Styles Of Flowers Research Articles

Floral morphology and breeding system in Polygonum hastato-sagittatum Mak. (Polygonaceae)

Distyly has been clearly confirmed in Polygonum hastato-sagittatum Mak, which is dimorphic for the intrinsic features of style height, anther height and a suite of ancillary pollen and stigma polymorphisms. The stigma width of long styled flowers is larger than that of short ones, and L-morph (long) stigmas have longer and less number of papillae than the S-morphs (short). Flowers produced significantly smaller pollen grains, but in greater numbers, in L-morph than in S-morph. In P. hastato-sagittatum, style-morph ratios were associated with population size: larger populations always exhibited 1:1 morph ratios, or were slightly L-biased, whereas smaller populations were often strongly L-biased, and only occasionally S-biased. Populations containing only the L-morph were occasionally found, but populations fixed for the S-morph were not observed. The biased style-morph ratios maybe result from morph-specific differences in assortative mating or artificial disturbance. The study supports the theory that evolution of heterostyly reduces the conflict that can occur in sexually monomorphic animal-pollinated species, achieving efficient cross-pollination but simultaneously avoiding self-interference between female and male sexual organs.

Female gamete competition in an ancient angiosperm lineage

In Trimenia moorei, an extant member of the ancient angiosperm clade Austrobaileyales, we found a remarkable pattern of female gametophyte (egg-producing structure) development that strikingly resembles that of pollen tubes and their intrasexual competition within the maternal pollen tube transmitting tissues of most flowers. In contrast with most other flowering plants, in Trimenia, multiple female gametophytes are initiated at the base (chalazal end) of each ovule. Female gametophytes grow from their tips and compete over hundreds of micrometers to reach the apex of the nucellus and the site of fertilization. Here, the successful female gametophyte will mate with a pollen tube to produce an embryo and an endosperm. Moreover, the central tissue within the ovules of Trimenia, through which the embryo sacs grow, contains starch and other carbohydrates similar to the pollen tube transmitting tissues in the styles of most flowers. The pattern of female gametophyte development found in Trimenia is rare but by no means unique in angiosperms. Importantly, it seems that multiple female gametophytes are occasionally or frequently initiated in members of other ancient angiosperm lineages. The intensification of pollen tube (male gametophyte) competition and enhanced maternal selection among competing pollen tubes are considered to have been major contributors to the rise of angiosperms. Based on insights from Trimenia, we posit that prefertilization female gametophyte (egg) competition within individual ovules in addition to male gametophyte (sperm) competition and maternal mate choice may have been key features of the earliest angiosperms.

Stylish lengths: Mate choice in flowers

The styles of flowers may represent an arena for pollen competition in the race to fertilize ovules. Accordingly, selection should favour a longer 'race' to better discriminate among variable pollen by increasing style length. Sampling across a taxonomically diverse range of wild and outcrossed species, we found that the distribution of style lengths within plants were skewed towards longer styles, as predicted. In self-pollinated domesticated species, where discrimination among pollen is less important, we found no such pattern. We conclude that style length is under directional selection towards longer styles as a mechanism for mate choice among pollen of variable quality.

Pollination and reproductive biology of thirteen species of <i>Begonia</i> in the Serra do Mar State Park, São Paulo, Brazil

The reproductive biology of 13 monoecious species of Begonia that occur in the Serra do Mar State Park, São Paulo, Brazil, was investigated. These species flower annually and present flowers with mostly white tepals, sweet odour, pollen as a reward but no nectar, numerous yellow stamens, and yellow styles. Anthesis is diurnal and floral duration is long (6 - 15 days). The unusual appearance of pistillate flowers of these species supports the view that they are intersexual mimics of the staminate flowers. Despite consistently high levels of fruit-set, none of the 11 species tested proved to be apomictic. In contrast to earlier reports of self-compatibility in Begonia, self-pollinations of B. integerrima and B. itatinensis produced no fruits or seeds, and the complete absence of pollen tubes in the styles of self-pollinated flowers of B. integerrima suggests that the species is self-incompatible. Flowers pollinated under natural conditions showed many pollen tubes that reached ovules, suggesting that adequate numbers of compatible pollen grains had been transported by pollinators. The principal pollinators were bees of the Apidae and Halictidae. Ten species of bees were observed to visit eight species of Begonia, and pollen collection occurred by vibration, except for Trigona spinipes. Visits to rewarding staminate flowers were significantly more frequent than visits to unrewarding pistillate flowers. Duration of visits to pistillate flowers also was significantly shorter than the duration of visits to staminate flowers. We conclude that visits to pistillate flowers occur by mistake but with sufficient frequency to allow for successful reproduction in natural populations of these species.

