Increase in ant density promotes dual effects on bee behaviour and plant reproductive performance

Floral rewards do not only attract pollinators, but also herbivores and their predators. Ants are attracted by extrafloral nectaries (EFNs), situated near flowers, and may interfere with the efficiency and behaviour of pollinators. We tested the hypothesis that the impacts of ant–pollinator interactions in plant–pollinator systems are dependent on (1) the seasonal activity of EFNs, which increase ant abundance closer to flowers; (2) consequently, an ant effect, where ants decrease the temporal niche overlap of bees due to predator avoidance; and (3) ant density, where higher densities may negatively affect plant–pollinator interactions and plant performance. We studied two ant–plant–pollinator systems based on Banisteriopsis campestris and Banisteriopsis malifolia plant species. The periods of high ant abundance coincided with plant species blooming. The presence of ants around flowers reduced the visitation rates of the smaller bees and the temporal niche overlap between bee species was not higher than randomly expected when ants had free access. Additionally, we observed variable ant effects on fruit set and duration of bee visits to both Malpighiaceae species when ant density was experimentally kept constant on branches, especially on B. campestris. Our goal was to show the dual role of ant density effects, especially because the different outcomes are not commonly observed in the same plant species. We believe that reduced temporal niche overlap between floral visitors due to ant presence provides an opportunity for smaller bees to improve compatible pollination behaviour. Additionally, we concluded that ant density had variable effects on floral visitor behaviours and plant reproductive performance.     

Effectiveness of ants as pollinators of<Emphasis Type="Italic"> Lobularia maritima</Emphasis>: effects on main sequential fitness components of the host plant

The effectiveness of ants as pollinators of Lobularia maritima (Cruciferae) was experimentally analyzed by assessing (1) their quantitative importance at flowers; (2) their effect on host plant seed production; (3) their effect on the performance of host plant progeny, estimated as seed germination, seedling emergence, seedling survival to flowering, and (4) the overall effect of ants on a cumulative, more realistic measure of plant fitness related to the recruitment probability. Flowers of L. maritima were visited during the 2 years of study (1996 and 1997) by more than 50 pollinator species belonging to about 30 families of disparate taxonomic affiliation, notably ants and flies. There was significant seasonal variability in insect abundance and type. Ants, especially Camponotus micans (Formicidae), visited the flowers of L. maritima in summer, representing 81.2% of the visits during this season. This ant species acted as a pollinator of L. maritima, with flowers visited exclusively by ants producing significantly more seeds than flowers from which all pollinators were excluded, whereas flowers visited by only winged insects did not differ from self-pollination. Ant-pollinated flowers produced seeds with a germination rate comparable to the other treatments. Moreover, seedlings from these seeds emerged as fast, and survived at the same rate as controls. Consequently, both ants and winged insects had similar overall effects on host plant recruitment probability (0.6 and 0.7% of initial ovules produced flowering offspring, respectively), a result similar to that of open-pollinated flowers (1.0%). This study demonstrated that the overall effectiveness of the ant C. micans as a summer pollinator of L. maritima was as high as that of other winged insects, contributing not only to the seed production of this crucifer but also to the recruitment of new flowering offspring. Received: 17 February 1999 / Accepted: 26 August 1999     

A comparison of floral resource exploitation by native and invasive Argentine ants

Ants are often considered antagonists when they visit flowers because they typically steal nectar without providing pollination services. Previous research on ant–flower interactions on two species of South African Proteaceae in the Cape Floral Kingdom revealed that the invasive Argentine ant (Linepithema humile), but not native ants, displace other floral arthropod visitors. To determine how common Argentine ant use of inflorescences is, how Argentine and native ant visits differ in the numbers they recruit to inflorescences, and what factors may affect Argentine and native ant foraging in inflorescences, I surveyed 723 inflorescences in 10 species in the genera Protea and Leucospermum across 16 sites and compared ant presence and abundance in inflorescences with abundance at nearby cat food and jam baits. Argentine ants were the most commonly encountered ant of the 22 observed. Argentine ants, as well as six species of native ants were present in all inflorescences for which they were present at nearby baits. Mean Argentine ant abundance per inflorescence was 4.4 ± 0.84 (SE) ants and similar to that of Anoplolepis custodiens and Crematogaster peringueyi, but higher than observed for the other most commonly encountered native ants, Camponotus niveosetosus and Lepisiota capensis. Both Argentine ants and A. custodiens were more likely to be found foraging in spring and under humid conditions, and in inflorescences closer to the ground, with lower sucrose concentrations, and with a greater proportion of open flowers. Argentine ants were more likely to be found in Protea inflorescences, whereas A. custodiens and L. capensis more often visited Leucospermum inflorescences. Considering its displacement of floral arthropods and widespread use of Proteaceae inflorescences, the Argentine ant could be posing a serious threat to plant and pollinator conservation in this biodiversity hotspot.     

