Geographic variation for elaiosome–seed size ratio and its allometric relationship in two closely related Corydalis species

Abstract

Background: Elaiosomes serve as a reward for seed-dispersing ants. The size of the elaiosome and the elaiosome–seed mass (ESM) ratio are expected to affect seed dispersal, whilst seed size affects the establishment of seedlings. Elaiosomes and seeds can undergo independent change, thus variation in these traits may arise through heterogeneous selection for seedling establishment and for dispersal. Only a few studies have examined intraspecific variation in these traits.

Aims: The aim of this study was to determine if the ratio of elaiosome–seed mass was different in two co-occurring congeneric plant species (Corydalis intermedia and C. solida). Under the hypothesis that the ESM ratio affected diaspore attractiveness to ants, the allometric relationship between elaiosome and seed mass was used to infer how selection by ants may shape the diaspore.

Methods: Seed and elaiosome mass were measured in fruits collected from central and marginal populations of the two plant species. The allometric relationship between seed and elaiosome mass was obtained using major axis regression. In situ cafeteria experiments estimated the removal rate of diaspores by ants.

Results: Intra- and interspecific variation in diaspore traits were found. The selfing C. intermedia produced heavier seeds and elaiosomes than the outcrossing C. solida. Ants removed more diaspores from C. intermedia where both species were present. A slope larger than one characterised the allometric relationship between elaiosome and seed mass in both species. This slope was twice as steep in the central populations of C. intermedia compared to marginal ones.

Conclusions: Results indicate that in C. intermedia elaiosome mass must increase more than proportionally with increasing seed mass for the diaspore to remain attractive to ants. The direction of interspecific differences suggests that a plant-mating system may affect selection for dispersal.     

Types, evolution and significance of plant – animal interactions

Abstract  Interactions between plants and animals are analyzed starting from the advantages gained by animals and proceeding to those gained exclusively by plants. These interactions are essentially of five types: 1. predation of plants by animals; 2. benevolence of plants towards certain animals to prevent or reduce predation; 3. predation by plants (carnivorous plants); 4. symbiosis and mutualism; 5. seduction and deception of animals by plants for dispersal of plant reproductive structures. All types of plants are preyed on by animals, though from as far back in evolution as algae, certain plant molecules reduce or prevent predation. In the most primitive land plants, other types of interactions beneficial for plants are encountered. More evolved land plants (angiosperms) show all facets of the five types of interaction, whereas in prokaryotic and eukaryotic algae there is only predation and in some cases countermeasures to avoid it. An evolutionary path leading from predation, the original condition, to seduction, deception and carnivory, is also postulated. Keywords Plants, Animals, Predation, Benevolence, Symbiosis, Mutualism, Pollination, Seed dispersal Subject codes: Animal Ecology, Plant Ecology, Evolutionary Biology     

Genetic and phenotypic variation,dispersal limitation and reproductive success in the invasive herb Eschscholzia californica along an elevation gradient in central Chile

Background: Reductions of genetic diversity and phenotypic changes in invasive plants are often observed to occur at high elevations. Genetic/phenotypic changes of invasive plants along elevation help to understand mechanisms of the presumed resistance of mountain ecosystems to invasion.

Aims: To assess genetic variability and phenotypic plasticity along an elevation gradient of Eschscholzia californica in the Andes, central Chile.

Methods: Eleven microsatellites were used to describe the genetic structure and the allelic diversity individuals, distributed at three elevations and two sites. We assessed the number of flowers per plant, floral biomass, leaf area, number of leaves, vegetative biomass and plant height of plants at each elevation.

Results: Genetic diversity as genetic structure did not decrease with elevations. Plant height and flower numbers decreased while leaf number and vegetative biomass increased with elevation. The ratio of the number of flowers to vegetative biomass, decreased significantly with elevation.

Conclusions: Strong genetic differences among elevations and similar genetic diversity along elevation do not suggest dispersal limitation to higher elevation. Reduction of reproductive and vegetative traits concomitantly with an increase of the reproductive cost suggests reproductive stress with increasing elevation, reducing the invasiveness of this species to higher elevation.     

