Critical studies on the sexuality of southern Argentinian Ericaceae

Summary The family Ericaceae is considered to be mostly hermaphroditic and only in a few cases unisexual or dioecious. Five Argentinian species (Gaultheria antarctica Hook, f., G. caespitosa P. et E., G. phillyreaefolia (Pers.) Sleumer, G. tenuifolia (Phil.) Sleumer and Pernettya insana (Molina) Gunckel), previously described as hermaphroditic, were found by us to have two types of flowers: female and male. Female flowers have both a rudimentary androecium with stamens, in which the anthers are small, collapsed and without pollen grains or are reduced to filaments only, and a perfect gynoecium with well-developed ovules filling the carpel locules. The stigma is expanded and of the wet, papillate type, with copious to slight secretion. The stigma protrudes above the anthers. Male flowers have a well-developed androecium included within the corolla and a reduced gynoecium. Anthers are as long as the filaments, except in G. caespitosa. Pollen is shed as tetrads which are 100% viable. Ovule development ranges from total absence, passing through aborted ovules of various sizes to apparently normal ones. Stigmata are neither expanded nor papillate, except in Pernettya insana. Only in two species do the style and stigma extend beyond the level of the anthers. Heterostyly does not occur in any of the five species studied. Functional dioecy thus characterizes the five species considered and is reported for the first time in the genus Gaultheria.     

Notes on the floral morphology in Vivianiaceae (Geraniales)

The functional floral morphology of the three genera of Vivianiaceae (= Ledocarpaceae, Geraniales), Rhynchotheca, Viviania and Balbisia, is compared. Likely pollination mechanisms are inferred from morphology and field observations. The flowers of Viviania are nectariferous and apparently zoophilous with nectar as the (primary) pollinator reward. Balbisia has pollen flowers without nectaries, its showy corolla indicates that it is also zoophilous with pollen as sole pollinator reward; bees were observed as flower visitors. One taxon (B. gracilis) may be anemophilous. Rhynchotheca has flowers without petals, with large, pendulous anthers and lacks nectaries. It shows synchronous mass flowering in its natural populations and is evidently anemophilous. A comparison with other Geraniales shows that nectar flowers with small anthers are likely the ancestral condition in Vivianiaceae. This suggests that the pollen flowers with larger anthers of Balbisia and Rhynchotheca may represent an apomorphic condition. The documentation of pollen flowers and anemophily in Vivianiaceae expands the range of known floral and pollination syndromes in Geraniales.     

Dioecy in the endemic genusDendrocacalia (Compositae) on the Bonin (Ogasawara) Islands

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.     

Corolla wilting facilitates delayed autonomous self-pollination in Pedicularis dunniana (Orobanchaceae)

Structural changes associated with corolla wilting may serve as a mechanism for effecting self-pollination. Low pollinator visitation, high seed production and a corolla that persists after anthesis indicates that Pedicularis dunniana is autogamous. Delayed autonomous self-pollination is facilitated by corolla wilting. Wilting of the upper lip (galea) brought the pollen laden anthers into contact with the stigma resulting in the deposition of self pollen on the stigma. The seed set of flowers either emasculated, or with restrained galeae thus preventing anthers brushing against the stigma, was significantly lower than that of open-pollinated flowers. This demonstrates that autogamy occurs in this species through corolla wilting. Germination experiments indicated that outcross seedlings were more vigorous than selfed seedlings as a result of inbreeding depression. It is likely that autogamy provides reproductive assurance for P. dunniana under conditions of pollinator scarcity.     

浙江木犀科一新种——浙南木犀

该文描述了采自浙江南部的木犀属(Osmanthus Lour.)一新种——浙南木犀(O.austrozhejiangensis Z.H.Chen,W.Y.Xie et X.Liu),并附有线描图和彩色照片。该种在具聚伞花序,叶柄、小枝、苞片、花梗被柔毛等性状上接近于毛柄木犀(O.pubipedicellatus Chia ex H.T.Chang),不同之处在于叶片倒卵形、倒卵状椭圆形或椭圆形,长(5.5~)8~10(~13)cm,宽(2.2~)3~4.5(~5)cm,先端急尖或短渐尖,叶缘具尖锐细锯齿或全缘,侧脉8~10对,花较大,花冠管长2.2~2.3 mm,裂片长2.2~3.0 mm,花丝长1.3~1.5 mm,花药长约1.2 mm。该新种的发现为研究东亚木犀属自西南向东北方向迁移与演化提供了新的材料。     

Karyological study in the genusTuberaria sect.Scorpioides (Cistaceae): Taxonomic and evolutionary inferences

A polyploid complex ofTuberaria sect.Scorpioides species in S Spain has been studied. We have found the chromosome numbers n = 12 and 18, which probably originated from the extinct base number x = 6 by means of allopolyploidy. Octoploids (n = 24) seem to be the result of different crossings, and fall morphologically withinT. guttata, T. inconspicua, orT. commutata. Backcrosses between octoploids and tetraploids originate new hexaploids (n = 18), which, once stabilized, behave as amphidiploids. Most of these also fall within the traditional concept ofT. guttata, so that the enormous polymorphism of this taxon seems to be justified.     