Experimental study of pollination by ants in Mediterranean high mountain and arid habitats

In this paper, we report the results of an experimental study on ant pollination of three plant species inhabiting the Mediterranean high mountains (Alyssum purpureum, Arenaria tetraquetra and Sedum anglicum) and four species inhabiting the aridlands (Lepidium subulatum, Gypsophyla struthium, Frankenia thymifolia and Retama sphaerocarpa) of South-eastern Spain. We determined several plant and ant traits, as well as the composition and abundance of the pollinator assemblage. Insects belonging to 29 families and five orders visited the flowers of the plant species studied. In all but two, L. subulatum and G. struthium, the ants comprised 70–100% of the flower visitors. The results clearly show that five out of seven of these plant species were pollinated by ants. The role of the ants as pollinators seems to depend heavily on the relative abundance of the ants with respect to the other species of the pollinator assemblage, ant pollination becoming evident when ants outnumber other floral visitors. The ant-pollination systems analysed in this study may be the result of prevailing ecological conditions more than an evolutionary result of a specialized interaction.     

Slippery flowers as a mechanism of defence against nectar-thieving ants

Background and AimsThe great diversity of floral characteristics among animal-pollinated plants is commonly understood to be the result of coevolutionary interactions between plants and pollinators. Floral antagonists, such as nectar thieves, also have the potential to exert an influence upon the selection of floral characteristics, but adaptation against floral antagonists has attracted comparatively little attention. We found that the corollas of hornet-pollinated Codonopsis lanceolata (Campanulaceae) and the tepals of bee-pollinated Fritillaria koidzumiana (Liliaceae) are slippery to nectar-thieving ants living in the plant’s habitat; because the flowers of both species have exposed nectaries, slippery perianths may function as a defence against nectar-thieving ants.MethodsWe conducted a behavioural experiment and observed perianth surface microstructure by scanning electron microscopy to investigate the mechanism of slipperiness. Field experiments were conducted to test whether slippery perianths prevent floral entry by ants, and whether ant presence inside flowers affects pollination.Key ResultsScanning electron microscopy observations indicated that the slippery surfaces were coated with epicuticular wax crystals. The perianths lost their slipperiness when wiped with hexane. Artificial bridging of the slippery surfaces using non-slippery materials allowed ants to enter flowers more frequently. Experimental introduction of live ants to the Codonopsis flowers evicted hornet pollinators and shortened the duration of pollinator visits. However, no statistical differences were found in the fruit or seed sets of flowers with and without ants.ConclusionsSlippery perianths, most probably based on epicuticular wax crystals, prevent floral entry by ants that negatively affect pollinator behaviour. Experimental evidence of floral defence based on slippery surfaces is rare, but such a mode of defence may be widespread amongst flowering plants.     

