<Emphasis Type="Italic">Hieracium</Emphasis> subgen. <Emphasis Type="Italic">Pilosella</Emphasis>: pollen stainability in sexual,apomictic and sterile plants

Two pollen stainability tests (Alexander’s stain and acetocarmine) were used to detect differences in pollen viability of the sexual, apomictic and sterile plants of Hieracium subgen. Pilosella. In sexual taxa (Hieracium bauhini and H. densiflorum), the average stainability was 93.7–98.4%. Similarly high stainability (92.2–97.2%) was found in the apomictic Hieracium pilosellinum and in the majority of the apomictic populations (or plants) of the pentaploid and hexaploid H. bauhini. In some apomictic plants of Hieracium bauhini the average pollen stainability was 49.0–75.4%. The lowest pollen stainability was found in the sterile plants, i.e. the triploid H. pistoriense (33.6%) and the pentaploid H. brachiatum (29.6%).     

Autogamy inHieracium Subgen.Pilosella

The presence of autogamy inHieracium subgen.Pilosella is reported for diploidH. lactucella and tetraploidH. pilosella. Self-compatibility is induced under the influence of pollen from another species (mentor effects).     

Freakish patterns – species and species concepts in apomicts

Apomict groups keep challenging taxonomists, in classifications as well as in more fundamental question about the nature of apomictic species. The latter question is not just an academic one, because the outcome influences practical decisions on biodiversity and conservation. A historical overview over the species problem shows that a period of confusion and proliferation of species concepts between 1940 and 1990 was followed by an increasing consensus at the end of the 20th century that the species category is heterogeneous. Species come in kinds, which is understandable in light of their different evolutional histories. Recently, Wilkins stated that we do not need a generally applicable species concept, because species are not an a priori category into which all biological organisms must fit, but salient phenomena that are to be explained. Not only biparental, but also asexual organisms often form such species‐as‐phenomena, explained as some combination of adaptation to an ecological niche and reproductive compatibility. The above is illustrated by historical and current studies in three well‐studied apomict groups, viz. Ranunculus cassubicus agg., Rubus subgen. Rubus and Hieracium (subgen. Hieracium and Pilosella). Species in the Ranunculus cassubicus aggregate are the few existing sexuals, which are surrounded by a hybrid swarm of only partial apomictic forms, whereas in Rubus subgen. Rubus and Hieracium s.s. sexuals as well as numerous apomicts form well defined species. How species should be circumscribed in Pilosella is yet to be clarified. Largely, the differences between these groups can be contributed to their different modes of apomixis and the associated retained sexuality. From this review it is clear that the question is not so much ‘What is a species?‘, but ‘What is a species in this particular group?‘ To answer this question a thorough knowledge and understanding of the biology of the genus in question is required.     

Evolution of apomixis loci in Pilosella and Hieracium (Asteraceae) inferred from the conservation of apomixis-linked markers in natural and experimental populations

The Hieracium and Pilosella (Lactuceae, Asteraceae) genera of closely related hawkweeds contain species with two different modes of gametophytic apomixis (asexual seed formation). Both genera contain polyploid species, and in wild populations, sexual and apomictic species co-exist. Apomixis is known to co-exist with sexuality in apomictic Pilosella individuals, however, apomictic Hieracium have been regarded as obligate apomicts. Here, a developmental analysis of apomixis within 16 Hieracium species revealed meiosis and megaspore tetrad formation in 1 to 7% of ovules, for the first time indicating residual sexuality in this genus. Molecular markers linked to the two independent, dominant loci LOSS OF APOMEIOSIS (LOA) and LOSS OF PARTHENOGENESIS (LOP) controlling apomixis in Pilosella piloselloides subsp. praealta were screened across 20 phenotyped Hieracium individuals from natural populations, and 65 phenotyped Pilosella individuals from natural and experimental cross populations, to examine their conservation, inheritance and association with reproductive modes. All of the tested LOA and LOP-linked markers were absent in the 20 Hieracium samples irrespective of their reproductive mode. Within Pilosella, LOA and LOP-linked markers were essentially absent within the sexual plants, although they were not conserved in all apomictic individuals. Both loci appeared to be inherited independently, and evidence for additional genetic factors influencing quantitative expression of LOA and LOP was obtained. Collectively, these data suggest independent evolution of apomixis in Hieracium and Pilosella and are discussed with respect to current knowledge of the evolution of apomixis.     

