Plant Fecundity Research Articles

Effects of Salinity on the Development of Hydroponically Grown Borage (Borago officinalis L.) Male Gametophyte

In this research, the effect of salinity on the development of anther in hydroponically-grown borage was studied. Plants grown on hydroponic media are rapidly and transiently stressed. The overall objective of this research was to elucidate the microscopic effects of salinity on the formation, development, and structure of anthers. Flowers, at different developmental stages, were removed, fixed in FAA, embedded in paraffin, and cut into 7-10 μm slices using a microtome. Staining was carried out with Hematoxylin-Eosine, and the developmental stages of the control and NaCl-treated plants were compared. In control plants young anther consisted of 4 pollen sacs. Anther wall development followed the typical dicotyledonous pattern and was composed of an epidermal layer, an endothecium layer, and the tapetum. Microspore tetrads were tetrahedral. Salinity caused certain abnormalities during pollen developmental processes, such as the destruction of the anther wall and both the degeneration and production of abnormal pollen grains. A decrease in plant fecundity, which involves aborting pollen, followed by a change in resource from reproductive activities to metabolic reactions is possibly a general response to the deleterious effects of salinity.

Yeasts in nectar of an early‐blooming herb: sought by bumble bees, detrimental to plant fecundity

Through their effects on physicochemical features of floral nectar, nectar-dwelling yeasts can alter pollinator behavior, but the effect of such changes on pollination success and plant reproduction is unknown. We present results of experiments testing the effects of nectar yeasts on foraging patterns of captive and free-ranging bumble bees, and also on pollination success and fecundity of the early-blooming, bumble bee-pollinated Helleborus foetidus (Ranunculaceae). Under controlled experimental conditions, inexperienced Bombus terrestris workers responded positively to the presence of yeasts in artificial sugar solutions mimicking floral nectar by visiting proportionally more yeast-containing artificial flowers. Free-ranging bumble bees also preferred yeast-containing nectar in the field. Experiments conducted in two different years consistently showed that natural and artificial nectars containing yeasts were more thoroughly removed than nectars without yeasts. Experimental yeast inoculation of the nectar of H. foetidus flowers was significantly associated with reductions in number of pollen tubes in the style, fruit set, seed set, and mass of individual seeds produced. These results provide the first direct evidence to date that nectar yeasts can modify pollinator foraging patterns, pollination success, and the quantity and quality of seeds produced by insect-pollinated plants.

The ages and fecundity of some arid-zone plants in Western Australia

Since 1960, 22 species of individually marked, arid-zone perennial plants in the Murchison District and Gibson Desert of Western Australia have been monitored for flowering, fecundity, and survival. The age to which individual species survive was determined in terms of half-life, i.e. the time elapsed for half of the marked sample to die. The estimates ranged from 6.5 to 535 years. Phenology was recorded by observing whether the plants carried buds, flowers, fruits, or any combination of these, or were sterile. Fecundity of each species was measured by recording each year the percentage of the sample trees that carried fruit, by collecting seeds in trays placed beneath the plants and by counting the pods produced by some species. Fecundity was related to seasonal rainfall, most species responding positively to summer rainfall. The concept of mast years, as utilised in the northern hemisphere, was applied to recorded fecundities and some evidence was found that, after a year of high fecundity, the plants responded less vigorously to conditions of high rainfall than they did in the previous year of high rainfall. This suggests that, in years when fecundity is high, it diminishes the resources available within the plants to respond to heavy rainfall the following year or reduces the soil nutrients available to them.

When bigger is not better: intraspecific competition for pollination increases with population size in invasive milkweeds

One of the essential requirements for an introduced plant species to become invasive is an ability to reproduce outside the native range, particularly when initial populations are small. If a reproductive Allee effect is operating, plants in small populations will have reduced reproductive success relative to plants in larger populations. Alternatively, if plants in small populations experience less competition for pollination than those in large populations, they may actually have higher levels of reproductive success than plants in large populations. To resolve this uncertainty, we investigated how the per capita fecundity of plants was affected by population size in three invasive milkweed species. Field surveys of seed production in natural populations of different sizes but similar densities were conducted for three pollinator-dependent invasive species, namely Asclepias curassavica, Gomphocarpus fruticosus and G. physocarpus. Additionally, supplemental hand-pollinations were performed in small and large populations in order to determine whether reproductive output was limited by pollinator activity in these populations. Reproductive Allee effects were not detected in any of the study species. Instead, plants in small populations exhibited remarkably high levels of reproductive output compared to those in large populations. Increased fruit production following supplemental hand-pollinations suggested that the lower reproductive output of naturally pollinated plants in large populations is a consequence of pollen limitation rather than limitation due to abiotic resources. This is consistent with increased intraspecific competition for pollination amongst plants in large populations. It is likely that the invasion of these milkweed species in Australia has been enhanced because plants in small founding populations experience less intraspecific competition for pollinators than those in large populations, and thus have the ability to produce copious amounts of seeds.

