Corolla Size Research Articles

Is pollen limitation linked to phenotypic selection on floral traits in the carnivorous plant Pinguicula moranensis (Lentibulariaceae)?

AbstractIn carnivorous plants, the fitness impacts of phenotypic variation in traits involved in prey attraction and capture have been well documented. However, floral traits could also contribute to the fitness of carnivorous plants. Pinguicula moranensis is a carnivorous plant that presents colorful zygomorphic flowers, which suggests some degree of specialization in its interactions with pollinators. We first tested pollen limitation experimentally by comparing the fruit set in plants that were manually cross‐pollinated with those that were pollinated naturally. Then, using a path analysis approach, we explored the effects of plant size and floral traits (corolla shape, corolla size, spur length, nectar guide size, and stalk length) on fitness (seed number per fruit). We performed two independent path analyses—one with the naturally pollinated plants and the other with the hand pollinated plants—to consider the impacts of these variables with and without the pressure of pollinator attraction. We expected stronger selection on floral traits in naturally pollinated plants. We found evidence of pollen limitation in the fruit set of the naturally pollinated group, suggesting that pollinator availability could impose selective pressures. The path analyses showed a marked direct positive effect of rosette size on plant fitness in both groups. The direct effects of all floral traits had similar magnitudes between the naturally pollinated and hand pollinated plants, except for corolla shape that showed higher coefficients in the first group. Thus, although we evidenced pollen limitation, our prediction about the role of pollinators as selective agents of floral traits in P. moranensis was barely supported.

Variation in floral morphology, histochemistry, and floral visitors of three sympatric morning glory species.

Three morning glory species in the genus Argyreia Lour., A. lycioides (Choisy) Traiperm & Rattanakrajang, A. mekongensis Gagnep & Courchet, and A. versicolor (Kerr) Staples & Traiperm, were found co-occurring and co-flowering. Argyreia mekongensis and A. versicolor are rare, while A. lycioides is near threatened and distributed throughout Myanmar and Thailand. We investigated key floral characters (floral morphology and phenology, as well as the micromorphology of the floral nectary disc and staminal trichomes) and screened for important chemical compounds hypothesized to contribute to pollinator attraction. Our findings demonstrate that some aspects of floral morphology (e.g., corolla size, limb presence, and floral color) of the three studied congeners exhibit significant differences. Moreover, pollinator composition appears to be influenced by floral shape and size; morning glory species with wider corolla tubes were pollinated by larger bees. The morphology of the floral nectary disc was similar in all species, while variation in staminal trichomes was observed across species. Glandular trichomes were found in all three species, while non-glandular trichomes were found only in A. versicolor. Histochemical results revealed different compounds in the floral nectary and staminal trichomes of each species, which may contribute to both floral attraction and defense. These findings demonstrate some segregation of floral visitors among sympatric co-flowering morning glory species, which appears to be influenced by the macro- and micromorphology of flowers and their chemical compounds. Moreover, understanding the floral morphology and chemical attractants of these sympatric co-flowering Argyreia species may help to maintain their common pollinators in order to conserve these rare and endangered species, especially A. versicolor.

Floral Trait Preferences of Three Common wild Bee Species.

The interaction between bees and flowering plants is mediated by floral cues that enable bees to find foraging plants. We tested floral cue preferences among three common wild bee species: Lasioglossum villosulum, Osmia bicornis, and Bombus terrestris. Preferences are well studied in eusocial bees but almost unknown in solitary or non-eusocial generalist bee species. Using standardized artificial flowers altered in single cues, we tested preferences for color hue, achromatic contrast, scent complexity, corolla size, and flower depth. We found common attractive cues among all tested bees. Intensively colored flowers and large floral displays were highly attractive. No preferences were observed in scent complexity experiments, and the number of volatiles did not influence the behavior of bees. Differing preferences were found for color hue. The specific behaviors were probably influenced by foraging experience and depended on the flower choice preferences of the tested bee species. In experiments testing different flower depths of reward presentation, the bees chose flat flowers that afforded low energy costs. The results reveal that generalist wild bee species other than well-studied honeybees and bumblebees show strong preferences for distinct floral cues to find potential host plants. The diverse preferences of wild bees ensure the pollination of various flowering plants.

Hybrid Mimulus flowers attract a new pollinator.

