Selfed Flowers Research Articles

Mating system, pollination, and seed dispersal in the Pennsylvania endangered Iris verna

Iris verna L. var. smalliana Fernald ex M.E. Edwards (Family Iridaceae, hereafter referred to as Iris verna) is currently listed as endangered in Pennsylvania. The six extant populations in Pennsylvania are all located in one state forest and represent the northern end of the range for the species. There is little known about the basic biology of I. verna throughout its range, making preservation of threatened populations difficult. Iris verna was tested for self-compatibility and the ability to autonomously self-pollinate in 2016. Pollinator limitation studies were conducted on three of the Pennsylvania populations in 2015 and 2016 by comparing hand-pollinated and naturally pollinated flowers. Potential animal pollinators or seed dispersers were identified through in-person observation and video camera use. Iris verna was found to be self-compatible, with no significant reduction in seed production in selfed flowers, but the species does require a pollinator for pollen transfer. Seed production in I. verna was limited by pollinators during both years of the study and seed production in both control and hand-pollinated flowers was variable across years, suggesting resource availability also limits sexual reproduction. Ants were the only observed animals potentially coming in contact with reproductive organs while visiting flowers, and were also identified as seed dispersers. Our findings suggest that pollinators can be an important limiting factor to sexual reproduction in these endangered populations of I. verna in Pennsylvania.

Variation in Manduca sexta Pollination-Related Floral Traits and Reproduction in a Wild Tobacco Plant

Most flowering plants depend on animal pollination for successful sexual reproduction. Floral signals such as color, shape, and odor are crucial in establishing this (often mutualistic) interaction. Plant and pollinator phenotypes can vary temporally but also spatially, thus creating mosaic-like patterns of local adaptations. Here, we investigated natural variation in floral morphology, flower volatile emission, and phenology in four accessions of a self-compatible wild tobacco, Nicotiana attenuata, to assess how these traits match the sensory perception of a known pollinator, the hawkmoth Manduca sexta. These accessions differ in floral traits and also in their habitat altitudes. Based on habitat temperatures, the accession occurring at the highest altitude (California) is less likely to be visited by M. sexta, while the others (Arizona, Utah 1, and Utah 2) are known to receive M. sexta pollinations. The accessions varied significantly in flower morphologies, volatile emissions, flower opening, and phenology, traits likely important for M. sexta perception and floral handling. In wind tunnel assays, we assessed the seed set of emasculated flowers after M. sexta visitation and of natural selfed and hand-pollinated selfed flowers. After moth visitations, plants of two accessions (Arizona and Utah 2) produced more capsules than the other two, consistent with predictions that accessions co-occurring with M. sexta would benefit more from the pollination services of this moth. We quantified flower and capsule production in four accessions in a glasshouse assay without pollinators to assess the potential for self-pollination. The two Utah accessions set significantly more seeds after pollen supplementation compared with those of autonomous selfing flowers, suggesting a greater opportunistic benefit from efficient pollinators than the other two. Moreover, emasculated flowers of the accession with the most exposed stigma (Utah 2) produced the greatest seed set after M. sexta visitation. This study reveals intraspecific variation in pollination syndromes that illuminate the potential of a plant species to adapt to local pollinator communities, changing environments, and altered pollination networks.

Breeding Systems and Pollen-Ovule Ratios inEricaSpecies (Ericaceae) of the Cape Floristic Region

Premise of research. Breeding systems dictate the potential for self-fertilization in plants and may therefore have a strong influence on evolutionary and ecological processes. Previous investigations of breeding systems in Ericaceae indicate variation in self-sterility, but studies from the megadiverse genus Erica are almost entirely lacking. Here we quantify the degree of self-sterility and autofertility in Cape Erica species, quantify pollen-ovule ratios (P/Os), and test whether these are related to each other and vary across species with bird- versus insect-pollination syndromes.Methodology. We used controlled hand-pollinations, analyses of pollen tube development, and P/Os to investigate the breeding systems of 15 taxa (comprising 13 species) of Erica in the Cape Floristic Region of South Africa, spanning most main clades across the phylogeny.Pivotal results. In all but one species, seed set from autonomous selfing was almost absent and significantly lower than that from cross-pollination, and only one species had an autofertility index that was higher than 0.2. In 12 taxa, seed set following self-pollination was significantly reduced compared with that following cross-pollination, and the index of self-incompatibility (ISI) was higher than 0.8 for 10 taxa. Following self-pollination, pollen tubes reached the ovary in all species, and for two species with very low seed set in selfed flowers, fluorescence images revealed that self-pollen tubes entered into the ovules. P/Os ranged from 68 to 320 and are therefore low for obligate outcrossing species. These ratios did not correlate with the ISI and did not vary according to whether species conformed to insect- or bird-pollination syndromes.Conclusions. This study indicates that self-sterility is frequent in Cape Erica species and either involves a late-acting mechanism of self-incompatibility or is due to early inbreeding depression. P/Os in these species are consistently low and do not reflect variation in breeding systems and pollination syndromes.