Variation inHieracium subgen.Pilosella (Asteraceae): What do we know about its sources?

The present paper reviews mechanisms producing complicated patterns of variation withinHieracium subgen.Pilosella. The taxonomic complexity of this subgenus is due to highly variable basic species and intermediate (hybridogenous) species. The most important sources of variation are polyploidy, hybridization and (mostly) facultative apomixis of the aposporous type. The combination of hybridization, apomixis and clonal growth leads to the maintenance of various hybrids having originated from backcrossing and hybridization among more than two species, which is possible because of the fertile pollen of apomictic hybrids. Ever since Mendel’s experiments, some of F₁ hybrids have been found to be highly variable, probably reflecting the high heterozygosity of some of the basic species. Variable progeny can also result from unreduced gametes, or the rare parthenogenetic development of reduced gametes. While these processes were detected in experiments, their role within field populations remains unknown. However, multiple origins of intermediate species, and introgression within basic species are highly likely to result in high levels of variation. While few population level studies have been undertaken in Europe, several such studies have been carried out on adventive populations in New Zealand, and these show a different pattern. Aneuploid plants, rare in Europe, are common in New Zealand, and there is frequently more than one ploidy level within a population.     

Kinetoplast DNA in the insect trypanosomes Crithidia luciliae and Crithidia fasciculata: III. Heteroduplex analysis of the C. luciliae minicircles

We have investigated the nature of the sequence heterogeneity of the minicircles of Crithidia luciliae kinetoplast DNA by EM heteroduplex analysis of minicircles cleaved with endonuclease HindIII. Approximately 40% of the minicircles showed—after denaturation and reannealing—structures indicative of sequence rearrangements: the majority contained heteroduplex “eyes” interpreted as due to inversions; about 10% of the heteroduplexes yielded structures interpreted as due to translocations and a similar fraction showed insertions and deletions. The category of “eyed” molecules was analyzed in detail: four minicircle segments were found that displayed a high incidence of such eyes indicating that the rearrangements were not scattered at random over the minicircles. Moreover, since also “eyes” were found overlapping two or three of the four regions, we postulate that these segments are capable of recombining with each other. We conclude that specific segmental rearrangements form the main basis of the minicircle sequence heterogeneity in Crithidia.     

Floral scent and intrafloral scent differentiation inMoneses andPyrola (Pyrolaceae)

Floral scent was collected by headspace methods from intact flowers, petals, and stamens of four species ofPyrolaceae. The scent samples were analyzed by coupled gas chromatography-mass spectrometry (GC-MS). The floral scent inPyrola spp. is differentiated into a characteristic petal scent—phenyl propanoids and a characteristic stamen scent—methoxy benzenes. InMoneses the scent is characterized by isoprenoids and benzenoids, with a larger proportion of benzenoids in the stamens compared to the petals. Specific anther scents may promote foraging efficiency in buzz-pollinated species and enhance flower fidelity. Variation in floral scent composition is consistent with the taxonomic relationships among the genera and species examined.     

