Effects of pollination distance on reproduction and offspring performance in Hypochoeris radicata: Experiments with plants from three European regions

Fragmentation of habitats has resulted in increased inbreeding for many plant species, while the introduction of foreign seed material for ecological restoration has resulted in crosses between plants from distant populations. Both processes may reduce plant fitness and increase the risk of extinction. Variation in the expression of inbreeding and outbreeding depression has been found among different genotypes and among populations, but little is known about large scale geographical patterns within species. We studied the effects of cross-proximity on seed production and offspring performance in the perennial meadow plant Hypochoeris radicata (Asteraceae) from five populations in each of three European regions (Bohemia in northwest Czechia, Northern Hesse in central Germany, and Salland in the central Netherlands). Five artificial cross types were conducted with varying proximity of mates: selfing (self), within family crosses (WF), within population crosses (WP), between population crosses (BP), and between region crosses (BR), and the offspring were grown in a common garden. Independent of the region of origin of the maternal plant, selfing, WF and BP crosses resulted in lower seed set and germination than WP crosses, indicating partial self-incompatibility, inbreeding depression and reduced performance in the F1 progeny resulting from outbreeding. However, crosses between regions resulted in similar seed set and germination as within population crosses. For late traits, the effects of inbreeding and interpopulation crosses differed among regions. WP crosses exhibited the highest survival, flowering and multiplicative fitness only in progeny from Czech maternal plants. Our results suggest that the sensitivity of populations to introgression may vary among regions and that outbreeding depression does not necessarily increase with interpopulation distance. However, the current study investigated only effects in the F1 in a common garden and outbreeding depression may be stronger in the F2 and in field populations.     

Reduced seed production, inbreeding, and pollen shortage in a small population of a threatened tree, Magnolia stellata

We investigated how genetic factors and pollen shortage affect seed production in a small population of Magnolia stellata, a threatened insect-pollinated tree. We used microsatellite and manual pollination techniques, and compared a small population to a large one. Compared to the large population, the small population showed low allelic variation and had an F_IS significantly greater than 0 in adults, indicating that genetic deterioration, including genetic drift and inbreeding, may have occurred in adults. Manual self-pollination lowered seed production relative to manual cross-pollination to a different extent between populations: δ (the magnitude of inbreeding depression due to self-fertilization) was lower in the small population than in the large population. However, under natural pollination, the estimated embryo mortality rates after ovules self-fertilized were similar between the two populations because the primary selfing rate was higher in the small population. The ovule mortality rate due to pollen shortage and that due to factors independent of pollen shortage and selfing were both approximately 10% higher in the small population, suggesting that pollen transfer may have decreased and genetic deterioration effects may have increased in that population. These factors reduced seed production in the small population (female reproductive success = 0.3%) compared to the large population (2.6%). Our results suggest that seed production in the small population of M. stellata is strictly limited by elevated pollen shortage, selfing, and genetic deterioration in adults, which accelerate the risk of extinction.     

Gene flow after inbreeding leads to higher survival in deer mice

We test the ability of gene flow to alleviate the deleterious effects of inbreeding in a small mammal, the deer mouse (Peromyscus maniculatus). After three generations of sib-sib mating, individuals from three lines of mice were either subject to further inbreeding or were mated with an outbred individual. Subsequently, these mice, plus a control line, which were first generation (F₁) mice from unrelated individuals kept in captivity for the same duration as the treatment lines, were released into isolated pens in a forest in western Montana. Survival of individual mice was recorded. Survival models that allowed variation in breeding treatments were well supported, whereas models explaining variation in line, or release location were not well supported. Survival was highest for offspring of the outcross group, intermediate for the inbred animals, and lowest for the control group. This suggests that the introduction of migrants can reduce inbreeding depression, as theory predicts. We also show limited evidence for purging of deleterious recessive alleles that can cause inbreeding depression. While purging may have occurred, the demographic cost was non-trivial as 5 of 8 of our inbred mouse lines went extinct during the inbreeding process.     

