Plasticity of seed output in response to soil nutrients and density in Abutilon theophrasti: implications for maintenance of genetic variation

 Seed output is determined by two processes: resource acquisition and the allocation of resources to seeds. In order to clarify how the reaction norm of seed output is controlled by the phenotypic expression of its two components, we examined the genetic components of plasticity of seed dry mass, plant size, and reproductive allocation under different conditions of soil nutrient availability and conspecific competition among eight families of Abutilon theophrasti. Without competition, the reaction norm of seed mass of the families crossed between the lowest and other nutrient levels, although neither of its components, plant size and reproductive allocation, showed such a response. The crossing reaction norm (i.e., reversal of relative fitnesses of different genotypes along the environmental gradient) of seed mass resulted from (1) a trade-off between plant size and reproductive allocation, and (2) changes in the relative magnitude of genetic variances in plant size and reproductive allocation with soil nutrient availability. While allocation was more important in determining seed mass under limiting nutrient conditions, plant size became more important under high-nutrient conditions. There were no significant genetic variances in seed mass, plant size, and reproductive allocation in the competition treatment, except at the highest nutrient level. The results show that plant competition mitigated the effects of genetic differences in plant performance among the families. We discuss the results in relation to maintenance of genetic variation within a population. Received: 16 August 1996 / Accepted 26 April 1997     

Vulnerability and determinants of reproductive success in the narrow endemic Antirrhinum microphyllum (Scrophulariaceae)

The breeding system and flowering phenology of the narrow endemic Antirrhinum microphyllum (Scrophulariaceae) were studied in order to assess the main factors affecting female reproductive success and to identify existing or potential threats to the viability of its populations. Hand-pollination experiments showed that A. microphyllum is an allogamous self-incompatible species. In both populations studied, the flowering season was 4 mo long and mean flowering duration per plant was about 1 mo. Peak flower production took place between mid-April and mid-May and overlapped with the period of activity of the main pollinator, Rhodanthidium sticticum (Megachilidae). Estimated mean number of seeds produced per plant was 9391, showing that population viability is not presently limited by seed output. The study of the direct and indirect effects of plant size, phenological traits (first flowering date, flowering duration, and flowering synchrony), and distance to neighbor plants on reproductive success was performed using structural equation modeling (SEM). In both populations, number of flowers and plant size were the main factors that determined the total number of fruits produced by a plant. First flowering date and flowering synchrony also affected fruit production. Multisample comparison of path coefficients for the two populations rejected the possibility that reproductive patterns could be described by one single model.     

内蒙古库布齐沙地和呼和浩特平原黑线仓鼠种群繁殖特征的比较

为了解不同地理种群在适应当地栖息环境过程中的差异,于１９９６年利用直线夹地对内蒙古呼和浩特平原和由齐沙地环境,两个种群基因交流严重受阻的黑线仓鼠种群生殖特征进行了比较研究,结果表明,雌雄必比在平原环境较大,且秋季雌性明显增多,沙地环境全年维持稳定,平原环境雄性睾丸下降率在各季高于沙地环境近２０％。平原环境雌性在夏季性成熟率较高,沙地环境季最高。平原环境中雌性怀孕率为春、夏季较高,沙地环境仅在春季最高,且小胎仔（窝仔数少于４）所占缃例较高（１９．５％）,两个种群平均胎仔数分别为６．０（平原）和５．９（沙地）,这一结果说明不同地理种群生殖特性的差异受环境条件限制明显。     

BREEDING SYSTEM EVOLUTION IN LEAVENWORTHIA: BREEDING SYSTEM VARIATION AND REPRODUCTIVE SUCCESS IN NATURAL POPULATIONS OF LEAVENWORTHIA CRASSA (CRUCIFERAE)

