Variation in breeding system among populations of the common woodland herbAnemone nemorosa (Ranunculaceae)

Recent studies of germination in natural habitats, of genetic variation within populations and of the relative proportion of vegetative and sexual reproduction in the clonal plant speciesAnemone nemorosa suggest that sexual recruitment by seeds from outcrossed flowers is important for the maintenance of this species' populations. Because published reports on its breeding system are controversial, pollination experiments were performed in five natural populations ofA. nemorosa. Differences in ovule number per flower were recorded among populations, but they were not related to obvious habitat differences. Seed/ovule-ratios were significantly higher after open pollination and artificial crossing than after either artificial or spontaneous selfing. Populations had no effect on seed/ovuleratios. Different breeding indices indicated thatA. nemorosa is mainly self-incompatible. Nevertheless, some seed set also occurred after selfing, and both artificial and spontaneous selfing exhibited higher variation in seed/ovule-ratios than open pollination and artificial crossing. Continuous variation in seed/ovule-ratios after selfing suggested that the expression and effectiveness of the self-incompatibility system ofA. nemorosa is influenced by both genetic variation and phenotypic plasticity.     

Life History Studies on the Genus Trillium (Liliaceae) III. Reproductive Biology of Six Sessile-flowered Species Occurring in the Southeastern United States with Special Reference to Vegetative Reproduction

Abstract Life history characteristics, e.g., stage class structures of natural populations and associated reproductive characteristics, were studied for six sessile-flowered, diploid Trillium (Liliaceae) species that are restricted to the Coastal Plain region of the southeastern United States.
These sessile-flowered species reproduce primarily by vegetative propagation. Leaf area measurements were used to categorize stage class distributions of natural populations. Populations propagating mainly by vegetative reproduction had non-sigmoidal, convex-shaped population structures with most plants being in the intermediate stage classes. Low numbers of individuals in smaller stage classes and an abundance of intermediate sized individuals are due to the fact that vegetative propagules are the primary method for maintenance of local populations.
Characteristics associated with sexual reproduction were also examined. Seed output averaged about 20 seeds per plant, except for T. lancifolium which produced 9.7 seeds on the average. Seed setting rates varied between 15.61–44.15% and mean seed weight varied from 4.89 to 10.75 mg. The dominance of vegetative versus sexual reproduction may be due to the fact that all six species occur in ecologically unstable flood plain habitats.     

Reproductive versatility in legumes: the case of amphicarpy in Trifolium polymorphum

Amphicarpy is a fascinating reproductive strategy, defined as fruit produced both below the soil surface and as aerial fruit on the same plant. Trifolium polymorphum is a grassland species subject to herbivory that combines amphicarpy with vegetative reproduction through stolons. Underground flowers have been described as obligate autogamous and aerial ones as self‐compatible allogamous, with aerial floral traits favouring cross‐pollination. In the present work we performed different pollination treatments on aerial flowers to analyse rates of pollen tube development and offspring fitness, measured as fruit set, seed production and germination percentage. This last variable was compared to that of seeds produced underground. No significant differences were found between fruit set in self‐ and cross‐pollinations. Seed production was higher in self‐pollinations, which is consistent with the higher rate of pollen tube development observed in self‐crosses. Spontaneous self‐pollination is limited in aerial flowers; thus pollen transfer by means of a vector is required even within the same flower. Germination tests showed that aerial seeds produced after self‐ and cross‐pollination did not differ in fitness, but underground seeds had higher germination percentage than aerial ones. Thus, we conclude that T. polymorphum has a mixed mating system. In grasslands with heavy grazing pressure, clonal propagation and underground seed production ensure persistence in the field. An intermediate level of selfing in aerial flowers ensures offspring, but morphological (herkogamy) and functional (dicogamy) floral traits maintain a window to incorporate genetic variability, allowing the species to tolerate temporal and spatial pressures.     

