Morphometric analysis of floral variation in the Pyrola picta species complex (Ericaceae): interpretation and implications for ecological and phylogenetic differentiation

The Pyrola picta species complex of western North America comprises four species (P. picta, P. dentata, P. aphylla and P. crypta) that grow sympatrically in some parts of their collective ranges, have remarkably similar flowers and share pollinators. These species do not exhibit the genetic signatures typical of random or heterospecific mating, but instead show genetic divergence patterns indicating that they maintain surprising levels of reproductive isolation. To better understand how species boundaries are maintained, the current study uses statistical ordination analyses to determine whether species isolation across shared geographical ranges might be achieved through subtle differences in floral characters among species. The possible contribution of differences in flowering phenology (e.g. temporal reproductive isolation) to reproductive isolation was also evaluated for the small subset of populations in which two or more species occur in direct sympatry. Among species in the P. picta complex, there are both phylogenetic and geographical trends in some floral characteristics, whereas other characters do not covary with either geography or species identity. In several sympatric populations, differences in flowering phenology among species suggest that timing plays a major role in non‐random (i.e. mainly conspecific) mating. The conclusions of this study are that reproductive isolation in the P. picta species complex is reinforced by differences in the timing of floral maturation and the morphologies of androecium and floral display characters. © 2015 The Linnean Society of London, Botanical Journal of the Linnean Society, 2015, 00 , 000–000.     

Search for Protein Markers for the Genetic CMS–Rf System in Sunflower

Pollen and anthers of the F₁ hybrid with the restored fertility and the parental forms, a maternal male-sterile line harboring the mitochondrial orfH522 gene and a paternal male-fertile line harboring dominant alleles of the nuclear Rf gene, were studied. In order to find protein markers for the genetic CMS–Rf system in sunflower, we analyzed cytoplasmic proteins by disc electrophoresis under denaturing conditions. As a result, a protein fraction with a mol wt of 43 kD specific for cytoplasmic proteins of the paternal anthers, and a protein fraction with a mol wt of 16 kD specific for cytoplasmic proteins of the maternal anthers, were detected. The electrophoretic patterns of water-soluble proteins from the hybrid and paternal lines did not differ.     

激光诱导杨树单性生殖的研究Ⅲ杨树花药愈伤组织的类型及其分化率

试验区分杨树花药愈伤组织三种类型：花粉、花丝和药壁或药隔愈伤组织。显然,激光能提高花粉愈伤组织的芽分化率。     

Features related to anther opening in Solanum species (Solanaceae)

The mode of anther opening and the morphological and histological variability of the stomium are described in 30 Solanum species. Poricidal, poricidal‐longitudinally dehiscing and longitudinally dehiscing anthers are observed. In the three types, the stomium may be diverse with regard to shape and histological characteristics before opening, but is always composed of small epidermal cells as the sole anther wall layer; the stomial cells may be differentiated only in part of the anther length. Particular crescent‐shaped structures in the epidermis, called ‘ridges’, are observed to line the stomium in most species. These ridges may be related to the stomium opening, working together with the cells with thickened walls of the anther. Cells with thickened walls are developed in the endothecium, middle layers and/or connective tissue at the apical end of the anther, surrounding the pore; only in the longitudinally dehiscing anthers of S. nitidum does an endothecium with thickened cell walls develop along its entire length. At least two histological features (the differentiation of small stomial epidermal cells as a unique layer, and the distribution of cells with thickened walls) seem to constrain the form of the open stomium. © 2008 The Linnean Society of London, Botanical Journal of the Linnean Society, 2008, 158 , 344–354.     

Visits to Manipulated Flowers by Episyrphus balteatus (Diptera: Syrphidae): Partitioning the Signals of Petals and Anthers

In a number of previous studies attention has been directed to the selection on corolla dimensions by pollinator preference, but anthers may also be a signal. This experiment examined the relative importance of petals and anthers in the attraction of male Episyrphus balteatus (Diptera, Syrphidae) to individual oil-seed rape flowers (Bracus rapae oleifera). Rape flowers have four petals and six anthers. Nine treatments were created, of flowers with four, two, or zero petals and six, three, or zero anthers. Twenty males were tested for preference among the experimental flowers by recording the sequence and duration of their visits (which were all for feeding) to the flowers. The number of first visits and the duration of visits on each flower were significantly related to the number of anthers but not the number of petals. There was no correlation between petal area and pollen load of control flowers. It is suggested that Syrphidae may not always attend to petals, and variation in preference of different pollinator taxa should be taken into account when discussing the evolution of floral characters.     

Development of the gametophytes, flower, and floral vasculature in Dichorisandra thyrsiflora (Commelinaceae)

The flowers of Dichorisandra thyrsiflora (Commelinaceae) are monosymmetric and composed of three sepals, three petals, six stamens, and three connate carpels. The anthers are poricidal and possess a wall of five cell layers (tapetum included). This type of anther wall, not previously observed in the Commelinaceae, is developmentally derived from the monocotyledonous type via an additional periclinal division and the persistence of the middle layers through anther dehiscence. Secondary endothecial thickenings develop in the cells of the two middle layers only. The tapetum is periplasmodial and contains raphides. Microsporogenesis is successive and yields both decussate and isobilateral tetrads. Pollen is shed as single binucleate grains. The gynoecium is differentiated into a globose ovary, hollow elongate style, and trilobed papillate stigma. Each locule contains six to eight hemianatropous to slightly campylotropous crassinucellar ovules with axile (submarginal) placentation. The ovules are bitegmic with a slightly zig-zag micropyle. Megagametophyte development is of the Polygonum type. The mature megagametophyte consists of an egg apparatus and fusion nucleus; the antipodals having degenerated. The floral vasculature is organized into an outer and inner system of bundles in the pedicel. The outer system becomes ventral carpellary bundles. All other floral vascular traces originate from the inner system.     

Close clustering of anthers and stigma in Ipomoea hederacea enhances prezygotic isolation from Ipomoea purpurea

Theory predicts that, for taxa that are already substantially postzygotically isolated but for which hybrid mating is still costly, enhanced prezygotic isolation will be favored. Here, we tested this hypothesis by examining the potential contribution of one particular floral trait, herkogamy, to prezygotic isolation between two species of morning glory, Ipomoea hederacea and Ipomoea purpurea. This trait was experimentally manipulated to determine whether it is a likely prezygotic isolating barrier in naturally pollinated arrays in the field. Emasculated I. hederacea flowers set significantly fewer seeds than did control flowers, indicating that clustering of anthers and stigma in I. hederacea enhances prezygotic isolation from I. purpurea. We hypothesize that this occurs through some combination of mechanical protection and increased self-pollination, with the effect of mechanical protection estimated to be 30% greater than the effect of increased selfing. Our results identify stigma-anther proximity as a likely prezygotic isolating barrier and target of selection in the presence of heterospecific pollen flow, and provide motivation for further study of the role of floral morphology in reproductive isolation in this system.     

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.