Factors affecting the biological control of the spiralling whitefly Aleurodicus dispersus (Hemiptera: Aleyrodidae) in banana plantations in Costa Rica: a study case

ABSTRACT

A study was conducted to reveal the causes for Aleurodicus dispersus outbreak in commercial banana plantations in Costa Rica. Biotic and abiotic factors affecting the abundance of the spiralling whitefly were determined. Four nymph parasitoids and nine predators were found to affect A. dispersus population. Seventeen families of host plants for A. dispersus in the banana area were identified, allowing the whitefly to reach a high reproductive and dispersal rate and pest status in short periods. The use of nematicides during the dry season was the key factor for mortality of natural enemies responsible for maintaining pest populations under economic levels.     

Peduncles elicit large-mammal endozoochory in a dry-fruited plant

Background and Aims

Plants have evolved a variety of seed dispersal mechanisms to overcome lack of mobility. Many species embed seeds in fleshy pulp to elicit endozoochory, i.e. disseminating seed through the animal gut. In contrast to well-studied fleshy fruited plants, dry-fruited plants may exploit this dispersal mutualism by producing fleshy appendages as a nutritional reward to entice animals to swallow their diaspores, but this has been little studied. In this study, it is hypothesized that these accessory fruits represent co-adaptations facilitating the syndrome of mammalian endozoochorous dispersal.

Methods

Field observations (focal tree watches, faecal surveys and fruiting phenology) with experimental manipulations (examination of seed germination and feeding trials) were conducted over 2 years in a native population of the raisin tree, Hovenia dulcis, which produces enlarged, twisted brown peduncles with external black seeds, in central China.

Key Results

Birds were not observed to swallow seeds or carry infructescences away during 190 h of focal tree watches. However, H. dulcis seeds were detected in 247 faecal samples, representative of two herbivore and four carnivore mammalian species. Feeding trials revealed that peduncles attracted mammals to consume the entire infructescence, thereby facilitating effective seed dispersal. The germination rate of egested seeds proved higher than that of unconsumed seeds. It was also noted that this mutualism was most vulnerable in degraded forest.

Conclusions Hovenia dulcis

peduncle sets are confirmed to adapt primarily to mammalian endozoochory, a mutualistic association similar in function to fleshy pulp or foliage. This demonstrates that plant organ systems can be adapted to unique mutualisms that utilize animal dispersal agents. Such an ecological role has until now been attributed only to bird epizoochory. Future studies should consider more widely the putative role of peduncle sets and mammalian endozoochory as a dispersal mechanism, particularly for those plants that possess relatively large accessory fruits.     

Low plant density enhances gene dispersal in the Amazonian understory herb Heliconia acuminata

In theory, conservation genetics predicts that forest fragmentation will reduce gene dispersal, but in practice, genetic and ecological processes are also dependent on other population characteristics. We used Bayesian genetic analyses to characterize parentage and propagule dispersal in Heliconia acuminata L. C. Richard (Heliconiaceae), a common Amazonian understory plant that is pollinated and dispersed by birds. We studied these processes in two continuous forest sites and three 1‐ha fragments in Brazil's Biological Dynamics of Forest Fragments Project. These sites showed variation in the density of H. acuminata. Ten microsatellite markers were used to genotype flowering adults and seedling recruits and to quantify realized pollen and seed dispersal distances, immigration of propagules from outside populations, and reproductive dominance among parents. We tested whether gene dispersal is more dependent on fragmentation or density of reproductive plants. Low plant densities were associated with elevated immigration rates and greater propagule dispersal distances. Reproductive dominance among inside‐plot parents was higher for low‐density than for high‐density populations. Elevated local flower and fruit availability is probably leading to spatially more proximal bird foraging and propagule dispersal in areas with high density of reproductive plants. Nevertheless, genetic diversity, inbreeding coefficients and fine‐scale spatial genetic structure were similar across populations, despite differences in gene dispersal. This result may indicate that the opposing processes of longer dispersal events in low‐density populations vs. higher diversity of contributing parents in high‐density populations balance the resulting genetic outcomes and prevent genetic erosion in small populations and fragments.     

The phenology,mortality, dispersal and canopy species interaction of Colpomenia peregrina (sauv.) Hamel in British Columbia

The phenology, mortality rate, dispersal and interactions with canopy species of in situ populations of Colpomenia peregrina (Sauv.) Hamel were recorded in British Columbia. Colpomenia produced uprights at different times of the year depending upon the locality. All populations studied had few delophycean (visible) plants in mid-winter. Colpomenia was fertile throughout the year, and the presence of reproductive tissue was largely independent of plant size. Mortality rates were lowest for large plants. The dispersal distance in the field was ≈2m. Canopy species removal did not affect the seasonality nor density of C. peregrina.     