Contrasting effects of invasive plants in plant–pollinator networks

The structural organization of mutualism networks, typified by interspecific positive interactions, is important to maintain community diversity. However, there is little information available about the effect of introduced species on the structure of such networks. We compared uninvaded and invaded ecological communities, to examine how two species of invasive plants with large and showy flowers (Carpobrotus affine acinaciformis and Opuntia stricta) affect the structure of Mediterranean plant–pollinator networks. To attribute differences in pollination to the direct presence of the invasive species, areas were surveyed that contained similar native plant species cover, diversity and floral composition, with or without the invaders. Both invasive plant species received significantly more pollinator visits than any native species and invaders interacted strongly with pollinators. Overall, the pollinator community richness was similar in invaded and uninvaded plots, and only a few generalist pollinators visited invasive species exclusively. Invasive plants acted as pollination super generalists. The two species studied were visited by 43% and 31% of the total insect taxa in the community, respectively, suggesting they play a central role in the plant–pollinator networks. Carpobrotus and Opuntia had contrasting effects on pollinator visitation rates to native plants: Carpobrotus facilitated the visit of pollinators to native species, whereas Opuntia competed for pollinators with native species, increasing the nestedness of the plant–pollinator network. These results indicate that the introduction of a new species to a community can have important consequences for the structure of the plant–pollinator network.     

A trade-off between the frequency and duration of bumblebee visits to flowers

Pollinator behavior influences plant reproduction in many ways. A traditional measure of pollination, the number of visits received, may be a poor predictor of plant reproductive success, particularly when there are trade-offs between visit quantity and components of visit quality. For example, the duration of pollinator visits may be negatively correlated with the number of visits received by a flower. We tested for a trade-off between the number of bumblebee visits and the duration of those visits in an experimental population of snapdragons (Antirrhinummajus: Scrophulariaceae). The duration of a bumblebee visit to a flower increased significantly with the time interval since the flower had last been visited. Over the lifetime of a flower the correlation between the total number and average duration of visits received by a flower was weakly negative. However, at the whole-plant level the correlation was positive: plants whose flowers received more visits also received visits of longer duration. Factors affecting the relationship between quantity and duration of pollinator visits to flowers also were investigated. Two factors weakened the negative dependence of average visit duration on number of visits received by individual snapdragon flowers: (1) the correlation between the total number of visits to a flower and the average interval between visits was only −0.53, as visits to individual flowers were not very evenly spaced over time, and (2) newly opened flowers received fewer and shorter visits than older flowers. Comparing whole plants, nectar production per flower varied dramatically across individuals, a probable explanation for the positive correlation between visit number and average duration per flower observed at the plant level. The potential for a trade-off between these two components of pollinator service exists when visit duration depends on reward quantity; whether the trade-off is realized will depend on variation in nectar production and on whether pollinators forage systematically. Received: 3 October 1997 / Accepted: 16 June 1998     

Production of food bodies on the reproductive organs of myrmecophytic Macaranga species (Euphorbiaceae): effects on interactions with herbivores and pollinators

In protective ant–plant mutualisms, plants offer ants food (such as extrafloral nectar and/or food bodies) and ants protect plants from herbivores. However, ants often negatively affect plant reproduction by deterring pollinators. The aggressive protection that mutualistic ants provide to some myrmecophytes may enhance this negative effect in comparison to plant species that are facultatively protected by ants. Because little is known about the processes by which myrmecophytes are pollinated in the presence of ant guards, we examined ant interactions with herbivores and pollinators on plant reproductive organs. We examined eight myrmecophytic and three nonmyrmecophytic Macaranga species in Borneo. Most of the species studied are pollinated by thrips breeding in the inflorescences. Seven of eight myrmecophytic species produced food bodies on young inflorescences and/or immature fruits. Food body production was associated with increased ant abundance on inflorescences of the three species observed. The exclusion of ants from inflorescences of one species without food rewards resulted in increased herbivory damage. In contrast, ant exclusion had no effect on the number of pollinator thrips. The absence of thrips pollinator deterrence by ants may be due to the presence of protective bracteoles that limit ants, but not pollinators, from accessing flowers. This unique mechanism may account for simultaneous thrips pollination and ant defense of inflorescences.     

Competition hierarchy and plant defense in a guild of ants on tropical Passiflora

In facultative ant–plant interactions, ants may compete with each other for food provided by extrafloral nectar (EFN) plants. We studied resource competition and plant defense in a guild of ants that use the same EFN resource provided by two species of Passiflora in a seasonal rain forest in tropical China. At least 22 ant species were recorded using the EFN resource, although some of those species were rare. Among these ants, Paratrechina sp.1 and Dolichoderus thoracicus were more aggressive than other species. Ant aggressiveness measured as ant behavioral dominance index (BDI) was positively correlated with ant abundance on the Passiflora species studied. Ant BDI was also positively correlated to the protection that ants provided against herbivory. In Passiflora siamica, the number of workers patrolling on the plants did negatively correlate with average leaf loss per plant. We conclude that in this facultative Passiflora–ant system, plant defense upon herbivore was indeed influenced by the total number of ants present on plant and the aggressiveness of these ants.     

