (Vandel, 1972), I. amazonica Lemos de Castro, 1955 and I. bolivari Vandel, 1968 are redescribed in detail.  相似文献   

5.
Doxomysis algoaensis sp.nov. is described from Algoa Bay, South Africa where it is common in nearshore marine waters just beyond the breaker line. D. algoaensis sp.nov. is morphologically similar to D. australiensis, but can readily be distinguished by the shape and armature of the telson and the length of the exopod of the fourth male pleopod. The apical cleft is one fifth the telson length in the former species and one third the length in D. australiensis. The telson apex on each side of the cleft is also armed with five and four stout spines in the two species, respectively. In D. australiensis, the exopod of the fourth male pleopod is almost three times the length of the endopod; in D. algoaensis sp.nov., the exopod is only slightly longer than the endopod. Other distinctive features of D. algoaensis sp.nov. include the maxillary palp, which is only slightly broader than long and the greater number of spines on the endopod of the uropod.  相似文献   

6.
The flower organs of Circaeaster are spiral in origin. The primordia of the tepals, stamens and carpels are almost the same in shape and size in early development. Carpel conduplication takes place only in the middle part of the carpel. The basal part of the carpel differentiates into a short stalk and the upper part into the style and the stigma. Flower development is similar to that of Kingdonia. Floral development of Circaeaster is compared with that of other Ranunculales.  相似文献   

7.
Larger male Caribbean fruit flies are more likely to be chosen as mates and defeat rivals in territorial contests. Yet males are smaller than females. Adaptive explanations for relatively small male size include (1) acceleration of male development to maximize female encounter rates, (2) selection for greater female size to increase fecundity, and (3) selection for body sizes most suitable for sexually dimorphic degrees of mobility, speed, and distance flight. None of these unambiguously accounts for the degree of sexual dimorphism. Male development is not accelerated relative to that of females. On average, males remain inside fruit longer than females and those males with extended development periods are smaller than more rapidly developing individuals. There is no evidence that female enlargement alone, presumably for greater fecundity, has generated the degree of dimorphism in the Caribbean fruit fly or other fruit flies. The relationship between dimorphism and mean female body size in 27 species of Tephritidae is the opposite of what would be predicted if differences in dimorphism were due to differences in unilateral female enlargement. Larger size in a species or in one sex of a species may be an adaptation for extensive flight. In general, among 32 species of fruit flies, as body size increases, wing shape becomes progressively more suited for distance flight. However, there are important exceptions to this correlation. Both sexual selection and nonadaptive allometries may contribute to the range of dimorphisms within the family.  相似文献   

8.
The development of male gametes (spermacia) in the red alga Gracilaria verrucosa has been studied using methods of transmission electron microscopy. Early spermatangia located along the wall of the conceptacle show an elongated shape in the thin sections. In the central part of the electron-dense cytoplasm of these cells there is a nucleus; numerous fibrous vesicles are arranged in the periphery. During the process of differentiation, the spermatangia become more rounded in shape and a large spermatangial vesicle is developed. The subsequent development of spermatium is accompanied by polarization of the spermatangium and the subsequent excretion of the spermatangial vesicle. The spermatia are oval cells containing a nucleus and fibrous vesicles. The process of differentiation of male gametes in G. verrucosa does not differ from that in five species of the genus Gracilaria, where it has already been studied. However, any conclusions about the degree of similarity between the spermatia in all the studied species can be made only after a detailed comparative analysis of the ultrastructural characteristics of these gametes.  相似文献   

9.
A new sanguinicolid trematode, Cardicola aurata sp. n., is described from gilthead seabream Sparus aurata L., from off the Spanish Mediterranean coast. The morphology of C. aurata sp. n. generally agrees with the diagnosis of the genus, however, in contrast to all other reported Cardicola spp. the male pore is located sub-medially at the posterior end of the body instead of sinistrally before the posterior end of the body. Based on a comparison of the morphology as well as partial 28S and ITS2 rDNA sequence data from the present species with that from closely related species, it was decided to emend the diagnosis of Cardicola rather than create a new genus, as the aberrant position of the male pore is likely to be an autapomorphy. The phylogenetic analyses revealed a close relationship between Cardicola and Paradeontacylix, two genera with considerable morphological differences; C. aurata sp. n. occupies a position intermediate to these genera. Thus, a morphological comparison of Cardicola, Paradeontacylix and Braya, a genus which is morphologically similar to Cardicola but clusters basal to the Cardicola/Paradeontacylix clade, was conducted. The results of this comparison showed that despite large differences with regard to body shape, the organisation of the internal organs is very similar in species of Cardicola and Paradeontacylix. The synopsis of morphological data and molecular phylogeny allows for interpretations regarding the importance of different morphological features for the phylogenetic inference of the Sanguinicolidae.  相似文献   

10.
The behavioural development of a juvenile male spider monkey (Ateles geoffroyi) preceding and subsequent to a traumatic injury resulting in the loss of his tail, was documented over a nine-month period in Santa Rosa National Park, Costa Rica. The juvenile became heavily reliant on his mother, who readily provided compensatory care, including nursing the juvenile even though he had previously been weaned. In comparison to another juvenile male spider monkey of similar age, the development of the injured animal was severely retarded and even five months after the accident, the juvenile was still nursing and being carried by his mother. As injuries may be relatively common among primates it is suggested that the provision of compensatory care is an important trait in many primate species.  相似文献   