Breeding System, Seed Germination and Recruitment of A Threatened, Southeastern U.S. Endemic,Ribes echinellum(Grossulariaceae)

abstract Reproductive ecology studies of rare species can provide information pertinent to population growth and persistence. One rare species confined to two disjunct localities, one on private land located in Florida and the other one that is composed of two subpopulations on public land in South Carolina, is the federally threatened Miccosukee gooseberry, Ribes echinellum. Studies were carried out in the Florida population to determine change in abundance between 1992 and 2012 and to understand the lack of seedling recruitment in the wild. In Florida, the number of patches increased in the northern part of the study area but decreased in the southern part. Hand pollination experiments indicate Ribes echinellum exhibits a mixed mating system. Although autogamous pollination occurred, it did not result in fruit production. Reduced seed set of selfed flowers and seedling size provided some support for inbreeding depression, yet small sample sizes precluded full evaluation. No asexual seed production was d...

The effect of pollination mode on seed performance ofGentiana lutea: a laboratory evaluation of seed germinability

Gentiana lutea L. (yellow gentian, Gentianaceae) is a protected orophyte of central and southern Europe, mainly threatened by the uncontrolled collection of its rhizome, used in traditional medicine and for liquor production. The species is self-compatible, but outcrossing mediated by pollinators is needed to obtain a viable progeny. In this study, we considered five natural populations belonging to the four subspecies of G. lutea. We performed controlled pollinations in the field (self- versus cross-pollination) followed by seed germination tests in laboratory conditions, adding a solution of gibberellic acid, in order to evaluate the seed performance. A cumulative index of inbreeding depression was calculated considering maternal reproductive output as well as seed performance traits. Seed weight and seed germination performance was similar between seeds resulting from naturally pollinated and pollen-augmented flowers and higher compared to selfed flowers, highlighting a disadvantage of selfing and the importance of cross-pollen transfer in natural conditions. However, in the small and isolated population of G. lutea subsp. symphyandra on Mt Grande we found a general reduction in seed germination rate, likely due to increased selfing or mating among close relatives as a consequence of a severe bottleneck. We discuss our results with regards to implications for conservation practices.

Ruellia subsessilis (Nees) Lindau (Acanthaceae): A species with a sexual reproductive system that responds to different water availability levels

In Ruellia subsessilis the typical cleistogamy (cleistogamous and chasmogamous morphs), which is common in species of this genus, was not observed. Flowering and fruiting of this species are continuous and the selfing flowers are polymorphic. Objective of present study was to analyze the mechanisms of self-pollination in R. subsessilis. In addition, we studied its reproductive phenology, floral biology, breeding system, seed germination and how its sexual reproductive system responds to different water availability levels. The study was conducted with plants of a natural population and others in a greenhouse, under different water availability levels, in southeastern Brazil. The distribution of the reproductive phenophases was seasonal and concentrated in the rainy season. Production of distinct floral morphs could be observed. These different morphs are named ‘reduced chasmogamous morphs’ (RC), in the dry season, and ‘normal chasmogamous morphs’ (NC), which latter develop in the rainy season. The morph production of the cultivated plants was likewise influenced by water availability: RC developed under drought stress and NC in moist soil. Significant differences between morphs were observed in size parameters of the corolla, androecium and gynoecium, and concerning the number of ovules and pollen grains. In both morphs, selfing occurred late (delayed self-pollination), and pre-anthesis cleistogamy (early self-pollination) occurred sporadically in RC. The seeds resulting from self-pollination were more vigorous and germinated faster than those from cross-pollination.

