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1.
Recent works have shown that mixed mating systems often evolve despite strong inbreeding depression and reproductive assurance, which is one of the widely accepted explanations for the evolution of selfing. However, there have been few empirical studies on the relationship between mixed mating and reproductive assurance in perennial plants. In the herbaceous perennial, Kosteletzkya virginica, delayed selfing induced from context-dependent style curvature offers reproductive assurance, and adverse weather conditions significantly reduce pollinator visitation rates. In this study, our goals were (i) to experimentally evaluate pollinator failure rate, reproductive assurance, selfing rate and the relationships between them, and (ii) to measure inbreeding depression across multiple growth seasons. Results indicate that both population selfing rates and reproductive assurance are significantly and positively correlated with field estimates of pollinator failure rates, and there is a strong relationship between selfing rates and reproductive assurance. Inbreeding depression across multiple growth seasons ranged from 0.621 to 0.665, and there were no significant differences among different seasons. Our data demonstrates that a mixed mating system is beneficial because frequent pollinator failure has allowed reproductive assurance to evolve through delayed selfing which minimizes the risk of seed discounting and is still advantageous despite high inbreeding depression. 相似文献
2.
H. C. Becker C. Damgaard B. Karlsson 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1992,84(3-4):303-306
Summary Rapeseed (Brassica napus) is a predominantly selfpollinated crop with about one-third outcrossing. The outcrossing rate may be influenced by environmental factors, and hence changes in the heterozygosity level of a variety may occur during multiplication. In an investigation on environmental variation in outcrossing, we estimated the outcrossing rate in the Swedish spring rapeseed cv Topas by isozyme analysis and found that outcrossing varied from 12% to 47% over five locations in Sweden, Denmark and Germany. Among flowers at different positions on the same plant, average outcrossing varied from 11% at the top to 39% at the bottom of the plant. In conclusion, environmental factors can greatly influence the outcrossing rate in rapeseed, and an investigation therefore merit further studies. 相似文献
3.
Deborah A. Cook Debra M. Decker John L. Gallagher 《Plant Cell, Tissue and Organ Culture》1989,17(2-3):111-119
Organogenic callus cultures of seashore mallow, Kosteletzkya virginica (L.) Presl., originated from excised mature embryos or stem sections of aseptically germinated plants initially cultured on Murashige & Skoog minimal organics medium containing 30000 mg l-1 glucose, 2.0 mg l-1 indoleacetic acid and 1.0 mg l-1 kinetin. Plants were regenerated via shoots and roots from callus cultures following transfer through a series of media with different cytokinin/auxin ratios and changes in carbohydrate source. Meristematic regions, shoot and root primordia were observed during histological examination of the tissues. Somatic embryos were not found. 相似文献
4.
Herkogamy may act as a mechanism to reduce interference between the reproductive functions of female and male organs, but too great a distance between stigmas and anthers may also decrease the outcross pollen transfer and male and female fitness. Our goal was to quantify the effect of movement herkogamy in Kosteletzkya virginica on reproductive success and its contribution to pollen receipt and reproductive assurance. Field investigations and hand-pollination experiments were performed to test: (1) the relationship between herkogamy before curvature of un-pollinated lobes and reproductive success under pollinator exclusion; (2) the contribution of movement herkogamy to pollen receipt; and (3) the relationship between pollen load and seed set. We noted that variation in herkogamy before curvature of un-pollinated lobes did not affect the outcome of autogamous self-pollination measured by fruit set and mean number of seeds per fruit. Under natural conditions, 39% of pollen grains deposited per flower were from autogamous self-pollination via movement herkogamy resulting in contact between anthers and stigmas. The relationship between the amount of pollen grains and the number of seeds per capsule was highly significant. Flowers producing four or five seeds received more pollen grains than those producing only one seed. Our data provides experimental evidence that movement herkogamy, which decreases the separation between anthers and stigmas and results in delayed self-pollination, contributes to pollen receipt and further enhances seed set when pollinators are scarce or absent. 相似文献
5.