11.
Structure and function of floral bracts, anthesis and breeding systems were investigated in greenhouse plants ofSarcandra chloranthoides, Sarcandra glabra, andChloranthus spicatus (Chloranthaceae). In early developmental stages the floral bract replaces the lacking perianth as a protective structure by enclosing the floral organs completely in a pocket-like structure, which is formed by the u-shaped attachment zone of the floral bract to the spike axis. The floral bract has a tip with an epithem tissue, from which traces of secretion seem to be released by the stomata. All species investigated have protogynous and longlasting flowers. The female phase begins five to seven days earlier than the male phase. It continues during the male phase and for some time thereafter. The male phase lasts between one day (Chloranthus spicatus) and seven days (Sarcandra chloranthoides). This is the first study on breeding systems of Chloranthaceae. They are of special interest in such a basal family of the angiosperms. Although the investigatedSarcandra andChloranthus species have similar flowers with entomophilous features, surprisingly their breeding systems are diverse:Sarcandra glabra is self-compatible,S. chloranthoides is agamospermous andChloranthus spicatus is self-incompatible.  相似文献   

12.
Simmondsia chinensis (Link) Schneider, a multipurpose dioecious shrub of arid zones, has emerged as a cash crop. It is being cultivated for its seeds which store liquid wax whose properties are similar to spermaceti (Sperm whale oil), a substitute for petro products and precious high-priced lubricants. Jojoba is a slow-growing desert shrub having a male biased (5:1; male:female ratio) population. Since there is no method available to determine the sex at the seedling stage, current investigations have been carried out to generate a sex-specific random amplified polymorphic DNA (RAPD) marker in jojoba which is based on the PCR amplification of random locations in the genome of plant. Of the 72 primers tested, only one random decamer primer, OPG-5, produced a unique ∼1,400 base pairs fragment in male DNA. To validate this observation, this primer was re-tested with the individuals of male and female samples of four cultivars. The unique ∼1,400 bp fragment was present in male individuals of all the four cultivars and completely absent in respective female individuals tested. To the best of our knowledge, this is the first report to ascertain the sex of jojoba plants at an early stage of development of the taxon.  相似文献   

13.
记述采自浙江省西闪岛的三突多足摇蚊亚属1新种:杯状三突多足摇蚊Polypedilum (Tripodura) cypellum sp. nov.。该新种与哈氏三突多足摇蚊P. (T.) harteni Andersen & Mendes, 2010相似,区别于本亚属其它已知种的主要特征是具高脚杯状的上附器。文中提供了雄成虫的翅、前足胫节端部、生殖节、上附器等特征图。  相似文献   

14.
半蓝角伪叶甲Cerogria basalis(Hope,1831)为角伪叶甲属Cerogria Borchmann,1909的1个大型种,过去仅知道分布于印度,尼泊尔,波斯尼亚和黑塞哥维那,一直缺乏详细和正式的形态描述。近年来,我们从云南采集到该种的雌虫和雄虫。本文对该种雌性和雄性成虫,特别是触角、腹板和雄性外生殖器特征作了详细描述。提供了该种雌、雄两性成虫的背面观和腹面观以及生境照片,以及触角、雄性末节腹板以及雄性外生殖器特征图片。本文还讨论了种内变异。这些工作为该种的正确鉴定提供了依据。  相似文献   

15.
The structure of the penial bulb and male efferent duct system of Grania species may be used in addition to setal pattern and spermathecal shape to distinguish species. Six penial bulb types are distinguished: (1) a simple, small, glandular bulb surrounding the male pore; (2) a small, glandular bulb, with a large, associated, dorso-medial gland mass; (3) a small glandular bulb, medial to the male pore, with an elongate male bursa (the aglandular sac), the vas deferens exitting directly into the invaginated male pore; (4) a glandular bulb with an aglandular sac and a small, cuticular stylet embedded in the bulb, extending from the ectal end of the vas deferens; (5) a glandular bulb and an aglandular sac with a long stylet extending from the vas deferens, through the bulb into the sac; and (6) glandular bulb reduced or absent, with or without an aglandular sac; with a long stylet and other prominent modifications, usually muscular, of the vas deferens. The details of the male duct structure were consistent within specimens grouped on the basis of setal distribution and shape and detailed spermathecal structure. Diverse male duct patterns are found within the polytypic species G. macrochaeta and G. postclitellochaeta. The positions of the spermathecal and male pores in their respective segments are distinctive for some species.  相似文献   

