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SUMMARY: The successful interaction between pollen and stigma is a critical process for plant sexual reproduction, involving a series of intricate molecular and physiological events. After self‐compatible pollination, a significant reduction in reactive oxygen species (ROS) production has been observed in stigmas, which is essential for pollen grain rehydration and subsequent pollen tube growth. Several scavenging enzymes tightly regulate ROS homeostasis. However, the potential role of these ROS‐scavenging enzymes in the pollen‐stigma interaction in Brassica napus remains unclear. Here, we showed that the activity of ascorbate peroxidase (APX), an enzyme that plays a crucial role in the detoxification of hydrogen peroxide (H2O2), was modulated depending on the compatibility of pollination in B. napus. We then identified stigma‐expressed APX1s and generated pentuple mutants of APX1s using CRISPR/Cas9 technology. After compatible pollination, the BnaAPX1 pentuple mutants accumulated higher levels of H2O2 in the stigma, while the overexpression of BnaA09.APX1 resulted in lower levels of H2O2. Furthermore, the knockout of BnaAPX1 delayed the compatible response‐mediated pollen rehydration and germination, which was consistent with the effects of a specific APX inhibitor, ρ‐Aminophenol, on compatible pollination. In contrast, the overexpression of BnaA09.APX1 accelerated pollen rehydration and germination after both compatible and incompatible pollinations. However, delaying and promoting pollen rehydration and germination did not affect the seed set after compatible and incompatible pollination in APX1 pentuple mutants and overexpression lines, respectively. Our results demonstrate the fundamental role of BnaAPX1 in pollen rehydration and germination by regulating ROS homeostasis during the pollen‐stigma interaction in B. napus. Significance Statement: Our research found that self‐incompatibility in Brassica napus requires the accumulation of reactive oxygen species (ROS) levels in the stigma. We identified the importance of BnaAPX1 in regulating ROS homeostasis, which is critical for pollen rehydration and germination in B. napus. [ABSTRACT FROM AUTHOR]

The genus Dyckia (Bromeliaceae) is endemic to South America, and its species show important ecological roles in xeric environments. The flowering phenology as well as floral and reproductive biology were monitored monthly in Dyckia dissitiflora at two sites (Bela Vista: 11°42′03.4″ S 39°05′21.7″ W and Barra do Vento: 11°37′58.1″ S 39°03′33.7″ W) in the municipality of Serrinha, Bahia, Brazil. Flowering occurs in the early austral summer with a peculiar time of beginning of anthesis (10:00–11:00), offering resources 18 h after the first petal movements. Pollen viability was 98%, with a high production of pollen grains. Stigma receptivity is continuous from flower opening to senescence, and nectar production initiates at 04:00 and extends until 18:00. The species is self‐compatible and autogamous, but not agamospermic. Pollen tubes developed and reached the micropyle within 24 h in all of the reproductive tests. The hummingbird Chlorostilbon lucidus was the only floral visitor and pollinator (frequency = 0.82 ± 0.02). Fruiting occurs 3 days after anthesis, and the seeds are wind‐dispersed. Self‐compatibility and autogamy are essential strategies for the reproductive success of D. dissitiflora in light of the low number and visit frequency of its pollinators, and it is favored by slow floral movements and the position of the stigmas in relation to stamens. [ABSTRACT FROM AUTHOR]

Summary: Self‐incompatibility plays a vital role in angiosperms, by preventing inbreeding depression and maintaining genetic diversity within populations. Following polyploidization, many angiosperm species transition from self‐incompatibility to self‐compatibility.Here, we investigated the S‐locus in Brassicaceae and identified distinct origins for the sRNA loci, SMI and SMI2 (SCR Methylation Inducer 1 and 2), within the S‐locus. The SMI loci were found to be widespread in Cruciferae, whereas the SMI2 loci were exclusive to Brassica species.Additionally, we discovered four major S‐haplotypes (BnS‐1, BnS‐6, BnS‐7, and BnS‐1300) in rapeseed. Overexpression of BnSMI‐1 in self‐incompatible Brassica napus ('S‐70S1300S6') resulted in a significant increase in DNA methylation in the promoter regions of BnSCR‐6 and BnSCR‐1300, leading to self‐compatibility. Conversely, by overexpressing a point mutation of BnSmi‐1 in the 'S‐70S1300S6' line, we observed lower levels of DNA methylation in BnSCR‐6 and BnSCR‐1300 promoters. Furthermore, the overexpression of BnSMI2‐1300 in the 'SI‐326S7S6' line inhibited the expression of BnSCR‐7 through transcriptional repression of the Smi2 sRNA from the BnS‐1300 haplotype.Our study demonstrates that the self‐compatibility of rapeseed is determined by S‐locus sRNA‐mediated silencing of SCR after polyploidization, which helps to further breed self‐incompatible or self‐compatible rapeseed lines, thereby facilitating the utilization of heterosis. [ABSTRACT FROM AUTHOR]

When reproductive success is determined by the relative availabilities of a series of essential, non‐substitutable resources, the theory of balanced fitness limitations predicts that the cost of harvesting a particular resource shapes the likelihood that a shortfall of that resource will constrain realized fitness. Plant reproduction through female function offers a special opportunity to test this theory; essential resources in this context include, first, the pollen received from pollinators or abiotic vectors that is used to fertilize ovules, and, second, the resources needed to provision the developing seeds and fruit. For many plants realized reproductive success through female function can be readily quantified in the field, and one key potential constraint on fitness, pollen limitation, can be assessed experimentally by manually supplementing pollen receipt. We assembled a comparative dataset of pollen limitation using only studies that supplement pollen to all flowers produced over the plant's reproductive lifespan. Pre‐ and post‐pollination costs were estimated using the weight of flowers and fruits and estimates of fruit set. Consistent with expectations, we find self‐incompatible plants make greater pre‐pollination investments and experience greater pollen limitation. However, contrary to theoretical expectations, when variation due to self‐compatibility is accounted for by including self‐compatibility in the statistical model as a covariate, we find no support for the prediction that plants that invest more heavily in pre‐pollination costs are subject to greater pollen limitation. Strong within‐species, between‐population variation in the expression of pollen limitation makes the quantification of mean pollen limitation difficult. We urge plant ecologists to conduct more studies of pollen limitation using whole‐plant pollen supplementation to produce a richer comparative dataset that would support a more robust test of the balanced limitations hypothesis. [ABSTRACT FROM AUTHOR]

Reproductive systems and pollination modes (pollination by animals vs. wind) can switch within clades, and many species with an intermediate pollination mode (ambophily, pollination by animals and wind) exist. Here, we investigate the reproductive systems and pollination modes of two common Eurasian species from the Agrimonieae (Rosaceae) that occur in open habitats, Sanguisorba minor and Sanguisorba officinalis. Based on observations from literature, the flowers of both species are visited by insects, but due to flower morphology S. minor is commonly regarded as wind pollinated, while S. officinalis is classified as insect pollinated. By measuring floral traits, such as pollen grain and ovule number per flower, observing flower visitors in natural habitats as well as in the botanical gardens and conducting pollination experiments we found that the reproductive systems and pollination modes of the two species differ: Sanguisorba minor is commonly but infrequently visited by short‐tongued insects but is nevertheless exclusively wind pollinated. However, in contrast to most other wind‐pollinated species, S. minor is highly self‐compatible and even able to set seeds by autogamous selfing. Sanguisorba officinalis, on the other hand, is largely insect pollinated, but wind also contributes to seed set (⁓17% after insect exclusion). This species is able to set seeds by geitonogmous selfing but seed set is higher by outcrossing than by selfing. Thus, our study demonstrates another example of a plant species with small, open flowers arranged in large inflorescences that can be shown to be ambophilous. Further, the study will help to reconstruct the complex evolution of pollination modes in Agrimonieae (Rosaceae). [ABSTRACT FROM AUTHOR]