The Effect of Mycorrhizae on Plant Growth and Reproduction Varies with Soil Phosphorus and Developmental Stage

Abstract Determining the impact of both environmental variation and developmental stage on plant-mycorrhizal associations is important, as both can shift the association along the mutualism-parasitism continuum. This study examines the effect of phosphorus level on the response of Allium vineale to mycorrhizae across all plant life stages, including plant fecundity and the relative allocation of resources to three different reproductive modes (flowers, asexual underground offsets, and asexual aerial bulbils). For A. vineale, the impact of mycorrhizae varies significantly with life stage, as an early growth depression at 1 mo was reversed by 15 mo, resulting in mycorrhizal plants having larger bulbs over all P levels and producing more bulbils and larger offsets than nonmycorrhizal plants at lower P levels. However the presence of mycorrhizae did not affect the relative allocation of resources among the three reproductive modes. These results emphasize the importance of long-term studies of plant-mycorrhiz...

Eutrophication and drought disturbance shape functional diversity and life-history traits of aquatic plants in shallow lakes

Theories that link plant strategies and abiotic filters discriminate between three strategies: competitive, ruderal or stress-tolerant species, and suggest that functional diversity is higher at intermediate values along the gradients of productivity and disturbance. The mechanism by which abiotic filters screen plant traits in aquatic plant communities has been poorly tested and has led to contrasting results. The present study aimed to test whether functional diversity and abundance of life-history traits corresponding to morphology, fecundity and longevity of aquatic plants were linked to disturbance and productivity. Fifty-nine shallow lakes that were arranged along a gradient of productivity (estimated through total phosphorus concentration) and drought-disturbance frequency were sampled for aquatic plants. Species traits were documented and functional diversity was calculated (richness, dispersion and evenness) for each lake. Increasing total phosphorus concentration was associated with decreased functional richness and dispersion but not functional evenness. Functional diversity did not differ according to disturbance frequency, regardless of the index that was measured. High productivity favoured floating species with storage organs and vegetative reproduction, especially at low disturbance frequency. For all disturbance frequencies, low productivity favoured small species without storage organs and sexual reproduction. The present study partly supports the theoretical model. At high productivity levels, because phytoplankton is a better competitor for light than aquatic plants, plant traits are screened stringently, and species with traits that allow them to reach the photic zone are selected.

Adult plant abundance, reproductive efficiency, and recruitment patterns in two tropical areas

The recruitment patterns of trees, shrubs and climbers were studied in two contrasting geographical areas in Venezuela: the Venezuelan Central Plain (VCP), and shrubland. The main purpose was to determine whether recruitment was simultaneously affected by adult plant abundance and relative fecundity in two different geographical areas, and if such relationships were influenced by life forms, vegetation types, dispersal syndromes, and within and between habitats in the VCP. Multiple regressions were used to determine the effect of adult plant abundance and relative fecundity on seedling and juvenile plant abundance. The relative abundance of juvenile plants increased significantly with the simultaneous increment of relative adult abundance and relative fecundity. However, the best predictor of plant recruitment was adult plant abundance. The effect of adult abundance and the fecundity of life forms on recruitment varied according to habitat in the VCP. Significant regressions were also found for species with animal dispersed plant species in the VCP and animal and wind dispersed species in the shrubland. This agrees with the associations between shrubs with animals dispersal in the VCP. Although plants tended to recruit mainly in those habitats where the parent plants were found, recruitment also depended upon the fecundity and adult abundance of plants from different habitats. It is suggest that there is a progressive colonization from the forest to the forest border and from the border to the savanna, and that there is a high interdependence between adjacent habitats for recruitment in the VCP.