Types of pollination and seed dispersal in Mediterranean plants

Abstract

Selected examples of pollen and seed dispersal in Mediterranean plants are described. The aspects of pollination considered are: comparison between cleistogamous and chasmogamous forms in the same species; differences in attractants and rewards; duration of pollen viability according to pollination syndrome. The aspects of seed dispersal considered are: presence or absence of specialized structures for dispersal; examples of active, passive and induced dispersal; animals involved in seed dispersal and their reward; type and functions of elaiosomes.     

Reproductive phenology of Melastomataceae species with contrasting reproductive systems: contemporary and historical drivers

• Flowering and fruiting are key events in the life history of plants, and both are critical to their reproductive success. Besides the role of evolutionary history, plant reproductive phenology is regulated by abiotic factors and shaped by biotic interactions with pollinators and seed dispersers. In Melastomataceae, a dominant Neotropical family, the reproductive systems vary from allogamous with biotic pollination to apomictic, and seed dispersal varies from dry (self‐dispersed) to fleshy (animal‐dispersed) fruits. Such variety in reproductive strategies is likely to affect flowering and fruiting phenologies.
• In this study, we described the reproductive phenology of 81 Melastomataceae species occurring in two biodiversity hotspots: the Atlantic rain forest and the campo rupestre. We aim to disentangle the role of abiotic and biotic factors defining flowering and fruiting times of Melastomataceae species, considering the contrasting breeding and seed dispersal systems, and their evolutionary history.
• In both vegetation types, pollinator‐dependent species had higher flowering seasonality than pollinator‐independent ones. Flowering patterns presented phylogenetic signal regardless of vegetation type. Fruiting of fleshy‐fruited species was seasonal in campo rupestre but not in Atlantic rain forest; the fruiting of dry‐fruited species was also not seasonal in both vegetation types. Fruiting showed a low phylogenetic signal, probably because the influence of environment and dispersal agents on fruiting time is stronger than the phylogenetic affinity.
• Considering these ecophylogenetic patterns, our results indicate that flowering may be shaped by the different reproductive strategies of Melastomataceae lineages, while fruiting patterns may be governed mainly by the seed dispersal strategy and flowering time, with less phylogenetic influence.

     

Additions To The Flora Of Shetland

ABSTRACT

Background: Pallenis spinosa (Asteraceae) produces both winged and wingless achenes. Both achene morphs are non-dormant and show a similar embryo size, rendering dispersal ability as their only apparent functional difference.

Aims: We studied morph-specific release and spatial dispersal patterns to ascertain whether the common view of seed dimorphism as a mixed strategy, that is functionally fully differentiated morphs, is appropriate for this system.

Methods: For three years, at the onset of achene release, in early autumn, we placed achene traps at different distances from source plants, censusing achene arrival at 3–4 day intervals. We constructed morph-specific dispersal kernels and related release intensity to prevailing meteorological conditions in census intervals. Selected kernel models were used to describe dispersal effects of observed changes in the proportion of winged achenes (p_w) in successive released fractions.

Results: Achene release extended up to early-mid winter, peaking in rainy, windy intervals. Throughout the season, p_w decreased progressively. Unexpectedly, the wingless morph produced the longest dispersal tails and it only showed ability for fat-tailed dispersal. Consequently, maximum dispersal distances steadily increased throughout the season.

Conclusions: Achene dimorphism in P. spinosa appears to allow a within-season continuous reshaping of the seed-dispersal kernel instead of representing a mixed strategy.     

A role for fruit structure in seed survival and germination of Swartzia langsdorffii Raddi beyond dispersal