Floral ecology of Oreocharis acaulis (Gesneriaceae): An exceptional case of “preanthetic” protogyny combined with approach herkogamy

Protogyny is supposed to represent the ancestral form of dichogamy in the angiosperms, but is rare in advanced groups such as the Asteridae, in which protandry prevails by far. Here we report on an unusual form of protogyny combined with herkogamy in a Chinese species of Gesneriaceae (Asteridae–Lamiales): Oreocharis acaulis (formerly Opithandra acaulis). This is characterized by a conspicuous protrusion of the style from the flower bud and the stigma becoming receptive before corolla opening (female-only stage; preanthetic protogyny) and both sexes staying functional during anthesis (hermaphroditic stage), with the stigma presented above the anther level (approach herkogamy). The plants studied were found to be self-compatible, but autonomous self-pollination and apomixis were not observed. Successful pollination was found to depend fully on the presence of insect pollinators (Bombus sp.). The visiting frequency was higher in the hermaphroditic stage (in which also more nectar was produced) than in the female-only stage. The out-crossed flower buds opened earlier and had a shorter flowering period than selfed flowers. Similarly, the outcross-pollen germinated earlier and the pollen tube growth was faster than in self-pollen. Anthers, pistil and corolla of O. acaulis obviously form an integrative functional unit in which the elongated style plays a key role both in pollen-dispensing and pollen-deposition. The combination of preanthetic protogyny with herkogamy has probably arisen through selection for promoting out-crossing and prolonging the exposition time of the receptive stigma in order to capture a higher amount of pollen grains. This may be understood as a strategy to cope with scarcity of pollinators in the plants’ habitat.

Plant evolutionary ecology: molecular genetics, global warming and invasions, and the novel approaches we are using to study adaptations

Plant evolutionary ecology: molecular genetics, global warming and invasions, and the novel approaches we are using to study adaptations

An Asian orchid, Eulophia graminea (Orchidaceae: Cymbidieae), naturalizes in Florida

Eulophia graminea, a terrestrial orchid native to Asia, has naturalized in southern Florida. Orchids naturalize less often than other flowering plants or ferns, but E. graminea has also recently become naturalized in Australia. Plants were found growing in five neighborhoods in Miami-Dade County, spanning 35 km from the most northern to the most southern site, and growing only in woodchip mulch at four of the sites. Plants at four sites bore flowers, and fruit were observed at two sites. Hand pollination treatments determined that the flowers are self compatible but fewer fruit were set in selfed flowers (4/10) than in out-crossed flowers (10/10). No fruit set occurred in plants isolated from pollinators, indicating that E. graminea is not autogamous. Pollinia removal was not detected at one site, but was 24.3 % at the other site evaluated for reproductive success. A total of 26 and 92 fruit were found at these two sites, where an average of 6.5 and 3.4 fruit were produced per plant. These fruits ripened and dehisced rapidly; some dehiscing while their inflorescences still bore open flowers. Fruit set averaged 9.2 and 4.5 % at the two sites. No floral visitors were seen during limited (6.5 hr duration) timed watches of flowers. Individual flowers are open an average 11 days, and the inflorescences may bear flowers for at least one month. How E. graminea entered Florida is unknown, but capsules, bulbs and plantlets in flasks are available for sale and/or trade via the internet from Thailand and other places outside the U.S. The occurrence of the orchid at 900-1000 m elevation its native Sikkim (27-28oN) and in Kashmir (above 32oN), suggest that it can live well north of current area of naturalization in southern Florida, which is at sea level and 26oN latitude.

No inbreeding depression in an outcrossing alpine species: The breeding system of Campanula thyrsoides