Plants have evolved various strategies to avoid inbreeding, but the mass flowering displayed by many plants predisposes them to within‐plant pollen movements and self‐pollination. Mistletoes often aggregate at multiple spatial scales. Their bird pollinators often visit several flowers of the same individual and of others on the same host tree. We hypothesized that hermaphroditic mistletoes have self‐incompatibility mechanisms that reduce or prevent selfing. Whether their spatial distribution, affected by host specificity, host distribution, and the behaviour of seed dispersers, influences their mating system and population genetic structure remains unclear. We studied how mating system and spatial distribution affect genetic structure in four populations of the host‐generalist mistletoe Dendrophthoe pentandra in southwestern China using microsatellite markers and progeny arrays. We also characterized the fine‐scale spatial genetic structure among 166 mistletoes from four host trees in one population. Prevalence and intensity of infection both appeared to vary among host species, strongly affecting the degree of aggregation. Host tree size had a strong effect on infection intensity. Surprisingly, manual pollination experiments indicated that D. pentandra is self‐compatible, but genetic analyses revealed that outcrossing rates were higher than expected in all four populations (MLTR tm 0.83–1.20, Bayesian tm 0.772–0.952). Spatial genetic structure was associated with distance between host trees but not at shorter scales (within hosts). Our results demonstrate that the combination of bird pollination, bird‐mediated seed dispersal, and post‐dispersal processes result in outcrossing and maintain relatively high diversity in the presence of biparental inbreeding, despite very high local densities and possible self‐compatibility. [ABSTRACT FROM AUTHOR]

Summary: In the recent years, the agricultural world has been progressing towards integrated crop protection, in the context of sustainable and reasoned agriculture to improve food security and quality, and to preserve the environment through reduced uses of water, pesticides, fungicides or fertilisers. For this purpose, one possible issue is to cross‐elite varieties widely used in fields for crop productions with exotic or wild genetic resources in order to introduce new diversity for genes or alleles of agronomical interest to accelerate the development of new improved cultivars. However, crossing ability (or crossability) often depends on genetic background of the recipient varieties or of the donor, which hampers a larger use of wild resources in breeding programmes of many crops. In this review, we tried to provide a comprehensive summary of genetic factors controlling crossing ability between Triticeae species with a special focus on the crossability between wheat (Triticum aestivum L.) and rye (Secale cereale), which lead to the creation of Triticale (x Triticosecale Wittm.). We also discussed potential applications of newly identified genes or markers associated with crossability for accelerating wheat and Triticale improvement by application of modern genomics technologies in breeding programmes. [ABSTRACT FROM AUTHOR]

Pollinator shift and its influence on floral traits have been well documented to explain the diversity of angiosperms, but such effects are still less known at the intraspecific level, especially the responses of different morphs of distylous plants. We hypothesized that the pollen transfer efficiency would decrease if the pollinator shifted from a long‐tongued to short‐tongued insect across populations, and plants would evolve towards selfing in response to the stressed pollination environment. Given the gender specialization between flower morphs, the long styled (L‐morph) plants would increase female reproduction. Our study showed that the short‐tongued Bombus tianshanicus, the most‐visit pollinator in high elevation populations of distylous Primula nivalis, was less efficient in pollen transfer than long‐tongued Bombylius major. The plants evolved to promote selfing through reducing the anther–stigma separation and increasing intramorph self‐compatibility. The hand pollination experiment showed that after intramorph selfing, the fruit set and seed set increased with increasing elevation. Moreover, anther and stigma were closer in the L‐morph than in the short styled (S‐morph) plants, and the L‐morphs showed higher pollen transfer efficiency than the S‐morphs. Along with increased self‐compatibility, the fruit set and seed set of L‐morph plants were significantly higher than those of S‐morph plants. We described the pollinator shifts along an elevation gradient in a distylous plant and the response of plants by promoting selfing, which confirmed our hypothesis and supported the pollinator‐shift model. Our study also highlighted the different response in self‐compatibility between flower morphs. [ABSTRACT FROM AUTHOR]

Invasive alien plants often influence pollinator visitation to native plants when sharing pollinator guilds. It is of conservation concern when the invasive alien plant is characterized by floral resources that attract pollinators, thereby reducing the reproductive success of native species. This is well studied for insects, but whether the same is true for bird pollinators is largely unknown. We address this by considering the impact of an invasive alien plant (Banksia speciosa) on visitation rates of nectar‐feeding bird pollinators to native Protea compacta in the Cape Floristic Region of South Africa.We determined bird pollinator visitation rate to B. speciosa and P. compacta over 21 h of observation at three sites. We also quantified how visitation rate influenced reproductive success of both study species through different breeding experiments.Sugarbird visitation to P. compacta was significantly lower in the presence of B. speciosa, while there was no effect for sunbirds as they mostly avoided B. speciosa. Protea compacta had higher nectar volumes and sucrose per flower than B. speciosa. Sucrose per hectare was higher in all P. compacta plots compared to B. speciosa. Neither study species is pollen limited and they are self‐compatible to some extent. But pollinator visitation enhanced seed production in both species.We show here that the invasive alien B. speciosa flowers attract sugarbirds – but not sunbirds – away from native P. compacta. The long‐term effect of reduced pollinator visitation may reduce the fitness of P. compacta, but the long‐term demographic impact is unknown and would require further study. [ABSTRACT FROM AUTHOR]

Having hundreds of big mountains, the Qinghai–Tibetan Plateau and its southern boundary, the Hengduan Mountains Region, represent one of the world's biodiversity hotspots. In the so‐called "Third Pole of the earth", diverse effects of climate change and habitat heterogeneity could have driven the evolution of plant adaptive strategies. In this review, we collected and compiled recent sources of reproductive biology in animal‐pollinated plants, stressing the questions that need further attention, including pollination system, pollen limitation, self‐compatibility, and sexual system. We constructed plant–pollinator interaction networks based on the case studies from this region, showing that the majority of pollinators were bees, moths, butterflies, and flies were also important, and bats and birds were rare. As the unpredictable (cold, rainy or windy) weather affects pollinator activities, sexual reproduction seemed to be pollen limited, but available studies show that the exact pattern of pollen limitation is still under debate. Self‐compatibility could be either a solution, or a result from pollen limitation. Moreover, plant sexual systems can be regarded as an integrated module that counters pollen limitation. As phylogenetic relationships were constructed, diverse genera experienced rapid radiation were revealed in these mountainous areas. Further studies of evolutionary transitions in reproductive systems of congeners will unveil potential factors shaping the general pattern of adaptive strategies in animal‐pollinated plants. Further studies will be beneficial in using advanced new techniques, examining phenotypic selection under common gardens, and considering chemical ecology in interactions between plants and florivores, particularly in pollen fate. [ABSTRACT FROM AUTHOR]

Interspecific hybridization events have played a major role in plant speciation, yet the evolutionary origin of hybrid species often remains enigmatic. Here, we inferred the evolutionary origin of the allotetraploid species Coffea arabica, which is widely cultivated for Arabica coffee production. We estimated genetic distances between C. arabica and all species that are known to be closely related to C. arabica using genotyping‐by‐sequencing (GBS) data. In addition, we reconstructed a time‐calibrated multilabeled phylogenetic tree of 24 species to estimate the age of the C. arabica hybridization event. Ancestral states of self‐compatibility were also inferred to shed new light on the evolution of self‐compatibility in Coffea. Coffea canephora and C. eugenioides were confirmed as the putative progenitor species of C. arabica. These species most likely hybridized between 1.08 million and 543 000 years ago, coinciding with periods of environmental upheaval, which may have induced range shifts of the progenitor species that facilitated the emergence of C. arabica. [ABSTRACT FROM AUTHOR]