Sexual tetraploid and apomictic pentaploid populations ofHieracium pilosella (Compositae)

Five species are recognized inHieracium subgen.Pilosella sect.Pilosellina Fries. Four are diploid (2x, 2n = 18), one (H. pilosella L.) is highly variable morphologically and cytologically (from 2x to 10x), in its mode of reproduction (self-incompatibility, agamospermy, amphimixis, apo-amphimixis) and in its hybridization pattern. A part of this huge agamic complex was analysed by comparing sexual 4x and apomictic 5x plants (crossing and germination experiments, measurements of vegetative reproduction by stolons etc.). In the experimental garden apomictic 5x produced more stolons than the sexual 4x plants and the total length of the stolons per rosette was greater. However, in nature, the competitive potential of the sexual plants seems to be higher, presumably as a result of the higher mortality of ramets in 5x. Sexual 4x plants often grow in dense and grazed grass vegetation, whereas 5x apomicts often occur in dunes with patchy vegetation. Apomicts produce more capitula per rosette, and sexual rosettes form only about 60% of the number of viable achenes as compared to apomictic ones. Therefore, apomicts appear to be characterized by a greater colonizing ability than sexual plants. Apomictic plants produce equal numbers of viable achenes under conditions of both open pollination and isolation. Sexual plants do not form any viable achenes after isolation and produce a somewhat lower percentage of achenes after open pollination than do apomictics. 5xreproduce exclusively apomictically. Apo-amphimixis was never observed in pentaploids and only very rarely in tetraploids. Addition hybrids are very rare. The cross sexual 4x × apomictic 5x failed in 70% of the attempts, but the recombination of genomes carrying genes for apomixis is possible and results in apomictic 4x and sexual 5x, both with a reduced number of viable achenes. In nature sexual and apomictic plants may occur in close proximity. In such cases the germination rate of the achenes of 4x and 5x is lower; this may indicate that apomictic plants fertilize sexual plants in nature (unidirectional gene-flow). 5x plants form euploid gametes carrying two or three genomes. The results of the crossing experiments can be explained in terms ofNogler's theory of monogenic inheritance of apospory.Variation and evolution inHieracium subg.Pilosella sect.Pilosellina I.     

Mentor effects in the genus<Emphasis Type="Italic">Hieracium</Emphasis> S.STR. (<Emphasis Type="Italic">Compositae,Lactuceae</Emphasis>)

Self-incompatibility was demonstrated in the diploid taxaHieracium alpinum andH. umbellatum using isolation experiments. However, self-incompatibility was broken down in diploidH. alpinum under the influence of foreign pollen from another species of this genus (mentor effects) during a series of crossing experiments. Interestingly, failure of the SI system was also recorded in diploidH. alpinum in an intergeneric cross with the representative of the closely related genus ofPilosella. This is the first record of autogamy in the genusHieracium s.str. The possible evolutionary significance of this phenomenon is discussed.     

Beitrag zur Kenntnis der GattungHieracium L. in den Kaukasusländern

Taxonomic and chorological remarks on theHieracium flora of the Caucasian countries are given. A list contains localities of 28 taxa of the genusHieracium (incl.Pilosella) from Georgia and Armenia.H. piloselloides (sensu auct. medioeurop.) is new for the Soviet part of Transcaucasia.     

A review of chromosome cytology in Hyacinthaceae subfamily Ornithogaloideae (Albuca, Dipcadi, Ornithogalum and Pseudogaltonia) in sub-Saharan Africa

