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Distyly has been interpreted as a mechanism that promotes cross-pollination between floral morphs. According to this hypothesis, pollen from anthers positioned at different heights could adhere to different body parts of the pollinator that would correspond to those points where stigmas of compatible morph contact the animal. In this regard, hummingbird species with different bill sizes may play different roles as pollinators of each morph. If pollinators mobilize more legitimate pollen towards one of the two morphs, gender specialization may occur. This work aimed to assess experimentally the role of long- and short-billed hummingbirds as pollinators of short-style (SS) and long-style (LS) flowers of Palicourea demissa, a distylous, hummingbird-pollinated treelet in Venezuelan cloud forests. Flowers were emasculated and exposed to a single visit of the hummingbird Coeligena torquata (long-billed), Heliangelus spencei (short-billed) or Adelomyia melanogenys (short-billed). Later, stigmas were removed, and pollen load counted under a microscope to calculate the probability of legitimate- and illegitimate-pollen transfer by hummingbirds. The probability analyses of pollen transference showed that short-billed hummingbirds have higher pollination probabilities from SS-anthers to LS- and SS-stigmas, and from LS-anther to LS-stigmas than from LS-anther to SS-stigmas. In contrast, long-billed hummingbirds have higher probabilities of pollen transference from LS-anthers to SS-stigmas than in other directions. A deeper view of the sexual expression of each morph in P. demissa will depend on future studies that determine possible morpho-differences in the biological function of male and female floral structures, and the role played by less frequent floral visitors as mediators of legitimate pollination between floral morphs. [ABSTRACT FROM AUTHOR]

Populations of heterostylous plant species are ideally composed of equal frequencies of two (distylous) or three (tristylous) morphologically different floral morphs. Intra‐morph incompatibility helps to avoid inbreeding and to maintain genetic diversity, supporting plant fitness and long‐term viability. Habitat fragmentation can lead to skewed morph ratios and thereby reduce the abundance of compatible mates. This, in turn, can result in a loss of genetic diversity. We tested whether the genetic diversity of heterostylous plants is affected by morph ratio bias using populations of the distylous grassland plant Primula veris in recently fragmented grasslands.We recorded morph frequencies and population sizes in 30 study populations of P. veris on two Estonian islands characterised by different degrees of habitat fragmentation. Examining variation of thousands of single nucleotide polymorphisms (SNPs) and heterostyly‐specific genetic markers, we quantified overall and morph‐specific genetic diversity and differentiation in these populations.Morph frequencies deviated more in smaller populations. Skewed morph ratios had a negative effect on the genetic diversity of P. veris in more fragmented grasslands. In the populations of better‐connected grassland systems, genetic differentiation among S‐morphs was higher than among L‐morphs.Our study shows that deviations from morph balance are stronger in small populations and have a negative impact on the genetic diversity of the distylous plant P. veris. Together with the direct negative effects of habitat loss and decreased population size on the genetic diversity of plants, morph ratio bias may intensify the process of genetic erosion, thus exacerbating the local extinction of heterostylous species. [ABSTRACT FROM AUTHOR]

Ophiorrhiza caudata is a creeping, perennial herb distributed along wet and shady areas. The species is distylous with two distinct floral morphs: pin and thrum. Flowering usually occurs during the monsoon season. No particular difference was noticed in the flowering phenology of the two morphs. Presently the species is self-incompatible, however, it shows a tendency towards intramorph compatibility. Fruit set is above 60% in open pollination and intermorph pollination. Bees and butterflies are the major pollinators. The pollen flow between the two floral morphs varies depending upon floral morphology and pollinators. Fruit is a bi-valved capsule which dehisces by a splashing drop mechanism. The seeds are very minute. The rate of seed germination and seedling establishment in the wild condition is very poor due to adverse climatic factors. Ophiorrhiza caudata is struggling for survival in its natural habitat, where habitat fragmentation, climatic factors and poor seedling establishment could account for its narrow distribution. [ABSTRACT FROM AUTHOR]