Plants that live in fragmented landscapes, where populations are isolated from each other and in which long-distance dispersal is essential for colonization of empty sites, reproduction should be favoured by self-compatibility (Baker's law). Nevertheless, outcrossing mechanisms, such as self-incompatibility and dichogamy, are common in many species and are often maintained by inbreeding depression in the fitness of selfed progeny. Here, we studied the breeding system and the consequences of selfing and sister mating in Campanula thyrsoides, a short-lived perennial monocarp, which is found in the naturally fragmented landscape of the Alps. An experiment with controlled pollinations was set up in the common garden with plants grown from seeds originating from 14 seed families, collected in the siliceous Central Alps, where this plant is found on isolated carbonate bearing outcrops. Our results indicate that C. thyrsoides has a strong self-incompatibility system (SI) with no or low seed set in selfed flowers compared to outcrossed and sister-crossed flowers. Moreover, the SI system in C. thyrsoides did not break down with flower age as in some other Campanula species. Surprisingly, there was no significant difference in seed set, seed weight, germination percentage, seedling survival and size between outcrossed and sister-crossed offspring, which indicates no inbreeding depression. We suggest that the absence of inbreeding depression in this outcrossing species might be a result of frequent bottlenecks during colonization of the isolated habitats in the alpine landscape.

Self-incompatibility and Self-fruitfulness in Pear cv. Agua de Aranjuez

Most pear (Pyrus communis L.) cultivars are impaired to set fruit under self-pollination, because self-fertilization is prevented by a gametophytic self-incompatibility system. However, accumulated information in this species shows that often for a same cultivar, after self-pollination, a variable response in fruit set can be obtained in different years or growing conditions. In this work, we characterize self-incompatibility and self-fruitfulness in ‘Agua de Aranjuez’, the main Spanish pear cultivar, which also shows a variable response to self-pollination. Two years with a different fruit setting response after self-pollination, one with no fruit set and the other with a moderate fruit set, were compared for parthenocarpic fruit development and for pollen tube performance. Results show that in both years, this cultivar behaves as self-incompatible with absence of parthenocarpy. In selfed flowers, most pollen tubes are arrested in the upper half of the style, although in a small proportion of the styles, a pollen tube can reach the base of the style and eventually effect fertilization. Self-fertilization, although occurring at a low level, can explain the fruit set levels obtained under self-pollination given that flowers with just one fertilized ovule are able to set fruit. This behavior could explain confusing results about self-fruitfulness in ‘Agua de Aranjuez’ and other pear cultivars.

The role of spontaneous selfing in the pioneer species Saxifraga aizoides

A large variety of reproductive patterns is present among alpine plants to ensure the persistence of populations in such harsh environments. In the present study, the role of spontaneous selfing and its contribution to the actual reproductive success of an alpine pioneer plant was investigated. The results showed that Saxifraga aizoides is clearly self-compatible. Open-pollinated flowers exhibited higher seed numbers per capsules than selfing flowers, albeit the difference was not significant. Although seed weight seemed to be independent from the kind of pollination, open-pollinated flowers had a significantly higher proportion of germinated seeds than selfed ones. Furthermore, the ability of fast germination found in S. aizoides enables the seeds to take advantage of all possible opportunities for germination. In summary, S. aizoides exhibits a successful recruitment strategy for an alpine pioneer species.

The first record of gynodioecy in a species of Gnidia (Thymelaeaceae) from South Africa

Sexual polymorphism was studied in the shrub Gnidia wikstroemiana (Thunb.) Meisn. from the semiarid Nama Karoo Biome, South Africa. The populations comprised plants bearing either female flowers, or hermaphrodite flowers with variable female function. In two populations, female plants accounted for 36–37% of the flowering plants. Female flowers were smaller and their stamens were reduced to staminodes, but their styles were significantly longer than those of hermaphrodite flowers. Energy investment in flowers and fruits for females and hermaphrodites was measured using bomb calorimetry. Females produce a greater number of less costly flowers than hermaphrodites, and invest less energy per unit in production of flowers and inflorescences. In contrast, females invest more energy per unit in production of fruits and infructescences than hermaphrodites. Females overall invest 7.3% more energy in reproduction than hermaphrodites. Female flowers were obligate out-crossers (xenogamous), with 35% of nonmanipulated, open-pollinated flowers setting fruit, comparable with fruit set among selfed hermaphrodite flowers. The breeding strategy of G. wikstroemiana most closely resembles gynodioecy. This is the first report of sexual dimorphism in Gnidia L. and sub-Saharan Thymelaeaceae. © 2006 The Linnean Society of London, Botanical Journal of the Linnean Society, 2006, 152, 219–233.