Summary: Mating system transitions from self‐incompatibility (SI) to self‐compatibility (SC) are common in plants. In the absence of high levels of inbreeding depression, SC alleles are predicted to spread due to transmission advantage and reproductive assurance.We characterized mating system and pistil‐expressed SI factors in 20 populations of the wild tomato species Solanum habrochaites from the southern half of the species range.We found that a single SI to SC transition is fixed in populations south of the Rio Chillon valley in central Peru. In these populations, SC correlated with the presence of the hab‐6 S‐haplotype that encodes a low activity S‐RNase protein. We identified a single population segregating for SI/SC and hab‐6. Intrapopulation crosses showed that hab‐6 typically acts in the expected codominant fashion to confer SC. However, we found one specific S‐haplotype (hab‐10) that consistently rejects pollen of the hab‐6 haplotype, and results in SI hab‐6/hab‐10 heterozygotes.We suggest that the hab‐10 haplotype could act as a genetic mechanism to stabilize mixed mating in this population by presenting a disadvantage for the hab‐6 haplotype. This barrier may represent a mechanism allowing for the persistence of SI when an SC haplotype appears in or invades a population. [ABSTRACT FROM AUTHOR]

Variation in plant breeding systems has implications for pollinator‐mediated selection on floral traits and the ecology of populations. Here we evaluate pollinator contribution to seed production, self‐compatibility and pollen limitation in different floral colour forms of Drosera cistiflora sensu lato (Droseraceae). These insectivorous perennial plants are endemic to fynbos and renosterveld vegetation in the Cape Floristic Region of South Africa, and the species complex includes five floral colour forms (pink, purple, red, white and yellow), some of which are known to be pollinated by beetles.Controlled hand‐pollination experiments were conducted in 15 populations of D. cistiflora s.l. (two to four populations per floral colour form) to test whether the colour forms vary in their degree of self‐compatibility and their ability to produce seeds through autonomous self‐fertilization.Yellow‐flowered forms were highly self‐incompatible, while other floral colour forms exhibited partial self‐compatibility. Seed set resulting from autonomous selfing was very low, and pollinator dependence indices were high in all populations. Since hand cross‐pollination resulted in greater seed set than open pollination in 13 of the 15 populations, we inferred that seed production is generally pollen‐limited.Drosera cistiflora s.l. typically exhibits high levels of pollinator dependence and pollen limitation. This is unusual among Drosera species worldwide and suggests that pollinators are likely to mediate strong selection on attractive traits such as floral colour and size in D. cistiflora s.l. These results also suggest that the floral colour forms of D. cistiflora s.l. which are rare and threatened are likely to be vulnerable to local extinction if mutualisms were to collapse indefinitely. [ABSTRACT FROM AUTHOR]

One of the most fundamental, although controversial, questions related to the evolution of plant mating systems is the distribution of outcrossing rates. Self‐compatibility, and especially autonomous self‐pollination, can become particularly beneficial in anthropogenically degraded habitats with impoverished pollinator assemblages and increased pollen limitation.In a hand‐pollination experiment with 46 meadow plants from the Železné hory Mts., Czech Republic, we evaluated the species' ability to adopt different mating systems. For a subset of the species, we also tested seed germination for inbreeding depression. Subsequently, we analysed relationships between the species' mating systems and 12 floral and life‐history traits.We found a relatively discrete distribution of the studied species into four groups. Fully and partially self‐incompatible species formed the largest group, followed by self‐compatible non‐selfers and mixed mating species. The germination experiment showed an absence of inbreeding depression in 19 out of 22 examined species. Nectar sugar per flower, nectar sugar per shoot and dichogamy were significant associated with the mating system.Spontaneous selfing ability and self‐incompatibility in species of the meadow communities had a discrete distribution, conforming to the general distribution of mating and breeding systems in angiosperms. The low frequency of spontaneous selfers and the lack of inbreeding depression at germination suggest the existence of a selection against selfing at the later ontogenetic stages. Some floral traits, such as the level of dichogamy and amount of nectar reward, may strongly impact the balance between selfing and outcrossing rates in the self‐compatible species and thus shape the evolution of mating systems. [ABSTRACT FROM AUTHOR]

Summary: A crucial step in the transition from outcrossing to self‐fertilization is the loss of genetic self‐incompatibility (SI). In the Brassicaceae, SI involves the interaction of female and male specificity components, encoded by the genes SRK and SCR at the self‐incompatibility locus (S‐locus). Theory predicts that S‐linked mutations, and especially dominant mutations in SCR, are likely to contribute to loss of SI. However, few studies have investigated the contribution of dominant mutations to loss of SI in wild plant species.Here, we investigate the genetic basis of loss of SI in the self‐fertilizing crucifer species Capsella orientalis, by combining genetic mapping, long‐read sequencing of complete S‐haplotypes, gene expression analyses and controlled crosses.We show that loss of SI in C. orientalis occurred < 2.6 Mya and maps as a dominant trait to the S‐locus. We identify a fixed frameshift deletion in the male specificity gene SCR and confirm loss of male SI specificity. We further identify an S‐linked small RNA that is predicted to cause dominance of self‐compatibility.Our results agree with predictions on the contribution of dominant S‐linked mutations to loss of SI, and thus provide new insights into the molecular basis of mating system transitions. [ABSTRACT FROM AUTHOR]

Premise: As Baker's law suggests, the successful colonization of oceanic islands is often associated with uniparental reproduction (self‐fertility), but the high incidence of dimorphism (dioecy, gynodioecy) on islands complicates this idea. Lycium carolinianum is widespread, occurring on the North American mainland and the Hawaiian Islands. We examined Baker's ideas for mainland and island populations of L. carolinianum and examined inbreeding depression as a possible contributor to the evolution of gynodioecy on Maui. Methods: Controlled crosses were conducted in two mainland populations and two populations in Hawaii. Treatments included self and cross pollination, unmanipulated controls, and autogamy/agamospermy. Alleles from the self‐incompatibility S‐RNase gene were isolated and compared between mainland and island populations. Given self‐compatibility in Hawaii, we germinated seeds from self‐ and cross‐ treatments and estimated inbreeding depression using seven traits and a measure of cumulative fitness. Results: Mainland populations of Lycium carolinianum are predominately self‐incompatible with some polymorphism for self‐fertility, whereas Hawaiian populations are self‐compatible. Concordantly, S‐RNase allelic diversity is reduced in Hawaii compared to the mainland. Hawaiian populations also exhibit significant inbreeding depression. Conclusions: Self‐compatibility in Hawaii and individual variation in self‐fertility in mainland populations suggests that a colonization filter promoting uniparental reproduction may be acting in this system. Comparison of S‐RNase variation suggests a collapse of allelic diversity and heterozygosity at the S‐RNase locus in Hawaii, which likely contributed to mate limitation upon arrival to the Pacific. Inbreeding depression coupled with autonomous self‐fertilization may have led to the evolution of gynodioecy on Maui. [ABSTRACT FROM AUTHOR]

Abstract: Plant species that are effective colonisers of transient habitats are expected to have a capacity for uniparental reproduction and show flexibility in pollination systems. Such traits may enable populations to be established from a small number of founding individuals without these populations succumbing to reductions in fecundity arising from pollinator limitation. We tested these predictions for Aloe thraskii (Xanthorrhoeaceae), a succulent treelet that colonises shifting coastal dunes and has both bird and bee pollinators. We performed hand‐pollination experiments, and selectively excluded bird visitors to determine differences in pollinator effectiveness. We measured pollinator visitation rates and fecundity in populations varying in their size, density and isolation distance. Controlled hand‐pollinations revealed that unlike most other Aloe species, A. thraskii is self‐compatible and thus capable of uniparental reproduction. The species does however depend on pollinators and is visited by various bird species as well as by bees. Fruit and seed set are not affected by selective exclusion of birds, thus indicating that bees are effective pollinators. Bird visitation rates increased with increasing plant height and population size, while bee visitation rates increased with increasing population size and density. We found that seed set per flower was lower in large populations than in small populations. These results suggest that establishment of populations of A. thraskii from a small number of individuals is unlikely to be limited by the fecundity of individual plants. [ABSTRACT FROM AUTHOR]