Distinct expression patterns of two Arabidopsis phytocystatin genes, AtCYS1 and AtCYS2, during development and abiotic stresses

The phytocystatins of plants are members of the cystatin superfamily of proteins, which are potent inhibitors of cysteine proteases. The Arabidopsis genome encodes seven phytocystatin isoforms (AtCYSs) in two distantly related AtCYS gene clusters. We selected AtCYS1 and AtCYS2 as representatives for each cluster and then generated transgenic plants expressing the GUS reporter gene under the control of each gene promoter. These plants were used to examine AtCYS expression at various stages of plant development and in response to abiotic stresses. Histochemical analysis of AtCYS1 promoter- and AtCYS2 promoter-GUS transgenic plants revealed that these genes have similar but distinct spatial and temporal expression patterns during normal development. In particular, AtCYS1 was preferentially expressed in the vascular tissue of all organs, whereas AtCYS2 was expressed in trichomes and guard cells in young leaves, caps of roots, and in connecting regions of the immature anthers and filaments and the style and stigma in flowers. In addition, each AtCYS gene has a unique expression profile during abiotic stresses. High temperature and wounding stress enhanced the expression of both AtCYS1 and AtCYS2, but the temporal and spatial patterns of induction differed. From these data, we propose that these two AtCYS genes play important, but distinct, roles in plant development and stress responses.

Functional analysis of a cotton cellulose synthase A4 gene promoter in transgenic tobacco plants

A 1,482-bp promoter sequence of the cotton cellulose synthase gene (GhCesA4) was isolated from Chinese cultivar CRI12 of Gossypium hirsutum, and transcriptionally fused to a beta-glucuronidase (GUS) reporter gene for investigation of important regions controlling gene expression in transgenic tobacco plants. Histochemical staining showed that the full-length promoter directs efficient expression of the reporter gene in the roots, hypocotyls, vascular tissues of stems, trichomes, the central leaf veins, as well as in the anthers and pollen. Quantitative measurements of GUS activity demonstrated that higher expression levels were detected in the stems, fully expanded leaves, and styles of flowers. A series of 5' progressive deletions of the promoter revealed the presence of a negative regulatory region (-767 to -424) for promoter activity and a 247-bp fragment (-247 to -1) with the vascular tissue specificity of the basic transcription activity in the GhCesA4 promoter. Exposure of the transgenic tobacco to various abiotic stresses showed that the full-length construct predominantly responded to NAA, kinetin, and sugar. Furthermore, the NAA-response region was found to be located in the -1,482/-1204 fragment, while the element(s) for the sucrose-responsive expression may be present in the -247/-1 region in the GhCesA4 promoter. These findings will not only contribute to an explanation of the molecular mechanisms by which GhCesA4 participates in secondary cell wall morphogenesis and stress responses, but will also provide a good candidate for expression or accumulation of foreign genes of interest whose products are preferentially required in vascular tissues and are inducible under auxin treatment.

Contribution of small insects to pollination of common buckwheat, a distylous crop

AbstractCrop pollination by animals is an essential ecosystem service. Among animal‐pollinated crops, distylous plants strongly depend on animal pollination. In distylous pollination systems, pollinator species are usually limited, although flowers of some distylous plants are visited by diverse animals. We studied the pollination biology of common buckwheat (Fagopyrum esculentum), a distylous crop mainly pollinated by honeybees and visited by many insect species, to evaluate the effects of non‐honeybee species on pollination services. We focused on insects smaller than honeybees to determine their contribution to pollination. We applied pollination treatments with bags of coarse mesh to exclude flower visits by honeybees and larger insects and compared the seed set of bagged plants with that of untreated plants for pin and thrum flower morphs. We found a great reduction of seed set only in bagged pin flowers. We also confirmed that small insects, including ants, bees, wasps and flies, carried pin‐morph pollen. These small insects transfer pollen from the short anthers of pin flowers to the short styles of thrum flowers, leading to sufficient seed set in thrum flowers. Consequently, small, non‐honeybee insects have the potential to maintain at least half of the yield of this honeybee‐dependent distylous crop.