D. V. Shaw 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1995,90(2):237-241
Progenies from first-generation self, half-sib, full-sib, and cross fertilizations were generated to evaluate the magnitude of inbreeding depression for vegetative and production traits in strawberry. Tests were conducted to determine the linearity of trait mean depression with inbreeding rate (F) over this range of inbreeding values, as an indication of the presence of non-additive epistasis. A control population, for which a similar range of coancestry had accumulated over several cycles of breeding and selection, was also generated to compare the consequences of ancestral and current-generation inbreeding. Trait means for crosses among current-generation half-sibs, full-sibs, and selfs were 2–17%, 3–12%, and 14–45% lower than for unrelated crosses among the same set of parents, respectively. Linear regression of progeny means on current generation F was significantly negative for all traits and explained 17–44% of the variance among progeny means. Mean depression was largely linear over the range of inbreeding rates tested in this population, indicating the absence of epistasis for the traits evaluated. Conversely, (F) regressions of progeny means on pedigree inbreeding coefficients, where coancestry had accumulated over several cycles of breeding and selection, were uniformly non-significant and explained 0–10% of the variance among cross means. Further, multiple regression of progeny means for current-generation relatives on pedigree F failed to improve fit significantly over regression on current-generation F alone for all traits. Together, these results suggest that pedigree inbreeding coefficients are poor predictors of changes in homozygosity when populations are developed through multiple cycles of breeding and selection. They also imply that inbreeding depression will be of minor importance for strawberry breeding populations managed with adequate population sizes and strong directional selection. 相似文献
6.
延迟自交被认为是一种生殖适应性,因为它保证了传粉者稀少情况下的种子生产,但当传粉者丰富时,又允许异交占优势。海滨锦葵花在传粉者不足或缺乏时能通过主动的柱头裂片弯曲运动成功实现延迟自花传粉。2002~2005年对江苏盐城滩涂海滨锦葵栽培群体花中发生延迟自花传粉花所占的百分比进行了观测,并于2005年对花内不同停止类型的柱头裂片比进行了调查,结果表明,2002 ~ 2005年间发生延迟自花传粉花所占百分比分别为13.50%±1.62%、14.39%±1.50%、1405%±1.82%和13.47%±1.51%,不同年份间并无显著差异 (F (3, 189) = 6.128, P = 0.085 )。发生延迟自花传粉花所占百分比与气候条件有密切关系,不利天气(多云/雨) (22.11%±0.94%) 明显高于有利天气(晴天) (5.43%±0.43%) (F(1, 189) = 8009.780, P < 0.001)。花内通过花部运动实现自花传粉而停止运动的柱头裂片比在有利天气(晴天)下(18.64%±1.61%)明显低于不利天气(多云/雨天) (70.58%±2.06%) (U = 0.000, W = 465.000, P <0.001)。海滨锦葵这种直接响应于影响传粉者环境之气候条件的延迟自花传粉策略为从个体或花水平上验证繁殖保障假说提供了可能。 相似文献
7.
G. N. Atlin 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1995,91(6-7):1173-1176
In addition to their application in the production of F1 hybrids in rape (Brassica napus L.), cytoplasmic male-sterility (CMS) systems may be used to produce synthetic varieties with much higher levels of heterozygosity than those expected in conventional rape synthetics. CMS synthetics are produced by compositing a CMS A-line with several male-fertile (MF) B-lines lacking nuclear alleles for fertility restoration, and increasing the resulting mixture by natural pollination. Over generations of increase, pollination of the CMS component by the MF component of the synthetic results in the progressive loss of A-line nuclear genes from the population. The initial proportions of CMS and MF plants are expected to be preserved over several generations of natural pollination if CMS and MF plants are equal in yield. Methods for estimating the heterozygosity level of CMS synthetics, taking into account the proportion of CMS plants, number of MF parents in Syn 0, and selfing rate (s) of MF plants, are presented. If completely inbred Syn 0 parents and s of 0 and 0.75 for CMS and MF plants respectively, are assumed, the heterozygosity level (1-F) of a synthetic derived from four inbred MF parents each comprising 6.25% of Syn 0 and one inbred CMS parent comprising 75% of Syn 0 is predicted to be 0.66 in Syn 5, compared to 0.30 in synthetics derived from four MF parents only. CMS synthetics offer a novel, low-cost approach to the exploitation of heterosis in rape and other species with mixed mating systems in which self-pollination predominates. 相似文献
8.