Pigment patterns in corollas are common, and act as nectar guides for pollinators. We discovered multiple floral morphs of Justicia adhatoda L. (Acanthaceae) with variable extents of corolla vein pigmentation in a population in Sariska, Rajasthan. Two floral morphs, one completely white and the other white with dark purple vein pigmentation, were compared in order to investigate any possible differences relating to: (a) corolla surface structure, (b) pollinator visitation, (c) reward for the pollinator, and (d) fitness parameters in the morphs. Both morphs showed similar UV reflectance, had distally located conical cells in petals, indicated similar pollinator visitation and had similar nectar content. Contrastingly, seed germination and seed weight were significantly higher in the purple-veined morph, while fruit set and seed set were higher in the white morph which also showed higher amounts of saturated fatty acids in the seeds. The results about aborted seeds differed inconsistently. Thus, variation in corolla pigmentation in J. adhatoda suggests fitness trade-off between the morphs with higher fruit and seed set, but lower seed germination and seed weight in the white morph compared to the purple-veined. We are led to the possibility of different selective pressures acting on the morphs and resulting in adaptive polymorphism. [ABSTRACT FROM AUTHOR]

The taxonomic boundaries of Centaurea L. species and infraspecific taxa are often blurred by hybridizations. However, counterbalancing genetic isolation contributes to maintaining taxonomic limits and fostering rapid speciation processes. Radiant (R) and non-radiant (NR) capitula are two major floral morphs present in Centaurea. However, it is unclear how gene flow affects the distribution of floral morphotypes across populations and taxa. We have investigated the taxonomic differentiation and potential effect of genetic isolation in R and NR populations of Iberian Centaurea sects. Jacea (Mill.) Pers. ex Dumort. and Lepteranthus (Neck. ex DC.) Dumort. A total of 510 individuals from 58 populations (12 taxa) were analyzed using 165 amplified fragment length polymorphism (AFLP) markers. Genetic diversity and structure parameters were estimated at the taxon, population, and floral morphotypic levels. We tested whether there was correlation between population pairwise fixation index (Fst) genetic distances and the inbreeding coefficient (Fis), taken as a surrogate of reproductive isolation between the R and NR morphotypes of each group, and also taking into account geographic distances, using distance-based redundancy analysis (dbRDA). We also performed isolation by distance (IBD) tests between different floral morphotypes, aiming to infer the impact of genetic isolation on evolutionary and taxonomic divergence of the individuals. The taxa of Centaurea sects. Jacea and Lepteranthus constitute independent evolutionary lineages. Most of the detected genetic clusters match the taxonomic circumscription proposed in our most recent treatments. Genetic diversity was highest in C. debeauxii Godr. & Gren. subsp. debeauxii and subsp. grandiflora (Gaudin ex Schübl. & G. Martens) Devesa & Arnelas and in C. jacea L. subsp. angustifolia (DC.) Gremli (R) and lowest in C. nevadensis Boiss. & Reut. (NR) within the Centaurea sect. Jacea clade, whereas it was highest in C. linifolia L. within the Centaurea sect. Lepteranthus clade. Population-level dbRDA tests did not detect a significant correlation of R versus NR genetic distances and Fis values in any of the studied cases; by contrast, they detected significant correlation with longitude (C. jacea subsp. angustifolia, C. debeauxii, C. linifolia-C. stuessyi Arnelas, Devesa & E. López) or latitude (C. nigra L.). IBD analysis at the individual level showed that, in addition to geography, other morphotype-related factors may affect the genetic differentiation of R versus NR morphs in C. nigra, C. debeauxii, and C. linifolia-C. stuessyi. These results suggest that the fixation of the different morphs within the same taxon or group may be explained by geographic isolation, though we could not discount other potential unknown factors that could have contributed to microspeciation in these recently divergent populations, which originated only several thousands of years ago. [ABSTRACT FROM AUTHOR]