16.
Krischik VA  Denno RF 《Oecologia》1990,83(2):182-190
Summary Patterns of growth, reproduction, defense (leaf resin) and herbivory were compared between the sexes of the dioecious shrub Baccharis halimifolia (Compositae). Male plants possessed longer shoots and more tender leaves, grew faster, and flowered and senesced earlier than female plants. Levels of leaf nitrogen, water content, and acetone-soluble resin (shown to deter feeding by polyphagous insect herbivores) did not differ between male and female plants. When offered a choice between leaves from male and female plants, adults of two leaf beetles (Chrysomelidae), the monophagous Trirhabda bacharidis and the polyphagous Paria thoracica, both preferred to feed on male leaves. Similarly, the daily fecundity of older females of T. bacharidis was higher when they were fed leaves from male compared to female plants. However, adult survivorship and total fecundity of T. baccharidis did not differ between male and female leaf treatments. We attribute the feeding preference for and slight increase in fecundity on male plants to the tenderness of male leaves. Larvae of the fly Tephritis subpura (Tephritidae) fed exclusively in the sterile receptacle of male flower heads (85% infested), but the phenology was such that pollen production was not adversely affected. Larvae of two other flies Dasineura sp. and Contarinia sp. (Cecidomyiidae) occupied >95% of only female flower heads where they fed among and on the developing seeds. We conclude that foliage-feeding herbivores are unlikely candidates to explain the female-biased sex ratio (59% female) of B. halimifolia plants in the field, and that their preference for male plants is a result of plant characteristics (e.g. rapid growth) that have been selected by some other factor. However, our data on selective floral herbivory in B. halimifolia are in accord with the argument that dioecy reduces the inadvertent loss of flower parts of one sex when herbivores feed on flower parts of the opposite sex.  相似文献   

17.
Summary Phylogenetic analysis based on sequence data of the mitochondrial COI gene confirms the species status of the recently described Lasius austriacus. The five haplotypes of L. austriacus do not cluster according to their geographic origin, indicating a recent gene flow among the populations. The molecular data corroborate the morphology based hypothesis that L. austriacus belongs to the Lasius (Lasius s.str.) brunneus group. The invasive species Lasius neglectus forms a sister taxon with L. turcicus, both next related to L. austriacus. Other phylogenetic relationships within the genus Lasius are in accordance with morphological data.First data on the bionomics of L. austriacus are discussed in context with its phylogenetic position. Based on gyne and male morphology, excavations of nests, pitfall trapping and observations in formicaries, we hypothesize that L. austriacus is a mainly hypogaeic, monogynous species with nuptial flight. These are characters of the Lasius brunneus group in general, except the polygynous-polycalic, intranidally copulating L. neglectus. Aggression tests, however, revealed non-aggressive behaviour (antennation) between separated L. austriacus populations, but pronounced interspecific aggression against L. neglectus. This confirms the species status of L. austriacus and indicates a reduced level of intraspecific aggression, similar to L. neglectus.The status of L. austriacus as a native species in Central Europe is confirmed.Received 10 February 2003; revised 24 June 2003; accepted 23 July 2003.  相似文献   

18.
Three species of the genus Laboulbenia were recorded on Chydaeus bedeli (Coleoptera, Carabidae, Harpalini) from high-altitude localities in Asia. Laboulbenia obtusa was obtained from tarsi of the midlegs of the male hosts; Laboulbenia acrogeniodontis was on the margins of the elytra of the male and female hosts; and Laboulbenia polyphaga was on the elytra (near the apex) and the pronotum (at the base) of the male and female hosts. Each of the three species is distinct in the shape of the perithecia and the structure of the appendages.  相似文献   

19.
In the Iberian Peninsula and Balearic Islands pollen dimorphism was found inTeucrium fruticans L.,T. pseudochamaepitys L., andT. rotundifolium Schreber. Generally, this dimorphism shows two sizes of pollen grains, the smaller more or less collapsed. The percentage of pollen viability is calculated. Differences in size between viable and nonviable pollen grains are similar, being about 40% inT. fruticans andT. pseudochamaepitys, and about 26% inT. rotundifolium. With regard to pollen viability, the percentage of male sterility is higher inT. fruticans, in which from male sterile (ms) plants, 100% nonviable pollen was obtained from every flower observed. InT. pseudochamaepitys andT. rotundifolium with rare exceptions, the percentage of nonviable pollen does not seem to be significant.  相似文献   

20.
We associated nymphs of Labiobaetis sp. G and Labiobaetis sp. Q from Japan with imagoes reared from nymphs in the field. Labiobaetis sp. G was identified with L. atrebatinus (Eaton 1870) based on characters of the reared male and female imagoes, nymphs, and eggs. We also synonymized a Taiwanese species, L. morus (Chang and Yang 1994), with L. atrebatinus. After further examination of the characters of male imagoes from Japan and Korea and nymphs from Japan and Taiwan, we found them to be correspondent to subspecies L. atrebatinus orientalis (Kluge 1983). Thus, we reerected the subspecific status of L. a. orientalis, although it had been considered not distinguishable from the nominotypical subspecies L. a. atrebatinus. Labiobaetis a. orientalis is distributed in the Russian Far East, Japan, Korea, and Taiwan. We identified Labiobaetis sp. Q with L. tricolor (Tshernova 1928) based on characters of the reared male and female imagoes, nymphs, and eggs. Labiobaetis tricolor was recorded from Japan for the first time.  相似文献   

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