Constanza Celedón-Neghme Wilfredo L. Gonzáles Ernesto Gianoli 《Evolutionary ecology》2007,21(2):247-257
The maintenance of flower size variation within populations might be explained by conflicting selection pressures on floral traits that may involve biological agents, such as mutualists and antagonists, and allocation costs associated with floral display. The annual species Madia sativa (Asteraceae) exhibits ample variation in the number of ray florets in natural populations. This field study aimed at evaluating the costs and benefits associated with floral traits in M. sativa. In particular, we addressed two main questions: (1) Is the number of ray florets positively associated with pollinator visitation rate? (2) Is there a fitness cost of ray floret maintenance when pollinators are absent? We detected one benefit of conspicuous ray capitula: a strong preference by insect pollinators. We also confirmed the occurrence of costs: when pollinators were excluded conspicuous ray capitula had a reduced reproductive assurance via autogamous selfing, and there were trade-offs between the number of ray florets and seed mass and seed germination. Results suggest that the maintenance of within-population variation in the number of ray florets in M. sativa is explained, at least in part, by the balance between costs and benefits associated with this floral trait. 相似文献
9.
Margaret E.K. Evans Eric S. Menges Doria R. Gordon 《Biodiversity and Conservation》2004,13(10):1819-1832
We used hand-pollination experiments to test the mating systems of and evaluate limits to seed production in two federally listed endangered plants endemic to the Lake Wales Ridge in Florida, USA: Dicerandra frutescens Shinners ssp. frutescens Huck and D. christmanii Huck and Judd (Lamiaceae). Both are nonclonal, short-lived perennials found in gaps created by disturbance (e.g., fire, roads) in Florida scrub. We found that both species require pollen and insect visitation to produce seeds. We detected pollinator limitation of seed production in D. christmanii but not D. frutescens ssp. frutescens, which we suggest is a function of time-since-disturbance or gap size rather than intrinsic differences between the two species. Both species are self-compatible. Inbreeding depression reduced seed set by 60% in D. frutescens ssp. frutescens but did not occur in D. christmanii. We conclude that pollinator limitation (in fire-suppressed populations of both species) and inbreeding depression (in D. frutescens ssp. frutescens) have the potential to limit seed production in these seed-dependent, rare species. Appropriate fire management should mitigate both of these risks, by maintaining large populations and conditions attractive to pollinators. Although these two species are very similar in reproductive biology, comparisons with other Florida scrub endemics and with rare plants in general suggest that potential threats to conservation via reproductive biology are difficult to predict, depending on combinations of ecology, life-history, and phylogenetic history. 相似文献
10.
Effects of self-pollination and maternal resources on reproduction and offspring performance in the wild lupine, Lupinus perennis (Fabaceae) 总被引:2,自引:0,他引:2
We examined the effects of self-pollination and resource addition to maternal plants of Wild Lupine on seed production in
the field, and on offspring performance in the greenhouse. Although 24% of flowers set fruits when open-pollinated, only 11%
of flowers set fruits when self-pollinated. Self-pollination significantly reduced fruit and seed production per inflorescence
and increased aborted seeds per fruit. Resource addition to maternal plants significantly increased fruit and seed number
in the field. Moreover, selfed plants exhibited greater variability in seed production in the absence of resource addition
to the maternal plant. We planted a total of 1,306 of the seeds from this experiment in the greenhouse. While self-pollination
did not affect the proportion of seeds emerging, it slowed seedling emergence by 5–10%, and reduced offspring biomass by 25–35%.
