Explore the vast range of titles available.

Heterostyly is a fascinating adaptation to promote outbreeding and a classical paradigm of botany. In the most common type of heterostyly, plants either form flowers with long styles and short stamens, or short styles and long stamens. This reciprocal organ positioning reduces pollen wastage and promotes cross-pollination, thus increasing male fitness. In addition, in many heterostylous species selfing and the generation of unfit progeny due to inbreeding depression is limited by a self-incompatibility system, thus promoting female fitness. The two floral forms are genetically determined by the S locus as a complex supergene, namely a chromosomal region containing several individual genes that control the different traits, such as style or stamen length, and are held together by very tight linkage due to suppressed recombination. Recent molecular-genetic studies in several systems, including Turnera, Fagopyrum, Linum, and Primula have begun to identify and characterize the causal heterostyly genes residing at the S locus. An emerging theme from several families is that the dominant S haplotype represents a hemizygous region not present on the recessive s haplotype. This provides an explanation for the suppressed recombination and suggests a scenario for the chromosomal evolution of the S locus. In this review, we discuss the results from recent molecular-genetic analyses in light of the classical models on the genetics and evolution of heterostyly.

• Distyly is an intriguing floral adaptation that increases pollen transfer precision and restricts inbreeding. It has been a model system in evolutionary biology since Darwin. Although the S-locus determines the long- and short-styled morphs, the genes were unknown in Turnera. We have now identified these genes. • We used deletion mapping to identify, and then sequence, BAC clones and genome scaffolds to construct S/s haplotypes. We investigated candidate gene expression, hemizygosity, and used mutants, to explore gene function. • The s-haplotype possessed 21 genes collinear with a region of chromosome 7 of grape. The S-haplotype possessed three additional genes and two inversions. TsSPH1 was expressed in filaments and anthers, TsYUC6 in anthers and TsBAHD in pistils. Long-homostyle mutants did not possess TsBAHD and a short-homostyle mutant did not express TsSPH1. • Three hemizygous genes appear to determine S-morph characteristics in T. subulata. Hemizygosity is common to all distylous species investigated, yet the genes differ. The pistil candidate gene, TsBAHD, differs from that of Primula, but both may inactivate brassinosteroids causing short styles. TsYUC6 is involved in auxin synthesis and likely determines pollen characteristics. TsSPH1 is likely involved in filament elongation. We propose an incompatibility mechanism involving TsYUC6 and TsBAHD.

Main conclusionThis paper reviews the progress of research on the morphology, physiology and molecular biology of distyly in plants. It will help to elucidate the mysteries of distyly in plants.Distyly is a unique representative type of heterostyly in plants, primarily characterized by the presence of long style and short style within the flowers of the same species. This interesting trait has always fascinated researchers. With the rapid development of molecular biology, the molecular mechanism for the production of dimorphic styles in plants is also gaining ground. Researchers have been studying plant dimorphic styles from various perspectives. The researchers are gradually unravelling the mechanisms by which plants produce distyly traits. This paper reviews advances in the study of plant dimorphic style characteristics, mainly in terms of the morphology, physiology and molecular biology of plants with dimorphic styles. The aim is to provide a theoretical basis for the study of the mechanism of distyly formation in plants.

I review theoretical models for the evolution of supergenes in the cases of Batesian mimicry in butterflies, distylous plants and sex chromosomes. For each of these systems, I outline the genetic evidence that led to the proposal that they involve multiple genes that interact during ‘complex adaptations’, and at which the mutations involved are not unconditionally advantageous, but show advantages that trade‐off against some disadvantages. I describe recent molecular genetic studies of these systems and questions they raise about the evolution of suppressed recombination. Nonrecombining regions of sex chromosomes have long been known, but it is not yet fully understood why recombination suppression repeatedly evolved in systems in distantly related taxa, but does not always evolve. Recent studies of distylous plants are tending to support the existence of recombination‐suppressed genome regions, which may include modest numbers of genes and resemble recently evolved sex‐linked regions. For Batesian mimicry, however, molecular genetic work in two butterfly species suggests a new supergene scenario, with a single gene mutating to produce initial adaptive phenotypes, perhaps followed by modifiers specifically refining and perfecting the new phenotype.