Molecular Characterization of Lal2, an SRK-Like Gene Linked to the S-Locus in the Wild Mustard Leavenworthia alabamica

Single-locus sporophytic self-incompatibility inhibits inbreeding in many members of the mustard family (Brassicaceae). To investigate the genetics of self-incompatibility in the wild mustard Leavenworthia alabamica, diallel crosses were conducted between full siblings. Patterns of incompatibility were consistent with the action of single-locus sporophytic self-incompatibility. DNA sequences related to S-locus receptor kinase (SRK), the gene involved in self-pollen recognition in mustards, were cloned and sequenced. A single sequence with high identity to SRK and several other groups of sequences (Lal1, Lal2, Lal3, Lal8, and Lal14) were isolated from L. alabamica. We propose that either Lal2 sequences are divergent alleles of SRK or Lal2 is in tight linkage with SRK because (1) Lal2 alleles cosegregate with S-alleles inferred from dialleles in all 97 cases tested in five families; (2) Lal2 sequences are highly diverse at both synonymous and nonsynonymous sites and exhibit patterns of selective constraint similar to those observed at SRK in Brassica and Arabidopsis; and (3) transcripts of one Lal2 allele were detected in leaves and the styles of open flowers, but were most abundant in the stigmas of maturing buds. We discuss the utility of the S-linked polymorphism at Lal2 for studying the evolutionary forces acting on self-incompatibility in Leavenworthia.

Identification of a cluster IV pleiotropic drug resistance transporter gene expressed in the style of Nicotiana plumbaginifolia

ATP-binding cassette transporters of the pleiotropic drug resistance (PDR) subfamily are composed of five clusters. We have cloned a gene, NpPDR2, belonging to the still uncharacterized cluster IV from Nicotiana plumbaginifolia. NpPDR2 transcripts were found in the roots and mature flowers. In the latter, NpPDR2 expression was restricted to the style and only after pollination. A 1.5-kb genomic sequence containing the putative NpPDR2 transcription promoter was fused to the beta-glucuronidase reporter gene. The GUS expression pattern confirmed the RT-PCR results that NpPDR2 was expressed in roots and the flower style and showed that it was localized around the conductive tissues. Unlike other PDR genes, NpPDR2 expression was not induced in leaf tissues by none of the hormones typically involved in biotic and abiotic stress response. Moreover, unlike NpPDR1 known to be involved in biotic stress response, NpPDR2 expression was not induced in the style upon Botrytis cinerea infection. In N. plumbaginifolia plants in which NpPDR2 expression was prevented by RNA interference, no unusual phenotype was observed, including at the flowering stage, which suggests that NpPDR2 is not essential in the reproductive process under the tested conditions.

Detoxification of cyanide by plants and hormone action.

In higher plants cyanide is a co-product of ethylene synthesis. The increase in ethylene production that occurs during the senescence of certain flowers and the ripening of climacteric fruit is accompanied by a rise in beta-cyanoalanine synthase activity. Although these events correlate temporally and spatially, the potential for cyanide detoxification in these tissues is high compared with the expected rate of cyanide formation from the ethylene pathway. However, in stigmas and styles of Petunia flowers a semi-quantitative relationship exists between the activity of beta-cyanoalanine synthase and the activity of ACC (1-aminocyclopropane-1-carboxylic acid) oxidase, the last enzyme in the ethylene pathway. To account for these observations it is proposed that ACC oxidase can react with other amino acids by a general mechanism that liberates cyanide. This hypothesis could also account for the substrate stereospecificity of ACC oxidase, for the extreme lability of this enzyme and for the high accumulation of asparagine in some tissues.

EFFECT OF PLANT DISTANCE ON FLOWER YIELD AND QUALITATIVE AND QUANTITATIVE CHARACTERISTICS OF FORAGE PRODUCTION OF SAFFRON (CROCUS SATIVUS) IN MASHHAD CONDITIONS

EFFECT OF PLANT DISTANCE ON FLOWER YIELD AND QUALITATIVE AND QUANTITATIVE CHARACTERISTICS OF FORAGE PRODUCTION OF SAFFRON (CROCUS SATIVUS) IN MASHHAD CONDITIONS

ATHB23, an Arabidopsis class I homeodomain-leucine zipper gene, is expressed in the adaxial region of young leaves