Interestingly, resource addition to the maternal plants significantly decreased proportion of seedlings surviving after 5 months.
Moreover, offspring from maternal plants with resource addition expressed more inbreeding depression in the seedling stage
compared to offspring from maternal plants without resource addition, for which more inbreeding depression occurred during
seed maturation and emergence. These results indicate that conservation efforts using benign environments to increase number
of seeds or offspring may face compensating reductions in survivorship at other life stages. 相似文献
11.
Mating system and inbreeding depression in quantitative traits of whitebark pine (Pinus albicaulis Engelm.) was determined using isozymes and a seedling common garden experiment. Simultaneous isozyme analysis of embryo and
haploid megagametophyes from progeny arrays of families in three distinct geographic regions (Oregon, Montana, and southern
British Columbia) was used to estimate parental and progeny inbreeding coefficients, as well as regional and family mean multilocus
outcrossing rates (t
m). Quantitative trait family means of seedlings from the same families growing in two temperature treatments in a common garden
experiment were regressed on the estimated inbreeding coefficient to determine the presence and magnitude of inbreeding depression.
Regional estimates of t
m ranged from 0.73 to 0.93, with a mean over all regions of 0.86. Family mean t
m values indicated predominant outcrossing; however, some individuals experienced substantial inbreeding. The Oregon region
had a significant excess of heterozygotes in the parental generation relative to Hardy–Weinberg equilibrium, while both the
Oregon and southern BC regions had a heterozygote deficiency in progeny, suggesting selection against inbred individuals.
Biomass in the ambient temperature treatment for the southern BC region was the only trait significantly related to inbreeding
coefficient. The mean inbreeding coefficient for this region was 0.25, and based on this relationship, mean predicted biomass
would be reduced by 19.6% in this region if inbred individuals are not removed by selection. The estimated outcrossing rate
of whitebark pine is slightly lower than most wind-pollinated conifers, and while most individuals are highly outcrossing,
some experience substantial inbreeding. 相似文献
12.
Harder LD Richards SA Routley MB 《Evolution; international journal of organic evolution》2008,62(1):157-172
Hermaphroditism allows considerable scope for contributing genes to subsequent generations through various mixtures of selfed and outcrossed offspring. The fitness consequences of different family compositions determine the evolutionarily stable mating strategy and depend on the interplay of genetic features, the nature of mating, and factors that govern offspring development. This theoretical article considers the relative contributions of these influences and their interacting effects on mating-system evolution, given a fixed genetic load within a population. Strong inbreeding depression after offspring gain independence selects for exclusive outcrossing, regardless of the intensity of predispersal inbreeding depression, unless insufficient mating limits offspring production. The extent to which selfing evolves under weak postdispersal inbreeding depression depends on predispersal inbreeding depression and the opportunity for resource limitation of offspring production. Mixed selfing and outcrossing is an evolutionarily stable strategy (ESS) if selfed zygotes survive poorly, but selfed offspring survive well, and maternal individuals produce enough \"extra\" eggs that deaths of unviable outcrossed embryos do not impact offspring production (reproductive compensation). Mixed mating can also be an ESS, despite weak lifetime inbreeding depression, if self-mating reduces the number of male gametes available for outcrossing (male-gamete discounting). Reproductive compensation and male-gamete discounting act largely independently on mating-system evolution. ESS mating systems always involve either complete fertilization or fertilization of enough eggs to induce resource competition among embryos, so although reproductive assurance is adaptive with insufficient mating, it is never an ESS. Our results illustrate the theoretical importance of different constraints on offspring production (availability of male gametes, egg production, and maternal resources) for both the course and outcome of mating-system evolution, whereas unequal competition between selfed and outcrossed embryos has limited effect. These results also underscore the significance of heterogeneity in the nature and intensity of inbreeding depression during the life cycle for the evolution of hermaphrodite mating systems. 相似文献
13.