Populations of Leavenworthia crassa (Cruciferae) studied for 3 years exhibited among- and within-population genetic variation for a suite of floral and reproductive traits (flower width, petal length, anther position, ability to set seeds in the absence of pollinators, time to first flowering) associated with breeding system. We used electrophoretic markers to show that a population with small, monomorphically colored flowers with introrse anthers had a significantly lower outcrossing rate (t = 0.03) than did a population with larger, polymorphically colored flowers with extrorse anthers (t = 0.33). In the more-outcrossing population the correlation between higher maternal plant outcrossing rate and the suite of six traits approached significance (P < 0.067), with greater petal size, greater flower width, and reduced ability to set seeds in the absence of pollinators contributing significantly. Plants in selfing populations had a generally higher reproductive success, with a higher number of flowers per plant, a smaller proportion of unfertilized ovules, a smaller proportion of fertilized ovules aborted, a higher rate of fruit set, and overall a larger number of seeds matured than did plants from the more outcrossing populations. Pollen limitation did not appear to account for lower reproductive success in outcrossing populations. Resource limitation did not differ substantially between populations. However, within-ovary patterns of fertilization, abortion, and seed weight were significantly less random in outcrossing populations than in selfing populations, suggesting that differential gamete and embryo success may be responsible for lower reproductive success in outcrossing populations.     

Effects of plant size and weather on the flowering phenology of the organ pipe cactus (Stenocereus thurberi)

Background and Aims

Flowering phenology is a critical life-history trait that influences reproductive success. It has been shown that genetic, climatic and other factors such as plant size affect the timing of flowering and its duration. The spatial and temporal variation in the reproductive phenology of the columnar cactus Stenocereus thurberi and its association with plant size and environmental cues was studied.

Methods

Flowering was monitored during 3 years in three populations of S. thurberi along a latitudinal gradient. Plant size was related to phenological parameters. The actual and past weather were used for each site and year to investigate the environmental correlates of flowering.

Key Results

There was significant variation in the timing of flowering within and among populations. Flowering lasted 4 months in the southern population and only 2 months in the northern population. A single flowering peak was evident in each population, but ocurred at different times. Large plants produced more flowers, and bloomed earlier and for a longer period than small plants. Population synchrony increased as the mean duration of flowering per individual decreased. The onset of flowering is primarily related to the variance in winter minimum temperatures and the duration to the autumn–winter mean maximum temperature, whereas spring mean maximum temperature is best correlated with synchrony.

Conclusions

Plant size affects individual plant fecundity as well as flowering time. Thus the population structure strongly affects flowering phenology. Indications of clinal variation in the timing of flowering and reproductive effort suggest selection pressures related to the arrival of migrating pollinators, climate and resource economy in a desert environment. These pressures are likely to be relaxed in populations where individual plants can attain large sizes.Key words: Flowering phenology, optimal timing, plant size, Sonoran Desert, Stenocereus thurberi, temperature     

Offspring fitness in relation to population size and genetic variation in the rare perennial plant species Gentiana pneumonanthe (Gentianaceae)

Seeds were sampled from 19 populations of the rare Gentiana pneumonanthe, ranging in size from 5 to more than 50,000 flowering plants. An analysis was made of variation in a number of life-history characters in relation to population size and offspring heterozygosity (based on seven polymorphic isozyme loci). Life-his-tory characters included seed weight, germination rate, proportion of seeds germinating, seedling mortality, seedling weight, adult weight, flower production per plant and proportion of plants flowering per family. Principal component analysis (PCA) reduced the dataset to three main fitness components. The first component was highly correlated with adult weight and flowering performance, the second with germination performance and the third component with seed and seedling weight and seedling mortality. The latter two components were considered as being maternally influenced, since these comprised life-history traits that were significantly correlated with seed weight. Multiple regression analysis showed that variation in the first fitness component was mainly associated with heterozygosity and not with population size, while the third fitness component was only correlated with population size and not with heterozygosity. The latter relationship appeared to be non-linear, which suggests a stronger loss of fitness in the smallest populations. The second (germination) component was neither correlated with population size nor with genetic variation. There was only a weak association between population size, heterozygosity and the population coefficients of variation for each life history character. Most correlation coefficients were negative, however, which suggests that there is more variation among progeny from smaller populations. We conclude that progeny from small populations of Gentiana pneumonanthe show reduced fitness and may be phenotypically more variable. One of the possible causes of the loss of fitness is a combination of unfavourable environmental circumstances for maternal plants in small populations and increased inbreeding. The higher phenotypic variation in small populations may also be a result of inbreeding, which can lead to deviation of individuals from the average phenotype through a loss of developmental stability.     