Variation of pollen and ovule parameters among different ploidy levels ofCorydalis (Fumariaceae)

The size and number of pollen grains and ovules are compared between 20 populations of different ploidy levels in two self-incompatible species ofCorydalis (Fumariaceae), to test the presence of ploidy-related variation in these reproductive characters. In both species, higher ploidy levels are associated with larger pollen grains, ovules and corolla, but the number of pollen grains and ovules are not different between ploidy levels. The investment per flower is consequently larger at higher ploidy levels, but the flower number per individual is lower, suggesting that the mode of partition of the investment for sexual reproduction varies between different ploidy levels. InC. orthoceras, sex allocation estimated by pollen:ovule ratios in number and volume is more female-biased in polyploids than in diploids. In spite of these variations, the characters studied can not be used as indicators of ploidy level due to the large overlaps between the ploidy levels.     

Stamen movements in flowers ofOpuntia (Cactaceae) favour oligolectic pollinators

Opuntia brunneogemmia andO. viridirubra occur sympatrically in the Serra do Sudeste, Rio Grande do Sul, Brazil. Their flowers have 450–600 thigmonastic stamens and provide large amounts of pollen and nectar for bees. Bees of 41 species were registered at the flowers ofO. brunneogemmia and 30 at the flowers ofO. viridirubra. Females of three oligolectic species are the only effective pollinators:Ptilothrix fructifera (Anthophoridae),Lithurgus rufiventris (Megachilidae), andCephalocolletes rugata (Colletidae). During their visits inOpuntia-flowers, bees touch the filaments and stimulate the movement of the stamens to the centre of the flower. At the end of this movement, the anthers are densely packed around the style. As a consequence the pollen is presented in an easily accessible upper layer of anthers and various, nearly inaccessible lower layers. The lower layers contain about 80% of the pollen reward. Only females of the three oligolectic pollinators exploit the pollen from the lower layers and reach the nectar furrow. Therefore, through their stamen movements,Opuntia flowers hide most of their pollen from flower visitors but favour effectively pollinating, oligolectic bees.     

Size-dependent reproduction in Australian alpine Ranunculus

Abstract The effect of plant size on reproduction in four species of alpine Ranunculus (R. muelleri, R. dissectifolius, R. graniticola and R. niphophilus) was investigated in two sites over two seasons in the field on a total of 190 plants. The effects of plant size (number of leaves) and number of flowers on the number of anthers, ovules and seed per flower and per plant were determined. There was a positive relationship between several measures of reproduction and plant size in all four species, indicating that reproduction is size-dependent. All the results indicate that the main factor controlling the amount of seed produced by alpine Ranunculus is the size of the plant. Specifically, bigger plants produced more seed by producing more flowers, not by producing more ovules per flower, or higher seed set per flower. Correspondingly, bigger plants produced more anthers by producing more flowers, rather than by producing flowers with more anthers. The total number of seeds produced by a plant was directly proportional to plant size in the four species. Therefore, reproductive effort should not vary with plant size in the four species.     

FLORAL PARAMETERS,BREEDING SYSTEM AND POLLINATOR TYPE IN TRICHOSTEMA (LABIATAE)

Diversity in flower size and degree of exsertion of anthers and stigma from the corolla in the California species of Trichostema appear to be correlated with breeding system and pollinator type (bee vs. bird). Autogamous (self-pollinating) species unlike xenogamous (cross-pollinating) species lack spatially separate anthers and stigma and nototribic pollination. The outcrossing species have significantly larger flowers, significantly larger nectar volumes and significantly higher pollen-ovule ratios than do selfing species. Because autogamous species are less reliant on flower visitors to facilitate pollination, there may be relaxed selection for large nectar producing flowers. Pollen-ovule ratios are correlated with breeding system and reflect the efficiency of pollen transport. Data on floral parameters suggest xenogamous species expend more energy per floral unit and are less efficient seed producers than closely related autogamous species.     

