Cleistogamy as a bet‐hedging strategy in Oxalis acetosella, a perennial herb

1 Phenology and reproduction were studied in three populations of the cleistogamous herb Oxalis acetosella during three growing seasons, in order to see how the balance between chasmogamous (CH) and cleistogamous (CL) reproduction varies with temporal and spatial environmental variation and with plant size. The numbers of CH and CL flower buds, flowers, immature capsules and mature capsules were counted per ramet, ramet sizes were estimated, and mature capsules were collected for seed counts.
2 Both CH and CL flower numbers were positively correlated with ramet size expressed as leaf number, but the correlation was much stronger in the CL phase. CL flower production also varied significantly between years and sites. Thus, CL production in O. acetosella was not independent of resources and climatic variation.
3 When the effects of year and site were taken into account, the probability of an individual flower developing into a mature fruit was not higher in the CL phase than in the CH phase.
4 CL production was affected by fertilization success in the CH phase. Ramets with one or more CH flowers left unfertilized generally produced more CL buds than ramets with all their CH flowers fertilized. The former group also tended to have more seeds per CL capsule.
5 Since reproductive success in the two phases varies in different temporal and spatial patterns, cleistogamy in O. acetosella is considered to be a bet‐hedging strategy optimizing reproductive output in fluctuating environments.
6 The findings of this study are in conflict with the general view on cleistogamy as a fail‐safe mechanism for back‐up seed production, unaffected by variations in resource supply and environmental conditions.     

The maintenance of mixed mating by cleistogamy in the perennial violet Viola septemloba (Violaceae)

The production of both potentially outcrossed (chasmogamous) and obligately self-fertilized (cleistogamous) flowers presents a clear exception to the prediction that the only evolutionarily stable mating systems are complete selfing and complete outcrossing. Although cleistogamy has evolved repeatedly, the reason for its stability is not known for any species. We tested the hypothesis that the production of cleistogamous and chasmogamous flowers by a perennial violet constitutes adaptive phenotypic plasticity. We manipulated the season of flowering for each flower type and determined fruit set and the germination percentage of seeds produced by cleistogamous and chasmogamous flowers to test the hypothesis that adaptive plastic response to seasonal environmental variation makes mixed mating stable. Cleistogamous flowers had greater fruit set in all seasons and produced seeds with germination percentages as great as or greater than those from chasmogamous flowers. The consistent advantage of cleistogamous flowers is clearly not consistent with a role of adaptive plastic response to seasonal variation. The biomass cost of seed production by chasmogamous flowers was nearly three times that for cleistogamous flowers. Explaining why chasmogamous flower have not been eliminated by natural selection requires that this difference be balanced by an advantage to chasmogamous flowers that has not yet been identified.     

Cleistogamy: A tool for the study of floral morphogenesis,function and evolution

Cleistogamy—the production of open (chasmogamous—CH) and closed (cleistogamous—CL) floral forms by a species—is widespread among the angiosperms. While the CL flower is autogamous, the CH flower may provide a means for outcrossing. The term “cleistogamy” has also been used to describe other phenomena. A classification of types of cleistogamy is proposed. In this review, a restricted definition of cleistogamy is used to refer to species which show real floral dimorphisms, with divergent developmental pathways leading to CL and CH as well as intermediate floral forms. Reductions in the androecium and corolla are the most common feature of the CL flowers. The structural, developmental, and functional aspects of cleistogamy are reviewed. Evidence is presented to show that the CL flowers have modifications in their development which ensure self pollination. A proposal is made for using this phenomenon of dimorphic flower production as a system for the study of floral morphogenesis, function and evolution.     

The Effect of Pollen Source vs. Flower Type on Progeny Performance and Seed Predation under Contrasting Light Environments in a Cleistogamous Herb