The role of sexual and vegetative reproduction in the population maintenance of a monocarpic perennial herb,Cardiocrinum cordatum var. glehnii

Because monocarpic perennial plants have only one reproductive opportunity in their entire life, they need to ensure offspring production. Some plants reproduce both sexually and vegetatively, and vegetative reproduction could possibly compensate for seed production. Therefore, the role and significance of these reproductive modes is likely to differ between monocarps and polycarps, which can reproduce many times. Cardiocrinum cordatum var. glehnii is a monocarpic perennial that reproduces both sexually and vegetatively (bulblet formation). Here, we investigated the characteristics and contribution to population maintenance of sexual and vegetative reproduction to reveal the significance of these two reproductive modes in this species. First, we found that bulblet formation occurred in plants after the three‐leaved rosette stage. Second, resource allocation experiments revealed that although resources were mainly invested in fruit maturation after the flowering season, resource allocation was switched from sexual reproduction to vegetative reproduction if seed production was insufficient. Third, the outcrossing rate in this species varied greatly according to the environment surrounding the population. However, reproductive assurance by selfing kept seed production stable even if flowers did not receive sufficient pollen for full seed set via outcross pollination, and moreover, there was no intensive inbreeding depression. Finally, genotypic identification of ramets suggested that daughter ramets derived from vegetative reproduction received the space that the mother flowering ramet had occupied until the previous year.     

Potential contribution to the invasion process of different reproductive strategies of two invasive roses

The type of reproductive system may be an important trait for the establishment and maintenance of populations of invasive plant species in new areas, as it can influence their demography and genetics. We studied the breeding system of two exotic invasive species, Rosa rubiginosa and R. canina, in a natural reserve in Argentina, using a combination of pollination experiments. We asked how the different reproductive modes of these species affect the quantity and quality of the fruits and seed produced. Our results show that both invasive rose species have an array of reproductive strategies, and that they are able to invade without pollinators, as they can produce seeds in the same quantity and quality through wind-pollination, self-pollination, and apomixis. Such lack of dependence on pollinators and pollination for reproduction should enhance colonization into new areas, suggesting the need of intensive monitoring of spread and dispersal. Considering that both species are successful invaders in the region, our results are in line with Baker’s rule, which posits that plants capable of uniparental reproduction are more likely to invade new areas.     

The productive and reproductive biology of flowering plants

The life cycles, programme of energy expenditure and allocation to reproduction, and the reproductive efforts of three wildAllium species, i.e.,A. Victorialis ssp.platyphyllum, A. monanthum, andA. Grayi, all native to Japan, were studied and compared. Furthermore, their adaptive strategies were discussed from the point of view of life history strategy. First, the reproductive systems, number of male and female gametes borne, and the number and size of propagules produced were critically investigated. In order to estimate the crude reproductive efficiency (sensu Harper and Ogden, 1970) of these species, sequential harvests were taken and the plants were divided into their component structures, dried and weighed. The quantity of dry weight allocated to sexual or vegetative reproduction was obtained by weighing the seeds, bulbils, or bulblets produced at the end of the season. A. Victorialis ssp.platyphyllum showed a rather low reproductive effort. However, the mean seed output per plant was 34.8±16.8 and the productivity appeared very constant every season. Thus, in the natural populations young plants are borne and recruited every season by means of sexual reproduction. A. monanthum was found to be characterized by annual type dry matter economy. The sexuality and reproductive systems of this species turned out to be extremely complex, and ten different reproductive types were distinguished. The exceedingly low efficiency of sexual reproduction in this species is apparently supplemented by vegetative propagation. The dry matter allocation to daughter bulbs at final harvest was very high; whereas the allocation to sexual reproduction was extremely low. InA. Grayi (a polyploid complex of 4X, 5X, and 6X), a surprisingly high amount of the total annual net assimilate is allocated to the bulbils and bulblets. On the other hand, sexual reproductive effort in this species is exceedingly low, even in obligate amphimictic plants. Thus, the recruitment of individuals in a population of this species appears to be largely dependent on vegetative reproduction. Considering the number of bulbils produced in the scape heads, their dispersibility, germinability, and rapid growth after sprouting, the bulbils evidently possess a function almost comparable to seeds. This species no doubt possesses an adapative strategy to unstable, open habitats exposed to frequent disturbances. It is concluded that the life history strategies of plants, as characterized here in this paper for three wildAllium species, have doubtlessly differentiated by adapting to the respective ecological backgrounds of their habitats.     