Pollination of four sympatric species ofAngelonia (Scrophulariaceae) by oil-collecting bees in NE. Brazil

The manner whereby the oil-producing bisaccate flowers ofAngelonia (Scrophulariaceae) are pollinated by female oil-collecting bees is reported for the first time. Observations were made in the Caatinga formation of Pernambuco, NE. Brazil, on four synchronopatric species. These differ in sizes and structural details of the corolla, level of flower exposition, and habitat preferences. All legitimate visitors wereCentris spp. (Anthophoridae):Angelonia hirta was mainly pollinated byC. fuscata andA. pubescens byC. hyptidis; A. bisaccata andA. hookeriana shared an unidentified species. Several exomalopsine, tetrapediine and meliponid bees exploit the flowers less descriminately for oil or pollen, respectively, without regularly contacting anthers and stigma. The flowers are protandrous, and are self-incompatible except those of the annualA. pubescens. After alighting, theCentris bees introduce their front legs simultaneously into each of the pouches and start alternate collecting movements to gather the oil from the trichome elaiophores. While doing so, they are forced by projections of the corolla floor to press their head under the anthers and stigma, whereby pollen is transferred with their frons or clypeus. On account of their collector type and behaviour,C. fuscata andC. spec. are not specialized toAngelonia but may equally exploit other nonrelated taxa for oil, whereasC. hyptidis exhibits oligolecty onA. pubescens. It possesses relatively elongate forelegs with padlike collectors suitable for sweeping the lipids from the scattered glandular hairs inside the divergent spurs of its host. It is the only species that also collects pollen (by buzzing) from the oil host.A. hirta and relatives, provided with dense elaiophore carpets, are, for their part, adapted to scrapingCentris species with typical oil collectors. Flower and bee phenologies, although largely dependent on the irregular rainfalls, are not always coincident.     

Visibility vs. biomass in flowers: exploring corolla allocation in Mediterranean entomophilous plants

Background and Aims

While pollinators may in general select for large, morphologically uniform floral phenotypes, drought stress has been proposed as a destabilizing force that may favour small flowers and/or promote floral variation within species.

Methods

The general validity of this concept was checked by surveying a taxonomically diverse array of 38 insect-pollinated Mediterranean species. The interplay between fresh biomass investment, linear size and percentage corolla allocation was studied. Allometric relationships between traits were investigated by reduced major-axis regression, and qualitative correlates of floral variation explored using general linear-model MANOVA.

Key Results

Across species, flowers were perfectly isometrical with regard to corolla allocation (i.e. larger flowers were just scaled-up versions of smaller ones and vice versa). In contrast, linear size and biomass varied allometrically (i.e. there were shape variations, in addition to variations in size). Most floral variables correlated positively and significantly across species, except corolla allocation, which was largely determined by family membership and floral symmetry. On average, species with bilateral flowers allocated more to the corolla than those with radial flowers. Plant life-form was immaterial to all of the studied traits. Flower linear size variation was in general low among conspecifics (coefficients of variation around 10 %), whereas biomass was in general less uniform (e.g. 200–400 mg in Cistus salvifolius). Significant among-population differences were detected for all major quantitative floral traits.

Conclusions

Flower miniaturization can allow an improved use of reproductive resources under prevailingly stressful conditions. The hypothesis that flower size reflects a compromise between pollinator attraction, water requirements and allometric constraints among floral parts is discussed.Key words: Allometry, biomass, corolla, drought, evolution, flower, Mediterranean, sclerophyllous, size, variation, water     

Choices and Consequences of Oviposition by Hylemya (Delia) Sp. (Diptera: Anthomyiidae)

Hylema sp. ⁵ females oviposit on the undersides of sepals of developing buds of both Ipomopsis aggregata and Polemonium foliosissimum. Eggs deposited on the latter are significantly more likely to be fully protected by the sepal than are eggs deposited on the former. Unexposed eggs have a significantly greater likelihood of successfully developing to the larval stage than do exposed eggs. The difference in frequency of egg exposure on the two plant species can be attributed to differences in sepal morphology: I. aggregata sepals are significantly narrower than those of P. foliosissimum. The hypothesis that females preferentially oviposit on larger flowers was unconfirmed by a manipulative choice experiment. Plants differing in the size of their flowers were potted together and presented to Hylemya in arrays in the field. Flowers of the larger-flowered pair were no more likely to be oviposited on than flowers of the smaller-flowered pair. However, there were significant negative correlations between the corolla length and the percentage of flowers laid on per day at each of two sites. There was also a significant positive correlation between the corolla width and the percentage of flowers laid on at one site. Thus females appear to be using some measure of flower morphology, or a correlated trait, in making oviposition decisions. The degree to which Hylemya is making suboptimal choices between host plant species is discussed and requires further examination.     