An Evaluation of Pollination Mechanisms for Purple Prairie-clover, Dalea purpurea (Fabaceae: Amorpheae)

Abstract Purple prairie-clover (Dalea purpurea Ventenat) is a common perennial forb that flowers during mid-summer throughout the Great Plains and adjacent biomes. Seed of D. purpurea is used for prairie restoration. This study characterizes the reproductive biology of D. purpurea. Manual pollination field trials showed that D. purpurea has a mixed pollination system. It is primarily xenogamous (45% of flowers manually pollinated with outcross pollen yielded plump seeds), but partially self-compatible (19% of selfed flowers yielded seeds). Flowers neither visited by bees nor manually pollinated rarely yielded mature seed (0–6% of flowers). A review of extensive bee community surveys from sites with prairie wildflower communities revealed that D. purpurea attracts a rich and diverse native bee fauna. Managed agricultural pollinators (Apis mellifera, Megachile rotundata) also work its flowers for pollen and nectar, yielding >20,000 seeds per plant. These observations bode well both for pollinating D. purpur...

Competition‐dependent incompatibility in Phormium tenax: Does self‐fertilisation provide reproductive assurance?

New Zealand flax (Phormium tenax) has a reproductive system in which the early abscission of selfed flowers is determined by the degree of competition with crossed fruits on the same plant. It has been suggested that this functions as a form of reproductive assurance, allowing for high levels of outcrossing when pollinators are abundant, while ensuring seedset when pollinators are scarce. We performed experimental crosses and mating system estimation in natural populations to determine whether P. tenax can set seed in the absence of pollinators, and how pure and mixed pollen loads influence reproductive success and population‐level selfing rates. Phormium tenax can set seed autonomously, although if other flowers on the plant are available for outcrossing, resources are preferentially allocated to maturing those fruits. Experimental crosses suggest that flowers pollinated with mixtures of selfed and outcrossed pollen can result in fruitset, although fruitset is reduced if flowers pollinated with mixed pollen loads compete with cross‐pollinated flowers. Despite the potential for geitonogamy in P. tenax, outcrossing rates from five populations showed that these populations were universally outcrossing (t = 0.83–1.06). In P. tenax, self‐compatibility in the absence of competition from outcrossed pollen can provide some reproductive assurance, but in large populations, selfing and mixed mating rarely occur.

Effects of self-, chase and mixed self/cross-pollinations on pistil longevity and fruit set in Ceiba species (Bombacaceae) with late-acting self-incompatibility.

Late-acting self-incompatibility (LSI), in which selfed flowers fail to form fruits despite apparently successful growth of the pollen tubes to the ovules, is a contentious and still poorly understood phenomenon. Some studies have indicated pollen tube-pistil interactions, and major gene control. Others favour an early acting inbreeding depression explanation. Experimental pollinations, including selfs (in a subsample of which the style was cut before pollen tubes reached the ovary), chase self/cross-pollinations, crosses, and mixed self/cross-pollinations were used to study floral/pistil longevity and effect on fruit set and seed yield in two Ceiba species known to have LSI. Self-pollinations, including those with a cut style, had extended floral longevity compared with unpollinated flowers. Chase pollinations in which cross-pollen was applied up to 3 h after selfing set fruits, but with reduced seed set compared with crosses. Those with cross-pollen applied at 4 and 8 h after self-pollination all failed to set fruits. Flowers subjected to 1 : 1 and 2 : 1 self/cross-pollinations all produced fruits but again with a significantly lower seed set compared with crosses. Extended floral longevity initiated with self-pollen tubes growing in the style indicates some kind of pollen tube-pistil interaction. Fruit set only in chase pollinations up to 3 h implies that self-pollen tubes either grow more slowly in the style or penetrate ovules more slowly on arrival at the ovary compared with cross-tubes. This agrees with previous observations indicating that the incidence of penetrated ovules is initially lower in selfed compared with crossed pistils. However, the low seed yield from mixed pollinations indicates that self- and cross-pollen tubes arrive at the ovary and penetrate ovules more or less simultaneously. Possible explanations for these discordant results are discussed.

Homomorphic Self‐Incompatibility, with Stylar Rejection Site, in Luehea grandiflora Mart. and Zucc. (Tiliaceae‐Malvaceae s.l.)