Homeobox genes are essential regulators of plant development. ATHB23, a class I homeodomain leucine zipper gene of Arabidopsis, was found to be induced by treatment with the phytohormone gibberellin (GA). In order to clarify its role in development, we performed a histochemical analysis of transgenic plants containing a construct with a GUS::GFP reporter under the control of the 1.5 kb upstream region of ATHB23. The construct was mainly expressed in young leaves and the styles of flowers but not in mature leaves. Microscopic examination of young leaves revealed that it was expressed in the adaxial domain of leaf primordia and the rib meristem. Expression of ATHB23, like that of GA5 encoding GA 20-oxidase, was reduced in mutants related to adaxial-abaxial leaf polarity (phb-1d, se-2, and kan1 kan2). Reduced expression of the GUS::GFP reporter gene was also observed in an se-2 background. These results indicate that ATHB23 is under the control of GA and other activators such as PHB, and is involved in establishing polarity during leaf development.

Enantiostyly in angiosperms and its evolutionary significance

Enantiostyly, deflection of style to left or to right side of floral axis, is a kind of style polymorphism. Based on organization of left- and right-styled flowers present on individual plants, enantiostyly can be expressed as two quite distinct forms: monomorphic and dimorphic enantiostyly. In monomorphic enantiostyly, individual plants produce both floral forms, either mixed within an inflorescence or segregated between left- and right-styled inflorescences, and this condition is not a genetic polymorphism. In dimorphic enantiostyly, plants are exclusively left- and right-styled, and this condition is a genetic polymorphism. Based on patterns of arrangement of style and stamens in individual flowers, enantiostyly can be expressed as reciprocal and nonreciprocal enantiostyly. Reciprocal enantiostyly is commonly associated with the reciprocal deflection of a pollinating anther, but in nonreciprocal enantiostyly there are no pollinating anther deflections. Enantiostyly has been reported in 11 families of angiosperm. It is generally considered to play an important role in (1) protecting the functional pistil and stamens, (2) insuring reproduction by selfing, and (3) increasing male fitness and outcrossing rates by reducing sexual interference between female and male function. Enantiostyly has been hotly-debated in plant reproductive biology. The purpose of this paper is to review and analyze recent advances in enantiostyly research, with emphases on 1) types of enantiostyly and morphological differentiation and floral characteristics of mirror-image flowers; 2) taxonomy, genetics and evolution of angiosperms that exhibit enantiostyly; and 3) the evolutionary biology of mating patterns and pollinating characteristics associated with enantiostyly. Finally, prospects for further research in this area are discussed. Our review provides a database for further study of the evolutionary biology of enantiostylous species and points out the significance of enantiostyly in the evolution of breeding systems of plants.

Scale‐Dependent Effects of Habitat Fragmentation on Hawthorn Pollination, Frugivory, and Seed Predation

Habitat fragmentation is a major cause of functional disruption in plant-animal interactions. The net effect on plant regeneration is, however, controversial because a given landscape change can simultaneously hamper mutualism and attenuate antagonism. Furthermore, fragmentation effects may emerge at different spatial scales, depending on the size of the foraging range of the different interacting animals. We studied pollination by insects, frugivory by birds acting as seed dispersers, and postdispersal seed predation by rodents in 60 individual hawthorn (Crataegus monogyna Jacq.) trees in relation to structural fragmentation in the surrounding habitat. We evaluated fragmentation at three spatial scales by measuring the percentage of forest cover in three concentric areas around each tree of, respectively, 10-m, 20- to 50-m, and 50- to 100-m radius. The number of developing pollen tubes per flower style and fruit set decreased in proportion to the decrease of forest cover. Similarly, the magnitude of frugivory in focal trees was negatively affected by habitat loss. In contrast, seed predation was higher under plants in highly fragmented contexts. The effect of fragmentation was additive in terms of reducing the potential of plant regeneration. Moreover, the functional scale of response to habitat loss differed among interactions. Fragmentation effects on pollination emerged at the largest scale, whereas seed predation was mostly affected at the intermediate scale. In contrast to expectations from the larger foraging range of birds, fragmentation effects on frugivory mainly operated at the finest scale, favored by the ability of birds to cope hierarchically with spatial heterogeneity at different scales. Given that two opposing demographic forces (frugivory and seed predation) would be potentially affected by fine-scale features, we propose structural scale as the primary spatial dimension of fragmentation effects on the process of plant regeneration.