Effects of disperser abundance, seed type, and interspecific seed availability on dispersal distance

Seed dispersal distance is influenced by a variety of seed properties and functional responses of dispersers. However, to our knowledge, how and why seed dispersal distances are determined remains poorly understood. In the present study, seeds of sympatric tree species, Pinus koraiensis, Corylus mandshurica, Corylus heterophylla, and Quercus mongolica were released to investigate the effects of rodent abundance, seed type, and seed availability on seed dispersal. Our results showed that seeds of P. koraiensis were dispersed further than those of C. heterophylla and C. mandshurica regardless of the ambient rodent and seed abundances, reflecting a consistent effect of seed type on seed dispersal distances. Seed dispersal distance was greatly facilitated by lower per-capita seed abundance (the ratio of seeds to rodents); however, seed caching and cache survival were benefited from higher per-capita seed abundance. Although seed dispersal and seed caching of a particular tree species can be enhanced by its own seed availability, no consistent influence was detected at interspecific levels, reflecting different interspecific effects of seed availability on seed dispersal of sympatric seed species. Our results provide evidences that the effect of seed availability on seed dispersal should be evaluated in terms of per-capita seed abundance and interspecific effects, rather than the independent influence of seed or disperser abundances.     

Reproductive ecology of Aloe plicatilis,a fynbos tree aloe endemic to the Cape Winelands,South Africa

While the pollination ecology of many Aloe species is well-documented, knowledge on aloe seed ecology, and hence aloe reproductive ecology in its entirety is limited. The aim of this study was to investigate the reproductive ecology of Aloe plicatilis, a Cape fynbos tree aloe endemic to the Cape Winelands, South Africa. Results from a pollinator exclusion experiment conducted at an A. plicatilis population on Paarl mountain suggests pollination primarily by insects, although bird visitation significantly increased seed set/fruit indicating possible co-pollination with insects. The species' long-tubed flowers and production of concentrated nectar, with observations of malachite sunbirds as the most common avian visitors to A. plicatilis flowers indicate the importance of long-billed specialist avian nectarivores as floral visitors. Analysis of the relationship between plant size and inflorescence production for five populations combined revealed a significant, positive linear relationship between plant size and the logarithm of the number of inflorescences/plant. Natural fruit and seed set determined for three populations (1325, 27,930 and 251,616 seeds/population) suggests low reproductive output compared to several other Aloe species. The smallest (31 individuals) and least dense (75 plants/ha) A. plicatilis population produced the lowest seed set/plant (128 seeds) and per population (1325 seeds), suggesting an Allee effect. Evaluation of seed dispersal potential showed that potential dispersal distances were approximately three times the canopy height; however, the occurrence of A. plicatilis on mountains isolated from more continuous mountain ranges on which the species also occurs suggests the possibility of long-distance dispersal by strong, gusty, summer winds. Soil seed bank samples collected from 13 populations yielded close to zero seedling emergence, indicating the absence of persistent seed banks. A. plicatilis seeds stored under ambient laboratory conditions for 3, 18 and 24 months were germinated in an environmental control chamber and a laboratory. High percentage germination was recorded for 18- and 24-month-seed (86 and 80%, respectively), while germination of 3-month-old seeds was three times lower, suggesting the need for after-ripening. Germination of fresh and one-year-old seed under ambient nursery conditions at the Karoo Desert National Botanical Garden in Worcester yielded emergence percentages of 67 and 44%, respectively, and were therefore less successful than germination under more controlled conditions. This is the first known study to investigate the reproductive ecology of a tree aloe species and that of a Cape fynbos aloe. The study highlights the importance of further studies on aloe seed ecology, particularly for rare and threatened species.     

Effects of habitat fragmentation on the reproductive success of the nectar-producing orchid Gymnadenia conopsea and the nectarless Orchis mascula

Habitat fragmentation decreases plant population sizes and increases spatial isolation, which hampers the exchange of seeds and pollen between fragmented populations. This may result in decreased population viability. We compared the effects of population size and isolation on the reproductive success of two orchid species, Gymnadenia conopsea (nectar-producing) and Orchis mascula (nectarless) growing in highly fragmented calcareous grassland in southern Belgium. We expected that the nectar-producing species would be more susceptible to the negative reproductive consequences of habitat fragmentation compared to the nectarless species. Nectar production has been associated with increased geitonogamous pollination and, therefore, with lower seed viability. Our results show that seed viability increased with increasing population size in O. mascula, whereas it was always low in G. conopsea, even in large populations. In contrast, percentage fruit set was positively related to population size in the nectar-producing G. conopsea, but no such effect was observed in the nectarless O. mascula, where fruit set was low even in large populations. Population isolation was not related to reproductive success for either species. Our results suggest that even in large populations, where pollinators are expected to be more abundant, increased geitonogamous pollination reduces seed viability in the nectar-producing G. conopsea. In contrast, seed viability in O. mascula seems to benefit from increased pollinator availability in larger populations. For the latter species, however, fruit set remains low, even in large populations, compared to G. conopsea. This may be explained by the relatively low attractiveness of nectarless orchid species for pollinators. Our results indicate that small population size may negatively influence reproductive success in both nectarless and nectar-producing orchids by reducing seed viability and fruit set, respectively.     