Abstract: The breeding system of Luehea grandiflora (Tiliaceae‐Malvaceae s.l.) was investigated using hand pollinations and fluorescence microscopy studies of pollen tube growth. Although selfed flowers persisted for some 10 days, our study indicates that L. grandiflora is self‐incompatible, with self pollen tube inhibition in the upper style, as occurs in many taxa with homomorphic, gametophytic self‐incompatibility (GSI). L. grandiflora is only the second species reported within the Malvales with homomorphic stylar inhibition. This result is discussed within the context of a report for self‐compatibility in this species, and we also consider the phylogenetic implications for the occurrence of GSI in the family Malvaceae s.l.

Conservation implications of the reproductive ecology ofAgalinis acuta(Scrophulariaceae)

Reproductive ecology of Agalinis acuta was investigated by examining potential for self-fertilization before and at anthesis, reproductive output from outcrossed vs. selfed matings, and effects of browsing, plant size, and conspecific plant density on seed and fruit production. These features of a plant species can provide indirect information pertinent to conservation such as patterns and maintenance of genetic diversity, risk associated with inbreeding depression, and changes in pollinator abundance or effectiveness. The species is self-compatible, with 97% of selfed flowers setting fruit; pollinators were not required for reproduction. However, seed set in self-pollinated fruits averaged 17-20% less than that in open-pollinated fruits. Geitonogamous and facilitated selfing are possible throughout anthesis and autonomous selfing is possible late in anthesis as corollas abscise. Delaying self-pollination until after outcrossing opportunities likely limits selfing rates and thus reduces risks associated with inbreeding but allows reproduction in absence of pollinators. Supplementing pollen on open-pollinated flowers yielded no additional seed set over controls. Neither early-season browsing of primary stems nor conspecific plant density had significant effects on number of fruits per plant, on fruit size, or on number of seeds from open-pollinated flowers. Currently, reproduction appears to be high (about 2400 seeds/plant), and future risks due to lack of genetic diversity are likely low.

Differential outcrossing rates in dispersing and non-dispersing achenes in the heterocarpic plant Crepis sancta (Asteraceae)

The association between mating systems and dispersal in plants has been studied mostly in cleistogamous species where, generally, seeds produced by cleistogamous (selfed) flowers are less dispersed than seeds produced by chasmogamous (potentially outcrossed) flowers. In heterocarpic Asteraceae, non-dispersing fruits (achenes) are produced at the periphery of the capitulum (outer florets) whereas dispersing achenes are produced by inner florets in the same capitulum. Since all the florets are protandrous, the outer floret developing first are in female phasis when anthesis of inner florets takes place. Thus, outer florets can be potentially selfed by the inner florets of the same capitulum whereas the latter must be pollinated by flowers of other capitula. Therefore outer florets should be more inbred than inner florets. To test this hypothesis, we measured the natural outcrossing rate in outer and inner florets using allozymes in three populations of the heterocarpic Crepis sancta. The results showed that the outcrossing rate was highest for non-dispersed achenes. Moreover, among the outcrossed achenes within a capitulum it was observed that the number of paternal parents of non-dispersing achenes was higher than for dispersing achenes. The pattern observed was therefore the opposite to the pattern of cleistogamous plants and contradicts the putative pollination mechanism we proposed for Asteraceae. The results agree with the predictions of sib competition theory which considers that outcrossing may minimize competitive interactions among relatives (sibs) falling near the mother plant. Higher outcrossing rate in outer florets could also occur because pollinators are more attracted to these florets.

Postzygotic Control of Selfing inHymenaea stigonocarpa(Leguminosae‐Caesalpinioideae), a Bat‐Pollinated Tree of the Brazilian Cerrados

The pollination biology and breeding system of Hymenaea stigonocarpa, a common tree of the Brazilian cerrados, were investigated. The flowers have nocturnal anthesis, produce copious nectar, and are visited by at least four species of bats, including the specialized nectivorous Glossophaga soricina and the less specialized frugivores Platyrhinus lineatus and Carollia perspicillata. Controlled hand‐pollination results indicate the species is basically allogamous. Almost all selfed flowers abscised within 7–8 d, but rejection was due to a postzygotic mechanism, since self‐pollen tubes grew to the ovary and penetrated ovules with equal facility to cross tubes, and selfed ovules at 5 d contained a zygote with endosperm nuclei. The causes of selfed pistil abscission were not established, but selfed ovules were smaller than crossed ones at every stage over the first 5 d postpollination, indicating an early recognition or differential development of selfed ovules.