Floral Anatomy of Paepalanthoideae (Eriocaulaceae, Poales) and their Nectariferous Structures

Eriocaulaceae (Poales) is currently divided in two subfamilies: Eriocauloideae, which comprises two genera and Paepalanthoideae, with nine genera. The floral anatomy of Actinocephalus polyanthus, Leiothrix fluitans, Paepalanthus chlorocephalus, P. flaccidus and Rondonanthus roraimae was studied here. The flowers of these species of Paepalanthoideae are unisexual, and form capitulum-type inflorescences. Staminate and pistillate flowers are randomly distributed in the capitulum and develop centripetally. This work aims to establish a floral nomenclature for the Eriocaulaceae to provide more information about the taxonomy and phylogeny of the family. Light microscopy, scanning electron microscopy and chemical tests were used to investigate the floral structures. Staminate and pistillate flowers are trimerous (except in P. flaccidus, which presents dimerous flowers), and the perianth of all species is differentiated into sepals and petals. Staminate flowers present an androecium with scale-like staminodes (not in R. roraimae) and fertile stamens, and nectariferous pistillodes. Pistillate flowers present scale-like staminodes (except for R. roraimae, which presents elongated and vascularized staminodes), and a gynoecium with a hollow style, ramified in stigmatic and nectariferous portions. The scale-like staminodes present in the species of Paepalanthoideae indicate a probable reduction of the outer whorl of stamens present in species of Eriocauloideae. Among the Paepalanthoideae genera, Rondonanthus, which is probably basal, shows vascularized staminodes in their pistillate flowers. The occurrence of nectariferous pistillodes in staminate flowers and that of nectariferous portions of the style in pistillate flowers of Paepalanthoideae are emphasized as nectariferous structures in Eriocaulaceae.

Estrutura sexual e ecologia reprodutiva de Amaioua guianensis Aubl. (Rubiaceae), uma espécie dióica de formações florestais de cerrado

The breeding biology of Amaioua guianensis was studied in a forest area at Parque do Sabia in Uberlândia, MG, Brazil, between September 2003 and April 2005. Phenology, breeding system, flower morphology, pollinator and disperser's assemblages, and sexual structure of the reproductive individuals were investigated. Amaioua guianensis is a woody dioecious species common in Brazilian forest areas. Flowers are hexamerous, tubular, whitish and odoriferous, pollinated by relatively specialized vectors as large bees and hawkmoths. Pistilate flowers produced nectar earlier and in larger amounts than the staminate ones. Staminate flowers were produced in larger numbers per inflorescence and were significantly larger than the pistilate ones. Flowers were presented in terminal inflorescences, composite umbels in the staminate and simple ones in pistilate individuals. Both male and female flowers produced non-functional sexual structures of the opposite morph, but the style of male flowers act as a pseudo-stamen, a secondary pollen presentation mechanism which is common in the tribe Gardenieae but had not been described previously to the species. Sexual ratio was significantly male biased and gender was distributed contagiously in the area, probably due in both cases to vegetative multiplication and disturbance. Natural pollination was as high as 98.6% and fruit set was 75.7%. Apomictic fruit production was very low (3.4%). Fruits were dispersed by birds. Floral morphology and relatively specialized pollinator's fauna rendered efficient pollination service and fruit production in the species even in the relatively disturbed study area.

Gynodioecy in native New Zealand Gaultheria (Ericaceae)

The breeding systems of Gaultheria native to New Zealand were investigated. Gaultheria antipoda and G. depressa var. depressa populations contained only hermaphrodites. Populations of five other taxa were found to be gynodioecious in natural populations, with 4–67% females, and evidence from the literature and herbarium sheets suggests that an additional five taxa are gynodioecious. Comparisons of flower parts, flower number, and fruit set of females and hermaphrodites in three taxa revealed few significant differences. Corollas of G. paniculata were smaller in females, but style length and flower number per raceme were not significantly different between the two sexes. Flower number per raceme and fruit set also did not differ significantly between females and hermaphrodites of G. crassa and G. oppositifolia. The similarities in fruit set between the sexes (always within 5% of each other within populations), combined with high female frequencies, suggest that male sterility is caused by cytoplasmic factors. Gynodioecy is widespread but not ubiquitous in New Zealand Gaultheria.