狮耳草属——中国唇形科植物一新归化属

该文报道了中国唇形科植物一新归化种——荆芥叶狮耳草[Leonotis nepetifolia(L.)R.Br.],该种的发现代表狮耳草属[Leonotis(Pers.)R.Br.]在中国的新归化。狮耳草属的主要特征为轮伞花序腋生,苞片和萼齿顶端针刺状,花冠桔红色或黄色,冠唇上唇较大,下唇较小;其与绣球防风属(Leucas R.Br)较为接近,但后者的萼齿等大,花冠通常白色,花冠筒不超出萼外,冠檐下唇长于上唇,二者区别较为显著。荆芥叶狮耳草为一年生草本。轮伞花序球形,多花密集,其下承以多数密集苞片;苞片细长,向下微弯曲,先端针刺状。花萼管状,先端膨大而略折曲;萼齿针刺状,最上面一枚较大。花冠桔红色,密被桔红色绒毛;花冠筒细长,伸出萼筒之外;冠檐二唇形,上唇较大,下唇较小。荆芥叶狮耳草与同属植物Leonotis leonurus R.Br.最为相似,但前者叶为卵圆形或心形,后者的叶片多为披针形。根据该研究的标本和相关文献资料,该文还提供了狮耳草属和荆芥叶狮耳草的形态描述、地理分布的讨论,以及荆芥叶狮耳草的资源价值、归化途经、繁殖和危害的讨论和野外生态照片。     

Flowering seasonality and flower characteristics ofLoranthus acaciae Zucc. (Loranthaceae): Implications for advertisement and bird-pollination

The flowering biology and pollination ecology ofLoranthus acaciae was studied at Hazeva in the northern Arava Valley in Israel. Flowers at anthesis had red anthers, a red stigma and a green corolla which turned red as a postfloral phenomenon. Their flowering period was approximately 10 months long (from mid-June until mid-April) during which time two main flowering patterns were distinguished. Some plants flowered twice a year, with separate summer and winter flowering periods; other plants flowered continuously, with two peaks, one in the summer and one in the winter. Several significant differences between summer and winter flowering and fruiting were found: (1) the summer flowering period was shorter than that of winter, (2) flowering synchrony between individual plants was lower in summer than in winter, (3) in summer the plants produced a larger proportion of female flowers, whereas in winter most of the plants produced a larger proportion of hermaphrodites, (4) in summer a limited number of plants produced smaller flowers while the majority produced normal-sized flowers, whereas in winter the entire population produced only normal-sized flowers, and (5) fruit set percentage was lower in summer than in winter.L. acaciae was found to be self-compatible, but, since it was not spontaneously self-pollinated, it showed high dependence on pollinator activity. In summer the flowers were visited by a wide spectrum of pollinators, both birds and insects, while in winter flowers were visited almost exclusively by the orange-tufted sunbird (Nectarinia osea osea, Nectariniidae). These seasonal changes in flowering characteristics and pollinator activity could explain why reproductive success is higher in winter than in summer.     

Floral rewards in someScrophularia species (Scrophulariaceae) from the Iberian Peninsula and the Balearic Islands

The genusScrophularia in the Iberian Peninsula and Balearic Islands comprises two sections,Scrophularia andCanina G. Don. Analyses were carried out on flower production, flower duration and their sexual phases, pollen and nectar production together with observations on their pollinators. Nectar production is correlated with corolla size and pollen production with anther size. The taxa of sect.Scrophularia show greater nectar and pollen production than those of sect.Canina. Also, those of the first section produce more ovules per ovary than those of the second group, production being correlated with the ovary size.Some observations on floral and reproductive biology in some species ofScrophularia from the Iberian Peninsula and the Balearic Islands. I.     