Summary: Cultivated potato (Solanum tuberosum L.) is a highly heterozygous autotetraploid that presents challenges in genome analyses and breeding. Wild potato species serve as a resource for the introgression of important agronomic traits into cultivated potato. One key species is Solanum chacoense and the diploid, inbred clone M6, which is self‐compatible and has desirable tuber market quality and disease resistance traits. Sequencing and assembly of the genome of the M6 clone of S. chacoense generated an assembly of 825 767 562 bp in 8260 scaffolds with an N50 scaffold size of 713 602 bp. Pseudomolecule construction anchored 508 Mb of the genome assembly into 12 chromosomes. Genome annotation yielded 49 124 high‐confidence gene models representing 37 740 genes. Comparative analyses of the M6 genome with six other Solanaceae species revealed a core set of 158 367 Solanaceae genes and 1897 genes unique to three potato species. Analysis of single nucleotide polymorphisms across the M6 genome revealed enhanced residual heterozygosity on chromosomes 4, 8 and 9 relative to the other chromosomes. Access to the M6 genome provides a resource for identification of key genes for important agronomic traits and aids in genome‐enabled development of inbred diploid potatoes with the potential to accelerate potato breeding. [ABSTRACT FROM AUTHOR]

Sweet cherry ( Prunus avium L.) has stylar gametophytic self-incompatibility, which is controlled by the multi-allelic S-locus and encompasses the highly polymorphic genes for the S-ribonuclease ( S-RNase) and S-haplotype-specific F-box ( SFB), which are female and male determinants, respectively. The self-compatible mutant SFB4′ corresponds to an allele variant of SFB4 and presents a frameshift mutation. Even though male-determinant molecular markers can discriminate between SFB4 and SFB4′ alleles, the methods required are laborious, time-consuming and expensive, and not suitable for massive analysis and integration into breeding programmes. Our aim was to develop molecular markers for the evaluation of self-compatibility alleles in sweet cherry, that could be used as a high-throughput screening strategy to identify SFB4 and SFB4′ alleles, based on a marker for male determinacy. Our results were consistent using primers flanking the mutation responsible for the SFB4′ allele. We designed a specific molecular marker and confirmed it in sweet cherry commercial varieties. This new molecular marker is feasible for self-compatibility alleles in the male determinant in sweet cherry-assisted breeding programs. [ABSTRACT FROM AUTHOR]

This study tested the hypothesis that self-compatibility would be associated with floral traits that facilitate autonomous self-pollination to ensure reproduction under low pollinator visitation. In a comparison of two pairs of Ipomoea species with contrasting breeding systems, we predicted that self-compatible ( SC) species would have smaller, less variable flowers, reduced herkogamy, lower pollinator visitation and higher reproductive success than their self-incompatible ( SI) congeners., We studied sympatric species pairs, I. hederacea ( SC)- I. mitchellae ( SI) and I. purpurea ( SC)-I. indica ( SI), in Mexico, over two years. We quantified variation in floral traits and nectar production, documented pollinator visitation, and determined natural fruit and seed set. Hand-pollination and bagging experiments were conducted to determine potential for autonomous self-pollination and apomixis., Self-compatible Ipomoea species had smaller flowers and lower nectar production than SI species; however, floral variation and integration did not vary according to breeding system. Bees were primary pollinators of all species, but visitation rates were seven times lower in SC than SI species. SC species had a high capacity for autonomous self-pollination due to reduced herkogamy at the highest anther levels. Self-compatible species had two to six times higher fruit set than SI species., Results generally support the hypothesis that self-compatibility and autonomous self-pollination ensure reproduction under low pollinator visitation. However, high variation in morphological traits of SC Ipomoea species suggests they maintain variation through outcrossing. Furthermore, reduced herkogamy was associated with high potential for autonomous self-pollination, providing a reproductive advantage that possibly underlies transitions to self-compatibility in Ipomoea. [ABSTRACT FROM AUTHOR]

Premise of the study: Dichogamy is a common characteristic among angiosperms, including Piper species. In this genus, the tiny flowers are morphologically similar and have an asynchronous stamen development. However, there is no information on the duration of stigma receptivity and whether it overlaps with pollen release. To better understand mechanisms of floral function in Piper vicosanum, we provide a detailed characterization of the timing of pollen release from the four stamens and the period of stigma receptivity and exposure mode of the receptive areas. Methods: We investigated plants of a natural population in a semideciduous seasonal forest (Vigosa, Minas Gerais State, southeastern Brazil), based on chemical tests, light microscopy, and scanning electron microscopy analyses. Key results: Incomplete protogyny--a mechanism that favors outcrossing--was recorded. The period of stigma receptivity was long (14 d), and the sequential exposure and senescence of stigmatic papillae occurred gradually and in a basipetal direction. Pollen release began 2-6 d after the beginning of the pistillate phase, with an average pollen viability of 87.7%, during the bisexual flower phase. Pollen was released for up to 6 d and occurred in one stamen at a time. The fruit set observed in tests of self-pollination indicated self-compatibility. Conclusions: The gradual and sequential exposure of stigmatic papillae in P. vicosanum flowers is described here as the mechanism for the long duration of receptivity. Anther development and pollen release were also sequential. These findings are yet unreported reproductive characteristics of the genus and offer new perspectives for future studies on the floral biology of other Piper species. [ABSTRACT FROM AUTHOR]

Miniature inverted-repeat transposable elements ( MITEs) are known to contribute to the evolution of plants, but only limited information is available for MITEs in the Prunus genome. We identified a MITE that has been named Falling Stones, FaSt. All structural features (349-bp size, 82-bp terminal inverted repeats and 9-bp target site duplications) are consistent with this MITE being a putative member of the Mutator transposase superfamily. FaSt showed a preferential accumulation in the short AT-rich segments of the euchromatin region of the peach genome. DNA sequencing and pollination experiments have been performed to confirm that the nested insertion of FaSt into the S-haplotype-specific F-box gene of apricot resulted in the breakdown of self-incompatibility (SI). A bioinformatics-based survey of the known Rosaceae and other genomes and a newly designed polymerase chain reaction ( PCR) assay verified the Prunoideae-specific occurrence of FaSt elements. Phylogenetic analysis suggested a recent activity of FaSt in the Prunus genome. The occurrence of a nested insertion in the apricot genome further supports the recent activity of FaSt in response to abiotic stress conditions. This study reports on a presumably active non-autonomous Mutator element in Prunus that exhibits a major indirect genome shaping force through inducing loss-of-function mutation in the SI locus. [ABSTRACT FROM AUTHOR]

Impact of pollinator shift on differentiation of floral morphology has attracted the interest of naturalists for many years. A comparative investigation was conducted for determining the pollination characteristics, including pollinator assemblage, floral morphology, flowering phenology, and self-compatibility, of two closely related Clerodendrum species-insular C. izuinsulare and widespread C. trichotomum. Japanese black swallowtail butterflies were the predominant flower visitors in mainland Japan, whereas diurnal hawk moths were predominantly found on the Izu Islands, a chain of oceanic islands located off the southeastern coast of the main Japanese island of Honshu in the west Pacific Ocean. The corolla tube of C. izuinsulare was longer than that of C. trichotomum, whereas the filaments and petals of C. izuinsulare were shorter than those of C. trichotomum. The flowering season of C. izuinsulare was later than that of C. trichotomum. The self-compatibility of C. izuinsulare was higher than that of C. trichotomum. These differences might be associated with the low density of Japanese black swallowtail butterflies and dominance of diurnal hawk moths on the Izu Islands. [ABSTRACT FROM AUTHOR]