Influence of Reproductive Impairment of Most Developed Flowers on Fruit Set and Fruit Quality in Pear

The lowest flower in the pear (Pyrus communis L.) cluster usually develops and blooms first and also has a greater sink potential. For this reason, resources are preferentially utilized by the lowest fruit, and this is also one of the reasons why most thinning practices tend to favor their set. However, it is not always possible to perform selective thinning. This study was undertaken to determine if hindering pollination in the most developed flowers in the cluster influences yield or quality compared to that obtained in a whole open-pollinated cluster. The treatments were made in `Blanquilla' (Spadona, Agua de Aranjuez) and `Conference' pear within a wide range of flower densities for each cultivar. Pollination was hindered by cutting off the flower styles. The factor tested was style removal intensity (SRI). Treatments consisted in removing the styles of two, four(always the most developed), or all flowers in each cluster. Flower density was used as a covariate in an analysis of covariance to account for differences in flower densities in response to SRI treatments. In all experiments the covariate was not significant; therefore, SRI effect was not affected by flower density. `Blanquilla' and `Conference' had similar responses to treatments, so that when at least three flowers are susceptible to be openly pollinated, fruit set, seed content, and cluster yield were similar to control clusters, therefore the growth potential of fruit from partially damaged clusters in their most developed flowers is similar to undamaged open pollinated clusters. The reduced set of parthenocarpic clusters implies yield reductions ranging between 40% and 60% in `Conference', and up to about 60% in `Blanquilla'.

Effects of putrescine application on fruit set in ‘Housui’ Japanese pear ( Pyrus pyrifolia Nakai)

In Japan, artificial pollination is practiced to improve fruit set as well as fruit size and to obtain perfect round shapes in ‘Housui’ (S 3S 5) Japanese pear and most commercial cultivars that present gametophytic self-incompatibility. The period of artificial pollination application is limited by environmental conditions and the availability of a labor force. The present study aimed to determine if pre-pollination applications of putrescine (1.0 and 0.01 mM) positively affect fruit set in ‘Housui’ after hand-pollination. During 2002 and 2003, fruit set in late pollinated flowers increased with pre-pollination putrescine applications and concentrations of 1.0 mM had a better effect than 0.01 mM. In vitro pollination tests revealed that higher pollen germination was present in the stigmas of flowers sprayed with 1.0 mM of putrescine compared to the controls. Putrescine application did not affect post-pollination ethylene production in the styles. Moreover, in the styles of non-treated flowers, an increment of putrescine content and ethylene production after pollination was found, suggesting post-pollination responses and confirming the lack of antagonism between polyamines and ethylene at least during this process.

Preferential outcrossing in Banksia ilicifolia (Proteaceae)

The breeding system of Banksia ilicifolia was assessed by performing controlled hand-pollination manipulations on flowers in a natural population in Perth, Western Australia. The percentage of 2000 flowers per treatment converted to fruits and seeds was assessed across 24 recipient plants following (1) self-pollination, (2) local outcross pollination (same population), (3) non-local outcross pollination (pollen sourced from another population 30 km away), (4) unpollinated but bagged flowers and (5) unpollinated, unbagged flowers (natural pollination). The relative performance of the resulting seeds was assessed by seed weight, germination rates and, in an unplanned component of the study, resistance to a fungal pathogen. The percentage of flowers converted to fruits following self-pollination was low (0.9%), but demonstrated self-compatibility. Fruit set following cross-pollinations (3.6 and 3.3% for non-local and local crosses, respectively) was significantly greater than that following self-pollination, open-pollination (0.4%) and autogamous (0.04%) treatments. Low fruit set for open-pollinated flowers, compared with self- and outcross-pollination treatments, suggests pollen limitation. Pollen tubes were observed in 15 and 20% of upper styles of flowers hand-pollinated with self and local outcross pollen, respectively. Seed germination was dependent on the source of pollen, where fewer selfed seeds germinated (37%) than did both non-local and local outcrossed seeds (83 and 91%, respectively). Selfed seedlings showed poorer survival (33.3%) following fungal attack than both non-local and local outcrossed seeds (69.2 and 68.5%, respectively). Only 13% of selfed seeds survived to be 2-month-old seedlings, compared with 63% for non-local and 57% for local outcrossed seeds. Ultimately, for 2000 flowers hand-pollinated with self pollen, only three seedlings survived to an age of 16 weeks, compared with 37 and 45 seedlings for local-cross and non-local cross treatments on 2000 hand-pollinated flowers, respectively. These results indicate that in this population, B. ilicifolia is self-compatible, but preferentially outcrossing, with strong early acting inbreeding depression. Consequently, the breeding system of B. ilicifolia promotes the maintenance of genetic variation and a high genetic load.