Dimorphic cleistogamy is a specialized form of mixed mating system where a single plant produces both open, potentially outcrossed chasmogamous (CH) and closed, obligately self-pollinated cleistogamous (CL) flowers. Typically, CH flowers and seeds are bigger and energetically more costly than those of CL. Although the effects of inbreeding and floral dimorphism are critical to understanding the evolution and maintenance of cleistogamy, these effects have been repeatedly confounded. In an attempt to separate these effects, we compared the performance of progeny derived from the two floral morphs while controlling for the source of pollen. That is, flower type and pollen source effects were assessed by comparing the performance of progeny derived from selfed CH vs. CL and outcrossed CH vs. selfed CH flowers, respectively. The experiment was carried out with the herb Ruellia nudiflora under two contrasting light environments. Outcrossed progeny generally performed better than selfed progeny. However, inbreeding depression ranges from low (1%) to moderate (36%), with the greatest value detected under shaded conditions when cumulative fitness was used. Although flower type generally had less of an effect on progeny performance than pollen source did, the progeny derived from selfed CH flowers largely outperformed the progeny from CL flowers, but only under shaded conditions and when cumulative fitness was taken into account. On the other hand, the source of pollen and flower type influenced seed predation, with selfed CH progeny the most heavily attacked by predators. Therefore, the effects of pollen source and flower type are environment-dependant and seed predators may increase the genetic differences between progeny derived from CH and CL flowers. Inbreeding depression alone cannot account for the maintenance of a mixed mating system in R. nudiflora and other unidentified mechanisms must thus be involved.     

Reproductive investment in a cleistogamous morph of <Emphasis Type="Italic">Polygonum jucundum</Emphasis> (Polygonaceae)

Cleistogamy, a breeding system with permanently closed and self-pollinated flowers, is expected to assure reproductive success at a lower cost. Previous studies have inferred the occurrence of cleistogamous flowers in Polygonum, but there are no detailed studies on their reproductive investment compared with that of the chasmogamous flowers in this genus. Here, we studied a cleistogamous morph of P. jucundum to investigate the investment in pollen number, tepal and nectary size. The number of pollen grains per flower was counted with a light microscope. Nectaries and perianths were observed via scanning electron microscope and light microscopy, photographed and measured via ImageJ. The perianths of the cleistogamous flowers, as well as the pollen numbers and nectary sizes, were significantly smaller than those of the chasmogamous flowers. The pollen numbers of the CL flowers were seven times lower than those in the CH flowers. The tepal areas of the CL flowers were, on average, approximately 38% those of the CH flowers. The nectary areas of the CH flowers were almost twice those of the CL flowers. In addition, the nectaries of the cleistogamous flowers were degenerated and inconspicuous, in distinct contrast with the well-developed and conspicuous nectaries of the chasmogamous flowers. Self-fertilization was completed and produced seeds. The cleistogamous P. jucundum, compared with chasmogamous individuals, exhibited lower costs in male function, pollinator attraction and reward structure investment. This cleistogamy appears to be favourable for the plant reproduction under suboptimal conditions.     

Is plasticity across seasons adaptive in the annual cleistogamous plant Lamium amplexicaule?

Background and aims Many angiosperms exhibit cleistogamy, the production of both cleistogamous flowers (CL), which remain closed and obligately self-pollinated, and chasmogamous flowers (CH), which are potentially open-pollinated. The CH proportion can be plastic. Plasticity is adaptive if environmental changes can be reliably assessed and responded to with an appropriate phenotype and if plastic genotypes have higher fitness in variable environments than non-plastic ones.Methods We studied the plastic response of four natural populations from northern and southern France of an annual cleistogamous plant, Lamium amplexicaule, to predictable seasonal variation. Plants were grown in a semi-controlled environment in spring and in autumn. We assessed the variation in flower number, phenology and cleistogamy-related traits, which were all plastic with respect to season. The CH proportion was higher in spring than in autumn in all four populations.Key Results We showed significant stabilizing selection for cleistogamy traits, with higher optimal CH proportions and more pronounced stabilizing selection in spring than in autumn. Observed CH proportions were close to the predicted optimal CH proportions in each season except in autumn for southern populations, which do not experience the autumnal growing season in nature.Conclusions These results are consistent with adaptive plasticity across seasons of cleistogamy in L. amplexicaule. We propose that adaptive plasticity of cleistogamy could be driven by pollination environment variation, with CL flowers providing reproductive assurance when pollinators are scarce and CH flowers reducing the inbreeding depression in offspring when pollinators are abundant.     