Hybridization is common in flowering plants and is believed to be an important force driving adaptation and speciation. The flowers of hybrids often exhibit new trait combinations, which, theoretically, could attract new species of pollinators. In this study, we found that the hybrids between a hummingbird-pollinated species Mimulus cardinalis and a self-pollinated species Mimulus parishii attract bumblebees (Bombus impatiens), a pollinator not attracted to either of the progenitor species. This novel attraction is explained by new combinations of floral traits in hybrids, including, most importantly, petal color, in addition to nectar concentration and corolla size. To understand how petal color variation is perceived by bumblebees, we performed reflectance spectroscopy and multispectral imaging to model the flower appearance in bee vision. This analysis showed that color variation would impact the ease of detection. We also found that YUP, the genetic locus responsible for a large portion of floral color variation and previously shown to be important in bee interactions with other Mimulus species, also played an important role in this novel attraction. These results together suggest that the attraction of new pollinators to hybrid plants could be an underexplored avenue for pollinator shift and speciation.

Heterospecific pollen deposition in understory plants of a forest in central Amazon

In co-flowering plant communities, pollinator movement can lead to the transfer of heterospecific pollen among species. This can affect the reproductive success of individuals, either by preventing conspecific pollen from reaching the stigma or by allelopathy, but little is known about this process in tropical areas. To analyze heterospecific pollen transfer and deposition, we investigated attributes related to pollinator attraction, such as corolla size, number of flowers per individual, floral arrangement, floral asymmetry, and distance from one flowering individual to another in a Central Amazon forest. The study was carried out in riparian plots of the Adolpho Ducke Forest Reserve during the rainy season. Stigmas and anthers were removed from all individual understory plants found in bloom in permanent plots. Slides were mounted with glycerinated gelatin, and all conspecific and heterospecific pollen grains were identified and counted. We then used a generalized linear mixed model framework to determine how the measured variables were related to the proportion of heterospecific pollen deposition (HPD) on stigmas. We found that the mean proportion of HPD in individuals was 4.7%, and 60% of individuals had no heterospecific pollen; from the 14 species studied, two had no heterospecific pollen. Species with wider flowers received less HPD, while species with more flowers per individual and with solitary flowers received more heterospecific pollen. Despite the significant variation in floral types in the Adolpho Ducke Reserve, there was a low percentage of heterospecific pollen deposition, probably due to specialized plant-pollinator interactions.

Not just flowering time: a resurrection approach shows floral attraction traits are changing over time.

Contemporary anthropogenic changes in climate and landscape form a complex set of selective pressures acting on natural systems, yet, in many systems, we lack information about both whether and how organisms may adapt to these changes. In plants, research has focused on climate-induced changes in phenology and the resultant potential for disruption of plant-pollinator interactions, however, there remains a paucity of knowledge regarding how other pollinator-mediated traits may be involved in the adaptive response. Here, we use resurrection experiments to investigate the phenotypic basis of adaptation in a mixed-mating system plant, the common morning glory (Ipomoea purpurea). Specifically, we measure temporal and spatial changes in traits grouped into three categories relevant to plant-pollinator interactions - floral morphology, floral rewards, and floral phenology. We show a significant temporal increase in corolla size and shift to earlier flowering times, as well as a potential for increased investment in floral rewards, all of which are driven primarily by populations at more northern latitudes. Additionally, we find evidence for directional selection on floral morphology and phenology and evidence of balancing selection acting on anther-stigma distance. Overall, these results show an adaptive response in line with greater investment in pollinator attraction rather than self-pollination and fine-scale spatial differences in adaptive potential.

Unveiling Utricularia amethystina’s true colours: a taxonomic revision of one of the largest species complexes (U. sect. Foliosa, Lentibulariaceae)

The genus Utricularia (Lentibulariaceae) is the most diverse and cosmopolitan among carnivorous plants. Utricularia sect. Foliosa sensu Taylor (1989) is composed of three South American species, U. amethystina, U. tricolor and U. tridentata, the first species being recognized as highly diverse. In his taxonomic revision of the genus Utricularia, Taylor (1989) circumscribed the polymorphic U. amethystina comprising 27 synonyms involving a wide variation in corolla size and colour, morphology of corolla parts, indumentum, and overall plant size. The original publications of the synonyms provide limited information disencouraging a revision study and therefore inflating U. amethystina as new variations were discovered. In order to shed light onto the problem, a taxonomic revision, a morphometric and a molecular study showed evidence of a larger complex than previously thought, and U. amethystina s.str. sister to U. tricolor. A previously published molecular phylogeny provided strong support for all sampled U. amethystina synonyms and potential new taxa found to be nested outside the U. amethystina s.str. and U. tricolor clade. Here, we incorporate these new relationships and describe and comment on the species that comprise U. sect. Foliosa, including the restablishment of six synonyms, the description of three new species and lectotypification of five names. The current study disentangles U. amethystina complex so that further studies can approach it in a more realistic way, especially studies using population genetics tools. Our study shows that more needs to be done and here U. hirtella is presented as a new complex.