VARIATION IN A POLYPLOID,DIOICOUS LIVERWORT,MARCHANTIA GLOBOSA

This study was undertaken in order to determine the population structure in a tropical, geographically isolated liverwort, Marchantia globosa Brid. ex Web., a thallose species endemic to the Mascarenes and Comoro Islands. A survey of numerous populations on Réunion showed M. globosa to be ecologically tolerant and morphologically quite variable. The morphological differences between populations could only be explained by a size effect, due principally to altitude. Neither cytological nor electrophoretic analyses revealed any genetic basis for distinguishing subpopulations. In spite of an apparently high reproductive effort, sexual structures being produced abundantly, few spores reach maturity. No electrophoretically detectable genetic polymorphism was found. Morphological variation appears to result from phenotypic plasticity.     

The evolution of self-compatibility in geographically peripheral populations of Leavenworthia alabamica (Brassicaceae)

Self-compatibility and adaptations to self-fertilization are often found in plant populations at the periphery of species' ranges or on islands. Self-compatibility may predominate in these environments because it provides reproductive assurance when pollinators or availability of mates limits seed production. This possibility was studied in Leavenworthia alabamica, a flowering plant endemic to the southeastern United States. Populations at the center of the species' range retain sporophytic self-incompatibility, but peripheral populations are smaller, self-compatible, and have adaptations for self-fertilization. A reciprocal-transplant experiment was designed to test whether there is pollen limitation of seed set and to examine its strength in central and peripheral populations. Self-compatible genotypes produced more fruit and 17-22% more seed than self-incompatible genotypes in all environments, suggesting that the transition to self-compatibility may be favored by natural selection in all populations inhabited by L. alabamica. Sequence analyses demonstrated that two peripheral populations have 90-100% reductions in genetic variation, consistent with the effects of small population size or historical bottlenecks. Although pollen limitation of seed set occurs in all environments, self-compatibility may evolve at the periphery in L. alabamica because the benefits of reproductive assurance are influenced by population size or bottlenecks following extinction and colonization.     

Genetic determinism of reproductive fitness traits under drought stress in the model legume <Emphasis Type="Italic">Medicago truncatula</Emphasis>

Fitness traits that determine the reproductive ability of individuals and the persistence of populations are affected by drought stress. Medicago truncatula that commonly encounters drought stress in its natural area, and for which large natural diversity and genetic tools are available, is a suitable species to investigate genetic determinism of fitness traits under stress. In a common garden, three successive cycles of short drought stress were applied after flowering, during the reproductive stage that is the most susceptible to drought for that species. Ten genotypes derived from natural populations and a mapping population were used to investigate the genetic determinism of vegetative and reproductive traits as components of fitness. A large genetic variation was observed and transgressive genotypes (more resistant or more susceptible than the parental genotypes) were found in the mapping population. Fitness traits were reduced by 5–74% in drought condition compared to well-watered condition. The most affected characters were total pod number per plant and total pod weight per plant. A total of 49 QTL, explaining between 6 and 38% of phenotypic variation for vegetative and reproductive fitness traits, were detected on all chromosomes except chromosome 6. A major QTL for flowering date (R ² of 19 and 38%) that co-located with QTL for reproductive fitness traits were found on chromosome 7. In this study, no major QTL specific to drought-stressed or well-watered conditions were detected. We, thus, showed that QTL explaining fitness traits were numerous with small effects, in accordance with the genetic determinism of a complex trait.     

Is increased male flower production a strategy for avoidance of predispersal seed predation in andromonoecious plants?