This study aimed to assess the pollen availability and foraging behavior of visiting bees to identify the effective pollinators of Solanum lycocarpum at a forest fragment. Five flowers of each of two floral morphs were used to determine pollen viability using optical microscopy. Bees were collected during the first 15 minutes of every hour of collection and classified into large, medium and small. Behavioral observations were performed during the remaining 45 minutes. Both floral morphs presented high percentage of viable pollen, without much difference between them. A total of 322 bees from 12 species were collected. Visits were more frequent when the anthers were maintained. Epi charis flava, Centris scopipes and Oxaea flavescens, along with Centris analis had large body size and, due to the behavior presented, were considered effective pollinators of S. lycocarpum. The intense intraspecific and interspecific competition observed among visiting bees may be advantageous for S. lycocarpum reproduction. [ABSTRACT FROM AUTHOR]

Oxalis corymbosa , a tristylous species, lacks seed-set in Taiwan. In a previous survey, six floral types (3 floral morphs in combination with two types of anthers) of 23 populations in Taiwan were assigned based on qualitative visual observation. In this study, we conducted experiments on one of the populations to pursue following objectives: to analyze the floral types of the population based on quantitative measurement and to test the hypothesis that the lack of seed-set is partially attributed to pollination limitation. The heights of anthers and stigmata were measured and analyzed. The number of viable pollen grains per anther was estimated. Pollen germination and seed-production after hand-pollination treatments were examined. Variations in anther and stigma heights were found in each type of previously assigned flowers. Unequal heights of reciprocal sexual organs between floral types were also found. Each level of anthers of MS-Y (mid-styled bearing yellow anthers) and SHS-Y (semi-homostylous bearing yellow anthers) flowers contained about 60 and 25 viable pollen grains, respectively; while anthers of SHS-W (semi-homostylous bearing white anthers) flowers had no pollen. Among hand-pollination treatments of inter-morph, cross-intra-morph and self-intra-morph crossings, only in one inter-morph crossing, i.e. SHS-Y (pollen receiver) × l/MS-Y [pollen donor, pollen from lower (l)-level anthers of MS-Y], pollen tubes were found entering micropyles of the ovules, and seeds were built. Thus, this species can produce seeds by hand-pollination. The result supports that limitation of pollen transfer at least partially contributes to the absence of seed-production in field populations of O. corymbosa in Taiwan. [ABSTRACT FROM AUTHOR]

Nymphoides fallax Ornduff (Menyanthaceae) is an aquatic distylous plant endemic to the Mexican and Guatemalan highlands. Although vegetative reproduction is frequently reported for Nymphoides species, evidence suggests a high prevalence of sexual reproduction in N. fallax. This study aimed: (i) to test homomorphic self-incompatibility, (ii) to describe aspects of floral phenology, estimate the pollen/ovule ratio and the viability of pollen grains, (iii) to evaluate floral morph proportion in natural populations, and (iv) to identify the assemblage of floral visitors, estimating their frequency and capacity to transport N. fallax pollen. The studied populations were located in Central Mexico. We carried out a controlled pollination experiment with eight treatments (n = 80), and we also estimated pollen/ovule ratio and observed floral phenology aspects. We counted the proportion of floral morphs in seven natural populations and observed the presence of visitors to 891 flowers in three natural populations. We observed pollen on the insects using scanning electron microscopy. Our findings showed that N. fallax has diurnal flowers with one-day anthesis, high stigma receptivity, high pollen viability, and intramorph self-incompatibility. The average pollen/ovule ratio (5.1 × 103) was consistent with xenogamy. Five natural populations were found to have both morphs in approximately equal proportions, and two populations consisted only of the long-style morph. An assemblage of 28 floral visitor taxa was observed in 944 visits. The most frequent visitors were exotic bees (Apis mellifera : 43.5 %) and native dipterans (Ephydridae family: 33.3 %; Stratiomyidae and Syrphidae: 7.2 %). Pollen grains were observed attached to the bodies of the most frequent visitors, suggesting that they are potentially effective pollinators. This research expands the knowledge of heterostylous syndrome and sexual reproduction in N. fallax. • Nymphoides fallax has diurnal one-day flowers, high stigma receptivity, and high pollen viability. • We observed high intermorph compatibility and high intramorph self-incompatibility. • The average pollen/ovule ratio (5.1 × 103) is consistent with xenogamy. • Morph ratios approach equal proportions in a majority of populations. • Dipterans were the most frequent native visitors and had N. fallax pollen adhered on their bodies. [ABSTRACT FROM AUTHOR]