* Premise of the study: Vestigialization of traits that no longer enhance fitness is a common theme in evolution. Plants often use colorful, scented flowers to attract pollinators that mediate outcross pollination. After an evolutionary shift from outcrossing to self-fertilization, where cross-pollination is no longer necessary, attractive traits may be reduced, especially because these traits may also attract herbivores. Selection may be particularly strong in moth-pollinated lineages where pollinators are also herbivores. * Methods: We used field surveys and common garden glasshouse experiments to test this hypothesis by quantifying components of flower size and display and floral volatiles in outcrossing vs. selfing populations of the moth-pollinated Pacific coastal dune endemic Abronia umbellata. * Key results: Floral face diameter and flower tube length were 43% and 54% smaller in selfing than outcrossing populations, and selfers displayed 15% fewer flowers per umbel. Selfers emitted 99% less total floral volatiles per flower per hour than outcrossers; a much stronger reduction. The chemical composition of volatiles also differed between outcrossers and selfers. Similar differences were observed in a common glasshouse environment, suggesting genetic differentiation in these floral attractive traits among populations. Contrary to expectations, there were no differences in leaf or flower herbivory between selfing and outcrossing populations. * Conclusions: Floral fragrance is much more dramatically reduced in selfing compared to outcrossing populations than other floral attractive traits, but probably not due to selection exerted by moth herbivory. Reduction in aspects of flower size may be constrained by developmental linkages with fruit and seed size. [ABSTRACT FROM AUTHOR]

Gametophytic self-incompatibility (GSI) is controlled by a highly polymorphic locus called the S-locus, which is an important factor that can result in seedless fruit in Citrus. The S1 self-incompatibility locus-linked pollen 3.15 gene ( S1-3.15) belongs to a type of S locus gene. The role of S1-3.15 in the SI reaction of Citrus has not yet been reported. In this study, full-length sequences of cDNA and DNA encoding the S1-3.15 gene, referred to as CrS1-3.15, were isolated from 'Wuzishatangju' (Self-incompatibility, SI) and 'Shatangju' (Self-compatibility, SC). The predicted amino acid sequences of CrS1-3.15 between 'Wuzishatangju' and 'Shatangju' differ by only three amino acids. Compared to 'Wuzishatangju', three bases were substituted in the genomic DNA of CrS1-3.15 from 'Shatangju'. Southern blot results showed that one copy of CrS1-3.15 existed in the genomic DNA of both 'Wuzishatangju' and 'Shatangju'. The expression level of the CrS1-3.15 gene in the ovaries of 'Shatangju' was approximately 60-fold higher than that in the ovaries of 'Wuzishatangju'. When 'Wuzishatangju' was cross-pollinated, the expression of CrS1-3.15 was upregulated in the ovaries at 3 d, and the highest expression levels were detected in the ovaries at 6 d after cross-pollination of 'Wuzishatangju' × 'Shatangju'. To obtain the CrS1-3.15 protein, the full-length cDNA of CrS1-3.15 genes from 'Wuzishatangju' and 'Shatangju' was successfully expressed in Pichia pastoris. Pollen germination frequency of 'Wuzishatangju' was inhibited significantly with increasing CrS1-3.15 protein concentrations from SI 'Wuzishatangju'. [ABSTRACT FROM AUTHOR]

Erodium maritimum L. is an annual species presenting heterogeneous, sometimes very small, and distant populations, distributed along a discontinuous coastal strip of the European Atlantic and the central and western Mediterranean basin. The aim of this study is to investigate genetic variation and geographic structure changes across its large distribution. Fourteen populations of E. maritimum were studied using AFLP fingerprints, together with their population sizes, reproductive systems and flower visitors. AFLP markers revealed the genetic structure of the species to be weak. Many individuals from one population clustered together with those of other populations, showing a high degree of genetic admixture. Despite having a self-compatible reproductive system, populations (especially the largest ones) showed high levels of genetic polymorphism, and the majority of genetic variation was contained within populations. The low genetic structure suggests high levels of gene flow, which might be explained through the dispersability of the species' fruits. Finally, recommendations are provided for management strategies to facilitate the conservation of this endangered species. [ABSTRACT FROM AUTHOR]

Pollination systems may vary in their degree of specialization from generalist to specialist and this is associated with the frequency and efficiency of pollinators. Self-compatibility and a generalist pollination system appear to be adaptations that enhance the ability for colonizing new areas, which is typical of mangrove species. Avicennia schaueriana is a western mangrove species included in Acanthaceae, Lamiales, an order known to have specialized pollination. We aimed to describe the floral morphology and analyze the pollination and reproductive systems of A. schaueriana in a mangrove area on the northern coast of the state of Pernambuco, Brazil, to analyze the possible adaptations of this species to the environment. Avicennia schaueriana is self-compatible; however, pollination activity is essential because there is no spontaneous formation of fruit. Reproductive efficacy was high, indicating pollinator efficiency. Some floral attributes of A. schaueriana suggest specialization; however, the broad spectrum of pollinators observed suggests that it has a generalist pollination system. The way in which pollinators interact with flowers and the environmental conditions may have exerted a selective force on the floral attributes of A. schaueriana, characterizing an adaptive generalized pollination system, which is somewhat specialized. [ABSTRACT FROM AUTHOR]

Ocotea porosa has been extensively exploited over the past few decades because of the quality of its wood. Today, populations are reduced and the species is now included in the Red List of threatened species by the International Union for Nature Conservation. For conservation and management purposes, it is extremely important that we understand its reproductive ecology. Floral morphology was described based on field and scanning electron microscopic examination. The reproductive system was determined through experimentally controlled pollination along with observations of pollen tube growth. Pollinators were identified through field observations. Flowers of O. porosa are small, shallow, inconspicuous, asynchronous and grouped in inflorescences. This species presented self-compatibility, but did not reproduce through apomixy and spontaneous self-pollination was very rare (5%). Despite being monoclinal, flowers were protogynic, and the gynoecium was receptive after the first day of anthesis when the anthers were closed. Spontaneous self-pollination was avoided by the extrorse position of the anthers of the internal stamens. Frankliniella gardeniae (Thysanoptera) was the only pollinating species observed and, after visiting several asynchronous flowers in the same inflorescence, favors geitonogamy. Together the small distance supposedly achieved by thrips in flight and the small population density of O. porosa can reduce the chances of cross-pollination in this species. If so, conservation measures must include preservation of the current population and possibly planting to increase population density. This would reduce the distance between individuals and increase genetic variability. Thrips as pollinators must be included in conservation planning for O. porosa. [ABSTRACT FROM AUTHOR]