The chromosome cytology of Hyacinthaceae subfamily Ornithogaloideae is reviewed within the framework of a recent molecular-based classification, with particular emphasis on its center of diversity in sub-Saharan Africa. We also provide new chromosome counts for sections that are unknown or poorly known cytologically. Albuca subgen. Namibiogalum (9 spp.) probably has an ancestral base number of x = 10 but subgen. Albuca (± 70 spp), subgen. Monarchos (9 spp.) and subgen. Osmyne (36 spp.) have x = 9. The pattern in subgen. Urophyllon (3 spp.) is remarkable: although x = 6 is likely, the species in the section exhibit a range of 2n = 12, 10, 8, 6 and 4 (exclusive of polyploidy). All karyotypes have three large chromosome pairs and a variable number of small chromosomes. Pseudogaltonia (2 spp.) has x = 9 and Dipcadi (26 spp.) possibly x = 9 in series Uropetalum and x = 6 in series Dipcadi, which exhibits a pattern of descending dysploidy leading to n = 3 in D. marlothii. In Ornithogalum (± 130 spp.) chromosome numbers are known for only 24 of the ± 84 sub-Saharan species, mostly from subgen. Aspasia and subgen. Ornithogalum sect. Linaspasia, both of which have x = 6, and from subgen. Galtonia, which has x = 8. In contrast, x = 7 is basic for the Eurasian sects. Honorius and Melophis, and x = 18 seems likely for sect. Cathissa. Sect. Ornithogalum, the cytology of which we does not examine in detail, may have x = 9. Polyploidy is apparently rare in the sub-Saharan African ornithogaloids, in marked contrast to the high frequency of polyploidy among Eurasian species. In Albuca just 3 or possibly 4 sub-Saharan species (9% or 13% of those counted) are exclusively polyploid and 5 more have diploid and polyploid races; and in sub-Saharan Ornithogalum, only the tropical O. gracillimum is exclusively polyploid, and the western southern African O. hispidum has diploid and polyploid races.     

野生杜鹃杂交亲和性及适宜的评价指标

以映山红和马银花为母本,映山红亚属、羊踯躅亚属、杜鹃亚属、常绿杜鹃亚属以及马银花亚属的5个亚属16个中国野生杜鹃种为父本进行杂交授粉,统计子房膨大率、坐果率和种子萌发率,分析杜鹃属植物远缘杂交的亲和性,探讨其杂交亲和性适宜的评价指标。结果表明:映山红作为母本,与同亚属的杜鹃杂交亲和性较好,与其它亚属的杜鹃种的杂交亲和性存在显著的亚属间和种间差异;而马银花作为母本,与同亚属的西施花进行杂交,未获得杂交果实和种子,但与杜鹃其它亚属种的杂交,部分杂交组合显示出较好的杂交亲和性。这一结果表明,映山红作为母本,与马银花相比,有着较好的杂交亲和性,并且杜鹃属植物的杂交亲和性与目前杜鹃分类体系中的亲缘关系并没有直接关系。进一步的数据分析表明,子房膨大率与坐果率、坐果率与蒴果平均种子数之间呈显著正相关,但子房膨大率与果实内种子数无直接相关性;花粉活力(大于15%)、父母本花柱长度比(在0.50~2.12范围内)与子房膨大率等亲和性指标无显著相关性。     

In vitro allelopathic effects of pollen from three Hieracium species (Asteraceae) and pollen transfer to sympatric Fabaceae

Pollen allelopathy occurs when pollen toxins inhibit sexual reproduction in heterospecifics. To quantify pollen allelopathic effects in vitro, pollen of Hieracium aurantiacum, H. floribundum, and H. pratense was extracted with double distilled water into concentrations of 0 (control), 0.1, 1, 3, 5, 10, and 25 pollen grains/μl. A subset of these extracts was partitioned by ion-exchange chromatography into acidic, basic, and neutral fractions. Pollen from six sympatric species of Fabaceae (Lotus corniculatus, Medicago sativa, Trifolium hybridum, T. pratense, T. repens, Vicia cracca) and the species of Hieracium was germinated on agar media containing different extract concentrations. As extract concentrations from intact pollen or from acidic fractions increased, mean percent germination of pollen of all Fabaceae decreased nonlinearly. Extract concentrations of 0.1 grains/μl and above inhibited pollen germination in the Fabaceae. In no case was any Hieracium species affected, i.e., there was no autotoxicity. Similar results were obtained using plants from nine populations of H. floribundum and H. pratense across eastern Canada. Observation of floral visitors indicated that there were relatively few movements between Hieracium and the Fabaceae (about 15% of total visits). Hence there is limited opportunity for heterospecific pollen transfer. This was consistent with censuses of stigma, i.e., few pollen grains of Hieracium were found on stigma of the Fabaceae. Thus, pollen allelopathy in Hieracium is unlikely to affect reproductive success in these six species of Fabaceae.     