Floral gender in angiosperms often varies within and among populations. We conducted a field survey to test how predispersal seed predation affects sex allocation in an andromonoecious alpine herb Peucedanum multivittatum. We compared plant size, male and perfect flower production, fruit set, and seed predation rate over three years among nine populations inhabiting diverse snowmelt conditions in alpine meadows. Flowering period of individual populations varied from mid‐July to late August reflecting the snowmelt time. Although perfect flower and fruit productions increased with plant size, size dependency of male flower production was less clear. The number of male flowers was larger in the early‐flowering populations, while the number of perfect flowers increased in the late‐flowering populations. Thus, male‐biased sex allocation was common in the early‐flowering populations. Fruit‐set rates varied among populations and between years, irrespective of flowering period. Fruit‐set success of individual plants increased with perfect flower number, but independent of male flower number. Seed predation by lepidopteran larvae was intense in the early‐flowering populations, whereas predation damage was absent in the late‐flowering populations, reflecting the extent of phenological matching between flowering time of host plants and oviposition period of predator moths. Seed predation rate was independent of male and perfect flower numbers of individual plants. Thus, seed predation is a stochastic event in each population. There was a clear correlation between the proportion of male flowers and the intensity of seed predation among populations. These results suggest that male‐biased sex allocation could be a strategy to reduce seed predation damage but maintain the effort as a pollen donor under intensive seed predation.     

INTRAPOPULATIONAL VARIATION IN POLLEN-MEDIATED GENE FLOW IN PLANTAGO LANCEOLATA L.

The extent of genetic variation in pollen-mediated gene flow distance was measured for a population of the wind-pollinated herb, Plantago lanceolata. Twenty-nine genotypes were collected from a natural population, clonally replicated, and grown to reproductive maturity in a greenhouse. Relative gene flow distances were measured for each replicate and genotype in a wind tunnel. Approximately five percent of the total variation in gene flow distance was attributable to variation among genotypes. Most of the remaining variation was attributable to differences between the early part of the growing season, when most of the flowering occurs, and the remainder of the season, when flowering is sparse. The rankings of the genotypes' gene flow distances showed significant concordance between the early-season measures and measures from later in the summer. There was no correlation between the average inflorescence height for a plant and the average gene flow distance for that plant. For analysis of pollen characteristics suspected as causal factors of variation in gene flow distance, the variation in gene flow distance was divided into two components: that due to environmental (seasonal) differences, and that due to the differences among genotypes within runs. Variation in both the buoyant properties of the pollen grains and their adhesiveness was significantly partially correlated with environmental variation in gene flow distance, while only the buoyant properties of the pollen grains were significantly partially correlated with among-genotype variation in gene flow distances.     

Paternity analysis of the breeding structure of strangler fig populations: evidence for substantial long-distance wasp dispersal

Abstract. The mutualistic interaction of figs with their species-specific wasp pollinators and the role of figs as 'keystone' plant resources in tropical communities has received substantial attention from both plant and animal ecologists. Despite this focus on the reproductive biology of figs, the minute size of the wasps has effectively precluded our ability to monitor patterns of wasp dispersal and fig mating relationships in natural forest habitats. In this paper we use genetic markers and genealogy reconstruction techniques to examine the breeding structure of populations of four strangler fig species occurring in central Panama. The natural history of figs facilitates the genetic analysis of full-sib progeny arrays from which the genotypes of successful pollen donors can be reconstructed precisely. Paternity reconstruction in the four study species reveals that individual flowering trees may routinely receive pollen from numerous donors despite characteristically low densities of co-flowering individuals. These data indicate not only that breeding populations of these figs are larger than the minimum critical sizes predicted to be necessary to support populations of their species-specific pollinators, but are more extensive in size and area than has been described for any plant species yet examined. Further, the fig wasps are shown to be efficient agents of long-distance dispersal, routinely moving up to 10 km between flowering trees. In accord with the potential for substantial long-distance gene flow and large effective population sizes, ten of eleven species of Panamanian figs assayed were found to maintain exceptionally high levels of genetic variation within their populations. Combined with other reports of occasional long-distance dispersal, the results of this study suggest that fig wasps may be more effective at colonizing isolated fig populations than previously thought.     