Seed predator deterrence by seed-carrying ants in a dyszoochorous plant, <Emphasis Type="Italic">Chamaesyce maculata</Emphasis> L. Small (Euphorbiaceae)

Seeds are often carried by omnivorous ants even if they do not carry elaiosomes. Although many seeds carried by ants are consumed, both seeds abandoned during the seed carrying and leftover seeds are consequently dispersed (dyszoochory). These non-myrmecochorous seeds do not necessarily attract ants quickly. Therefore, these seeds often seem to be exposed to the danger of consumption by pre-dispersal seed predators. We propose the hypotheses, “seed predator deterrence hypothesis” that plants may benefit from seed-carrying ants if they deter seed predators from visiting plants, and seed-carrying ants may play additional roles in plant reproductive success, besides dyszoochory by ants. To test the hypotheses, we investigated the abundance of seed-carrying ants of the species Tetramorium tsushimae Linnaeus and Pheidole noda Smith F., and of the seed predatory stinkbug, Nysius plebeius Distat, on the spotted sandmat, Chamaesyce maculata L. Small, of which the seeds have no elaiosomes but are consumed by both ants and bugs. In the field, ants and stinkbugs seldom encountered each other on the plant. The number of stinkbugs beneath the plants with ants was smaller than that beneath the plants without ants. In laboratory experiments, the number of stinkbugs on the shoot was smaller when ants were present than when they were absent. These results might support the seed predator deterrence hypothesis: the probability of seed predation by stinkbugs seems to be reduced by the ant visits on plants and/or the existence of ants beneath the plants. This study highlights a new ant–plant interaction in seed dispersal by ants.     

Initial floral visitor identity and foraging time strongly influence blueberry reproductive success

Priority effects occur when the order of species arrival affects subsequent ecological processes. The order that pollinator species visit flowers may affect pollination through a priority effect, whereby the first visitor reduces or modifies the contribution of subsequent visits. We observed floral visitation to blueberry flowers from honeybees, stingless bees or a mixture of both species and investigated how (i) initial visits differed in duration to later visits; and (ii) how visit sequences from different pollinator taxa influenced fruit weight. Stingless bees visited blueberry flowers for significantly longer than honeybees and maintained their floral visit duration, irrespective of the number of preceding visits. In contrast, honeybee visit duration declined significantly with an increasing number of preceding visits. Fruit weight was positively associated with longer floral visit duration by honeybees but not from stingless bee or mixed species visitation. Fruit from mixed species visits were heavier overall than single species visits, because of a strong priority effect. An initial visit by a stingless bee fully pollinated the flower, limiting the pollination contribution of future visitors. However, after an initial honeybee visit, flowers were not fully pollinated and additional visitation had an additive effect upon fruit weight. Blueberries from flowers visited first by stingless bees were 60% heavier than those visited first by honeybees when total floral visitation was short (∼1 min). However, when total visitation time was long (∼ 8 min), blueberry fruit were 24% heavier when initial visits were from honeybees. Our findings highlight that the initial floral visit can have a disproportionate effect on pollination outcomes. Considering priority effects alongside traditional measures of pollinator effectiveness will provide a greater mechanistic understanding of how pollinator communities influence plant reproductive success.     