Background Understanding floral biology and phenological variation patterns in plant species is crucial for hybridization and genetic improvement. In Synsepalum dulcificum (Sisrè berry plant), the lack of such knowledge hinders proper mastering of the pollination ecology of this species, with drawbacks in terms of cross success. A total of 100 S. dulcificum juveniles from two sites and 250 flowers were selected, monitored for two years, and assessed for phenological phase durations, synchronization pattern, flower abortion and floral morphometrics. Data were analyzed by combining generalized linear models with binomial and Poisson error structures, t-test, Mann-Whitney test and circular statistics. Results Our results revealed that S. dulcificum is a non-classical distylous species with an isoplethy (equal frequency of floral morphs) marked by all individual plants unexpectedly exhibiting both S- and L- floral morphs. Abortion was as high as 86%, culminated at the phases of style and petal wilting (26%) and fructification onset (28.7%), and varied from year 1 (93.7%) to year 2 (79.8%) (χ 2  = 23.63, df = 1, p < 0.001, Cohen’ d effect size = 0.42). The length of the phenological phases varied across (85 days for year 1 vs 86 days for year 2) and within the year (85 days for dry season vs 91 days for rainy season), with an average fruiting cycle of 87 ± 2 days. Flowering and fruiting were highly synchronous across sites with a marked seasonality whose extent was site- and phenophase- specific (Flowering: Rayleigh Z = 0.0534, p  = 0.001 for site 1 and Rayleigh Z = 0.2213, p  < 0.001 for site 2; Fruiting: Rayleigh Z = 0.4672, p  < 0.001 for site 1 and Rayleigh Z = 0.4502, p  < 0.001 for site 2). January and April represent peak periods for most of the phenological events in the species. Conclusion These findings suggest a need to redefine individual-level morph classification in distylous species and explore the biological drivers of high abortion rates in S. dulcificum.

Different strategies to reduce selfing and promote outcrossing have evolved in hermaphroditic flowers. Heterostyly, a complex floral polymorphism that occurs in at least 27 families of angiosperms, is hypothesized to achieve both goals by optimizing cross‐pollination (via disassortative pollen transfer) and restricting gamete wastage to autogamy (via the reduction in sexual interference between male and female organs). In heterostylous flowers, the reciprocal positioning of sexual organs in different morphs and the pollen incompatibility system within flower or between flowers of the same morph are thought to optimize both male and female functions, reducing the conflicts inherent to the occurrence of both sexual organs in the same reproductive unit. Specific elements of the disassortative‐pollination and sexual‐interference hypotheses have been tested individually before. However, despite the long‐standing interest in heterostyly – ever since Darwin's seminal work on primroses – the predictions derived from these two hypotheses have never been experimentally and systematically examined in the same system. Using distylous primroses (Primula elatior, P. vulgaris), we compare pollen transfer (i) between reciprocal and non‐reciprocal flowers; (ii) from anthers onto different parts of the pollinator's body; and (iii) within flower and between flowers of the same morph. We further test whether (iv) anther–stigma distance correlates with self‐pollen transfer and whether (v) seed set differs after pollinations with compatible, incompatible and both pollen types. Reciprocal herkogamy promotes differential placement of pollen onto different parts of the pollinator's body, thus effecting transfer of more pollen to reciprocal than to non‐reciprocal stigmas and realizing the key predictions of the disassortative‐pollination hypothesis. However, short‐styled flowers transfer pollen more disassortatively than long‐styled flowers in both species, whereas long‐styled flowers export more pollen to non‐reciprocal than to reciprocal stigmas in P. vulgaris, thus compromising male function in this species. Furthermore, larger distance between sexual organs lowers self‐ and intra‐morph pollination and the pollen incompatibility system decreases seed production after self‐pollination, thus diminishing sexual interference. Our results help us understand how the morphological and physiological components of heterostyly contribute to optimizing pollen transfer and minimizing self‐ and intra‐morph pollination, thus promoting more efficient outcrossing in species with this floral polymorphism.