Pollen-limited production of viable seeds in an endemic dwarf birch, Betula apoiensis, and incomplete reproductive barriers to a sympatric congener, B. ermanii

An endemic dwarf birch, Betula apoiensis, is critically endangered, and two populations of this species are restricted to the ridges of Mt. Apoi in Hokkaido, Japan. We observed the flowering phenology, pollen dispersal, and viable seed production and conducted pollination experiments in order to examine pollen limitation and hybridization with a sympatric congener, B. ermanii. B. apoiensis flowered earlier than B. ermanii but had a more variable flowering time among trees than B. ermanii. The female flowering of B. apoiensis temporally overlapped with the male flowering of B. ermanii as well as with that of B. apoiensis. Pollination experiments demonstrated that seed set and seed germination were higher in female flowers outcrossed than in those that were non-pollinated, selfed, hybridized with B. ermanii pollen, or pollinated naturally. A few selfed or hybrid seeds were filled and germinated, which indicates that self-incompatibility and reproductive barriers are not complete. Logistic regressions of local density of conspecific trees on natural seed set and seed germination were significantly positive. These results suggest that B. apoiensis is pollen-limited.     

Effects of root fragmentation on generative reproduction of Sonchus arvensis

To develop better mechanical management strategies, more information on the impact of root partitioning on generative reproduction of Sonchus arvensis L. is needed. Therefore, an outdoor experiment was performed in Sweden in 2008, to evaluate the effect of root fragmentation on generative reproduction of S. arvensis. Two artificial populations of S. arvensis with the same total root length per area but with different initial root lengths and different numbers of root fragments were planted. Cumulative numbers of flower receptacles which had shed mature seeds over the season were assessed. Changes in the number of seeds per flower receptacle and average seed weight were monitored over time during the late season. Plants from long root fragments produced more flower receptacles than plants from short ones. Per area, however, the number of mature flower receptacles did not differ. The number of seeds per flower receptacle and individual seed weight were not affected by initial root length for the first cohort of shoots which sprouted from the initially planted roots. A second cohort, from roots produced during the season, resulted, irrespective of its initial root length, in fewer flower receptacles per plant and per area, with less seeds per receptacle, but with the same average seed weight as the first cohort. The number of seeds per flower receptacle was higher in mid-September than earlier or later. Average seed weight slightly decreased over time. The weight of seeds produced in early September was inversely related to the number of seeds per receptacle, but this trade-off disappeared over time. Root fragmentation alone in pure populations of S. arvensis does not impede generative reproduction, but is likely to decrease input of seeds to the seed bank, when combined with crop competition.     

Critical resource levels of pollen for the declining bee Andrena hattorfiana (Hymenoptera, Andrenidae)

The native bee fauna provides an important ecosystem function, but a large proportion of this fauna in Europe is threatened as a result of habitat loss and fragmentation. The solitary bee Andrena hattorfiana is specialised on collecting pollen from the plant-family Dipsacaceae. In northern Europe the major pollen resource is the insect-pollinated herb Knautia arvensis. We quantified the available K. arvensis resource, measured habitat characteristics and performed a flower-visitor survey in 57 well-defined K. arvensis populations in southern Sweden. There was a strong relationship between bee and plant population sizes. In populations with A. hattorfiana present (N = 26), the female bees utilised on average 39% (12-80%) of the total available pollen resource. The nest architecture and nesting biology of A. hattorfiana is described for the first time. By excavating nests, we found that the provisioning for one average bee nest (containing 6 cells) required ca. 72 inflorescences or 11 plant individuals. The results suggest a certain minimum pollen amount needed to host an A. hattorfiana population. For example, for a population of ten reproducing A. hattorfiana ♀ with the average degree of utilisation, the critical resource was predicted as 156 ± 16 individuals (±SE) of the plant K. arvensis, which corresponds to 780 inflorescences or 36,731,978 pollen grains. These findings suggest that calculations via a ‘pollen budget’ can predict critical resources for a given size of specialised bee population, and thereby provide a tool in conservation.     

The role of floral biology and breeding system on the reproductive success of the narrow endemic Petrocoptis viscosa rothm. (Caryophyllaceae)

Morphological and functional characteristics of flowers may have major effects on their reproductive success. Here, we report a study on the characteristics of flowers of Petrocoptis viscosa, a herb species endemic to the northwest Iberian Peninsula, restricted to crevices in limestone outcrops, and currently occurring in only three populations within an area of less than 30 km². We also investigated the effects of pollen source on indicators of reproductive success. The results show that Petrocoptis viscosa flowers are well adapted to autogamy. Inbreeding depression (as determined by comparison of results obtained after selfing and outcrossing) was negligible for fruit production (δ=−0.05) and mean seed number (δ=−0.11), low for seed germination percentage (δ=0.08), but relatively high for mean seed weight (δ=0.23). The spatial structure and small size of population of Petrocoptis viscosa may mean that inbreeding is frequent in natural habitats. Adaptation of plants to autogamy may therefore be energetically beneficial (i.e. less wasted expenditure on rewards and flowers).     