Flower number and distance to neighbours affect the fecundity of Goetzea elegans (Solanaceae)

Abstract:Pollinator visits to flowers of self-incompatible tropical trees are critical for plant fecundity. However, few studies have examined how much of the variance in tropical tree fecundity is explained by individual attributes of trees (e.g. number of flowers), and how much is due to contextual variables such as distances to nearest flowering neighbours. Using multiple regressions we examined the relative contributions of these factors to the pollination and fecundity of Goetzea elegans, a mainly self-incompatible tree endemic to Puerto Rico. We studied the largest wild population of the species during the peak flowering and collected data on the frequency of pollinator visits (N = 25 trees), and the fecundity of the whole population (N = 105), including the visitation rate of two pollinators (the honey bee Apis mellifera and the bananaquit Coereba flaveola), the total number of flowers produced by each tree, and the total fruit set and seed viability per tree. We also recorded the distance to flowering conspecifics and heterospecifics, and the height for each tree. Flower number had a strong positive effect on pollinator visitation, but distance to nearest neighbours was equally or more important than flower number in influencing fecundity. Also, competition for limited pollinators between G. elegans and other species has a stronger effect than the facilitation that conspecifics may provide. Our results suggest that pollinator visits and aspects of fecundity of G. elegans depend both on the attributes of individual plants, and on those of the community of other nearby plants.

Integrating demographic data and a mechanistic dispersal model to predict invasion spread of Rhododendron ponticum in different habitats

Understanding the invasion potential of a species in different habitat types within the non-native range is crucial in prioritising management and control efforts, and in the protection of vulnerable habitats through monitoring. Here, using the invasive shrub Rhododendron ponticum as a case study, we integrate information on both the demographics and spatial dynamics within an individual-based, spatially-explicit model to investigate invasion potential in different habitats. Firstly, empirical demographic data were used to establish relationships between demographic traits, such as height and fecundity, and habitat variables. The outputs from models fitted using a Generalised Linear Model approach were then incorporated into an individual-based simulation model of plant spread to investigate the invasion potential in different habitats using a factorial design of treatments. Plant height, and thus seed release height, was the main driver of invasion speed through an increase in dispersal potential, which resulted in the highest invasion speeds predicted for evergreen woodlands, and relatively low speeds for open habitats. Conversely, invasion density was driven by plant fecundity and seedling survival and not dispersal potential; the highest invasion densities were predicted for open habitats, with relatively low densities for evergreen habitats. Deciduous woodland had features resulting in intermediate invasion potential, both in terms of speed and density and may, therefore be the habitat that is most vulnerable to relatively rapid and dense invasion.

The effects of earthworms on the demography of annual plant assemblages in a long-term mesocosm experiment

Abstract Earthworms have been shown to influence plant growth, survival and fecundity. They can therefore affect plant demography in plant communities changing their composition. A long term mesocosm experiment was set-up to test the effects of an endogeic (Aporrectodea caliginosa) and an anecic (Lumbricus terrestris) earthworm species on assemblages of four species of annuals: one grass (Poa annua), two forbs (Veronica persica and Cerastium glomeratum) and one legume (Trifolium dubium). The number of individuals and the biomass of each species were investigated. A. caliginosa and L. terrestris affected the density of T. dubium at each of the three monitored census dates. The other plant species responded to A. caliginosa and L. terrestris at the second and third generations. The presences of A. caliginosa and L. terrestris reduced the total number of plant individuals from the second to the third generation. At harvest (3rd generation), T. dubium and V. persica had more and larger individuals in the presence of A. caliginosa. When both earthworm species were present, T. dubium had few but larger individuals. Our study confirms that earthworms affect plant demography and plant community structure. Our results also show that accurate prediction of long-term effects of earthworms on plant communities cannot be achieved using results on their short-term effects on plant growth. This is due to the poor understanding of the effects of earthworms on plant resource allocation and demography, and also the possibility that earthworms may exert the opposite effect on the short and long-term availability of nutrients.