Abstract Sympatric congeneric species that overlap the flowering period and have morphologically similar flowers tend to be pollinated by the same groups of pollinators, facilitating interspecific pollination and hybridization. If that situation involves distylous taxa, interspecific fruit set will theoretically rely on the match of sexual organs of the different species, because distylous plants only set fruits after crosses between floral morphs that are reciprocal herkogamous (RH) and are produced in different individuals. In a Caatinga forest in NE Brazil, there are three distylous species of Erythroxylum P. Br (E. citrifolium A.St.-Hil., E. pauferrense Plowman and E. simonis Plowman; Erythroxylaceae) that overlap their flowering period and have a high similarity in floral attributes. Erythroxylum pauferrense is a rare and endemic species of the region. This study aimed to describe the distylous pattern of those three Erythroxylum species (i.e., reciprocal hercogamy, proportion of morphs in the population and breeding system) and to evaluate the reproductive isolation between them. Flowering synchrony, interspecific RH and pollination were the pre-zygotic barriers investigated, and the post-zygotic one was the fruit set after interspecific pollination experiments. The species completely overlapped their flowering periods and were pollinated by the same group of species (Apis mellifera, Tetragona sp., and Trigona spinipes). In a general matter, a low level of both intra and interspecific RH was revealed. Interspecific pollination set fruits only between E. pauferrense and E. simonis. A low level of both intra and interspecific RH was revealed for all species, except for the low-level organs of E. citrifolium. The atypical distyly observed in E. pauferrense and E simonis indicates a collapse in the distylous system and may be related to a relaxation in the interspecific incompatibility mechanism. Resumo Espécies sincronopátricas e congenéricas que têm flores morfologicamente semelhantes tendem a ser polinizadas pelos mesmos grupos de polinizadores, facilitando a polinização e a hibridização interespecíficas. Se tal situação envolver táxons distílicos, a frutificação interespecífica dependerá teoricamente da correspondência de órgãos sexuais das diferentes espécies, porque as plantas distílicas somente frutificam após cruzamentos entre morfos florais que possuem hercogamia recíproca (RH) e são produzidos em indivíduos diferentes. Em uma floresta de Caatinga no Nordeste do Brasil há três espécies distílicas de Erythroxylum P. Br (E. citrifolium A.St.-Hil., E. pauferrense Plowman e E. simonis Plowman; Erythroxylaceae) que se sobrepõem em seu período de floração e têm grande similaridade em atributos florais. Erythroxylum pauferrense é rara e endêmica da região. Este estudo teve como objetivo descrever o padrão distílico dessas três espécies de Erythroxylum (ou seja, hercogamia recíproca, proporção de morfos na população e sistema de reprodução) e avaliar o isolamento reprodutivo entre elas. Sincronia de floração, RH interespecífica e polinização foram as barreiras pré-zigóticas investigadas, e a pós-zigótica foi a frutificação após experimentos de polinização interespecífica. As espécies sobrepuseram completamente seus períodos de floração e foram polinizadas pelo mesmo grupo de espécies (Apis mellifera, Tetragona sp., e Trigona spinipes). Em geral, um baixo nível de RH intra e interespecífica foi revelado. A polinização interespecífica resultou em frutos apenas entre E. pauferrense e E. simonis. Um baixo nível de RH intra e interespecífica foi revelado para todas as espécies, exceto para os órgãos de nível inferior de E. citrifolium. A distilia atípica observada em E. pauferrense e E simonis indica um colapso no sistema distílico e pode estar relacionada a um relaxamento no mecanismo de incompatibilidade interespecífica