Inbreeding in red-cockaded woodpeckers: Effects of natal dispersal distance and territory location

Inbreeding depression constitutes a significant threat to the viability of small populations. In addition to small size and isolation of populations, short distance dispersal may elevate risk of inbreeding, but empirical evidence is scarce. Inbreeding depression has been demonstrated in the highly endangered red-cockaded woodpecker Picoides borealis. It has been suggested that conservation efforts to support extant populations should aim at spatially aggregating territories to enhance dispersal success. This however may aggravate inbreeding risk because distance between territories and hence dispersal distances become short. We analysed empirical data from a long-term study of the demography of the red-cockaded woodpecker and found that inbreeding risk varied inversely with natal dispersal distance of the mother. Using an individual-based, spatially explicit population model that incorporates simulations of environmental and demographic stochasticity and an empirically derived, species-specific estimate of inbreeding costs, we demonstrated that inbreeding depression significantly elevated extinction risk in this species. On the other hand, even though dispersal distances in populations with spatially aggregated territories were shorter and the proportion of inbred individuals was higher than in other populations of the same size, such populations were still more persistent. Despite the overall adverse effect of inbreeding depression on viability of red-cockaded woodpecker populations, lowering interterritorial distances can be viewed as a valuable conservation tool. Given the small size and isolated location of most extant red-cockaded woodpecker populations however, our findings suggest that inbreeding depression represents a significant threat to the survival of this species.     

Carbohydrates and thermal properties indicate a decrease in stable aggregate carbon following forest colonization of mountain grassland

In mountainous areas of Europe, the abandonment of grasslands followed by forest expansion is the dominant land-use change. Labile (i.e. easily decomposable) litter represents the major source for soil microbial products, which promote soil aggregation and long-term C stabilization. Our objective was to investigate changes in the content and origin of soil C components involved into aggregate stabilization (i.e. carbohydrates) following forest expansion on abandoned grassland in the Alps, where only few studies have been conducted.Changes in carbohydrates and thermally labile C were assessed along a land-use gradient in the Southern Alps (Italy) following analysis of carbohydrate monomers and thermal analysis of mineral soil and physical soil fractions. The land-use gradient comprised managed grassland, two transitional phases in which grassland abandonment led to colonization by Picea abies (L.) Karst., and an old forest dominated by Fagus sylvatica L. and P. abies.Grassland abandoned for 10 years tended to have higher levels of carbohydrate and thermally labile soil C than managed grassland and old forest, presumably caused by differences in the quality and amount of litter input. Carbohydrates and thermally labile C showed similar patterns in bulk soil, suggesting that thermal analysis can be used to complement chemical analysis although a straightforward relationship could not be established. Following forest expansion on abandoned grassland, ratios of microbially to plant-derived carbohydrates and thermally labile to resistant components decreased in bulk soil and soil fractions. Forest expansion entailed decreasing amounts of microbially derived compounds known to be important for aggregate stability, and corresponded to decreased soil C allocation to stable aggregates.The combination of carbohydrate and thermal analyses revealed a lower abundance of microbially derived C components after forest colonization on abandoned grasslands, thus resulting in lower physical protection of soil C considering that carbohydrates of microbial origin actively promote soil aggregation.     

The role of genetic mechanisms of sex determination in the survival of small populations of Silene littorea: A reintroduction experiment

Loss of genetic variation in populations may have other effects than inbreeding depression and loss of adaptive potential. In the case of the numerous gynodioecious plant species having cytonuclear systems of sex determination with dominant nuclear restorers of the male function, reduced genetic variation and increased inbreeding would increase the proportion of non-restorer recessive genes found in homozygosity, and therefore that of female plants producing pistillate flowers. This could have opposite effects on the extinction risk of the population. Female plants produce no pollen and may cause pollen limitation, but at the same time they may reduce average homozygosity and inbreeding depression because they are forced outcrossers. We observed that inbreeding indeed increased the frequency of female plants and pistillate flowers in the population, and that this effect was accompanied by reductions in population recruitment independent of inbreeding depression and likely due to pollen limitation. These results suggest that dominant nuclear restorers of pollen production speed up the extinction of small populations of Silene littorea, and that sex determination mechanisms might be an important factor to consider in the conservation of many plant species.     