Cleistogamy in the rare high Andean perennial herb Cryptantha capituliflora (Boraginaceae)

 Axial and apical flowers of Cryptantha capituliflora were analyzed with regard to morphology and pollen tube growth to assess the occurrence of cleistogamy. Although intermediate floral forms do occur, cleistogamous flowers were significantly smaller than chasmogamous flowers, had fewer anthers, and showed a distinctive stigmatic surface. Chasmogamous flowers can be cross-pollinated. Nevertheless, the growth of self-pollen tubes in few chasmogamous buds jointly with flower characters suggests that these flowers can probably produce fruits through autonomous selfing. The mean seed number per fruit did not differ between fruits from chasmogamous and cleistogamous flowers. Cleistogamous flowers were only observed in axial inflorescences, which are completely covered by the leaf. Other species of section Cryptantha also show the same trend, with cleistogamous flowers located in the lower half of the stems. This pattern is discussed in relation to dissimilarities in the outcrossing opportunities between flower types within the plant. Received May 22, 2002; accepted November 14, 2002 Published online: March 20, 2003     

Failure of reproductive assurance in the chasmogamous flowers of Polygala lewtonii (Polygalaceae), an endangered sandhill herb

Hypothetically, a species with both cleistogamous (CL) flowers and delayed selfing chasmogamous (CH) flowers should display high levels of reproductive assurance because, over time, obligate selfing by CL flowers should reduce inbreeding depression and delayed selfing in CH flowers should compensate for the absence of outcross pollen. We used pollinator-exclusion experiments to investigate reproductive assurance in the CH flowers of Polygala lewtonii, an herb with a mixed mating system. We followed CH flowers from bud-break to flower/fruit abscission to quantify fruit initiation and maturation and rates of floral development. We also evaluated the efficacy of the selfing mechanism, conducted pollinator watches to assess the likelihood of pollinator limitation, and performed regression analysis to determine the effect of flower position on fruit production. Pollinator exclusion significantly reduced fruit initiation and maturation. Investigation of floral development demonstrated that the selfing mechanism is largely dysfunctional in CH flowers, indicating the failure of reproductive assurance. Low observed rates of insect visitation appear to contradict high rates of CH fruit production in open-pollinated plants, particularly given the rarity of delayed selfing. In both treatments, flower position significantly affected fruit initiation, suggesting a role for resource limitation in both pollinator-excluded and open-pollinated flowers.     

Why is cleistogamy a selected reproductive strategy in Impatiens capensis (Balsaminaceae)?

Cleistogamy (self-fertilization in closed flowers) differs from chasmogamy (open-pollinated fertilization) mainly in sustaining selfing. Why numerous species develop both of the reproductive modes on the same individuals has long puzzled biologists. In a novel hypothesis presented here, I propose that cleistogamy could be a means by which inbred lines are created and maintained in natural populations; these lines would continuously experience self-improvement via natural selection and via crosses among lines at the chasmogamous flowers to benefit the populations. Supporting evidence for the hypothesis was found in Impatiens capensis where cleistogamous ovules were fertilized proportionately less (56%) than chasmogamous ovules (67%) in natural populations, but crosses among cleistogamous progeny in the greenhouse led to a nearly 10% increase of fertilized chasmogamous ovules. I established a novel fitness model specific to the cleistogamous species to further examine how various aspects of the mating system affect plant performance. A low inbreeding depression (0.07) was consequently found for the surveyed natural populations of I. capensis , suggesting that the individual-level percentage of cleistogamy and the population-level selfing rate may have evolved in the direction of reducing the overall inbreeding depression. © 2002 The Linnean Society of London, Biological Journal of the Linnean Society , 2002, 75 , 543–553.     

Analysis of mating system and genetic structure in the endangered,amphicarpic plant,Lewton’s polygala (<Emphasis Type="Italic">Polygala lewtonii)</Emphasis>

Polygala lewtonii is a federally endangered, amphicarpic plant with a mixed mating system and three types of flowers: (1) aboveground, chasmogamous flowers (i.e., open-pollinated; CH), (2) aboveground, cleistogamous flowers (i.e., closed, selfing; CL) and (3) CL flowers on belowground stems (amphicarpy). Aboveground seeds are ant-dispersed, whereas belowground seeds are spaced across the length of the rhizome. Here, we collected individuals of P. lewtonii at both range-wide and fine geographic scales and genotyped them at 11 microsatellite loci. We analyzed patterns of genetic diversity and structure to understand: (1) the predominant mating system (selfing or outcrossing), (2) the movement of pollen and seeds across the landscape, and (3) the optimal strategy to conserve the full range of genetic variation. P. lewtonii reproduces predominantly by selfing or bi-parental inbreeding, but reproduction occurred through each of the three flower types. Some individuals produced by selfing/inbreeding were tightly clustered spatially, and were likely produced either by belowground flowers or by aboveground flowers with limited seed dispersal. Other selfed/inbred individuals were spatially separated (maximum of 15 m), and were likely produced by aboveground flowers followed by seed dispersal by ants. Fine-scale patterns of genetic structure indicate that some gene flow is occurring among aboveground CH flowers but both pollen and outcrossed seeds are moving limited distances (maximum of 0.5 km). Because genetic variation is structured at a fine spatial scale, protecting many populations is necessary to fully conserve the genetic variation in P. lewtonii. Conservation seed banking, if accompanied by research on seed germination requirements, may also contribute to the effective protection of genetic variation in P. lewtonii.     