R. Frankham G. J. Smith D. A. Briscoe 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1993,86(8):1023-1027
The effects of inbreeding, with (IS) and without selection (IO) for reproductive fitness, on inbreeding depression and heterozygosity were evaluated in 20 lines of each treatment inbred over seven generations using full-sib mating. The survival of lines was significantly greater in IS (20/20) than in IO (15/20). The competitive index measure of reproductive fitness was significantly lower in the inbred lines than in the outbred base population, but not significantly different in surviving IS and IO lines. There was a trend for higher fitness in the IS treatment as relative fitnesses were 19% higher in IS than IO for surviving lines and 59% higher for all lines. Heterozygosities were lower in the inbred lines than in the base population, and significantly higher in the IS than the IO lines. Consequently, the reduction of inbreeding depression in IS has been achieved, at least in part, by slowing the rate of fixation. 相似文献
14.
N. K. Patra R. S. Ram S. P. Chauhan A. K. Singh 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1992,84(3-4):299-302
Summary Nearly 400 individuals at two locations and over a number of years were crossed and subsequently scored for selfing versus outcrossing in eight monohybrid populations of opium poppy (Papaver somniferum). Two different marker loci, petal colour (R/r) and capsule size (B/b) were used to determine the male gametes that had effected fertilizations in F2 recessives (rr and bb). The estimates of the outcrossing parameter were found to vary with year, location and for the marker locus used ( range: 0.0988–0.3704). Study of two dihybrid crosses involving the two loci simultaneously, further confirmed that outcrossing at the R/r locus was significantly greater than that at the B/b locus. The nature of the outcrossing was, in general, nonrandom. Selfmg predominated in this species; however, there was a high frequency of natural outcrossing for generating variations in P. somniferum.CIMAP publication No. 1086 相似文献
15.
C. Damgaard V. Loeschcke 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1994,88(3-4):321-323
Rapeseed plants, of the summer annual variety Topas, that had been selfed twice consecutively were compared to outcrossed half-sibs for inbreeding depression in a rapeseed population at mating equilibrium. The effect of dominance-suppression competition was included in the effect of inbreeding. Both female-and male-fitness characters showed significant inbreeding depression. Biomass decreased 17% with inbreeding and was highly correlated with seed weight. The total number of flowers decreased 15% with inbreeding. There was a significant effect of lines. The possible importance of experimental design in studies that estimate inbreeding depression is discussed. 相似文献
16.
Agricultural intensification has resulted in drastic regression of several arable land-dependent weeds. This decrease, along with reduced pollinator abundance, could lead to population-level extinction of self-incompatible species. Alternatively, it could drive adaptation to self-compatibility through selection on standing genetic variation. We investigated whether pseudo-self-compatible (PSC) or self-compatible (SC) plants are present in populations of the rarified weed Centaurea cyanus in the species’ extreme western distribution limits in Europe. We compared seed production of isolated plants and of pairs of plants in cages with or without pollinators. We showed that pollinators are necessary for self-fertilization. The majority of plants were self-incompatible (SI), but about 12% were PSC, and one was SC. Reproductive traits of PSC plants were not different from those of other plants. There was no difference between plants from two regions that differed in C. cyanus abundance. We conclude that the genetic variation necessary to transition to selfing is present in C. cyanus; this could help to maintain endangered populations, but the transition to selfing does not appear to have happened in nature yet. 相似文献
17.
As a basis for comparative studies of mating systems, we estimated genetic diversities and inbreeding coefficients for six perennial species of Ainsliaea and two shrubby species of Pertya (Asteraceae). These related species are known to vary from frequent cleistogamy to xenogamy by bumblebee pollination, and we examined allozyme variation in these species to describe mating system variation in further detail. Significant heterozygote deficit was found in five species, while no heterozygote deficit was found in three species. A cleistogamous species showed no genetic polymorphism. Multilocus average of inbreeding coefficients among seven species ranged from –0.12 to 0.78. These findings indicated that related species can vary from predominant selfers to predominant outcrossers under perennial life cycles. 相似文献
18.