The rapid appearance of homostyly in a cultivated distylous population of Primula forbesii.

Evolutionary breakdown from rigorous outbreeding to self-fertilization frequently occurs in angiosperms. Since the pollinators are not necessary, self-compatible populations often reduce investment in floral display characteristics and pollination reward. Primula forbesii is a biennial herb with distribution restricted to southwest China; it was initially a self-incompatible distylous species, but after 20 years of artificial domestication, homostyly appeared. This change in style provides an ideal material to explore the time required for plant mating systems to adapt to new environmental changes and test whether flower attraction has reduced following transitions to selfing. We did a survey in wild populations of P. forbesii where its seeds were originally collected 20 years ago and recorded the floral morph frequencies and morphologies. The floral morphologies, self-incompatibility, floral scent, and pollinator visitation between distyly and homostyly were compared in greenhouse. Floral morph frequencies of wild populations did not change, while the cultivated population was inclined to L-morph and produced homostyly. Evidence from stigma papillae and pollen size supports the hypothesis that the homostyly possibly originated from mutations of large effect genes in distylous linkage region. Transitions to self-compatible homostyly are accompanied by smaller corolla size, lower amounts of terpenoids, especially linalool and higher amounts of fatty acid derivatives. The main pollinators in the greenhouse were short-tongued Apis cerana. However, homostyly had reduced visiting frequency. The mating system of P. forbesii changed rapidly in just about 20 years of domestication, and our findings confirm the hypothesis that the transition to selfing is accompanied by decreased flower attraction.

Taxonomy and Relationships Within Polemonium foliosissimum (Polemoniaceae): Untangling a Clade of Colorful and Gynodioecious Herbs

Abstract— New molecular and ecological data have necessitated taxonomic revisions of several species complexes within Polemonium (Polemoniaceae), including P. foliosissimum, an herbaceous perennial widespread in the Intermountain West of the United States. As currently circumscribed, P. foliosissimum is a highly polymorphic species of four taxonomic varieties. One of the most striking morphological traits of the species is its diversity in flower color, which is unusual for the genus. Several species have been proposed based on this variation in flower color. However, these names have been treated as infraspecific taxa because previous authors have concluded that the presence of micropollen grains throughout the geographic range of the species complex indicated partial hybrid sterility and therefore incomplete barriers to gene flow. However, recent evidence suggests that micropollen is instead due to a gynodioecious breeding system. Using 128 nuclear loci and eight quantitative morphological traits, I clarify relationships and taxonomy within the species complex. I show that what is currently circumscribed as four varieties of P. foliosissimum represent five species that, in addition to differing in corolla color, differ in leaflet number, corolla size, and vegetative and floral pubescence. I propose a new species endemic to the White Mountains of southeastern Arizona, Polemonium apachianum. This study provides a new phylogenetic context and taxonomic circumscription to serve as a framework for future research on the evolution of floral color and sexual systems in a previously misunderstood but evolutionarily exciting system.

Phylogenomics, floral evolution, and biogeography of Lithospermum L. (Boraginaceae)

Lithospermum (Boraginaceae), a geographically cosmopolitan medium-sized genus, includes diverse floral morphology, with variation in corolla size and shape and in breeding system. Over the past decade, multiple studies have examined the evolutionary history of Lithospermum, with most utilizing DNA regions from the plastid genome and/or the nuclear ribosomal internal transcribed spacer. These studies have, in general, not resulted in well-resolved and well-supported phylogenies. In the present study, 298 nuclear DNA regions, amplified via target sequence capture, were utilized for phylogenetic reconstruction for Lithospermum and relatives in Boraginaceae, and patterns of floral evolution, species diversification, and biogeography were examined. Based on multiple phylogenetic methods, Lithospermum is resolved as monophyletic, and the New World species of the genus are also monophyletic. While minimal phylogenetic incongruence is resolved within the nuclear genome, incongruence between the nuclear and plastid genomes is recovered. This is likely due to incomplete lineage sorting during early diversification of the genus in the Americas approximately 7.8 million years ago. At least four shifts to longer corollas are identified throughout Lithospermum, and this may be due to selection for hummingbird-pollinated flowers, particularly for species in Mexico and the southwestern United States. In the New World, one clade of species of the genus diversified primarily across the United States and Canada, and another radiated throughout the mountains of Mexico.