Reproduction strategies in introduced Nymphoides peltata populations revealed by genetic markers

To determine whether introduced Nymphoides peltata populations reproduced vegetatively or sexually, microsatellites were used to study the genetic structure of the species in Sweden. Leaves from 156 plants and seeds from 4 plants were sampled from 7 water-systems and analysed. A total of 10 genotypes were found among the 156 leaves. Seeds accounted for one additional genotype per seed. Lack of genetic variation and entirely vegetative reproduction dominated in the introduced N. peltata populations although sexual reproduction was found in one water-system. However, even where the species reproduced sexually, vegetative reproduction constituted an important part of the total reproduction.     

Demand and supply of N in seed production of soybean (<Emphasis Type="Italic">Glycine max</Emphasis>) at different N fertilization levels after flowering

Nitrogen (N) has been suggested as a determinant of seed production especially in species with high seed N content. Assuming that seed yield was determined as the balance between N demand and supply for seed production, we studied the effect of N fertilization after flowering on soybean (Glycine max L. Merr.) yield. Seed N concentration was nearly constant irrespective of N fertilization, indicating that seed production was proportional to the amount of N available for seed growth. N demand for seed production was analyzed as the product of seed number, the rate of N filling in individual seeds, and the length of the reproductive period. N fertilization increased seed number and the reproductive period, but did not influence the N filling rate. Seed number was positively correlated with dry mass productivity after flowering. Three N sources were distinguished: mineral N uptake, symbiotic N₂ fixation and N remobilization from vegetative body. N fertilization increased N uptake and N remobilization, but lowered N₂ fixation. We concluded that N availability in the reproductive period determined seed yield directly through increasing N supply for seed growth and indirectly through increasing seed N demand with enhanced plant dry mass productivity.     

Population size, pollination and reproductive success in two endangered Genista species

Habitat fragmentation often leads to small and isolated plant populations as well as decreased habitat quality. These processes can fundamentally disrupt the interactions between plants and pollinators and decrease reproductive success. This concerns especially self-incompatible, non-clonal species that depend on pollination for successful reproduction.In two rare and endangered heathland plant species, Genista anglica and G. pilosa, we examined pollination and reproduction in relation to population size. Eight populations of G. anglica and ten populations of G. pilosa were surveyed in the vicinity of Bremen, NW-Germany. We counted the visits of pollinators (honeybees, bumblebees, and other insects) and determined the reproductive output of the observed shoots.Contrary to our expectation to find increased pollinator visitation rates in larger populations of both Genista species, the number of flower-visiting insects was unrelated to the number of flowering shoots. Increasing shoot length had a positive and increasing temperature a negative impact on the number of visiting honeybees and bumblebees. Despite the general absence of population size effects on pollinator numbers, the number of fruits and seeds in G. anglica increased with increasing population size. Fruit and seed set in G. pilosa were negatively related to the number of ‘other insects’. Our field observations showed that larger populations of both Genista species flowered earlier than smaller populations and much earlier than reported in the literature. Flowering in large populations therefore tends to coincide less well with pollinator abundance, and this may cause a disruption of the temporal coincidence between flowering phenology and pollinator activity.     

Sympatric reinforcement of reproductive barriers between <Emphasis Type="Italic">Neotinea tridentata</Emphasis> and <Emphasis Type="Italic">N. ustulata</Emphasis> (Orchidaceae)