* Premise of the study: A useful, but seldom applied, measure of the effectiveness of different pollinators is their contribution to the rate of outcrossing. This measure is particularly useful in facultatively autogamous plants for which seed set cannot be used as a direct measure of pollinator effectiveness. We used selective exclusion experiments to assess the importance of insects for outcrossing in Protea caffra, a facultatively autogamous shrub with scented flowers that are visited frequently by both birds and insects (mainly beetles). * Methods and results: Pollen loads on stigmas, pollen tube growth, seed set, seed mass, germination, and early seedling survivorship were similar for vertebrate-excluded and open-pollinated infl orescences. Pollen-supplementation mostly did not increase seed set, revealing resource limitation. Mean multilocus outcrossing rates, estimated using eight polymorphic allozyme loci, were similar for progeny from inflorescences excluded from bird visitors (0.65) and for those visited by both birds and insects (0.59). Wright's fixation indices indicated that the adult population is near Hardy--Weinberg equilibrium but differed markedly for maternal plants ( FIS = --0.187 ± 0.065) and their early stage progeny ( FIS = 0.258 ± 0.002). Since seed from self and cross hand-pollinations were equally viable in terms of germination, this discrepancy in FIS could be explained by inbreeding depression that occurs between germination and reproductive maturity. * Conclusions: Since outcrossing rates were not reduced when birds were excluded, we infer that insects are effective agents of cross pollination in P. caffra. This helps to explain the evolution of traits associated with insect pollination, such as fruity floral scent, in this species. [ABSTRACT FROM AUTHOR]

Pollen germination and pollen-tube growth under natural conditions were observed in a population of a distylous species, Primula sieboldii, in which partial self-compatibility has been demonstrated in some long-styled genets. We observed post-pollination processes microscopically in styles collected after self-morph and inter-morph hand pollination (with standardized pollen load on the stigmas) in four genets each from the following three 'genet types': self-incompatible long-styled (SI), partially self-compatible long-styled (SC) and self-incompatible short-styled morph genets. Irrespective of the genet type, pollen germination began within 24 h after pollination and tubes of pollen reached to the style base with 48-96 h after inter-morph pollination. Although pollen tubes germinated after self-pollination in the SC genets, the number of germinated pollen tubes was significantly lower than in the case of inter-morph pollination. Few pollen tubes germinated after self-pollination of the SI or short-styled genets. In SC genets, the rate of pollen-tube growth did not differ between self-morph and inter-morph pollination (∼1.9 mm/day). Therefore, differences in self-compatibility between SC and SI genets in P. sieboldii are likely to be attributable to differential pollen germination rates rather than to differential pollen-tube growth rates. [ABSTRACT FROM AUTHOR]

Summary [ABSTRACT FROM AUTHOR]

With 1 figure and 4 tables Self‐compatibility has become one of the most important traits in almond breeding programmes. This characteristic allows for the establishment of monovarietal almond orchards with many advantages for the grower. However, there are some uncertainties about the consequences of self‐fertilization regarding productivity and fruit quality. In this work, a new methodology was used to clarify the possible effects of self‐pollination on these parameters. Four different pollination treatments were applied to six self‐compatible almond genotypes by hand‐pollinating flowers on five different branches, so that along each branch the four treatments were distributed homogeneously. The pollinated flowers were later identified with wires of a particular colour for each treatment. Fruit set and fruit characteristics (weight in‐shell, kernel weight, percentage of kernel, percentage of defective kernels, double kernels and split kernels) were studied. With this methodology, results should only be influenced by the pollinator effect. In general, no significant differences were observed between self‐pollination and cross‐pollination for the characteristics studied. These findings demonstrate the absence of negative effects of self‐pollination on these agronomic traits. [ABSTRACT FROM AUTHOR]

1. Pollen-mediated gene flow from ecological core populations may hamper the ability of populations to invade new, closely adjacent habitats. The potential for the invasion of a new habitat is enhanced when selection against immigrants is augmented by the elevation of self-fertilization. This shift imparts a measure of reproductive isolation to the invader. 2. Whereas genetically mediated changes in selfing often accompany niche shifts in plants, the elevation of self-fertilization by plastic responses to novel, stressful, environments has not been explored. Here I will show that invaders of novel habitats may have elevated levels of self-fertility mediated by alterations in floral form and self-compatibility. 3. Heightened selfing facilitates the evolution of local adaptation by increasing the additive genetic variance for tolerance to the new habitat. Heightened selfing also facilitates local adaptation by increasing reproductive assurance. 4. Elevated levels of selfing based on developmental responses are immediate, as opposed to that obtained by multigenerational selection. 5. Synthesis. The likelihood of a niche shift will be substantially enhanced if the invader is protected from the swamping effect of gene flow from a nearby core population. This protection may be afforded by an environment-induced elevation of self-fertility. The likelihood of a niche shift also is enhanced by an increase in reproductive assurance which may be vital to the survival of an invading population whose reproductive success is density-dependent. [ABSTRACT FROM AUTHOR]

• Premise of the study: Embryonic inbreeding depression is a key influence on mating system evolution and can be difficult to estimate in self-incompatible species. A pollen chase experiment was used to estimate the magnitude of embryonic inbreeding depression in Costa Rican Witheringia solanacea, a species polymorphic for self-incompatibility (SI). In a pollen chase experiment, bud self-pollinations are followed after anthesis by outcross pollinations, with a comparable pair of outcross pollinations used as a control. Lowered seed set for the self-precedence treatment indicates embryonic inbreeding depression. • Methods: Embryonic inbreeding depression was assayed for self-compatible (SC) individuals and for SI plants from two populations that differ quantitatively in the onset and enzymatic activity of their SI response. Microsatellite markers were used to assay the selfing rate of a sample of surviving progeny from the prior self-pollination treatment. • Key results: SC individuals showed no evidence of embryonic inbreeding depression. In SI plants, prior self-pollination reduced seed number by 28-70%, depending on population. Microsatellite genotyping revealed that embryonic inbreeding depression was even more severe than estimated by the phenotypic data: for mature fruits resulting from self-pollination precedence, the majority of the progeny were the result of outcross fertilization. • Conclusions: Lineage-specific purging of recessive lethals has accompanied the evolution of SC in this species. SI populations show contrasting levels of embryonic inbreeding depression, with nearly complete embryonic lethality upon selfing in the Monteverde population. In the face of high embryonic inbreeding depression, an increase in selfing rate can evidently occur only under severe pollen limitation. [ABSTRACT FROM AUTHOR]

•Allopolyploid speciation is common in plants and is frequently associated with shifts from outcrossing, for example self-incompatibility, to inbreeding (i.e. selfing). Senecio cambrensis is a recently evolved allohexaploid species that formed following hybridization between diploid self-incompatible S. squalidus and tetraploid self-compatible S. vulgaris. Studies of reproduction in wild populations of S. cambrensis have concluded that it is self-compatible. •Here, we investigated self-compatibility in synthetic lines of S. cambrensis generated via hybridization and colchicine-induced polyploidization and wild S. cambrensis using controlled crossing experiments. •Synthetic F1 S. cambrensis individuals were all self-compatible but, in F2 and later generations, self-incompatible individuals were identified at frequencies of 6.7–9.2%. Self-incompatibility was also detected in wild sampled individuals at a frequency of 12.2%. The mechanism and genetics of self-incompatibility were tested in synthetic S. cambrensis and found to be similar to those of its paternal parent S. squalidus (i.e. sporophytic). •These results show, for the first time, that functional sporophytic self-incompatibility can be inherited and expressed in allopolyploids as early as the second (F2) generation. Wild S. cambrensis should therefore be considered as possessing a mixed mating system with the potential for evolution towards either inbreeding or outcrossing. [ABSTRACT FROM AUTHOR]

The degree to which plants self-fertilize may impact their potential for genetic adaptation. Given that the mating system influences genetic processes within and among populations, the mating system could limit or promote local adaptation. I conducted a literature survey of published reciprocal transplant experiments in plant populations to quantify the effect of mating system on the magnitude of local adaptation. Mating system had no effect on local adaptation. I detected no effect when species were categorized as either self-compatible or self-incompatible or when accounting for environmental differences between source populations. The results suggest that, despite limited genetic variation in selfing species and greater potential for gene flow in outcrossing species, mating system has little influence on adaptation of populations. [ABSTRACT FROM AUTHOR]