The selection of cleistogamy and heteromorphic diaspores

Models for the evolution of a mixture of cleistogamous (closed, autogamous) flowers and chasmogamous (open) flowers are described. The 'basic' model takes into account features associated with cleistogamous self-pollination, including the greater economy and certainty of cleistogamous fertilization and the inability of cleistogamous flowers to contribute pollen to the outcrossed pollen pool. Complete cleistogamous selfing is favoured when allocation to maternal function, fertilization rate, and viability of progeny are sufficiently greater for the cleistogamous component, and when the resources spent on ancillary structures in cleistogamous flowers, cleistogamous seed costs, and inbreeding depression are low. The result is discussed with respect to the cost of sex argument and relevant ecological data. Suggestions for the apparent rarity of cleistogamy are presented. The 'complex habitat' model extends the basic model to situations in which the success of reproduction by cleistogamy or chasmogamy varies according to the environment of the parent. In this situation, reproduction by both cleistogamy and chasomogamy is sometimes selected. A 'near and far dispersal' model addresses the question of the evolution of dual modes of dispersal, which occur in some cleistogamous and non-cleistogamous plants. A dual mode of dispersal may evolve if a narrowly dispersed seed type is more successful in establishing at the sites located within its dispersal range compared with a second, more widely dispersed seed type which experiences less sib competition. The prediction is discussed with respect to data from amphicarpic plants.     

CLEISTOGAMY IN MICROLAENA POLYNODA (GRAMINEAE): AN EXAMINATION OF SOME MODEL PREDICTIONS

A population of the cleistogamous grass, Microlaena polynoda, was investigated to determine some of the factors responsible for adjusting the balance between reproduction by chasmogamous (CH) and cleistogamous (CL) flowers, the tissue costs associated with the two reproductive modes, the fate of progeny produced by each mode, and the genetic diversity of the progeny. Cleistogamous flower production begins earlier in the season than CH flower production. There is a distinct threshold of low light intensity below which mostly CL flowers are produced. Paternal expenditure per plant is an order of magnitude larger for the CH than the CL component. The opposite relation holds for maternal expenditure. Increased maternal expenditure in the CL component may be due to greater fertilization success and retrieval of paternal costs. Cleistogamous seeds are dispersed later than CH seeds. Following dispersal, the spikelet encloses the CL seed but not the CH seed, and is responsible for inducing dormancy. The ratio of seedlings arising from CH seeds to that from CL seeds in a natural habitat is significantly lower than the ratio of estimated numbers of CH to CL seeds produced. There were no detectable polymorphisms among ten presumptive enzyme loci assayed. Many of the features associated with CH and CL reproduction in M. polynoda are in accord with the theoretical requirements for the evolution of closed flower self-pollination and the maintenance of two distinct methods of reproduction.     

SPATIAL AND TEMPORAL VARIATION IN CHASMOGAMY AND CLEISTOGAMY IN OXALIS MONTANA (OXALIDACEAE)

Chasmogamous (CH) and cleistogamous (CL) flower production was investigated in natural populations of the perennial herb Oxalis montana in southern Quebec, Canada. Every 10–12 days during two flowering seasons, we recorded the reproductive output of approximately 2,000 plants distributed among five forest sites. The percentage of plants flowering, proportion of flowering plants producing CH and CL flowers, CH and CL flower number per flowering plant, and the proportion of flowers that are CL differed significantly among sites and corresponded to site differences in forest type and habitat quality. Unlike patterns in most CL species, however, reproduction by cleistogamy increased in sites with habitat conditions favorable to plant growth and sexual reproduction, and decreased in less productive sites. Chasmogamous and CL flower production increased with increasing plant size but plant size explained a significantly greater proportion of the variation in CL flower numbers. The percentage of flowering plants producing CH flowers decreased between years while the proportion of CL flowers increased at all sites during the second flowering season. The somewhat unusual aspects of reproduction in Oxalis may stem from its perennial habit which allows use of stored resources in adjusting the balance of cleistogamy versus chasmogamy in different environmental regimes.     