Relationship between population size, allozyme variation, and plant performance in the narrow endemic Cochlearia bavarica

We studied population viability in relation topopulation size and allelic variation in thenarrowly-endemic, monocarpic perennial plantCochlearia bavarica in Bavaria. In 1996,we analysed allelic variation by allozymeelectrophoresis in 24 populations ranging from8–2000 flowering individuals. Fitness-relatedcharacters were investigated in 22 of the 24populations in the field in 1996 (reproductiveand vegetative traits) and 1998 (reproductivetraits only). Differences in allozyme patternwere large between a south-eastern and awestern population group. Genetic diversity,assessed by the Shannon-Wiener diversity index,was low within but high among populations.Small populations had fewer alleles per locus,fewer polymorphic loci, lower observedheterozygosity, and lower genetic diversitythan large populations. Environmentalvariables were not significantly correlatedwith population size or fitness with theexception of light availability, indicatingthat habitat quality was similar for large andsmall populations. Population size showedpositive correlations with number of flowers,fruit set per plant, number of seeds per fruit,and total seed output per plant. Fruit set andnumber of seeds per fruit were positivelycorrelated with the observed heterozygosity andthe proportion of polymorphic loci. We usedpath analyses to study the possible causalrelationships among population size, allelicvariation, and reproductive characters. Thesemodels showed that allelic variation had nodirect influence on reproductive characters,whereas population size did. We conclude thatat present population size reduces viabilityand also reduces allelic variation; but thereduced allelic variation may in the longerterm have negative feed-backs on bothpopulation size and viability.     

Impact of prairie fragment size on proportion of females and reproductive success of Lobelia spicata Lam., a gynodioecious species

• Due to ongoing human impacts, plant species increasingly occur in landscapes that are highly fragmented, with remaining natural habitats occupying small areas, resulting in populations that are smaller and more isolated than in previous time periods. This changed metapopulation structure is expected to have negative impacts on seed production. For example, the proportion of female plants within gynodioecious populations may be more volatile due to genetic drift in small populations associated with small habitat fragments, with concomitant impacts on seed production. My aims were to determine: (i) if variation in proportion of females is larger in smaller fragments; and (ii) if such changes in female frequency in small fragments result in reduced seed production.
• Thirty‐two populations of Lobelia spicata Lam., a gynodioecious species, were surveyed in 2000, 2001 and 2009 in the tallgrass prairie region of Midwestern North America (Illinois and Indiana, USA). Data were collected for: proportion of female plants, total number of flowering plants (measure of population size), seed set per plant and prairie fragment size (another measure of population size).
• The proportion of females is more variable in smaller prairie fragments. Seed number per fruit decreases as the proportion of females increases in a population, but only significantly for female plants. The number of flowering plants is positively associated with fruit production for both genders. Populations within larger prairie fragments have higher seed production.
• The reproductive consequences of habitat fragmentation depend on the plant breeding system. While both sexes were negatively impacted, females were more adversely affected.

     

Genetic structure and AFLP variation of remnant populations in the rare plant Pedicularis palustris (Scrophulariaceae) and its relation to population size and reproductive components