Connaraceae is a pantropical family of about 200 species containing lianas and small trees with remarkably diverse floral polymorphisms, including distyly, tristyly, homostyly, and dioecy. To date, relationships within the family have not been investigated using a targeted molecular phylogenetic treatment, severely limiting systematic understanding and reconstruction of trait evolution. Accordingly, their last infrafamilial classification was based only on morphological data. Here, we used phylogenomic data obtained using the Angiosperms353 nuclear target sequence capture probes, sampling all tribes and almost all genera, entirely from herbarium specimens, to revise infrafamilial classification and investigate the evolution of heterostyly. The backbone of the resulting molecular phylogenetic tree is almost entirely resolved. Connaraceae consists of two clades, one containing only the African genus Manotes (4 or 5 species), which we newly recognize at the subfamily level. Vegetative and reproductive synapomorphies are proposed for Manotoideae. Within Connaroideae, Connareae is expanded to include the former Jollydoreae. The backbone of Cnestideae, which contains more than half of the Connaraceae species, remains incompletely resolved. Reconstructions of reproductive system evolution are presented that tentatively support tristyly as the ancestral state for the family, with multiple parallel losses, in agreement with previous hypotheses, plus possible re-gains. However, the great diversity of stylar polymorphisms and their phylogenetic lability preclude a definitive answer. Overall, this study reinforces the usefulness of herbarium phylogenomics, and unlocks the reproductive diversity of Connaraceae as a model system for the evolution of complex biological phenomena.

Primula obconica is a perennial herbaceous flower of the Primulaceae that exhibits distinct heterostyly. Long(L)- and short(S)-styled morphs differ substantially in various ways, which can directly affect the genetic regulation of plants. We can improve genetic breeding by understanding their differences and the genetic mechanisms of heterostyly. This trial of P. obconica, which included material and morphological observation, cross-fertilization characteristics, and ISSR molecular markers, was carried out to analyze the difference in distyly comprehensively. The findings demonstrated that the pollen, anther and other floral characteristics of L- and S-morphs varied. The results of the breeding characteristics showed that there were different self-incompatible mechanisms between both morphs, the L-morphs showed partial fitness, while the S-morphs showed complete heteromorphic incompatibility. The ISSR analysis also revealed that 19 primer pairs were polymorphic, clearly banded, and stable, showing significant differences in molecular markers for different morphs. Our study reveals the differences between the morphs of the Primula, which can provide a basis for genetic evolution and breeding work on heterostyly.

Heterostyly is a genetically controlled style polymorphism, that plays an important role in promoting outcrossing and improving reproductive fitness. Although distyly is often studied in plants of the Rubiaceae family, little attention has been paid to the reproductive strategies of distylous species in fragmented habitats. Here, We report for the first time the growth of , a type distylous species, in karst areas and evaluate its reciprocity between long styled morph and short one. We analyze the two distyly morph differences in the ancillary polymorphic of flowers and explore their reproductive strategy in fragmented habitats. In this study, we measured the floral characteristics of different morphs and performed differential secondary metabolite analysis on different morphs and tissue organs; Different pollination treatments were carried out to observe the fruit set, pollen germination, and pollen tube elongation of . Our research indicates that is a typical distylous plant for the distyly has high reciprocity. Both morphs exhibit the highest fruit set of intermorph outcrossing; The pollen germination and pollen tube elongation experiments have also demonstrated that the affinity of pollen from intermorph outcrossing is highest, regardless of whether it is the long or short morph as the maternal parent; Meanwhile, is an incompletely self-incompatible plant that exhibits a certain degree of self-pollination and intramorph outcrossing, which may be one of the important means to ensure sustainable reproduction in severely disturbed habitats. In the ancillary polymorphic of flowers, L-morphs flowers produce more pollen, and S-morph flowers produce more ovules to improve their male-female fitness and compensate for the asymmetry of pollen flow; Compared with S-morphs, L-morphs contain significantly higher levels of several kinds of terpenoids. S-morphs produce more flavonoids than L-morphs. The differences in secondary metabolites between L-morphs and S-morphs are mainly reflected in the different nutritional organs (including stems and leaves). Overall, our work has revealed the unique reproductive strategy of in fragmented habitats based on the characteristics of distyly, verifying the hypothesis that the distyly of promotes outcrossing and avoids male-female interference, improving male-female fitness and this is the first time in the genus.