The contribution of evening primrose (Oenothera biennis) to a modern synthesis of evolutionary ecology

AbstractIn this review, I consider the contribution that common evening primrose (Oenothera biennis) has made towards integrating the ecology, evolution and genetics of species interactions. Oenothera biennis was among the earliest plant models in genetics and cytogenetics and it played an important role in the modern synthesis of evolutionary biology. More recently, population and ecological genetics approaches have provided insight into the patterns of genetic variation within and between populations, and how a combination of abiotic and biotic factors maintain and select on heritable variation within O. biennis populations. From an ecological perspective, field experiments show that genetic variation and evolution within populations can have cascading effects throughout communities. Plant genotype affects the preference and performance of individual arthropod populations, as well as the composition, biomass, total abundance and diversity of arthropod species on plants. A combination of experiments and simulation models show that natural selection on specific plant traits can drive rapid ecological changes in these same community variables. At the patch level, increasing genotypic diversity leads to a greater abundance and diversity of omnivorous and predaceous arthropods, which is also associated with increased biomass and fecundity of plants in genetically diverse patches. Finally, in questioning whether a community genetics perspective is needed in biology, I review several multifactorial experiments which show that plant genotype often explains as much variation in community variables as other ecological factors typically identified as most important in ecology. As a whole, research in the O. biennis system has contributed to a more complete understanding of the dynamic interplay between ecology, evolution and genetics.

Disentangling sources of maternal effects in the heterocarpic species Rumex bucephalophorus

Maternal effects are one of the most important influences on the offspring phenotype and their adaptive significance has been increasingly recognized. In this study we document the role of two sources of maternal effects, position and heterocarpy, on juvenile and adult traits of Rumex bucephalophorus, an annual plant that occurs in heterogeneous and unstable environments. Up to three different diaspore types can be found in populations of this species: buried diaspores (BD) at the plant base, and fixed diaspores (FD) and long dispersible diaspores (LD) both borne along aerial stems. The two sources of maternal effects affected most stages of the life cycle of R. bucephalophorus: seed size, dispersability, seedling size and survival, and adult plant fecundity. Maternal effects due to position affected mainly juvenile traits, while those due to heterocarpy were stronger and more persistent. In general, seedlings from FD showed higher survival and originated plants with higher fecundity but with lower dispersability than those derived from BD and LD. Dispersability was markedly affected by the two maternal effects at two different stages: first, there was a trend to place the slighter and more easily detachable diaspores (LD) at the optimal positions for dispersal, and second maternal effect due to heterocarpy surprisingly affected dispersability of the second generation progeny. Our study shows that maternal effects can play an important role in ecology, dynamic and evolution of populations and it adds to growing evidence about the important role of maternal effects.

Marcescent corollas as functional structures: effects on the fecundity of two insect-pollinated plants

Persistence of withered corollas after anthesis ('corolla marcescence') is widespread in angiosperms, yet its functional significance does not seem to have been explored for any species. This note reports the results of experiments assessing the fecundity effects of marcescent corollas in two southern Spanish insect-pollinated plants, Lavandula latifolia (Lamiaceae) and Viola cazorlensis (Violaceae). The effect of marcescent corollas on seed production was evaluated experimentally on wild-growing plants. Newly open flowers were randomly assigned to either control or treatment groups in experimental plants. After anthesis, withered corollas of treatment flowers were removed and those in control flowers were left in place. Fruits produced by treatment and control flowers were collected shortly before dehiscence and the number of seeds counted. In V. cazorlensis, removal of withered corollas had no effect on percentage of fruit set, but mean seeds per fruit increased from 9·5 to 11·4. In L. latifolia, corolla removal had no effect on the number of seeds per fruit, but reduced the proportion of flowers ripening fruit from 60 % to 40 %. The detrimental effect of corolla removal on L. latifolia fecundity resulted from the drastic increase in fruit infestation by seed-predatory cecidomyiid larvae, which occurred in 4 % and 34 % of control and treatment fruits, respectively. Because of their potential effects on plant fecundity, marcescent corollas should not be dismissed a priori as biologically irrelevant leftovers from past floral functions. The simplicity of the experimental layout required to test for short-term fecundity effects of corolla marcescence should help to achieve a better understanding of the ecological and evolutionary correlates of this widespread but poorly understood trait.