• Diaspore structure has been hypothesised to play a role in seed viability and/or germination of recalcitrant seeds, especially for Swartzia langsdorffii. Thus, this work aims to (i) investigate the in situ contribution of pericarp and aril on seed viability and germination, and (ii) identify morphoanatomical traits of S. langsdorffii diaspores that allow its desiccation‐sensitive seeds to remain viable.
• The role of the pericarp and aril in seed survival and germination was investigated by placing the whole fruit, whole seeds (arillate seed) and bare seeds (without aril) in soil in the forest understorey, assessing germination, emergence, dead, firm and predated seeds, and water content of pericarps, arils and seeds. Correlation analysis was performed between environmental variables and physiological parameters. Histochemical features of diaspores were also investigated.
• Pericarp water content fell after several months, while the aril maintained its water content. Seeds did not lose water even without the presence of the pericarp and aril. However, presence of the pericarp promoted seed water content, viability and germination long after dispersal. The embryo had a thickened outer periclinal cell wall.
• Pericarp and aril are not essential to prevent water loss in seeds, but do help to retain seed moisture, favouring viability maintenance and promoting germination during the rainy season. Morphoanatomical features of seeds are suggested as main factors that reduce water loss. Survival of these desiccation‐sensitive seeds upon dispersal during the dry season appears to be facilitated by multiple diaspore features that prevent viability loss.

     

Differential seed dispersal in Oxalis acetosella,a cleistogamous perennial herb

Explosive seed dispersal in the cleistogamous perennial forest herb Oxalis acetosella was studied during two growing seasons, to determine whether seeds derived from chasmogamous (CH) and cleistogamous (CL) flowers differ in dispersal distance. Seed dispersal distance, seed weight, and height of fruits were measured for both flower types, and the effects of phenology and year were also taken into account. The dispersal experiment was performed indoors, using plants transplanted from natural populations to pots. CL seeds were thrown significantly further than were CH seeds, though there was a considerable overlap in dispersal distances. There was also a significant positive relationship between seed weight and dispersal distance. No relationship was found between fruit height and dispersal distance. The results of this study contradict the common view that CL progeny should always be dispersed closer to the mother plant than CH progeny. The ecological implications of the dispersal difference are unclear, especially since it is uncertain whether CH seeds are generally outcrossed or not. Variation in dispersal distance in O. acetosella seems to be mainly dependent on a combination of reproductive mode and variation in seed weight.     

Diversification and the evolution of dispersal ability in the tribe Brassiceae (Brassicaceae)

MethodsThe phylogenetic analysis included 72 taxa sampled from across the Brassiceae and included both nuclear and chloroplast markers. Dispersal-related fruit characters were scored and climate information for each taxon was retrieved from a database. Correlations between fruit traits, seed characters, habitat, range and climate were determined, together with trait-dependent diversification rates.ConclusionsThis study provides evidence that the evolution of increased dispersal ability and larger seed size, which may increase establishment ability, can also influence macro-evolutionary processes, possibly by increasing the propensity for long-distance dispersal. In particular, it may increase speciation and consequent diversification rates by increasing the likelihood of geographic and thereby reproductive isolation.     

Size advantage for male function and size‐dependent sex allocation in Ambrosia artemisiifolia,a wind‐pollinated plant

In wind‐pollinated plants, male‐biased sex allocation is often positively associated with plant size and height. However, effects of size (biomass or reproductive investment) and height were not separated in most previous studies. Here, using experimental populations of monoecious plants, Ambrosia altemisiifolia, we examined (1) how male and female reproductive investments (MRI and FRI) change with biomass and height, (2) how MRI and height affect male reproductive success (MRS) and pollen dispersal, and (3) how height affects seed production. Pollen dispersal kernel and selection gradients on MRS were estimated by 2,102 seeds using six microsatellite markers. First, MRI increased with height, but FRI did not, suggesting that sex allocation is more male‐biased with increasing plant height. On the other hand, both MRI and FRI increased with biomass but often more greatly for FRI, and consequently, sex allocation was often female‐biased with biomass. Second, MRS increased with both height and MRI, the latter having the same or larger effect on MRS. Estimated pollen dispersal kernel was fat‐tailed, with the maximum distance between mates tending to increase with MRI but not with height. Third, the number of seeds did not increase with height. Those findings showed that the male‐biased sex allocation in taller plants of A. artemisiifolia is explained by a direct effect of height on MRS.     