Dynamics of the association between a long-lived understory myrmecophyte and its specific associated ants

Myrmecophytic symbioses are widespread in tropical ecosystems and their diversity makes them useful tools for understanding the origin and evolution of mutualisms. Obligate ant–plants, or myrmecophytes, provide a nesting place, and, often, food to a limited number of plant–ant species. In exchange, plant–ants protect their host plants from herbivores, competitors and pathogens, and can provide them with nutrients. Although most studies to date have highlighted a similar global pattern of interactions in these systems, little is known about the temporal structuring and dynamics of most of these associations. In this study we focused on the association between the understory myrmecophyte Hirtella physophora (Chrysobalanaceae) and its obligate ant partner Allomerus decemarticulatus (Myrmicinae). An examination of the life histories and growth rates of both partners demonstrated that this plant species has a much longer lifespan (up to about 350 years) than its associated ant colonies (up to about 21 years). The size of the ant colonies and their reproductive success were strongly limited by the available nesting space provided by the host plants. Moreover, the resident ants positively affected the vegetative growth of their host plant, but had a negative effect on its reproduction by reducing the number of flowers and fruits by more than 50%. Altogether our results are important to understanding the evolutionary dynamics of ant–plant symbioses. The highly specialized interaction between long-lived plants and ants with a shorter lifespan produces an asymmetry in the evolutionary rates of the interaction which, in return, can affect the degree to which the interests of the two partners converge.     

Pollination by ants: consequences of the quantitative effects on a mutualistic system

Summary We have analysed the importance of worker ants (Proformica longiseta, Formicidae) as pollinators of a mass-flowering woody plant (Hormathophylla spinosa, Cruciferae) in the high-mountain area of the Sierra Nevada (southern Spain). We have quantified the abundance and foraging behavior of P. longiseta in comparison with winged flower visitors. We have also examined, by means of selective exclusion experiments, the role of ants as true pollinators, comparing them with the winged flower visitors. A total of 39 species belonging to 18 families visited the flowers of H. spinosa. All the visitors were winged insects, except P. longiseta, a species which alone made up more than 80% of the total number of insects found on the flowers. All pollinators of H. spinosa had similar foraging patterns, with 98% of total movements made between flowers within the same plant. Ants always made contact with the plant reproductive organs when foraging for nectar, and transferred large numbers of pollen grains. However, pollen exposed to ants for brief periods exhibited reduced percentage of germination. P. longiseta is both the most abundant and spatio-temporally predictable flower visitor of H. spinosa. These characteristics, weighted by their flower visitation rate, make worker ants the pollinator that maintains the strongest mutualistic interaction with H. spinosa. The exclusion experiments show that workers behave as true pollinators, since they contribute to increase the number of viable seeds produced by H. spinosa. The key factor of this interaction is mainly the great density of workers throughout the flowering period. In short, the H. spinosa-P. longiseta mutualistic interaction mainly depends on its high probability of occurrence.     

Choice of food resource by bees and ants (Hymenoptera: Apoidea,Formicidae) on coconut tree inflorescences (Cocos nucifera,Arecaceae)

Coconut trees are mostly anemophilous; however, because bees and ants forage on coconut tree inflorescences for floral food, entomophilous pollination can also occur. The aim of this study was to determine the food resource preference of bees and ants while they collect pollen, nectar and, for ants, occasionally prey on coconut tree inflorescences, as well as to evaluate their impact on self-pollination. The number of ant visits to first female and then male flowers is significantly higher than that of bees. For Apis mellifera (L.) and Pseudomyrmex gracilis (Fabricius) 14% of the sequences were favorable to direct self-pollination. The probability of visits for all of the sequences was similar for both bees and ants and there was no difference in resource choice. For these reasons, neither can be considered a more effective pollinator of the coconut tree.     

Relationships among nectar‐dwelling yeasts,flowers and ants: patterns and incidence on nectar traits