Effectiveness of some management procedures for seed regeneration of plant genetic resources accessions

Procedures for seed regeneration of plant genetic resource accessions were investigated in terms of their effect on the variance effective population size and the probability that the initial allelic diversity is maintained after 10 and 20 cycles of regeneration. Four regeneration systems were compared: a bulk system (BL) where seeds are collected and treated in bulk, a partial sampling system (PS) where seeds are collected from not all, but some plants in the population with an equal number of offspring being raised from each sampled plant, a single seed system (SS) where accessions are regenerated so that each plant leaves one progeny, and the biparental mating system (BP) of Gale & Lawrence (1984) where plants are pollinated in pairs with one offspring being raised from each of the paired plants, or two offspring from one of the paired plants. It was shown that the relative efficiency of the four systems largely depends on the rate of selfing and that differences in the effective population size of the systems increase with increasing rates of selfing. The SS system gave by far the largest effective population size in regenerating the seed of moderately or highly selfing species. Although the BP system gave the largest effective size for outcrossing species, the SS system, when combined with selfing, gave a much larger effective size. The BL and PS systems were in no case the most effective. Of these two, PS system with a sampling fraction of 50% was as effective as BL, but less effective with a sampling fraction smaller than 50%. Calculations of the maintenance of the allelic diversity, however, revealed that differences between the systems are not appreciably large unless the accessions are regenerated over 10 or more cycles with 50 or fewer plants.     

Foliar applied harpin effects on fruit quality of peppers

Abstract

During the past century, changes in cropping systems have led to selective pressure on weed flora. The number of competitive species with decreased susceptibility to herbicides has increased, at the cost of more susceptible species. For a long period, the economically important perennial weed species Cirsium arvense (L.) Scop. and Sonchus arvensis L. have mainly been controlled by the herbicide MCPA (phenoxy-acetic acid), which stimulates the weed plant to abnormal growth. However, it has been reported from Sweden, Great Britain, Hungary and North America that C. arvense has become less susceptible to MCPA since the 1950s. Therefore, two greenhouse experiments were performed at Uppsala, Sweden with clones of C. arvense and S. arvensis. The purpose was to study whether ecotypes (clones) from high input farmland, where herbicides had been used intensively and regularly for a long time, were less susceptible to herbicide (MCPA) treatment than ecotypes from low input farmland. Sixty clones of C. arvense and 36 clones of S. arvensis were treated with nine different doses of MCPA. The results supported the suggestion that a shift towards less MCPA-susceptible ecotypes of C. arvense had occurred on high input farmland. Clone material from such farmland had, on average, significantly higher dry matter content after herbicide treatment than ecotypes from low input farmland. Similar decrease in susceptibility was not detected for S. arvensis. This was probably due to S. arvensis generally being less susceptible to MCPA than C. arvense. Sonchus arvensis has therefore being exposed to a lower selection pressure than C. arvense.     

New sources of resistance to Colletotrichum truncatum race Ct0 and Ct1 in Lens culinaris Medikus subsp. culinaris obtained by single plant selection in germplasm accessions

Anthracnose caused by the fungal pathogen Colletotrichum truncatum is a severe disease of lentil (Lens culinaris Medikus subsp. culinaris) causing premature defoliation and deep penetrating lesions on the stems leading to wilting and plant death. A total of 579 accessions from 20 countries were obtained from four germplasm collections in Russia, Poland, Bulgaria and Hungary. The accessions were collected between 1923 and 1988 and comprised mostly landraces. Consequently, many of the resistant entries contained susceptible plants which necessitated one or two cycles of selection of individual resistant plants for selfing and re-testing with the pathogen. Under controlled environmental conditions, plants of each accession were inoculated at early flower with C. truncatum race Ct0 (isolate 95A8) and race Ct1 (isolate 95B36), separately. Scoring of symptoms included number of lesions on the main stem, lesion penetration into the stem and amount of wilting. Resistance was obtained by single plant selection in 23 lentil accessions (4.0 %). Fifteen lines were generated with resistance to race Ct1 (2.6 %), seven with resistance to race Ct0 (1.2 %), and one line with resistance to both races. This is the first report on resistance in L. culinaris to C. truncatum race Ct0 as well as to the two races combined. Seed of homozygous resistant lines can be requested from the corresponding author, and are labeled with their original accession number with the prefix either -Ct0, -Ct1 or -Ct0Ct1 indicating resistance to one or both races of C. truncatum.     