Fruit removal efficiency and success: influence of crop size in a neotropical treelet

The reproductive success of animal-dispersed plants is closely linked to the number of seeds that they are able to disperse. The fruit crop size hypothesis states that a plant with large fruit crop size will attract more dispersers than a plant with a smaller fruit crop, which may result in more seeds being dispersed from the foremost. In this study, we experimentally examined the effect of crop size and other factors on primary seed dispersal in a neotropical shrub/tree, Casearia corymbosa (Flacourtiaceae). We used two predictive variables of reproductive success, which produce an accurate picture of seed dispersal ratio: fruit removal efficiency (proportion of a fruit crop removed by frugivores) and fruit removal success (relative contribution of each individual tree to the number of fruits removed in the population). We established two levels of fruit crop size at the C. corymbosa individuals, using plants with large (150 fruits) and small crops (50 fruits). We found that individual plants with larger crops had significantly higher values of fruit removal efficiency (92.6%) and success (5%) than plants with smaller crops (69.3% and 1.3%, respectively). Fruit removal efficiency was related to vegetation type, plant height and fruit width, but the variance explained by these variables was low ( < 8%). Fruit removal success was significantly related to crop size ( > 90% of the variance explained). These results suggest that fruit removal efficiency and success are strongly related to fruit crop size of C. corymbosa plants.     

Reproductive traits in the tropical moss Octoblepharum albidum Hedw. differ between rainforest and coastal sites

Abstract

Octoblepharum albidum Hedw. is an autoicous moss commonly occurring in tropical savannas, dry forests, rainforests and coastal habitats. It frequently reproduces by spores and asexual structures (gemmae and protonemata or buds at leaf tips), making it a good model for understanding how reproductive traits change with respect to habitat type. Our aims were to characterize the different life-history traits in O. albidum relative to sexual and asexual cycles and to detect variations in reproductive performance among the different habitats, trade-offs among these traits, and relationships among reproductive traits and plant length. We studied colonies from two Atlantic rainforests and two coastal sites in north-eastern Brazil. Shoots in the coastal sites, compared to those of the forest sites, had higher numbers of sporophytes, male and female branches per shoot, male gametangia per sexual branch, and longer setae. Numbers of female gametangia per sexual branch did not differ between forest and coastal sites. A male-biased sex ratio of branches and gametangia occurred in all sites. Compared to gemmae, sporophytes and protonemata or buds were more likely to be found on longer shoots than on shorter ones, but this relationship was only applicable to forest sites. The abundant production of gemmae and protonemata or buds at leaf tips, and sporophytes (spores) in O. albidum are important components in explaining colonization success and maintenance in this tropical moss. Longer sporophytic setae in addition to a higher reproductive performance (especially for number of male gametangia and sporophytes per shoot) may favour spore dispersal and colonization in plants of coastal sites.     

Long-distance endozoochorous dispersal of submerged macrophyte seeds by migratory waterbirds in northern Europe—a critical review of possibilities and limitations

We review whether migratory Anatidae, i.e., swans, geese and ducks, could be acting as vectors for dispersal of Zostera, Ruppia and Potamogeton propagules by endozoochory (carrying seeds in their guts). We list six prerequisites that must all be fulfilled, if successful dispersal should occur. Several Anatidae species feed on these macrophytes, and undertake rapid long-distance movements, making dispersal possible. We identify four problems, which in combination leads us to conclude that long-distance dispersal events are likely to be rare. (i) Most long-distance movements are out of phase with the reproductive efforts of the plants, and if birds arrive at sites when plants still bear seeds, they are likely to depart well after seed stocks have been depleted. (ii) Seed transport by birds will usually be uni-directional, from north to south on autumn migrations. (iii) Most of the gut contents of migratory birds are likely to have been discarded within 300 km of departure. (iv) In many cases, birds will arrive in habitats seriously different from those they departed, i.e., any seeds carried along will have low chances of surviving in their new site. We suggest that northbound dispersal by endozoochory can only occur during spring if waterbirds feed on seeds that have not been depleted and remained frozen down or buried in sediments, or during moult- or post-moult migrations. Moult migration takes place in summer in phase with the reproductive efforts of the plants. Also epizoochorous dispersal (external attachment) is subject to restrictions i, ii and iv.     