Sexual differences in reproductive characters and pollinator attractiveness in gynodioecious Glechoma longituba (Lamiaceae)

We quantified the differences in floral characters and attractiveness to flower visitors under natural conditions between the sexual types in the gynodioecious plant Glechoma longituba. We also manipulated flowers by altering corolla size or nectar volume, or by removing anthers, to examine the effect of these primary and secondary attractants (i.e. rewards and advertisements) on attractiveness. A change in corolla size and shape reduced visiting frequency and pollen load. Removal of anthers did not affect visiting rates, but significantly reduced pollination rates and stigmatic pollen load. A decrease in the nectar volume of a flower was associated with a reduction in handling time and pollen loads on stigmas. These results show that corolla size is an important advertisement to pollinators (particularly at greater distance), which associate hermaphrodite flowers with a larger corolla and a larger volume of nectar than female flowers. We found that artificial changes in population structure affected the behavior of pollinators as well as the pollination rates of flowers. We suggest that the pattern of distribution of hermaphrodite and female clones in a population may serve to avoid pollen limitation in a female clone or patch. This effect may ensure female reproductive success and allow for the maintenance of female individuals in natural populations of this gynodioecious plant.     

Bee-pollination inHibbertia fasciculata (Dilleniaceae)

In direct contrast to mostHibbertia spp., the flowers ofH. fasciculata R. Br. ex D. C. bear only a single whorl of stamens and these stamens are arranged separately (not in typical bundles). The short filaments are appressed to the three carpels so that the inflated, porose and introrsive anthers form a centralized cluster obscuring the three ovaries. The three slender styles emerge at right angles from between the filaments. These styles curve upward and the stigmas form the three points of a triangle; each stigma is approximately one millimeter outside the centralized cluster of anthers. The flowers are nectarless and bear a bright yellow corolla. A pungent and unpleasant fragrance appears to be concentrated within the pollenkitt. When native bees attempt to forage for the pollen, within the cluster of anthers, the ventrally deposited loads of pollen, on the bees' abdomens, contact the outer triangle of stigmas. The major pollinators ofH. fasciculata are female bees in the polylectic genera,Lasioglossum (subgenusChilalictus, Halictidae) andLeioproctus (Colletidae). These bees carry an average of more than two pollen taxa when they are caught foraging onH. fasciculata. 78% of the 47 bees, captured onH. fasciculata carried the pollen from at least one sympatric taxon bearing nectariferous flowers (e.g., genera in theMyrtaceae, Compositae, andEpacridaceae). The pollination biology ofH. fasciculata is assessed in relation to the known radiation of bee-pollinated flowers in the genusHibbertia, and within theDilleniaceae s. l.     

A preliminary study on pollination biology of Omphalogramma souliei Franch. (Primulaceae), a species endemic to China

The pollination biology of Omphalogramma souliei Franch., a species endemic to southwestern China, was investigated. Floral phenology, flower visitors, pollen/ovule ratio, attractants and rewards to the visitors were observed, measured, and recorded. Bagging experiments to exclude pollinators were carried out in the wild for two years. Our results revealed five important aspects of the reproductive biology of Omphalogramma souliei. 1) The pollen-ovule ratio was 1748±233. The breeding system was self-compatible, with facultative xenogamy. 2) The pollination syndrome is entomophily, and this species could not be pollinated by wind if the pollinators were unavailable. 3) Six insect species were observed visiting the flowers of Omphalogramma souliei in the wild, of them, three species of hymenoptera, Lasioglossum sp., Heriades parvula Cockerell and Micrapis florae Fabricius, are the principal floral visitors and effective pollinators. 4) The visual attractants to the visitors are floral color and shape, the large yellow anthers, and the rewards for visitors are pollen and nectar. 5) Cleistogamy may also occur, since the anthers of some flowers dehisced before opening of the corolla. The results of floral biology and pollination characters suggest that xenogamy predominated and autogamy played an assistant role in the evolution of reproduction and breeding system of O. souliei.     

AN ANATOMICAL BASIS FOR THE DIVERGENT FLORAL FORMS IN THE CLEISTOGAMOUS SPECIES,LAMIUM AMPLEXICAULE L. (LABIATAE)

The pattern of variation in mature corolla form has been documented throughout the main shoot inflorescence of the cleistogamous species Lamium amplexicaule L. A heteroblastic development occurs within the cymose inflorescence at a single node as well as between different nodes. Variation involves an increase in cell number and expansion in the upper corolla and also an increase in cell number in the anther sacs, expressed as pollen count increases, in progressively produced flowers in the inflorescence. The corolla base region in all flowers shows an increased cell expansion from the first produced cleistogamous (CL) flowers to the later produced chasmogamous (CH) flowers which expand at anthesis. Cell numbers are equivalent in the corolla base region of all flowers. It appears that in successively produced flowers in the inflorescence, prolonged cell division and expansion occurs in both the upper corolla region and the anthers until a threshold is reached, at which point flowers may undergo anthesis and become CH. The CL corolla form in Lamium amplexicaule is not caused by a lack of cell expansion alone; rather, both cell division and expansion are arrested in the upper corolla region.