Polygyny and female breeding failure reduce effective population size in the lekking Gunnison sage-grouse

Populations with small effective sizes are at risk for inbreeding depression and loss of adaptive potential. Variance in reproductive success is one of several factors reducing effective population size (N_e) below the actual population size (N). Here, we investigate the effects of polygynous (skewed) mating and variation in female breeding success on the effective size of a small population of the Gunnison sage-grouse (Centrocercus minimus), a ground nesting bird with a lek mating system. During a two-year field study, we recorded attendance of marked birds at leks, male mating success, the reproductive success of radio-tagged females, and annual survival. We developed simulations to estimate the distribution of male reproductive success. Using these data, we estimated population size () and effective population size N_e for the study population. We also simulated the effects of population size, skewed vs. random mating, and female breeding failure on N_e. In our study population, the standardized variance in seasonal reproductive success was almost as high in females as in males, primarily due to a high rate of nest failure (73%). Estimated N_e (42) was 19% of in our population, below the level at which inbreeding depression is observed in captive breeding studies. A high hatching failure rate (28%) was also consistent with ongoing inbreeding depression. In the simulations, N_e was reduced by skewed male mating success, especially at larger population sizes, and by female breeding failure. Extrapolation of our results suggests that six of the seven extant populations of this species may have effective sizes low enough to induce inbreeding depression and hence that translocations may be needed to supplement genetic diversity.     

Durchwurzelungsvergleich zwischen Fettwiese und angrenzender Brachwiese

Root systems of two contiguous grassland sites (fertilized meadow and abandoned grassland). In the course of an investigation on plant succession and soil development on abandoned grassland, we compared root systems in a fertilized meadow (Arrhenatheretum) with those in grassland abandoned 15 years ago (now being covered mainly by Brachypodium pinnatum). Root lengths were determined by the line intercept method developed by Newman (1966) and Evans (1970). In addition, surface areas and volumes of roots were calculated. In the top layer of the soil (0–5 cm) root lengths and root surfaces were nearly equal in the two sites, but the subsequent exponential decreases with depth were more pronounced in the meadow soil. Root volume (including rhizomes of Brachypodium pinnatum) was much larger in the abandoned grassland site. In addition, results are compared to other investigations on root density.     

Management of Vicia faba genetic resources: changes associated to the selfing process in the major, equina and minor groups

Conserving Vicia faba germplasm as a pure line collection requires reliable information of the selfing process. Previous knowledge about the effects of selfing was elaborated on the context of new data. In our study we increased the number of entries, 95 entries from the major, equina and minor groups were studied. The selfing process has been quantified by means of univariate as well as multivariate techniques. Effects of selfing on floral, yield and yield distribution traits were investigated by comparing two levels of selfing in open pollination conditions and in cages to exclude insects. Univariate analysis shows that selfing process results in plants with lower seeds per plant, seeds and ovules per pod and pod length. As selfing progressed there was change in yield distribution traits, the number of the lowest pod bearing node, the number of nodes between the first flower and the first pod increase and the number of nodes with pods decreases. Multivariate analysis indicates that: a) self-pollination profoundly influences plants performance and the three levels of selfing studied are clearly different; b) There is continuum pattern of change from one level of selfing to the another; c) The main characteristics that contributed to the separation among the levels of selfing varies with the botanical group. d) There was no significant contribution to the discrimination among levels of selfing of number of seeds per plant in the major group. Our results are relevant to the management of faba bean germplasm collections and enhance the formulation of integrated strategies of faba bean germplasm multiplication.     

Inbreeding and small population size reduce seed set in a threatened and fragmented plant species, Lupinus sulphureus ssp. kincaidii (Fabaceae)

Willamette Valley upland prairie in western Oregon, USA, has been reduced to less than 1% of its original historic range following European settlement in the 1850s. Lupinus sulphureus ssp. kincaidii (Kincaid's lupine), a threatened species and the primary larval host plant of the endangered Icaricia icarioides fenderi (Fender's blue butterfly), was historically a panmictic metapopulation. Habitat fragmentation may be causing many of the Kincaid's lupine colonies to display typical symptoms of inbreeding depression, such as low seed production. Hand outcrosses on bagged inflorescences significantly increased seed set and seed fitness compared to open pollination and within-colony pollen treatments. Natural seed set was positively correlated with an increase in the number of Kincaid's lupine patches, suggesting that population size limits seed set. An increase in fruit set was positively correlated with Kincaid's lupine raceme number, raceme density, and the number of lupine patches, demonstrating that floral display and population size increase pollinator service. Restoration of Kincaid's lupine populations should consider measures that lessen the effects of inbreeding depression, especially in small, isolated populations, for the long-term persistence of the species.     