Nectar‐dwelling yeasts are emerging as widely distributed organisms playing a potentially significant and barely unexplored ecological role in plant pollinator mutualisms. Previous efforts at understanding nectar–pollinator–yeast interactions have focused on bee‐pollinated plants, while the importance of nectarivorous ants as vectors for yeast dispersal remains unexplored so far. Here we assess the abundance and composition of the nectar fungal microbiota of the ant‐pollinated plant Cytinus hypocistis, study whether yeast transmission is coupled with ant visitation, and discern whether ant‐ transported yeasts promote changes in nectar characteristics. Our results show that a high percentage of flowers (77%) and plants (94%) contained yeasts, with yeast cell density in nectar reaching up to 6.2 × 10⁴ cells mm^?3, being the highest densities associated with the presence of the nectar‐specialist yeast Metschnikowia reukaufii. The establishment of fungal microbiota in nectar required flower visitation by ants, with 70% of yeast species transported by them being also detected in nectar. Ant‐vectored yeasts diminished the nutritional quality of nectar, with flowers exposed to pollinators and yeasts containing significantly lower nectar sugar concentration than virgin flowers (13.4% and 22.8%, respectively). Nectar of flowers that harbored M. reukaufii showed the lowest quality, with nectar concentration declining significantly with increasing yeast density. Additionally, yeasts modified patterns of interpopulation variation in nectar traits, homo genizing differences between populations in some nectar attributes. We show for the first time that the outcome of the tripartite pollinator–flower–yeast interaction is highly dependent on the identity and inherent properties of the participants, even to the extent of influencing the species composition of this ternary system, and can be mediated by ecological characteristics of plant populations. Through their influence on plant functional traits, yeasts have the potential to alter nectar consumption, pollinator foraging behavior and ultimately plant reproduction.     

Novel interactions of non-pollinating ants with pollinators and fruit consumers in a tropical forest

The tropical ants Ectatomma ruidum and E. tuberculatum (Formicidae) regularly patrol leaves, flowers, and fruits of the understory shrub, Psychotria limonensis (Rubiaceae), on Barro Colorado Island, Panama. Ant and pollinator exclusion experiments elucidated both positive and negative effects of ant attendance on plant reproductive success, including pollination, fruit set, fruit loss, and fruit removal. Ants did not pollinate flowers but did contribute to higher pollination success, probably by increasing the relocation frequency of winged pollinators and thus the rate of flower visitation. Ants also prevented fruit loss to herbivorous insects which were common during the early stages of fruit development. Thus, ant attendance strongly improved both pollination and fruit set whereby plants with ants set more fruit per flower and also lost fewer fruits during fruit maturation. In contrast, ants had a negative effect on the removal of ripe fruits by avian frugivores. Thus, ant attendance has a non-trivial influence on plant reproduction, this interaction being beneficial at some stages of the plant reproductive cycle and carrying costs at another stage. A tight ecological or co-evolved relationship between these Ectatomma spp. and P. limonensis is unlikely given that ant attendance of plants is detrimental to fruit removal. Received: 18 May 1998 / Accepted: 1 March 1999     

Intra‐floral resource partitioning between endemic and invasive flower visitors: consequences for pollinator effectiveness

1. Sympatric flower visitor species often partition nectar and pollen and thus affect each other's foraging pattern. Consequently, their pollination service may also be influenced by the presence of other flower visiting species. Ants are solely interested in nectar and frequent flower visitors of some plant species but usually provide no pollination service. Obligate flower visitors such as bees depend on both nectar and pollen and are often more effective pollinators. 2. In Hawaii, we studied the complex interactions between flowers of the endemic tree Metrosideros polymorpha (Myrtaceae) and both, endemic and introduced flower‐visiting insects. The former main‐pollinators of M. polymorpha were birds, which, however, became rare. We evaluated the pollinator effectiveness of endemic and invasive bees and whether it is affected by the type of resource collected and the presence of ants on flowers. 3. Ants were dominant nectar‐consumers that mostly depleted the nectar of visited inflorescences. Accordingly, the visitation frequency, duration, and consequently the pollinator effectiveness of nectar‐foraging honeybees (Apis mellifera) strongly decreased on ant‐visited flowers, whereas pollen‐collecting bees remained largely unaffected by ants. Overall, endemic bees (Hylaeus spp.) were ineffective pollinators. 4. The average net effect of ants on pollination of M. polymorpha was neutral, corresponding to a similar fruit set of ant‐visited and ant‐free inflorescences. 5. Our results suggest that invasive social hymenopterans that often have negative impacts on the Hawaiian flora and fauna may occasionally provide neutral (ants) or even beneficial net effects (honeybees), especially in the absence of native birds.     