The sex type of Trillium camschatcense has been considered to be strictly monomorphic, composed of only hermaphroditic individuals. However, field observations have detected anther-degenerated (AD) plants coexisting with hermaphrodites. The present study aimed to elucidate whether AD plants could be regarded as females and, if so, how their loss of male function is compensated. Because T. camschatcense retains both self-compatible (SC) and self-incompatible (SI) populations, the frequencies of AD plants in multiple populations (22 SC and eight SI) were examined to predict the fate of these individuals under contrasting breeding systems. Morphological and genetic analyses in a SC population demonstrated that AD plants were completely male sterile, but female fertile. Although the quantity of seed produced was similar, hermaphrodites produced seeds predominantly via selfing, whereas seeds of AD plants were entirely outcrossed. Because inbreeding depression was severe, AD plants achieved a fitness advantage through inbreeding avoidance. However, the frequency of AD plants varied among SC populations (0–42%), suggesting that environmental variance can modify the relative fitness. Conversely, the frequency was suppressed among SI populations (0–2%). Because SI hermaphrodites are free from inbreeding, AD plants would not benefit from inbreeding avoidance and would find it difficult to invade a SI population. [ABSTRACT FROM AUTHOR]

Coffea anthonyi Stoff. & F. Anthony from Cameroon and the Republic of Congo is formally described. Morphological, biochemical and molecular characteristics, isozyme diversity and phylogenetic relationships are discussed. The new diploid species has strong relationships with the East African C. eugenioides and the allotetraploid cultivated C. arabica. As such, it could be related to a progenitor species of C. arabica. The new species is self-compatible, being a rare character within the genus Coffea. This new small-leaved Central African species is of particular interest from a phylogenetic as well as from a breeding point of view. [ABSTRACT FROM AUTHOR]

The summer-blooming annual forbs Cleome lutea and Cleome serrulata (Cleomaceae) are native across the US Intermountain West and Rocky Mountains, respectively. Their farmed seed is sought to help rehabilitate western rangelands in those regions. This study of the reproductive biologies and pollinator faunas of C. lutea and C. serrulata is the first for this cosmopolitan family, the sister family to the Brassicaceae. Unlike the S-allele self-incompatibility systems of some Brassicaceae, both species of Cleome were found to be self-fertile and capable of some autogamy. Compared with selfing, outcrossing did not enhance seed set, seed viability or seedling vigor for either species (in fact, selfed progeny were more robust). Large, openly visited plants yielded >20 000 seeds each. Like several species of the sister family Capparaceae, flowers of both species first shed their pollen, secreted nectar and became receptive nocturnally. Although no nocturnal visitors were found, both Cleome species attracted a diverse array of diurnal native bees, wasps and butterflies. Among the many floral generalist bees that work Cleome flowers for pollen and nectar are two managed agricultural pollinators, Apis mellifera and Megachile rotundata. These observations bode well for pollinating C. lutea and C. serrulata in small commercial seed fields. It appears that diverse wild bees would benefit from the addition of native Cleome to restoration seed mixes, with the objective of sustaining native pollinator faunas during the first few years of postfire plant community rehabilitation. [ABSTRACT FROM AUTHOR]

The outcome of species interactions is often difficult to predict, depending on the organisms involved and the ecological context. Nectar robbers remove nectar from flowers, often without providing pollination service, and their effects on plant reproduction vary in strength and direction. In two case studies and a meta-analysis, we tested the importance of pollen limitation and plant mating system in predicting the impacts of nectar robbing on female plant reproduction. We predicted that nectar robbing would have the strongest effects on species requiring pollinators to set seed and pollen limited for seed production. Our predictions were partially supported. In the first study, natural nectar robbing was associated with lower seed production in Delphinium nuttallianun'i, a self-compatible but non-autogamously selfing, pollen-limited perennial, and experimental nectar robbing reduced seed set relative to unrobbed plants. The second study involved Linaria vulgaris, a self-incompatible perennial that is generally not pollen limited. Natural levels of nectar robbing generally had little effect on estimates of female reproduction in L. vulgaris, while e4erimentai nectar robbing reduced seed set per fruit but not percentage of fruit set. A meta-analysis revealed that nectar robbing had strong negative effects on pollen-limited and self-incompatible plants, as predicted. Our results suggest that pollination biology and plant mating system must be considered to understand and predict the ecological outcome of both mutualistic and antagonistic plant-animal interactions. [ABSTRACT FROM AUTHOR]

Seed production may be limited because flowers do not get enough suitable pollen or because plants lack the resources to make seeds. We used replicated plantings to test factors that influence effects of bumblebee behavior on pollen limitation, as measured by the difference in seed set between hand- and naturally pollinated flowers, of Penstemon digitalis in patches of four to 41 flowering individuals. Seed set per flower was 376% higher in the largest as compared with the smallest Penstemon patches. This positive density dependence reflects activity of long-tongued bees, which (1) have higher effective density as patch size increases, (2) visit greater proportions of plants as patch size increases, and (3) visit smaller proportions of flowers per visited plant as patch size increases. Our results suggest that economics of flight and maneuverability of large, long-tongued bumblebees lead them to transfer more pollen between than within Penstemon plants in large patches. Density of smaller, short-tongued bumblebees was not positively associated with Penstemon seed set, but these bees may be important pollinators at low plant densities. Our experimental system indicates a clear positive relationship between activity of effective pollinators and seed set in a species capable of pollinating itself. [ABSTRACT FROM AUTHOR]

Japanese pears exhibit S-RNase-mediated gametophytic self-incompatibility, and ‘Osa-Nijisseiki’ ( S2 S ; SM = stylar-part mutant) is a self-compatible mutant from ‘Nijisseiki’ ( S2 S4), in which the S4-allele exhibits style-specific inactivation, but behaves as the functional S4-allele in pollen. It was unclear how S4 RNase mutated to S RNase, despite many investigations having been carried out. In the present study, the S-RNase genes in ‘Osa-Nijisseiki’ and its self-compatible progenies were systematically investigated at genomic, transcriptional and translational level in comparison with its wild type, ‘Nijisseiki’. The results provided evidence that the S4 RNase gene is present in the genome and expressed in the ‘Osa-Nijisseiki’ style, especially in the stigma, but is not transmitted to its progenies. [ABSTRACT FROM AUTHOR]

• It has been suggested that clonality provides reproductive assurance in cross-fertilizing species subject to pollen limitation, relieving one of the main selective pressures favoring the evolution of self-fertilization. According to this hypothesis, cross-fertilizing species subject to pollen limitation should often be clonal. Here, we investigated the association between clonality and a genetic mechanism enforcing outcrossing, self-incompatibility, in Solanum (Solanaceae). • We collected self-incompatibility and clonality information on 87 species, and looked for an association between these two traits. To account for the contribution of shared evolutionary history to this association, we incorporated phylogenetic information from chloroplast (NADH dehydrogenase subunit F) sequence data. • We found that self-incompatibility is strongly associated with clonal reproduction: all self-incompatible species reproduce clonally, while the absence of clonality is widespread among self-compatible taxa. The observed correlation persists after taking into account shared phylogenetic history, assumptions about the evolutionary history of self-incompatibility, uncertainty associated with phylogeny estimation, and associations with life history (annual/perennial). • Our results are consistent with the hypothesis that clonality provides reproductive assurance, and suggest that the consequences of clonal growth in the evolution of plant reproductive strategies may be more significant than previously thought. [ABSTRACT FROM AUTHOR]