Meta-analysis on the association of population size and life history with inbreeding depression in plants

Inbreeding is common in plants and can have considerable effects on population viability, because of inbreeding depression. Understanding what determines the magnitude of inbreeding depression is of fundamental importance for conservation biology. We used meta-analysis of 116 studies and 107 plant species to investigate the effects of population size, test environment, life history characteristics and stage on the magnitude of inbreeding depression in 13 different fitness traits. We found that inbreeding depression levels significantly increase with population size. This may be a consequence of either, or both, a higher baseline of the level of inbreeding or increased impact of purging in small populations; unfortunately the available data did not allow distinguishing between these potential explanations. In general, inbreeding depression was found to be common across species and environments, and was significant in all traits examined. Yet, the magnitude of inbreeding depression was significantly influenced by plant longevity and life-history stage, and varied depending on how plant fitness was measured. Our findings highlight the fundamental role of population size in influencing the magnitude of inbreeding depression in plants. This clearly has important implications for conservation biology. Moreover, our findings on the overall generality of inbreeding depression confirm that inbreeding depression is one of the key factors reducing plant population fitness and viability. Hence, we need a better understanding on the architecture of inbreeding depression, how different ecological and historical conditions influence the levels of inbreeding depression in natural plant populations, and its impacts on community dynamics.     

Responses of butterfly and moth species to restored cattle grazing in semi-natural grasslands

The effects of restorative grazing on the abundance of butterfly and moth species were studied in mesic semi-natural grasslands of SW Finland differing in management history: (1) old continuously grazed, (2) restored (with ca 5 years of reinitiated grazing), and (3) abandoned former pastures.Generalized linear modelling of species abundances and indicator species analysis produced qualitatively similar results. Only three species (Polyommatus icarus, Lycaena hippothoe and Camptogramma bilineatum) were most abundant in old pastures, whereas 12 species (Polyommatus semiargus, Polyommatus amandus, Brenthis ino, Aphantopus hyperantus, Scopula immorata, Idaea serpentata, Scotopteryx chenopodiata, Epirrhoe alternata, Cybosia mesomella, Polypogon tentacularius, Hypena proboscidalis and Cryptocala chardinyi) were most abundant in abandoned pastures. None of the old-pasture species had become more abundant in restored pastures. Three species, Epirrhoe hastulata, Xanthorhoe montanata and Chiasmia clathrata, occurred equally abundantly in abandoned and in restored pastures indicating a slow progress of restoration.Species associated with old pastures differed from species associated with abandoned pastures in their recent distributional changes in Finland. The species of old pastures showed decreasing trends, whereas those of abandoned pastures showed mainly increasing trends in their distribution. In five out of 11 species, the preferred successional stage differed markedly between this study and previous studies conducted in Central Europe.We conclude that (1) ca 5 years of restorative grazing in mesic grasslands has been insufficient for the colonisation of old-pasture species in the restored sites, (2) different management intensities are needed regionally for the maintenance of grassland insect diversity and (3) application of the knowledge on successional preferences of different species in conservation management, even in climatically similar regions, should be made with caution.     

Reproductive biology and conservation implications of three endangered snapdragon species (Antirrhinum, Plantaginaceae)

About 32% of Antirrhinum species are considered to be endangered; however, no field studies have focused on their reproductive biology. In this work, several aspects of the reproductive biology (flowering phenology, floral biology, breeding system) and potential limits on seed quantity and quality (pollen limitation, inbreeding depression) were studied in natural populations of three endangered species of the genus (Antirrhinum charidemi, Antirrhinum subbaeticum, Antirrhinum valentinum). Results disclose that all three species need insect visitors for seed production since fruit set after autonomous self-pollination was lower than under hand cross-pollination. A. charidemi and A. valentinum were mainly self-incompatible, whereas A. subbaeticum was self-compatible but herkogamous. Supplementary pollination in open-pollinated flowers only increased fruit set and seed set relative to controls in a given population of A. valentinum. Preliminary data on inbreeding depression at early life-cycle stages of the self-compatible A. subbaeticum revealed that the cumulative level was low. Despite the three species being closely related and sharing many ecological characteristics, they show different mating systems, and different factors limit seed quantity and quality. Thus, caution should be taken when making a common conservation plan for a group of closely related taxa.