Reinforcement is the process by which selection favors traits that decrease mating between two incipient species in response to costly mating or the production of maladapted hybrids, causing the evolution of greater reproductive isolation between emerging species. I have studied a pair of orchids, Neotinea tridentata and N. ustulata, to examine the level of postmating pre- and post-zygotic isolating mechanisms that maintain these species, and the degree to which the boundary may still be permeable to gene flow. In this study, I performed pollen tube growth rate experiments and I investigated pre- and post-zygotic barriers by performing hand pollination experiments in order to evaluate fruit set, embryonate seed set and seed germination rates by intra- and interspecific crosses. Fruit set, the percentage of embryonate seeds and germinability of interspecific crosses were reduced compared to intraspecific pollinations, showing significant differences between sympatric and allopatric populations. While in allopatric populations the post-pollination isolation index ranged between 0.40 and 0.11, in sympatric populations orchid pairs showed total isolation due to post-pollination prezygotic barriers, guaranteed at the level of pollen–stigma interactions. Indeed, in sympatric populations, pollen tubes reached the ovary after 24 h in only 8 out of 45 plants; in the remaining cases, the pollen tubes did not enter the ovary, and thus no fruit set occurred. This pair of orchids is characterized by postmating pre-zygotic reproductive isolation in sympatric populations that prevents the formation of hybrids. This mechanism of speciation, starting in allopatry and triggering the reinforcement mechanisms of reproductive isolation in secondary sympatry, is the most likely explanation for the pattern of evolutionary transitions found in this pair of orchids.     

Burning grasses,poor seeds: post-fire reproduction of early-flowering Neotropical savanna grasses produces low-quality seeds

Fire is a key factor triggering ecological processes in old-growth grasslands and savannas and could have strong implications for reproduction via seeds for the herbaceous layer. In the Neotropical savannas, grasses show strong synchronous post-fire flowering, and their reproduction is often considered fire-dependent, with their massive post-fire seed production being suggested as a source of population maintenance. However, literature lacks studies to provide evidence of fire-dependent flowering and no study has assessed the quality of the post-fire seed production. Therefore, we aimed to describe a phenological pattern across early-flowering Neotropical savanna grasses in both recently burnt and unburnt cerrado communities addressing three questions: (1) Do the early-flowering species rely on fire for reproduction via seeds? (2) If no, what are the effects of fire on their reproductive phenology? (3) Does the massive seed production in post-fire cerrado communities lead to high-quality seeds? We recorded the reproductive phenology of nine early-flowering grasses for 17 weeks in unburnt and recently burnt cerrado communities. We collected the seeds, estimated the production of fertile seeds, and tested germination. No species showed a pattern of fire-dependent reproduction. Fire stimulated earlier flowering while reproduction in the unburnt community was related to continuous rainfall. Seed production following fire was of low quality, and no species produced?>?7% fertile seeds. Seed germination remained below 50% for most species. Post-fire seed production of early-flowering species led to poor seed quality, suggesting a constraint to the recruitment of new individuals of early-flowering Neotropical savanna grasses in recently burnt cerrados.

     

Bulbils contra seeds: reproductive investment in two species of Gagea (Liliaceae)

The reproductive biology of the sympatric species Gagea lutea and Gagea spathacea was analyzed morphologically and by resource allocation measurements. Both taxa reproduce vegetatively by bulbils. The hexaploid G. lutea regularly forms seeds, but flowering plants cease to produce bulbils. Seed set was never observed in nonaploid G. spathacea which does not stop vegetative reproduction when flowering. In this species, the pollen contains a high proportion of non-viable grains. Already sterile plants invest more resources (per cent of total nitrogen) into bulbils than G. lutea (10.9 vs. 5.9%). For flowering plants, the respective values are 6.1% (flowers) plus 18.4% (bulbils) for G. spathacea versus 14.8% (flowers only) for G. lutea. G. spathacea lost the ability to reproduce sexually and relies solely on vegetative reproduction. This seems to require the breakdown of the switch mechanism between the bulbil and flower formation (as in G. lutea) and a higher net investment in reproduction, hampering individual growth.     

内蒙古中东部草原不同生境克氏针茅（Stipa krylovii Roshev.）种群的形态差异分析

对内蒙古中东部草原分布的克氏针茅进行了种群内和种群间的形态差异分析。结果表明：（1）种群内不同的形态性状存在不同程度的差异;（2）种群间生殖枝中的一部分形态性状以及营养枝高度和营养枝干重均存在较大差异;（3）每穗小花数、每穗籽粒数、每穗小穗数、生殖枝高、穗干重、生殖枝干重、每穗种子重、种子重/生殖枝重比等性状的变化趋势相同,均表现为随生境条件变差而增加,即在生殖上投入增加以增大适合度;（4）主成分分析表明穗长、种子重/生殖枝重比、每穗小花数、每穗籽粒数、生殖枝高、基盘长、第二芒柱长、营养枝高、千粒重、芒针长是不同种群差异的主要指标。这些形态性状的差异可以看作克氏针茅对不同生境的适应性表现。     