Pollinator behaviour and resource limitation maintain honest floral signalling

Abstract In many communication systems, signal receivers profit from honest signals that indicate the signaller's quality, whereas low‐quality signallers should profit from cheating. Under such a conflict of interests between signallers and signal receivers, the maintenance of honest signals presents a puzzle. In theory, honesty can represent an evolutionarily stable strategy, but the actual mechanisms have been studied in few systems only. Here, we investigate honest signalling in a plant species, Brassica rapa, that advertises nectar volumes to pollinators by two honest floral signals; corolla size and the floral volatile phenylacetaldehyde. In a series of experiments we tested for physiological constraints and pollinator behaviours related to honest floral signals and nectar volume, incorporated the result into a mathematical model, and verified its predictions experimentally. While honest floral signals attracted pollinators, the bees’ flower visitation time depended on nectar volume and was associated with the number of seeds that flowers developed. Furthermore, honest floral signals and seed set without pollen limitation both increased after soil fertilisation, indicating nutrient limitation in these traits. The mathematical model which incorporates these findings showed that honest signalling in B. rapa can be maintained by a combination of pollinator behaviour and resource limitation causing differential benefits of nectar production. The study demonstrates how honest floral signalling can evolve as a stable strategy in a plant species. A free Plain Language Summary can be found within the Supporting Information of this article.

Research in Boraginaceae: A new variety of Cryptantha maritima, Cryptantha pondii resurrected, and Johnstonella echinosepala transferred back to Cryptantha

A review of the species Cryptantha maritima (Boraginaceae) supports the continued recognition of the three varieties, these differing in corolla size, ovule and nutlet number, and calyx vestiture. Mapping of these taxa from verified specimens demonstrates some geographic trends, but also some overlap in ranges. In the process of our study, we discovered a new taxonomic entity. Cryptantha maritima var. vizcainensis is described as new. This variety is restricted to the Vizcaíno Desert of Baja California Sur, Mexico and should be considered rare, as it is known to date from only eleven collections. It differs from the other three varieties of the species in having a canescent, appressed-strigose stem vestiture lacking spreading trichomes, in having a relatively large corolla, and in having a fruit derived from two 1-ovuled ovary lobes, developing into two heteromorphic nutlets. We also discovered that the species Cryptantha pondii, previously treated as a synonym of C. patula, should be resurrected as a distinct taxon. Cryptantha pondii is restricted to the western Vizcaíno Desert and to Natividad Island of Baja California Sur. It is morphologically distinctive in having bracteate flowers, relatively large corollas, and four smooth nutlets heteromorphic by size. It is to date known from only three collections and should be considered extremely rare. We also reviewed the morphological and phylogenetic status of Johnstonella echinosepala. This taxon shows similarities to Cryptantha maritima and also exhibits some morphological discontinuity between Pacific and Gulf populations in Baja California Sur. Evidence from both morphological and phylogenetic studies supports the transfer of this species from the genus Johnstonella back to the genus Cryptantha. Finally, we propose that both C. pondii and C. echinosepala are likely close relatives of C. maritima, all of the “Maritimae clade,” a group distantly related to the main core of the genus Cryptantha. This study confirms the great importance of studying herbarium specimens in taxonomic research.

Floral traits variation in Oenothera drummondii subsp. drummondii across a wide latitudinal range of native and non-native populations

Plant species with specialized pollination and wide geographic distribution can show variation in the size of floral traits related to environmental local conditions. We studied the floral traits of native and non-native populations of Oenothera drummondii under greenhouse conditions to test if their variation is related to latitude, or their native or non-native origin but displaying similar floral integration. Plants were obtained from seeds collected in six native and six non-native populations distributed across five continents. Eight floral traits were recorded in the flowers produced and examined across latitudinal variation between native and non-native ranges. The floral traits differed between the native and non-native populations, with corolla size the main contributor. Although each floral feature varied independently in response to the latitude and environmental conditions of the populations, there is a clear tendency for size reduction of the structures with latitudinal increase. In contrast, floral integration and flower lifetime remained similar across latitude. The floral traits variation of O. drummondii throughout its native and non-native distribution is the result of the latitudinal gradient and the local population environment. The similarity in floral integration and flower lifespan may favor the specialized reproduction in native populations, whereas flower size-reduction suggests potential local adaptation for pollinators in the non-native populations. The study of flower visitors will help to understand the local adaptation of Oenothera drummondii in each population.