高粱属植物的地理分布

为探讨高粱属(Sorghum Moench)的系统发育关系,通过野外调查及查阅标本和文献资料,对高粱属植物的地理分布进行了整理和研究。高粱属植物约有29种,分布于全世界热带到温带地区,其中澳大利亚22种,亚洲15种,非洲9种,欧洲3种,地中海2种,美洲6种。中国有5种,分布在东北、西南到华南各省(区)。高粱属有5亚属,仅高粱亚属(subgen.Sorghum)延伸至新世界,其他亚属均分布在旧世界,高粱亚属覆盖非洲并扩散到全世界热带到温带地区;拟高粱亚属(subgen.Parasorghum)分布在非洲、亚洲、澳大利亚;有柄高粱亚属(subgen.Stiposorghum)主要分布在澳大利亚,个别种分布到亚洲;多毛高粱亚属(subgen.Chaetosorghum)分布在澳大利亚;异高粱亚属(subgen.Heterosorghum)分布在澳大利亚和亚洲。这表明澳大利亚东北部是高粱属的现代分布中心和多样化中心,非洲东北部和热带亚洲是否是高粱属的起源地尚需确证。     

32种杜鹃花属植物亚属间杂交的可育性研究

为探索杜鹃花属植物亚属间杂交的可育性规律,该文对常绿杜鹃亚属(subgen. Hymenanthes)、杜鹃亚属(subgen. Rhododendron)及马银花亚属(subgen. Azaleastrum)、映山红亚属(subgen. Tsutsusi)和羊踯躅亚属(subgen. Pentanthera)的亚属间杂交进行了研究,共涉及杜鹃花属植物5亚属15亚组32种,杂交组合118个。结果表明:(1)杜鹃花属植物的亚属间杂交存在明显的生殖障碍,其可育性水平与亚属及其类群组合有关,高、中、低与不育比例为2∶16∶8∶92,可育比例仅20.0%,杜鹃亚属与马银花亚属等4个亚属级组合杂交未显现可育性。(2)亲本杂交组合方式对亚属间杂交有不同程度的影响,一些类群组合有明显的向性。以杜鹃亚属做母本与常绿杜鹃亚属的云锦杜鹃亚组杂交的可育组合比高于反交,且在有关大王杜鹃、粘毛杜鹃、露珠杜鹃和马缨花的杂交中也是如此,但与银叶杜鹃亚组杂交正好相反;另外,12对单向可育组合,分布于常绿杜鹃亚属与杜鹃亚属等4类亚属级杂交组合中。(3)杜鹃花属的亚属间杂交不亲和与败育现象明显,不可育组合百分率占80%,不能坐果是败育的主要表征,所有可育组合的绿苗率比值和单位种子数比值无一例达到相应母本的自然授粉水平。(4)双亲系统分类上的关系对亚属间可交配性具有重要影响并与可育程度一致,染色体倍性也有一定的作用。(5)有关研究为探索和认识杜鹃花属植物亚属间进化遗传联系提供了新的证据和思考,银叶杜鹃亚组可能是解释常绿杜鹃亚属与杜鹃亚属进化遗传联系的重要类群,杜鹃亚属的多鳞杜鹃可能与常绿杜鹃亚属具有广泛的血亲关系,其中多鳞杜鹃与岷江杜鹃彼此为生态相邻种并有可能在长期的演化过程中有遗传渗透,百合花杜鹃和毛肋杜鹃分别与映山红亚属、腺果杜鹃与马银花亚属,越峰杜鹃和繁花杜鹃分别与映山红亚属,大白杜鹃与羊踯躅亚属间的联系均需要深入研究。     

Evolution and diversity of floral scent chemistry in the euglossine bee-pollinated orchid genus Gongora