The role of distyly in the heteromorphic selfing incompatibility is a controversial question In order to dicusse this question, we chose Plumbago auriculata as material, observed it floral morphs, regulated the height of styles,polinate these style,and analyzed the fruit set. The results were as folows: (1) Significant differences were found in floral tube width,floral tube length,pistil height,stamen height,stigma length,anther width,stamen (L) and style (S) height There was no significant difference in corola width,petal length, calyx length, ovary diameter, an ther length,stamen (S) and style (L) height (S) and style (L); (2) Suitable IAA,NAA and GA could regulate the length of style; (3) There was no significant difference in fruit set of blank control and regulated style. There was typical dimorphism in the floral morphs of P. auriculata It was evolutionary adaptation strategy for reciprocal herkogamy in P. auriculata. The spatial distribution of sex-organ had absolutely no afect on incompatibility through the effective spread of legal polen,incompatibility of abnormal shape flower could be seen more clearly on physiological mechanism. [ABSTRACT FROM AUTHOR]

Oxalis pes- caprae, a tristylous flowering plant native to South Africa, is described in the western Mediterranean basin as an asexual-only 5 x short-styled morph (5 x S-morph) invasive weed losing all mating partners after introduction. The objective of this study was to reassess the patterns of floral morph and cytotype distribution and the sexual reproduction ability in this invaded range. For that, floral morph and cytotype composition were evaluated in 39 populations of O. pes- caprae in a methodical sampling. The reproductive success of natural populations was assessed as fruit and seed production and seed germination for all floral morphs and cytotypes detected. Self- and morph-incompatibility were also studied with controlled hand pollinations. A remarkable diversity in floral morph and cytotype composition was observed. Furthermore, we observed successful sexual reproduction in several localities across the surveyed area. The S-morph is still dominant in this invaded area, and although it was mostly 5 x, an additional cytotype (4 x) was also recorded. Records of both a mid-styled morph (M-morph) and an area with trimorphic populations of this species are reported here for the first time in the invasive range of the Mediterranean basin. The long-styled morph appears to occur randomly across the surveyed area, while the M-morph is concentrated mainly in Estremadura province (Portugal), where a breakdown in the incompatibility system was observed. These distribution patterns may result from events of sexual reproduction after incompatibility breakdown and/or from multiple introduction events from the native area. The ability to reproduce sexually, undetected so far, may have important impacts in the population dynamics and major consequences for the adaptation and selection potential of O. pes- caprae in this invaded area. [ABSTRACT FROM AUTHOR]

ABSTRACT Psychotria ipecacuanha, commonly known as Ipeca, is a medicinal plant of pharmacological and economic value. The species is distylous; it has populations with two floral morphs, one with long and one with short styles. Apart from the presence of two floral morphs in a balanced ratio (1:1), reciprocal herkogamy of the reproductive organs between alternative morphs is desirable to maintain cross-pollination. The risk factors for genetic erosion and conditions for sexual reproduction in natural populations of P. ipecacuanha were investigated. The main risks for genetic erosion in four populations studied were: habitat change in the forest fragment where they occurred and in the surrounding area over the last 20 years; proximity to agricultural areas; frequency of drought affecting the forest fragment; and the area occupied by the species within the forest fragment. All evaluated populations were isoplethic with the reciprocity of reproductive organs varying across populations. Anthropogenic factors, associated with morphological and reproductive characteristics (e.g., low reciprocity between anther and stigma and low pollen production), indicate risks for the maintenance and reproduction of Ipeca in the population of the municipality of Denise. Habitat loss, small clusters, and the low number of reproductive plants jeopardize the survival of the studied populations.