T. L. Wang R. Hagqvist P. M. A. Tigerstedt 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1996,92(3-4):471-476
Hybrid breeding is an effective approach in many agricultural crops. In allogamous tree species severe inbreeding depression and long reproductive cycles generally prohibit its use. However, three generations of selfing in silver birch (Betula pendula Roth) were obtained by forcing trees to flowering under greenhouse conditions. Hybrids were produced by crossing first-, second and third-generation selfed lines. The effects of different levels of parental inbreeding on the growth performance of hybrid families were observed in a 9-year-old field progeny test. Also, provenance crosses were carried out between selfed lines from different parts of Finland and several other European countries. Observations of growth performance of the provenance hybrids were made in the same trial. The results indicated that the mean stem volumes were significantly different between classes of parental in breeding coefficients (FP) (P<0.0001), and were positively correlated with FP (r=0.9106, P<0.05). Within-family variation of the hybrid families decreased with an increase of FP. The performance of the provenance crosses between parents at a relatively close distance did not depart significantly from the standard controls. However, when the cross distance was extended far to the south, hybrids grew faster, indicating either higher heterozygosity or an extended growth period. 相似文献
19.
Zhenxiang He Chengjiang Ruan Pei Qin Denise M. Seliskar John L. Gallagher 《Ecological Engineering》2003,21(4-5):271-276
Kosteletzkya virginica (L.) Presl. is a perennial dicot halophytic species, that grows in brackish portions of coastal tidal marshes of the mid-Atlantic and southeastern United States. New saline mudflats have been increasing every year in Northern Jiangsu, China. In 1993, we introduced K. virginica (L.) into China from the Halophyte Biotechnology Center (University of Delaware, USA) as a potential species to improve the soil and develop ecologically sound saline agriculture. Our nearly 10 years of experimental research, both in a test garden and in the field, indicated that K. virginica adapts excellently to the heavy saline soils of Jiangsu Province, China. The average seed yield of K. virginica in 2001 at Yancheng was 638 kg/ha from 1-year old seedlings. There were significant variations among individuals from the unselected population of K. virginica on growth, quality, and seed yield traits. There is great potential to increase the seed yield if superior clones are selected. The seed yield of 35 selected individuals was six times greater than that of the average. Four growth traits of K. virginica were found to have a significant correlation with seed yield. However, there was no strong positive or negative correlation among seed quality traits. The mean seed weight and the germination ratio of the 35 selected individuals of K. virginica were 16.36±0.32 g and 76.11±1.82%, respectively. The percentage content of oil and crude protein in the seeds was 11.28±0.67 and 8.17±0.19%, respectively. The percentage of seed vigor of the selected individuals was 99%, as determined by soft X-ray radiography. 相似文献
20.
N. G. Ehiobu M. E. Goddard J. F. Taylor 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1989,77(1):123-127
Summary This experiment was designed to study the relationship between rate of inbreeding and observed inbreeding depression of larval viability, adult fecundity and cold shock mortality in Drosophila melanogaster. Rates of inbreeding used were full-sib mating and closed lines of N=4 and N=20. Eight generations of mating in the N=20 lines, three generations in the N=4 lines and one generation of full-sib mating were synchronised to simultaneously produce individuals with an expected level of inbreeding coefficient (F) of approximately 0.25. Inbreeding depression for the three traits was significant at F=0.25. N=20 lines showed significantly less inbreeding depression than full-sib mated lines for larval viability at approximately the same level of F. A similar trend was observed for fecundity. No effect of rate of inbreeding depression was found for cold shock mortality, but this trait was measured with less precision than the other two. Natural selection acting on loci influencing larval viability and fecundity during the process of inbreeding could explain these results. Selection is expected to be more effective with slow rates of inbreeding because there are more generations and greater opportunity for selection to act before F=0.25 is reached. Selection intensities seem to have been different in the three traits measured. Selection was most intense for larval viability, less intense for fecundity and, perhaps, negligible at loci influencing cold shock mortality. 相似文献