Breakdown of genetically enforced self-incompatibility (SI), an extremely common and important evolutionary transition in plants, has conventionally been conceived as a qualitative rather than a quantitative change. We evaluated qualitative and quantitative variation in SI for four populations of Witheringia solanacea in Costa Rica, examining growth of self-pollen tubes in pollinations of buds and mature flowers. We also measured levels of RNase production in styles to determine whether enzyme production was correlated with differences in self-rejection. The two small populations contained both self-compatible (SC) individuals and obligate outcrossers (female or SI). Plants in the two large populations were uniformly SI as revealed by pollen tube growth, although several of these individuals sporadically set seed autogamously. Stylar RNase activity did not differ significantly between bud and mature flowers, but self-pollen tube growth did differ, suggesting that a gene product in addition to S-RNase is responsible for developmental onset of SI. Population-level differences in RNase activity were consistent with differences in the strength of the rejection response in bud pollinations, suggesting that a threshold level of S-RNase, in combination with other factors, is necessary for S1. Our results support a growing body of evidence that not only qualitative variation in SI, but also quantitative variation may be functionally significant. [ABSTRACT FROM AUTHOR]

To verify the compatibility behaviour of the almond cultivar ‘Francolí’ and to clarify its S genotype a combination of pollination tests, stylar ribonuclease and allele specific PCR analysis was used. ‘Francolí’ was released from IRTA's breeding programme in 1994, having been putatively raised from the cross ‘Cristomorto’ ( S1 S2) × ‘Gabaix’ ( S10 S25). This cultivar was also reported to be self-incompatible but revealing only one S band in the zymograms after S-RNases analysis. ‘Francolí’ sets nuts after test crossing with two S1 S25 cultivars, having a different genotype from that earlier reported. ‘Francolí’ was also observed to be self-compatible after selfing flowers in the field and in the laboratory. ‘Francolí’ was re-assigned the S1 S f genotype after test crossing, stylar ribonuclease and PCR data analysis. After microsatellite analysis, the self-compatible ‘Tuono’ ( S1 S f) cultivar is suggested as the male parent of ‘Francolí’ instead of the earlier reported ‘Gabaix’. [ABSTRACT FROM AUTHOR]

The effects of pollination competition between related species on pollen limitation, selfing ability and heterospecific incompatibility were studied in the alpine snowbed shrubs, Phyllodoce caerulea and Phyllodoce aleutica (Ericaceae) along local snowmelt gradients. The flowering season of these species highly overlapped and they shared the same method of pollination (via bumblebees). The floral density and nectar production were higher in P. caerulea in the early snowmelt habitat, but they were higher in P. aleutica in the late snowmelt habitat, reflecting the species-specific sensitivity to a short growing season. Bumblebee preference shifted from P. caerulea to P. aleutica along the snowmelt gradient, reflecting the changes in the relative reward level between the species. The extent of pollen limitation of P. caerulea was severe in the late snowmelt habitat, whereas that of P. aleutica was obvious in the early snowmelt habitat. A pollination experiment revealed that P. caerulea showed a consistently low selfing ability, whereas P. aleutica showed a high selfing ability in the early snowmelt habitat and shifted to an obligate outcrosser in the late snowmelt habitat. The frequency of interspecific bumblebee movement for P. caerulea from P. aleutica increased in the late snowmelt habitat. To the contrary, the frequency of interspecific movement for P. aleutica from P. caerulea decreased along the snowmelt gradient. P. caerulea did not indicate heterospecific incompatibility to P. aleutica pollen. In contrast, P. aleutica indicated heterospecific incompatibility to P. caerulea pollen, reflecting the high risk of receiving heterospecific pollen as a result of interspecific bumblebee movement. However, heterospecific compatibility of P. aleutica disappeared in the late snowmelt habitat, where the risk of heterospecific pollen receipt was low. Therefore, changes in interspecific bumblebee movement might have been responsible for the variation in heterospecific incompatibility among P. aleutica populations. The local snowmelt gradient creates diverse biological interactions and mating system evolution in the alpine ecosystem. [ABSTRACT FROM AUTHOR]

Sawgrass, Cladium jamaicense, is the dominant macrophyte in the Florida Everglades. We examined sawgrass flowering phenology and compatibility reactions in ex situ and in situ populations over 2 yr. Sawgrass flowers in May in southern Florida. Flower maturation was relatively synchronous within an inflorescence. Along the entire inflorescence, functionally male flowers emerged initially, followed by stigmas, then anthers of hermaphroditic flowers. Flowers of each sex expanded over 2 d with less than 1 d in between, totaling 6-7 d for an inflorescence to complete flowering. Hand pollinations showed that sawgrass was self-compatible and not pollen-limited, because open pollinations produced fruit set similar to self- and cross-pollinations. Fruit set was low in autogamy and manipulation treatments. Manipulation treatments were used to study the effect of exposure to airborne pollen during hand pollinations. This treatment thus provides a useful technique for studies on the in situ compatibility of wind-pollinated graminoids. Sawgrass was able to self- fertilize, but the timing of flower maturation on an inflorescence promoted outcrossing. Actual outcrossing rates in sawgrass thus depend on clonal architecture and the timing of floral maturation on other inflorescences within a clone rather than on inflorescences of other genets in a population. [ABSTRACT FROM AUTHOR]

Abstract Mating systems of sympatric related alpine shrubs, Phyllodoce caerulea and P. aleutica , were compared along snowmelt gradients at three snowbed sites in the Taisetsu Mountains, northern Japan. Seed-set success under natural pollination tended to decrease at late snowmelt places in both species, but the difference between the species was not clear. A pollination experiment revealed that selfing ability differed between the species along the snowmelt gradients. Phyllodoce caerulea showed consistently low selfing ability throughout the gradients even when artificial selfing treatment was performed. Phyllodoce aleutica , whereas, showed high selfing ability at the early and middle snowmelt plots but this abruptly decreased at the late snowmelt plots at every site. These results indicate that P. aleutica is predominantly a selfer at early and middle snowmelt places and shifts to an obligate outcrosser at late snowmelt places. Therefore, variations in the mating system actually occur among neighboring populations along snowmelt gradients probably because of directional selective forces such as interspecific competition for pollinators. [ABSTRACT FROM AUTHOR]

Pollen tubes reaching the ovary, fruit set and the main fruit characteristics of six self-compatible genotypes (`Marta', `Antoñeta', `Guara', `Lauranne', `S2332' and `S4017') of almond were studied after self- or cross-pollination. No significant differences after self- or cross-pollination were found in the number of pollen tubes reaching the ovary, the percentage of ovaries finally penetrated, fruit set and fruit characteristics. The results showed the possibility of obtaining suitable fertilization, yields and quality of fruits by self-pollination of self-compatible almond cultivars in a single cultivar orchard. [ABSTRACT FROM AUTHOR]

Abstract Deceptive orchid species that offer no floral rewards to pollinators often experience pollinator limitation because they. The breeding system and fruit set were investigated in order to examine pollinator limitation for a population of a deceptive orchid, Pogonia japonica , on a floating peat mat in Mizorogaike Pond, western Japan. Fruit sets for outcross-pollinated, self-pollinated and pollinator-excluded flowers were 75%, 80%, and 0%, respectively. Thus, this species was self-compatible but neither autogamous nor apogamous. The fruit set for open-pollinated flowers was 22.9% and 17.4% in 1994 and 1995, suggesting that pollinator limitation did occur in the field. Larger flowers were more likely to develop into fruit than smaller ones in open pollination (36%vs 8%). Thus, flower size seems to affect fruiting of this species. No effective visits by major pollinators such as bees, which could carry pollinia, were observed during 16.5 h of observation during daytime. Instead, thrips were often found moving on gynostemium or pollinia and circumstantial evidence that suggests thrips may partly transfer pollen in pieces out of a granular pollinium of P. japonica was obtained. Pogonia japonica should come to use thrips as a pollinator to supplement low fruit set under limited flower visitation by major pollinators. [ABSTRACT FROM AUTHOR]