•Background and Aims Animal-pollinated angiosperms have evolved a variety of signalling mechanisms to attract pollinators. Floral scent is a key component of pollinator attraction, and its chemistry modulates both pollinator behaviour and the formation of plant–pollinator networks. The neotropical orchid genus Gongora exhibits specialized pollinator associations with male orchid bees (Euglossini). Male bees visit orchid flowers to collect volatile chemical compounds that they store in hind-leg pouches to use subsequently during courtship display. Hence, Gongora floral scent compounds simultaneously serve as signalling molecules and pollinator rewards. Furthermore, because floral scent acts as the predominant reproductive isolating barrier among lineages, it has been hypothesized that chemical traits are highly species specific. A comparative analysis of intra- and inter-specific variation of floral scent chemistry was conducted to investigate the evolutionary patterns across the genus.•Methods Gas chromatography–mass spectrometry (GC-MS) was used to analyse the floral scent of 78 individuals belonging to 28 different species of Gongora from two of the three major lineages sampled across the neotropical region. Multidimensional scaling and indicator value analyses were implemented to investigate the patterns of chemical diversity within and among taxonomic groups at various geographic scales. Additionally, pollinator observations were conducted on a sympatric community of Gongora orchids exhibiting distinct floral scent phenotypes.•Key Results A total of 83 floral volatiles, mainly terpenes and aromatic compounds, were detected. Many of the identified compounds are common across diverse angiosperm families (e.g. cineole, eugenol, β-ocimene, β-pinene and terpinen-4-ol), while others are relatively rare outside euglossine bee-pollinated orchid lineages. Additionally, 29 volatiles were identified that are known to attract and elicit collection behaviour in male bees. Floral scent traits were less variable within species than between species, and the analysis revealed exceptional levels of cryptic diversity. Gongora species were divided into 15 fragrance groups based on shared compounds. Fragrance groups indicate that floral scent variation is not predicted by taxonomic rank or biogeographic region.•Conclusions Gongora orchids emit a diverse array of scent molecules that are largely species specific, and closely related taxa exhibit qualitatively and quantitatively divergent chemical profiles. It is shown that within a community, Gongora scent chemotypes are correlated with near non-overlapping bee pollinator assemblies. The results lend support to the hypothesis that floral scent traits regulate the architecture of bee pollinator associations. Thus, Gongora provides unique opportunities to examine the interplay between floral traits and pollinator specialization in plant–pollinator mutualisms.     

Scent chemistry and pollinator attraction in the deceptive trap flowers of Ceropegia dolichophylla

Ceropegia species (Apocynaceae, Asclepiadoideae) have pitfall flowers and are pollinated by small flies through deception. It has been suggested that these flies are attracted by floral scent. However, the scent that is emitted from Ceropegia flowers has not been studied using headspace and gas chromatography mass spectrometry methods. It has also been unclear whether or not the flowers are mimics of particular models that attract flies. In the present study, we determined the composition as well as the spatial and temporal patterns of floral scent emitted by C. dolichophylla. Furthermore, we determined the pollinators in the native (China) and non-native (Germany) range of this species, and tested the capability of the floral scent to attract flies in the non-native range. Our data demonstrate that the floral scent, which is emitted from morning until evening, primarily from the tips of the corolla lobes, consists mainly of spiroacetals and aliphatic compounds. Milichiid flies were common visitors/pollinators in the native as well as non-native range, and were attracted by floral scent in bioassays performed in the non-native range. The compounds emitted by C. dolichophylla are unusual for flowers, but are well known from insect pheromones and occur in the glandular secretions of insects. The milichiid flies that visit and pollinate the flowers are kleptoparasites that feed on the prey (haemolymph or other secretions) of predatory arthropods, e.g. spiders, to which they are attracted by scent. Our data thus suggest that the floral scent of C. dolichophylla mimics the feeding sites of kleptoparasitic flies.