Assessing ant seed predation in threatened plants: a case study

Erodium paularense is a threatened plant species that is subject to seed predation by the granivorous ant Messor capitatus. In this paper we assessed the intensity and pattern of ant seed predation and looked for possible adaptive strategies at the seed and plant levels to cope with this predation. Seed predation was estimated in 1997 and 1998 at the population level by comparing total seed production and ant consumption, assessed by counting seed hulls in refuse piles. According to this method, ant seed predation ranged between 18% and 28%. A more detailed and direct assessment conducted in 1997 raised this estimate to 43%. In this assessment spatial and temporal patterns of seed predation by ants were studied by mapping all nest entrances in the studied area and marking the mature fruits of 109 reproductive plants with a specific colour code throughout the seed dispersal period. Intact fruit coats were later recovered from the refuse piles, and their mother plants and time of dispersal were identified. Seeds dispersed at the end of the dispersal period had a greater probability of escaping from ant seed predation. Similarly, in plants with late dispersal a greater percentage of seeds escaped from ant predation. Optimum dispersal time coincided with the maximum activity of granivorous ants because, at this time, ants focused their harvest on other plant species of the community. It was also observed that within-individual seed dispersal asynchrony minimised seed predation. From a conservation perspective, results show that the granivorous ant–plant interaction cannot be assessed in isolation and that the intensity of its effects basically depends on the seed dispersal pattern of the other members of the plant community. Furthermore, this threat must be assessed by considering the overall situation of the target population. Thus, in E. paularense, the strong limitation of safe-sites for seedling establishment reduces the importance of seed predation.     

Nectar robbing improves male reproductive success of the endangered Aconitum napellus ssp. lusitanicum

Nectar robbery is usually thought to impact negatively on the reproductive success of plants, but also neutral or even positive effects have been reported. Very few studies have investigated the effects of nectar robbing on the behaviour of legitimate pollinators so far. Such behavioural changes may lead to the reduction of geitonogamy or to increased pollen movement. We simulated nectar robbing in experimental sites as well as in natural populations of Aconitum napellus ssp. lusitanicum, a rare plant pollinated by long-tongued bumblebees. In an experimental setup, we removed the nectaries of 40 % of the flowers, which is similar to rates of robbing observed in wild populations. Patches of plants with experimentally robbed flowers were compared with control patches containing plants with untreated flowers. We observed pollinator behaviour, mimicked male reproductive success (pollen dispersal) using fluorescent dye, and measured female reproductive success (seed set). The main legitimate visitors were bumblebees while honeybees were often observed robbing nectar. They did so by “base working”, i.e. sliding between tepals. Bumblebees tended to visit fewer flowers per plant and spent less time per single flower when these had been experimentally robbed. This change in behaviour consequently increased the proportion of flowers visited by bumblebees in patches with robbed flowers. Fluorescent dye mimicking pollen flow was dispersed larger distances after pollinators had visited patches with robbed flowers compared to control patches. Average seed set per plant was not affected by nectar robbing. Our results demonstrated that A. napellus does not suffer from nectar robbery but may rather benefit via improved pollen dispersal and thus, male reproductive success. Knowledge on such combined effects of behavioural changes of pollinators due to nectar robbery is important to understand the evolutionary significance of exploiters of such mutualistic relationships between plants and their pollinators.     

Are nectar-robbers mutualists or antagonists?

As exploiters of plant-pollinator mutualisms, nectar-robbers remove rewards (nectar) without providing pollination services. Though one might expect nectar-robbing to be costly to plants, it may instead benefit plants by indirectly increasing pollen dispersal. I investigated the direct effects of nectar-robbing bees (Xylocopa californica) on floral rewards and behaviors of pollinators visiting desert willow (Chilopsis linearis) and indirect effects of robbing on the reproductive success of the plant. Nectar-robbers reduced nectar; while unrobbed and robbed flowers were equally likely to contain nectar, nectar volumes were smaller in robbed flowers with nectar. Apis mellifera (honeybees), ineffective pollinators in terms of pollen deposition, avoided robbed flowers. In contrast, Bombus sonorus (bumblebees), effective pollinators, did not avoid robbed flowers. While bumblebees tended to spend less time in robbed flowers, the time that they spent in flowers was not correlated with pollen deposition. Using powder mimicking pollen, I found that on some days, powder was dispersed farther or to more flowers from robbed flowers, indicating that robbing may sometimes benefit plants by increasing male reproductive success. Powder movement suggested that the effect of robbing on male reproductive success ranged from costly to beneficial. The outcome for flowers that were marked early each morning was a function of prevalence of robbing and abundances of effective pollinators, but not a function of spatial variability among trees in prevalence of robbing or the abundance of ineffective honeybees. Unlike powder dispersal, female reproductive success, measured by fruit set and the number of pollen tubes growing in styles, was not affected by robbing. Thus, robbers did not reduce plants female reproductive success either directly by damaging flowers or indirectly by reducing pollen deposition by pollinators. Overall, this study indicates that nectar-robbers were not often costly to plants, and sometimes even benefited plants.