We investigated plant reproduction in relation to genetic structure, population size, and habitat quality in 13 populations of the rare biennial plant Pedicularis palustris with 3-28500 flowering individuals. We used AFLP (amplified fragment length polymorphism) profiles to analyze genetic similarities among 129 individuals (3-15 per population). In a cluster analysis of genetic similarities most individuals (67%) were arranged in population-specific clusters. Analysis of molecular variance indicated significant genetic differentiation among populations and among and within subpopulations (P < 0.001). Gene flow (N(e) m) was low (0.298). On average, plants produced 55 capsules, 17 seeds per fruit, and 42 seedlings in the following growing season. The number of seeds per capsule was independent of population size and of genetic variability. In contrast, the number of capsules per plant (P < 0.05) and the number of seedlings per plant (P < 0.05) were positively correlated with population size. The relation between population size and the number of seeds per plant was not significant (P = 0.075). The number of capsules and of seeds and seedlings per plant (P < 0.01) were positively correlated with genetic variability. Genetic variability was independent of actual population size, suggesting that historical population processes have to be taken into account, too. Stepwise multiple regressions revealed additional significant relationships of habitat parameters (soil pH, C:N ratio), vegetation composition, and standing crop on reproductive components. We conclude that populations of P. palustris are genetically isolated and that reproductive success most likely is influenced by population size, genetic variability, and habitat quality. Management strategies such as moderate grazing, mowing, and artificial gene flow should endeavor to increase population size as well as genetic variation.     

Potential ‘costs of reproduction’ in a skink: Inter‐ and intrapopulational variation

Reproductive costs are important determinants of reproductive effort in squamate reptiles. Consequently, differences in costs of reproduction between populations of geographically or climatically widespread species are likely to result in different patterns of reproductive effort. In the present study, the effect of pregnancy on sprint speed was examined in a small viviparous skink, Niveoscincus ocellatus (Gray 1845), from two populations at the climatic extremes of its distribution. Decreased sprint speed has the potential to be an important cost of reproduction in this species, through a reduced ability to avoid predation and/or decreased foraging efficiency. Lizards inhabiting the colder site were larger than those from the warmer site and, contrary to predictions from life history theory, had a higher reproductive effort. In both populations, sprint speed was lower in pregnant lizards than in either the same individuals after birth or non‐pregnant control lizards. Within each population, sprint speed was unrelated to the level of reproductive effort of the female in terms of either absolute mass of the reproductive burden or the burden relative to her post‐partum body mass. However, within each population, the mass of the clutch that an individual female was carrying relative to snout–vent length was an important determinant of her sprint speed while pregnant. Thus, within each population, a relatively high reproductive burden may potentially increase costs of reproduction in this species. Despite this relationship and predictions from life history theory suggesting that annual reproductive effort will be lower in populations with a large body size and delayed maturity, it is suggested that a higher reproductive effort at the cold site is possible because they have a higher absolute sprint speed because of their larger size and a relatively higher abundance of cover at the cold site, and differences in predation pressure may alter selective pressures on reproductive investment.     

Variations in age and size at maturity of female Nile tilapia, Oreochromis niloticus, populations from man-made lakes of Côte d'Ivoire

The reproductive characteristics of Oreochromis niloticus females were studied in two large hydroelectric dams and 6 small agropastoral reservoirs of Côte d'Ivoire, selected for their diversity of environmental conditions and sizes (6 to 80000 ha). Comparative analysis of age and size at maturity revealed large differences between the populations with early maturity, late maturity, and intermediate situations. All the populations matured in their first year, between 5.6 and 10 months. Age and size at maturity were positively correlated with the reservoir area. The range of variation in age at maturity between populations was far greater than that of size at maturity. However, size at maturity also appears to be very plastic as intra-population variations of 2 to 3 cm were found between consecutive years. A comparison of age at maturity for a population in 1994 and 1996 showed that this trait is also likely to vary significantly at the intra-population level. Environmental factors which could potentially affect age and size at maturity are discussed. Growth differences are the probable explanation for the observed patterns of variation between populations. Rapid changes in age and size at maturity at inter or intra-population levels suggest that the observed variations might be explained by differences in environmental variables (phenotypic plasticity) rather than by genetic differences.     