Population demography and fecundity do not decline with habitat fragmentation in the rainforest tree Macadamia integrifolia (Proteaceae)

Habitat fragmentation is often associated with reduced levels of fitness and local extinction of plant species, and consequently poses a major threat to the persistence of species worldwide. The majority of demography-based fragmentation studies to date have focussed primarily on fragmentation impacts on individual plant fecundity. Here we investigate the impact of habitat fragmentation on the demography (plant height classes and density) and key population dynamic processes for the rainforest tree species Macadamia integrifolia (Proteaceae). Raceme and fruit production and seedling emergence across fragmented sites exceeded that in more intact sites with no apparent difference in short-term mortality rates. Fecundity of flowering trees did not appear to be affected by fragmentation. Instead, overall reproductive output in fragmented sites was enhanced relative to undisturbed sites due to a higher proportion of reproductively active individuals. The probability of flowering and fruiting was negatively correlated with the projected foliage cover ( PFC) surrounding individual trees, and average PFC was significantly lower in small and medium fragments, suggesting light availability as a potential contributor to the trends observed here. This study demonstrates that the short-term effects of habitat fragmentation on population viability may not necessarily be detrimental for some species, and highlights the importance of assessing not only the fecundity of flowering individuals but also the proportion of individuals reproducing within fragments.

Comparative studies on plant range size: Linking reproductive and regenerative traits in two Ipomoea species

Reproductive and regenerative traits associated with colonization and persistence ability may determine plant range size. However, few comparative studies on plant distribution have assessed these traits simultaneously. Pollinator richness and frequency of visits, autonomous self-pollination ability, reproductive output (i.e., reproductive traits), seed bank strategy and seedling density (i.e., regenerative traits) were compared between the narrowly distributed Ipomoea rubriflora O’Donnell (Convolvulaceae) and its widespread congener Ipomoea purpurea (L.) Roth. The narrowly distributed species showed higher ecological specialization to pollinators and lower autonomous self-pollination ability. Frequency of visits, natural seed/ovule ratio and fruit set, and total fruit production did not differ between species. However, the number of seeds produced per fruit was lower in the narrowly distributed species, translating into lower total seed production per plant. Indeed, I. rubriflora formed smaller transient and persistent seed banks and showed lower seedling density than the widespread I. purpurea. These reproductive and regenerative trait results suggest that the narrowly distributed species may have lower colonization and persistence ability than its widespread congener. They further suggest that the negative effects of lower fecundity in the narrowly distributed species might persist in time through the long-lasting effects of total seed production on seed bank size, reducing the species’ ability to buffered environmental stochasticity. However, other regenerative traits, such as seed size, and processes such as pre- and post-dispersal seed predation, might modulate the effects of plant fecundity on plant colonization and persistence ability and thus range size.

Alternative oxidase, a determinant of plant gametophyte fitness and fecundity

The alternative oxidase (AOX) is the terminal oxidase that comprises the cyanide-resistant respiratory pathway in plant mitochondria. While the role of AOX in plant thermogenesis is well established, its role in the reproductive development of non-thermogenic species is not well understood. AOX genes can be separated into two groups based on sequence homology, AOX1 and AOX2. Reverse genetic experiments carried out primarily in Arabidopsis and tobacco have largely focussed on examining the role of AOX1-type genes in stress responses. We recently reported a systematic characterisation of the reproductive phenotypes of three AOX2 antisense lines of soybean. This addendum summarises the key evidence in our recent paper that points to a role for AOX in the development and function of both male and female gametophytes. Furthermore, we discuss the relative importance of AOX in the reproductive biology of plant species examined to date and highlight practical implications of our findings to crop improvement research.

Long‐term persistence of crop alleles in weedy populations of wild radish (Raphanus raphanistrum)

*Hybridization allows transgenes and other crop alleles to spread to wild/weedy populations of related taxa. Researchers have debated whether such alleles will persist because low hybrid fitness and linkage to domestication traits could severely impede introgression. *To examine variation in the fates of three unlinked crop alleles, we monitored four experimental, self-seeding, hybrid populations of Raphanus raphanistrum x Raphanus sativus (radish) in Michigan, USA, over a decade. We also compared the fecundity of advanced-generation hybrid plants with wild plants in a common garden experiment. *Initially, F(1) hybrids had reduced fitness, but the populations quickly evolved wild-type pollen fertility. In Year 10, the fecundity of plants from the experimental populations was similar to that of wild genotypes. Crop-specific alleles at the three loci persisted for 10 yr in all populations, and their frequencies varied among loci, populations and years. *This research provides a unique case study of substantial variation in the rates and patterns of crop allele introgression after a single hybridization event. Our findings demonstrate that certain crop alleles can introgress easily while others remain rare, supporting the assumption that neutral or beneficial transgenes that are not linked to maladaptive traits can persist in the wild.