Vegetation context modifies selection on flowering start and plant height in an orchid perennial herb

Abstract Aims Identifying the potential role of vegetation context (defined as the density, species identity/diversity and height of co-occurring plants) in modifying selection on floral traits is a critical step for clarifying and predicting the floral evolutionary trajectory in complex co-flowering species competition environments. It is also helpful to understand the variation in pollinator-mediated selection. Methods We experimentally reduced vegetation height around individual plants of Spiranthes sinensis (a bumblebee-pollinated perennial orchid herb) and estimated how vegetation context modified selection on four floral traits (flowering start, plant height, corolla size and number of flowers) through female function and pollen removal over two continuous years. We randomly selected independent plants in each year. Important Findings We demonstrated that vegetation context modified selection for earlier flowering start and shorter plant height of S. sinensis. The strength of selection differed between years. In addition, selection was stronger through female function than through pollen removal. Our findings indicate the potential role of vegetation context in shaping the differentiation and diversification of flowers in angiosperms.

Male sterility significantly elevates shape variation and fluctuating asymmetry of zygomorphic corolla in gynodioecious Glechoma hederacea (Lamiaceae)

Female flowers of gynodioecious plants usually have smaller corollas than bisexual flowers. This difference is explained as a developmental consequence of stamen abortion and as a result of stronger selection for larger corolla size in hermaphroditic flowers that solely ensure male function within populations. This study evaluated whether the size difference of zygomorphic corollas in a widely distributed gynodioecious herb Glechoma hederacea is accompanied by variation in shape and bilateral fluctuating asymmetry of sexually differentiated flowers. Geometric morphometric analyses of bilateral symmetry in the shapes of corolla lower lips showed that male-sterile flowers were significantly more plastic and asymmetric, implying that they may be subjected to weaker stabilizing selection for corolla shape in comparison to hermaphrodites. These results illustrated that sexual differentiation may be an important factor contributing to bilateral fluctuating asymmetry in the shape of zygomorphic flowers.

Inbreeding in Solanum carolinense alters floral attractants and rewards and adversely affects pollinator visitation.

Inbreeding depression is well documented in flowering plants and adversely affects a wide range of fitness-related traits. Recent work has begun to explore the effects of inbreeding on ecological interactions among plants and other organisms, including insect herbivores and pathogens. However, the effects of inbreeding on floral traits, floral scents, and pollinator visitation are less well studied. Using inbred and outbred maternal families of horsenettle (Solanum carolinense, Solanaceae), we examined the effects of inbreeding on traits associated with pollinator attraction and floral rewards. Specifically, we measured corolla size, counted pollen grains per flower, and analyzed floral volatile emissions via gas chromatography and mass spectrometry. We also examined pollinator visitation to experimental arrays of flowering inbred and outbred plants under field conditions. Compared to those of outbred plants, flowers of inbred plants exhibited reduced corolla size and pollen production, as well as significantly reduced emission of the two most abundant volatile compounds in the floral blend. Furthermore, bumblebees-the main pollinators of horsenettle-discriminated against inbred flowers in the field: bees were more likely to make initial visits to flowers on outbred plants, visited outbred flowers more often overall, and spent more time on outbred flowers. These results show that inbreeding can (1) alter floral traits that are known to mediate pollinator attraction; (2) reduce the production of floral rewards (pollen is the sole reward in horsenettle); and (3) adversely affect pollinator visitation under field conditions.

The genus Ipomoea (Convolvulaceae) in the Mata da Pimenteira State Park, semiarid region of Brazil

Abstract The Mata da Pimenteira State Park (MPSP) is an important remnant of caatinga vegetation in the semiarid region of Pernambuco state, Brazil. The park holds great biodiversity, but relatively few taxonomic studies have been undertaken in the area. We present a taxonomic study of Ipomoea in the MPSP based on field observations and collections deposited in the Herbarium of the Semiarid of Brazil - UAST / UFRPE (HESBRA). The species were identified based on the specialized literature, comparisons with type images available online, and protologues. Fourteen species of Ipomoea were identified - more than three times the previously known number. Two Ipomoea species recorded in the MPSP are endemic to Brazil (I. bahiensis and I. brasiliana), three others are exclusive to the Caatinga domain (I. marcellia, I. rosea, and I. tenera), and the remaining are widely distributed in South America. The habit, type and shape of leaf blade and sepals, corolla size and shapes, and presence or absence of subapical rostrum on the external sepals were the most relevant distinctive characteristics. An identification key, descriptions, comments on distribution and diagnostic characteristics, and phenological data of the species are presented.