Genetic and linkage analysis of cleistogamy in soybean

Early maturing cultivars of soybean [Glycine max (L.) Merr.] native to the shores of the Sea of Okhotsk (Sakhalin and Kuril Islands) and eastern Hokkaido (northern Japan) have been used in breeding for chilling tolerance. These cultivars have a strong tendency to produce cleistogamous flowers throughout their blooming period. This study was conducted to determine the genetic basis of cleistogamy in an early maturing cultivar, Karafuto-1, introduced from Sakhalin. Genetic analysis was performed using F1 plants, the F2 population, and 50 F3 families produced by crossing between Karafuto-1 and a chasmogamous cultivar, Toyosuzu. F2 plants had chasmogamous flowers, indicating that chasmogamy was dominant to cleistogamy. Analysis of F2 populations and F3 families generated segregation data that was close to a two-gene model with epistatic interactions, although a portion of the pooled F3 data on the frequency of chasmogamous segregants from cleistogamous families significantly deviated from the model. The results suggested that a minimum of two genes with epistatic effects were involved in the genetic control of cleistogamy. Furthermore, cleistogamy was associated with early flowering in the F2 and F3 populations. A gene for cleistogamy was linked to one of the recessive genes responsible for insensitivity to incandescent long daylength.     

Differential seed dispersal in Oxalis acetosella,a cleistogamous perennial herb

Explosive seed dispersal in the cleistogamous perennial forest herb Oxalis acetosella was studied during two growing seasons, to determine whether seeds derived from chasmogamous (CH) and cleistogamous (CL) flowers differ in dispersal distance. Seed dispersal distance, seed weight, and height of fruits were measured for both flower types, and the effects of phenology and year were also taken into account. The dispersal experiment was performed indoors, using plants transplanted from natural populations to pots. CL seeds were thrown significantly further than were CH seeds, though there was a considerable overlap in dispersal distances. There was also a significant positive relationship between seed weight and dispersal distance. No relationship was found between fruit height and dispersal distance. The results of this study contradict the common view that CL progeny should always be dispersed closer to the mother plant than CH progeny. The ecological implications of the dispersal difference are unclear, especially since it is uncertain whether CH seeds are generally outcrossed or not. Variation in dispersal distance in O. acetosella seems to be mainly dependent on a combination of reproductive mode and variation in seed weight.     

VARIATION IN THE DEGREE OF CLEISTOGAMY WITHIN AND AMONG SPECIES OF THE GRASS DANTHONIA

North American species of the grass Danthonia bear distinct chasmogamous and cleistogamous flowers. Four taxa occurring in North Carolina (D. compressa, D. epilis, D. sericea, and D. spicata) were examined for variation in the degree of cleistogamy. The flowering culms bear a single terminal panicle consisting of 4 to 12 spikelets of chasmogamous flowers. In each leaf axil, at the nodes of the flowering culm, is a single spikelet of cleistogamous flowers completely surrounded by the leaf sheath. The percentage of cleistogamous flowers produced on any culm depends on the number of chasmogamous and cleistogamous spikelets and the number of flowers in each type of spikelet. All four characters vary among the taxa examined. Danthonia compressa produces, on the average, 50% cleistogamous flowers; D. spicata, 25% cleistogamous flowers; D. sericea and D. epilis, 5% cleistogamous flowers. The degree of cleistogamy in D. spicata is associated with certain habitat features. Populations from mountain sites, disturbed sites, and non-woodland sites produced higher percentages of cleistogamous flowers than did populations from piedmont, undisturbed, and woodland sites, respectively. Grazing may favor increased cleistogamy because cleistogamous flowers are produced lower on the plant. In North Carolina, the most frequently grazed Danthonia taxa also produce the highest percentage of cleistogamous flowers.     