Variation in pollinator assemblages in a fragmented landscape and its effects on reproductive stages of a self-incompatible treelet, <Emphasis Type="Italic">Psychotria suterella</Emphasis> (Rubiaceae)

Few studies of plant–pollinator interactions in fragmented landscapes evaluate the consequences of floral visitor variation on multiple stages of plant reproduction. Given that fragmentation potentially has positive or negative effects on different organisms, and that self-incompatible plant species depend on pollinators for sexual reproduction, differences in floral visitor assemblages may affect certain plant reproductive stages. We evaluated how pollinator assemblage, availability of floral resources, pollination, reproductive output, and seed and seedling performance of Psychotria suterella Muell. Arg. varied among three fragmentation categories: non-fragmented habitats, fragments connected by corridors, and isolated fragments. Richness and frequency of floral visitors were greater in fragments than in non-fragmented sites, resulting mainly from the addition of species typically found in disturbed areas. Although 24 species visited Psychotria suterella flowers, bumblebees were considered the most important pollinators, because they showed the highest frequency of visits and were present in eight out of ten sites. Additionally, the number of pollen tubes per flower per visit was lower in areas without bumblebees. The increased visitation in fragments seemed to enhance pollination slightly. However, fruit and seed output, germination, and seed and seedling mass were similar in non-fragmented sites, connected sites, and isolated fragments. Our results suggested that, even for a self-incompatible species, responses to habitat fragmentation at different stages of plant reproduction might be decoupled from the responses observed in floral visitors, if fruit set is not pollen limited. If all reproductive stages were considered, variation on the small scale was more important than the variation explained by fragmentation category. In spite of its self-incompatible breeding system, this plant–pollinator system showed resilience to habitat fragmentation, mainly as a result of high availability of potential mates to P. suterella individuals, absence of pollen limitation, and the presence of bumblebees (Bombus spp.) throughout this highly connected landscape.     

Refuse attracts? Effect of refuse dumps of leaf‐cutting ants on floral traits

The nutrient‐rich organic waste generated by ants may affect plant reproductive success directly by enhancing fruit production but also indirectly, by affecting floral traits related with pollinator attraction. Understanding how these soil‐nutrient hot spots influence floral phenotype is relevant to plant–pollination interactions. We experimentally evaluated whether the addition of organic waste from refuse dumps of the leaf‐cutting ant Acromyrmex lobicornis (Hymenoptera: Formicidae: Attini) alters floral traits associated with pollinator attraction in Eschscholzia californica (Ranunculales: Papaveraceae), an entomophilous herb. We analysed flower shape and size using geometric morphometric techniques in plants with and without the addition of refuse‐dumps soil, under greenhouse conditions. We also measured the duration of flowering season, days with new flowers, flower production and floral display size. Plants growing in refuse‐dumps soil showed higher flower shape diversity than those in control soil. Moreover, plants in refuse‐dumps soil showed bigger flower and floral display size, longer flowering season, higher number of flowering days and flower production. As all these variables may potentially increase pollinator visits, plants in refuse‐dumps soil might increase their fitness through enhanced attraction. Our work describes how organic waste from ant nests may enhance floral traits involved in floral attraction, illustrating a novel way of how ants may indirectly benefit plants.     

Induced Floral and Extrafloral Nectar Production Affect Ant‐pollinator Interactions and Plant Fitness

Thousands of plant species throughout tropical and temperate zones secrete extrafloral nectar to attract ants, whose presence provides an indirect defense against herbivores. Extrafloral nectaries are located close to flowers and may modify competition between ants and pollinators. Here, we used Lima bean (Phaseolus lunatus L.) to study the plants interaction between ants and flower visitors and its consequences for plant fitness. To test these objectives, we carried out two field experiments in which we manipulated the presence of ants and nectar production via induction with jasmonic acid (JA). We then measured floral and extrafloral nectar production, the number of patrolling ants and flower visitors as well as specific plant fitness traits. Lima bean plants under JA induction produced more nectar in both extrafloral nectaries and flowers, attracted more ants and produced more flowers and seeds than non‐induced plants. Despite an increase in floral nectar in JA plants, application of this hormone had no significant effects on flower visitor attraction. Finally, ant presence did not result in a decrease in the number of visits, but our results suggest that ants could negatively affect pollination efficiency. In particular, JA‐induced plants without ants produced a greater number of seeds compared with the JA‐treated plants with ants.