The role of ontogenetic allometry and nonallometric flower shape variation in species-level adaptive diversification - Calceolaria polyrhiza (Calceolariaceae) as a case study.

Organism shape changes predictably during ontogeny, resulting in specific patterns of ontogenetic allometry. In several plant and animal lineages, among-species variation in the shape of mature organisms mirrors variation along their growth trajectories. Hence, ontogenetic allometry is an important bias in evolution. This bias should be stronger at reduced evolutionary time scales, in which among-trait correlations had less time to evolve. Nevertheless, it was shown that adaptation of organism shape frequently involved departures from the ancestral ontogenetic allometry. Moreover, only a moderate fraction of shape variation is correlated with size during ontogeny. Hence, nonallometric variation in shape (NAVSh) is likely to contribute to adaptation, even at reduced evolutionary time scales. We explored the contributions of allometric variation in shape (AVSh), NAVSh, and size variation to adaptive evolution in the angiosperm species Calceolaria polyrhiza. This strongly relies on oil-collecting bees for pollination and experienced transitions in the size of pollinators during the last 2 Ma. Using geometric morphometrics, we described corolla morphology in several populations across its distribution range. Variation in corolla shape was decomposed into an allometric and a nonallometric component, and corolla size was estimated. We then looked for the correlation between these aspects of morphology and the pollinator. Our results suggest that adaptation to pollinators with different sizes relied on NAVSh, which resulted from shifts in the allometric slope and from shape changes that occurred early in flower development. We conclude that NAVSh can contribute to adaptation in flowering plants, even at the species-level.

<div class="page" title="Page 1"><div class="layoutArea"><div class="column"><p><strong><em>Pertya ferruginea</em> (Asteraceae: Pertyeae), a new species from southeastern China, with a revision of <em>P. cordifolia</em> and <em>P. pubescens</em></strong></p></div></div></div>

Pertya ferruginea Cai F. Zhang, a new species of the genus Pertya (Asteraceae: Pertyeae) from southeastern China, is described and illustrated with a revision of P. cordifolia and P. pubescens. Specimens of the new species had been usually mis-identified as the latter two species because of unclear boundaries among most known species of the genus in southeastern China. Based on extensive field collections and much more herbarium specimens examined than previous studies, P. cordifolia and P. pubescens are revised with much narrower circumscriptions. Although very similar to P. pubescens, the new species differs in the indumentum, length of involucre, number of series of involucral bracts and corolla size. Conservation status of the new species and previous misidentifications relevant to the three species are briefly discussed.

Do annual and perennial populations of an insect-pollinated plant species differ in mating system?

Theory predicts that outcrossing should be more prevalent among perennials than annuals, a pattern confirmed by comparative evidence from diverse angiosperm families. However, intraspecific comparisons between annual and perennial populations are few because such variation is uncommon among flowering plants. Here, we test the hypothesis that perennial populations outcross more than annual populations by investigating Incarvillea sinensis, a wide-ranging insect-pollinated herb native to China. The occurrence of both allopatric and sympatric populations allows us to examine the stability of mating system differences between life histories under varying ecological conditions. We estimated outcrossing rates and biparental inbreeding in 16 allopatric and five sympatric populations in which both life histories coexisted using 20 microsatellite loci. In each population we measured height, branch number, corolla size, tube length and herkogamy for ~30 individuals. In a sympatric population, we recorded daily flower number, pollinator visitation and the fruit and seed set of annual and perennial plants. As predicted, outcrossing rates (t) were considerably higher in perennial (mean = 0.76) than annual (mean = 0.09) populations. This difference in mating system was also maintained at sympatric sites where plants grew intermixed. In both allopatric and sympatric populations the degree of herkogamy was consistently larger in outcrossing than selfing plants. Perennials were more branched, with more and larger flowers than in annuals. In a sympatric population, annuals had a significantly higher fruit and seed set than perennials. Genetically based differences in herkogamy between annuals and perennials appear to play a key role in governing outcrossing rates in populations, regardless of variation in local ecological conditions. The maintenance of mating system and life history trait differentiation between perennial and annual populations of I. sinensis probably results from correlated evolution in response to local environmental conditions.