Using experiments, demography and population models to estimate interaction strength based on transient and asymptotic dynamics

Summary 1. Despite a large literature documenting the effects of mutualists and/or antagonists on plant performance, we still have limited insight into the strength of these interactions, as this involves quantifying how one species influences the population dynamics of another. 2. Here, we use data from two example systems, Cynoglossum officinale and Calathea ovandensis, to illustrate how experiments, demographic data and stage‐based population models can be combined to estimate interaction strength of insect herbivores on plants. Because many plant populations may not be at equilibrium, we conduct transient analyses and contrast these results to more traditional asymptotic results. 3. We calculate three metrics of interaction strength, Δλasymptotic, the change in asymptotic annual per capita plant population growth rate resulting from herbivore exclusion, Δλ(t), the change in transient λ caused by herbivores at t = M (where M = the time of their maximum effect during the transient phase) and Δλtransient, a time‐averaged effect of consumers on λ across the entire transient phase. 4. Fairly strong impacts of insect consumers on plant fecundity do not translate similarly to Δλasymptotic. Results show that Δλ(t) can be larger (or smaller) than Δλasymptotic but in our examples Δλtransient was similar in magnitude to Δλasymptotic. 5. The transient effects of consumers on λ were driven by changes in the elasticity of fecundity across the transient phase. These effects were dynamic even though consumer impacts on demography and vital rates were held constant. The importance of particular stages and transitions to annual population growth vary during the transient phase. 6. Synthesis. We describe three metrics of interaction strength, Δλasymptotic, Δλ(t) and Δλtransient. These metrics have several advantages over more commonly used trait or performance measures that quantify the outcome of interactions. We illustrate how the transient impacts of consumers on λ are dynamic, with the changing stage distribution of a population and transient elasticities driving these effects. More generally, this study shows that the impacts of animals on plant performance do not translate equivalently to plant population growth, thereby underscoring the importance of using population models to extend the inference of individual‐level experiments.

Plant fecundity and pre‐dispersal reproductive losses in a common and a rareEuphorbiaspecies (Euphorbiaceae)

AbstractComparative studies on the reproductive biology of closely related plant species have provided valuable information to understand the causes and consequences of common‐rare differences with possible applications for the management of threatened populations. The magnitude and spatiotemporal variability of seed production and pre‐dispersal reproductive losses were studied for 3 years in the rare endemicEuphorbia welwitschiiand in its widespread congenerE. characias. The factors responsible for a decrease in potential seed production in these species were the lack of a functional ovary in the cyathium, ovary and fruit abortion, seed predation by insects and seed abortion. InE. characias, the mothAcroclita subsequanawas also responsible for minor reproductive losses. The proportion of male cyathia varied significantly between seasons, populations and species, being consistently higher inE. characiasthan inE. welwitschii. Reproductive losses that resulted in ovary, fruit and seed abortion affected mostly the endemic species and were heavier in the populations located near the sea due to local adverse climatic conditions. Seed predators inflicted higher reproductive losses to the endemic species than to its widespread congener and their impact was particularly heavy at Risco. The twoEuphorbiaspecies differed markedly in cyathia production, withE. welwitschiiproducing systematically a lower number of cyathia than its widespread congener and this, together with higher levels of ovary, fruit and seed abortion, seemed to be the main reasons for the low reproductive output of this rare species.

The functional consequences of diversity in plant–pollinator interactions

The role of biological diversity in maintaining ecosystem functioning is a central issue in ecology. Most studies on diversity–functioning relationships have focused on ecosystem and community levels, leaving the extension of those relationships to other organization levels, such as populations, as a challenging and unsolved issue. Empirical studies have shown links between pollinator diversity and plant fecundity, suggesting that a diversity–functioning relationship at the population level may occur in pollination systems. We theoretically explored the effect of pollinator diversity on plant reproduction. We found that low pollinator diversity is beneficial when the most abundant pollinators are the most effective. In contrast, when the most effective pollinators are not the most abundant, we found an optimal value of pollinator diversity at which plant fecundity is maximized. When we parametrized our model with real data, we obtained that an increase in pollinator diversity was beneficial for the reproduction of some plants whereas it was harmful for other plants, the outcome depending exclusively on the differences in effectiveness among pollinators. Consequently, our theoretical approach suggests that in pollination systems the diversity–function relationship may be explained as the consequence of the interaction between among‐pollinator differences in effectiveness and frequency of interaction, without the need to invoke additional ecological mechanisms.