CHASMOGAMY/CLEISTOGAMY IN TRIODANIS PERFOLIATA (CAMPANULACEAE): SOME CH/CL COMPARISONS IN FITNESS PARAMETERS

The chasmogamous/cleistogamous (CH/CL) breeding system has evolved independently many times, but its ecological role has been studied in few species. In Triodanis perfoliata, we studied the natural phenology of flowering and seed set, how successful CH flowers were at setting seed, whether seed from CH and CL flowers differed in germination behavior, and whether plants derived from these two seed types differed in vigor. Most notably, we found that the later the CH flowers were produced, the fewer seed they successfully matured. In general the two seed types did not show differences in germination behavior, but for some maternal parents the two seed types differed. For these, the CL seed germinated less readily. Finally, there was some indication that plants from CL seed were not as vigorous as those from CH seed.     

Reproductive ecology of Viola mirabilis var. subglabra representing intermediate flowering characteristics between stemless and stemmed Viola

Viola (Violaceae) is one of the largest genera in angiosperms. This genus is essentially classified into stemless and stemmed groups based on growth morphology. However, Viola mirabilis var. subglabra is an exception in having intermediate flowering characteristics; cleistogamous (CL) flowers are formed in the axils of stem leaves, whereas chasmogamous (CH) flowers arise from basal rosettes (radical CH (CH(r)) flowers) and also in the axils of the stem (axially CH (CH(a)) flowers). To understand why the pattern of flower production varies in this Viola species, flower production was investigated in 10 Japanese populations from Hokkaido to the western part of Honshu in 2014 and 2015. Furthermore, flower characteristics were also compared between CH(r) and CH(a) flowers in Hokkaido. In this species, the production of CH flowers varied among individuals, and they were categorized into three groups, individuals that produced (i) only CH(r) flowers, (ii) only CH(a) flowers and (iii) both CH flowers. The frequency of these groups differed among populations, but some individuals changed the category between 2014 and 2015. Thus, the production of CH(r) and CH(a) flowers plastically changes depending on individual conditions and/or environmental factors. On the other hand, CH(r) and CH(a) flowers differed in flower size and flowering phenology. These results suggest that two types of CH flowers may play different roles in reproduction in each population, but fruit sets and seed sets did not differ between two types of CH flowers.     

Effects of light and nutrient availability on chasmogamy and cleistogamy in an understory tropical herb,Calathea micans (Marantaceae)

The effects of light and nutrient availability on chasmogamous and cleistogamous flower and fruit production were investigated in an understory tropical herb, Calathea micans (Marantaceae). I censused chasmogamous and cleistogamous flower and fruit production at five permanently marked demographic study sites in Costa Rica, characterized by different successional stages. Using a transplant experiment, I examined whether an increase in light and/or nutrients would increase chasmogamous and/or cleistogamous flower production. In natural populations as well as in the experiment, chasmogamous reproduction increased with light; nutrient availability significantly increased chasmogamous reproduction in the transplant experiment. Field observations indicated that very few plants reproduced and low investment in reproduction might have been due to poor environmental conditions. Larger plants had a higher probability of reproducing, but plant size did not have an effect on the mode of reproduction, chasmogamy vs. cleistogamy. However, the production of new vegetative shoots increased the probability of producing chasmogamous inflorescences. Cleistogamy may allow the plant to reproduce even in conditions of poor habitat quality and assures some seed set even in conditions unfavorable to plant growth.     

GENETIC CONSEQUENCES OF OUTCROSSING IN THE CLEISTOGAMOUS ANNUAL,IMPATIENS CAPENSIS. II. OUTCROSSING RATES AND GENOTYPIC CORRELATIONS

The genetic consequences of a plant's mating system depend on both the degree of outcrossing and the genetic relationship between mates. We examined the electrophoretic genotypes of seeds derived from cleistogamous (CL) and chasmogamous (CH) flowers in six populations of the facultatively cleistogamous annual, Impatiens capensis. Multilocus estimates of the outcrossing rates for the strongly protandrous CH flowers ranged from 0.29 to 0.71 and were higher than estimates based on single-locus data. Such results suggest that the CH flowers experience variable levels of both geitonogamous self-fertilization and biparental inbreeding. A new and generally applicable technique based on the relative level of inbreeding within progeny groups provided direct estimates of the correlation between the genotypic values of outcrossed mates. These correlations varied widely among populations and contributed up to half of the inbreeding observed among the CH progeny. Such biparental inbreeding biases estimates of the outcrossing rate based on the mixed-mating model downward and influences mating-system evolution by decreasing the “cost of meiosis.”