Seed production and pre-dispersal reproductive losses in the narrow endemic <Emphasis Type="Italic">Euphorbia pedroi</Emphasis> (Euphorbiaceae)

Euphorbia pedroi is a narrow endemic species with three known populations located in coastal areas of western Portugal. This study focused on the reproductive biology of this species from flowering to dispersal, aiming to identify the factors causing decrease in seed production potential and to assess the spatio-temporal patterns of seed production at the individual and population levels. The abortion of reproductive structures, particularly seeds, represented a major fraction of losses in the potential seed production of E. pedroi. Moth larvae destroyed a variable proportion of cyathia in a large number of plants from the two populations regardless of their degree of isolation. Furthermore, generalist and specialist pre-dispersal seed predators were responsible for temporally variable seed losses unrelated with variables indicative of plant size and fecundity, and showing no consistency at the individual level. Specialist seed-wasps inflicted the highest losses to E. pedroi and their impact was intimately associated with the magnitude of yearly variation in seed production. This finding highlights the role of the inter-annual variation in seed production as a key feature in this plant-seed predator system. The effect of the two groups of seed predators on the reproductive output of E. pedroi was additive and those insects do not seem to exert an important selective pressure on the traits studied. The proportion of intact seeds produced by E. pedroi differed between locations, but not between individuals within each population, highlighting the major contribution of larger plants to the seed pool.     

Variation in reproductive modes and population genetic structures of a monocarpic perennial herb,Cardiocrinum cordatum,in relation to habitat fragmentation

Reproductive systems are recognized as having a profound influence on the extent and structure of genetic variation in plant populations. To investigate the spatiotemporal variation in the reproductive modes (sexual and vegetative reproduction) and population genetic structures of a monocarpic perennial herb, Cardiocrinum cordatum (liliaceae), we selected a variety of habitats (e.g. large forested area including primeval forest, small fragmented secondary forest, and so on) around Sapporo City, Japan. We conducted breeding experiments, monitored the fate and growth of marked individuals for 3 years, and also analyzed the spatiotemporal genetic variation of flowering plants within the populations using allozyme variation. Plants emasculated prior to anthesis produced mature fruits in all populations examined. However, seed production was significantly lower in the small fragmented populations, possibly because of the low availability of pollinators and subsequent pollen limitation. In these fragmented populations, the mature flowering plants tended to be more dependent on vegetative reproduction for their recruitment, because they can only produce flowers once in their lifetime. Genetic diversity using samples from mature flowering plants in each population was lower in the small fragmented populations than in the large populations. In addition, although genotypic compositions in the fragmented populations were more or less similar during the 3 years of the study, the dominant genotypes changed temporally and spatially every year in the large populations. The present study demonstrated that the reproductive features of C. cordatum can be altered in various environmental conditions, such as habitat fragmentation, and these changes considerably affected the population genetic structures and vice versa.     

Dissecting components of flowering pattern: size effects on female fitness

Flowering synchrony is essential for plant reproductive success, especially in the case of small‐sized populations of self‐incompatible species. Closely related to synchrony, flowering intensity influences pollinator attraction and pollinator movements. Thus, a high flowering intensity may increase pollinator attraction but, at the same time, may also increase the probability of geitonogamous pollinations. Depending on the mating system, the female fitness of plants in small populations may be affected by both the positive effects of higher flowering synchrony and pollinator attraction and the negative effects of geitonogamous pollinations induced by a high flowering intensity. It was hypothesized that different‐sized plants in a population would show contrasting flowering patterns, resulting in differences in pollinator behaviour. These influences could result in differences in mating and female reproductive success. This hypothesis was tested by studying the flowering pattern of Erodium paularense (Geraniaceae), a rare and endangered endemic of central Spain. The temporal distribution of flower production was explored throughout the reproductive season, and the probability of xenogamy and geitonogamy and their relationship to plant size and fitness components were calculated. The analysis of this partially self‐compatible species showed diverse flowering patterns related to different plant sizes. Small plants produced a larger number of seeds per fruit in spite of having lower values of flowering synchrony. By contrast, large plants produced a larger number of seeds from geitonogamous pollinations. The effect of different flower displays and outcrossing rates on seed set varied throughout the season in the different groups. Our findings highlight the relevance of individual plant size‐dependent phenology on female reproductive success and, in particular, on the relationship between flowering synchrony and fitness. © 2008 The Linnean Society of London, Botanical Journal of the Linnean Society, 2008, 156 , 227–236.