Effects of Local Plant Density and Incomplete Dichogamy on the Reproductive Success of the Rare Neotropical Palm Geonoma epetiolata

Density dependent processes are known to influence reproduction and establishment of plant populations. In this study, we evaluated the effects of local density and sexual expression on the reproductive success of the rare palm species Geonoma epetiolata in Costa Rica. We classified individuals in two density categories based on distances to the two nearest neighbors and recorded the occurrence of sexual overlap on each individual. Overlap between pistillate and staminate flowers in monoecious plants allows geitonogamous pollination, potentially reducing dependence on mates for reproduction. We measured plant size and light availability, and evaluated the influence of these variables on pollination success, fruit production, fruit abortion and seed mass. Pollination success significantly increased with density but there was no effect of sexual overlap. In contrast, there was no effect of density on the probability of initiated fruit, and a negative effect on fruit set. Fruit abortion was lowest in isolated plants with no sexual overlap. Plant size and light did not contribute to variation in reproductive success. In conclusion, the pollination advantage of plants in dense neighborhoods does not compensate reproductive losses incurred by fruit abortion, possibly due to mating among genetically related individuals. Geonoma epetiolata is threatened by habitat loss and poaching of seeds for the horticultural market. High fruit abortion rates associated with density in G. epetiolata suggest that seed collections from the remnant wild populations of this palm species may cause bottlenecks that further threaten population viability.     

Effects of pollen quantity and quality on reproduction and offspring vigor in the rare plant Scorzonera humilis (Asteraceae)

We studied the effects of pollinator exclusion, interparental distance, and supplementary hand pollination on reproduction and progeny vigor in Scorzonera humilis (Asteraceae), a rare plant of fragmented, nutrient-poor grasslands. Caged flowers produced no seeds and selfed flowers only very rarely, indicating that S. humilis is mainly self-incompatible. Seed production, seed mass, and seed germination following between-population crosses were consistently, but not significantly, higher than after within-population crosses. Seed set increased with local density of conspecifics, indicating that the reduced plant density in fragmented populations may reduce plant reproductive success. Seed set was pollen limited in all four populations studied. Supplementary hand-pollination strongly increased the survival of offspring, indicating that either pollinators transferred pollen from related individuals resulting in inbreeding depression in spite of the incompatibility system or that higher pollen loads increased pollen competition and the selectivity among gametes. In one of the populations, adding pollen from a different population strongly increased progeny fitness compared with both natural pollination and pollen supplementation from the same population. The results indicate that S. humilis is sensitive to inbreeding and that pollen limitation can reduce both the number and quality of offspring.     

Limitations to reproductive output and genetic rescue in populations of the rare shrub Grevillea repens (Proteaceae)

Background and Aims

When conserving rare plant species, managers are often faced with small and/or isolated populations displaying low levels of sexual reproduction and genetic variation. One option for reinvigorating these populations is the introduction of genetic material from other sites, but in some cases fitness may be reduced as a result of outbreeding depression. Here the pollination biology of the rare shrub Grevillea repens is studied across its natural range and reproductive responses following cross-pollination among populations are examined to determine factors that may be limiting sexual reproduction and the potential for genetic rescue.

Methods

Pollen manipulation treatments (self-, autogamous self-, cross- and open pollination) were applied to flowers to examine the breeding system and fruit and seed production in five populations of G. repens. Pollen production, presentation and viability were investigated and interpopulation crosses of increasing genetic distance performed among the populations.

Key Results

The study species is self-incompatible and displayed very low natural seed set over two seasons, due partly to low pollen viability in one of the populations. Within-population crossing increased fruit and seed production at some sites, indicating pollinator limitation. Interpopulation crosses further increased reproductive output in one population, suggesting mate limitation, and for this site there was a positive relationship between genetic distance among populations and the size of genetic rescue benefits. However, in other populations there was a decrease in fruit and seed set with increasing genetic distance.

Conclusions

The results highlight that management strategies involving interpopulation crosses can improve reproductive output in small, isolated populations of rare plants, but guidelines need to be developed on a population by population basis.Key words: Grevillea repens, Proteaceae, genetic rescue, pollination ecology, self-incompatibility, breeding system, interpopulation cross, outbreeding depression, pollinator limitation, mate limitation, resource limitation