Summary1. In hermaphroditic flowers, reciprocal herkogamy, for example heterostyly, enhances pollen transfer between floral morphs (disassortative pollination) while avoiding self-interference between sexual organs. By contrast, disassortative pollination might be compromised in style-dimorphic flowers, which lack perfect reciprocity between the two floral morphs. This suboptimal functioning has been considered to explain why stylar dimorphism is rare in nature.2. Some style-polymorphic species receive a wide array of floral visitors, including long-tongued insects that feed on nectar and short-tongued insects that feed on pollen. Differences in the morphology and behaviour of these two insect types could be manifested as different pollination patterns in each floral morph.3. By observing individual pollinators and pollen deposition and delivery in small field-based experimental arrays with emasculated and intact flowers, we studied pollination patterns mediated by different insect types (long-and short-tongued) in the two floral morphs (long-and short-styled) of the style-dimorphic Narcissus papyraceus. We investigated the patterns of pollen transfer between and within style morphs in cross-pollinations, as well as self-pollination and pollen removal rates, for each floral morph mediated by each insect type.4. Long-tongued insects were efficient pollinators of both floral morphs as they removed little pollen from the anthers but deposited comparatively large amounts on the stigmas. Although disassortative pollen transfer and assortative pollen transfer were equally high to the long-styled morph, the former prevailed in the short-styled morph. Short-tongued insects removed large amounts of pollen from the anthers but deposited only a few pollen grains on the long-styled stigmas and a negligible number of grains on short-styled stigmas regardless of the morph of the donor. 5.Synthesis. In this study, we provide empirical support for the hypothesis that, under the action of long-tongued pollinators, pollen transfer patterns in the stylar-dimorphic Narcissus papyraceus resemble in part those of heterostylous species. In addition, we found that short-tongued insects act mostly as pollen thieves, thereby limiting the male fitness of both style morphs, besides depleting the female fitness of S-morph plants. In view of these results, we propose that the differing pollination efficiencies of floral visitors, in addition to their frequency, are key in determining the morph ratio of populations in this Narcissus.

Different pollinators can exert different selective pressures on floral traits, depending on how they fit with flowers, which should be reflected in the patterns of variation and covariation of traits. Surprisingly, empirical evidence in support of this view is scarce. Here, we have studied whether the variation observed in floral phenotypic integration and covariation of traits in Narcissus species is associated with different groups of pollinators. Phenotypic integration was studied in two style dimorphic species, both with dimorphic populations mostly visited by long-tongued pollinators (close fit with flowers), and monomorphic populations visited by short-tongued insects (loose fit). For N. papyraceus , the patterns of variation and correlation among traits involved in different functions (attraction and fit with pollinators, transfer of pollen) were compared within and between population types. The genetic diversity of populations was also studied to control for possible effects on phenotypic variation. In both species, populations with long-tongued pollinators displayed greater phenotypic integration than those with short-tongued pollinators. Also, the correlations among traits involved in the same function were stronger than across functions. Furthermore, traits involved in the transfer of pollen were consistently more correlated and less variable than traits involved in the attraction of insects, and these differences were larger in dimorphic than monomorphic populations. In addition, population genetic parameters did not correlate with phenotypic integration or variation. Altogether, our results support current views of the role of pollinators in the evolution of floral integration.

Ovarian self-incompatibility, including pre-and post-zygotic reactions, is a complex mechanism for which we still lack many details relating to its function and significance. The joint presence of ovarian self-incompatibility with style polymorphism is a rare combination that is found in the genus Narcissus. Usually, style polymorphic species have heteromorphic (diallelic and linked to style length locus) incompatibility, which prevents fertilization between individuals of the same morph, thereby helping to maintain equal proportions of floral morphs in populations. However, when present, self-incompatibility in Narcissus is not linked to style polymorphism and cross-fertilization within each morph is possible. Hence, self-incompatibility in Narcissus is of particular interest when attempting to unravel the nature of the rejection reaction and aiming to assess possible cryptic differences in the fertilization process in intra-and inter-morph crosses, which might ultimately explain the wide variation of morph-ratio in the field. We examined the breeding system of Narcissus papyraceus, a style-dimorphic species that has biased morph ratios in most of its populations. We studied pollen-tube growth in the pistil and ovule fate after experimentally controlled hand pollinations. The growth of pollen tubes in self-and intra-and inter-morph crosses was similar up to the point of micropyle penetration in both morphs but, subsequently, a pre-zygotic failure appeared to affect male and female gametophytes in selfed pistils. A high proportion of ovules from self-pollinated flowers showed signs of collapse and self-pollen tubes were blocked or behaved abnormally before entering the embryo sac. Selfincompatibility was stronger in the long-styled morph than in the short-styled morph. We did not find any conclusive sign of differential functioning between intra-and inter-morph cross-pollinations in any morph. These results enable us to rule out the possible effects of pollen-pistil interactions in N. papyraceus as a cause of morph-ratio biases and confirm the exceptional nature of the self-incompatibility mechanism in this polymorphic species.

Evolution to reduce inbreeding can favor disassortative (inter-morph) over assortative (intramorph) mating in hermaphroditic sexually polymorphic plant species. Heterostyly enhances disassortative pollination through reciprocal placement of stigmas and anthers of morphs and appropriate pollinators. Stylar dimorphism in which there is not reciprocal anther placement may compromise disassortative mating, particularly when there is not intra-morph incompatibility. Variable rates of disassortative mating along with differential female fecundity or siring success among floral morphs could lead to variation in morph ratio. We investigated mating patterns, female fecundity and siring success of style-length morphs in Narcissus papyraceus, a self-incompatible but morph-compatible species with dimorphic (long-and short-styled) and monomorphic (long-styled) populations in central and north regions of its range respectively. We established experimental populations in both regions and exposed them to ambient pollinators. Using paternity analysis, we found similar siring success of morphs and high disassortative mating in most populations. Female fecundity of morphs was similar in all populations. Although these results could not completely explain the loss of dimorphism in the species' northern range, they provided evidence for the evolutionary stability of stylar dimorphism in N. papyraceus in at least some populations. Our findings support the hypothesis that prevailing inter-morph mating is key for the maintenance of stylar dimorphism.

Background: Single nucleotide polymorphisms (SNPs) are increasingly being used to study non-native populations. SNPs are relatively information poor on a per locus basis, but allow genotyping more loci than others markers (e.g., microsatellites) and have the advantage of consistent allele calls between studies.  Aims: We investigated the utility of a newly developed set of SNP markers, suitable for high throughput genotyping to characterise genotypic variation and population structure in non-native populations of the facultative clonal herb Mimulus guttatus in the United Kingdom (UK).  Methods: We analysed 62 SNP markers and using a high throughput platform genotyped 383 individuals from 10 populations from the native range in North America and 14 populations in the UK.  Results: We found wide variation in genotypic diversity within UK populations, indicating reproductive strategies that vary from mostly clonal to mostly sexual. All but one UK population were, on average, more closely related to each other than to North American populations, and the exceptional UK population showed strong affinity to native Alaskan plants.  Conclusions: A small number of SNPs can detect patterns of clonality and broad-scale relationships between native and introduced populations. However, elucidating population structure at a finer scale will require genotyping individuals at greater depth