Separating selection by diurnal and nocturnal pollinators on floral display and spur length in Gymnadenia conopsea

Most plants attract multiple flower visitors that may vary widely in their effectiveness as pollinators. Floral evolution is expected to reflect interactions with the most important pollinators, but few studies have quantified the contribution of different pollinators to current selection on floral traits. To compare selection mediated by diurnal and nocturnal pollinators on floral display and spur length in the rewarding orchid Gymnadenia conopsea, we manipulated the environment by conducting supplemental hand-pollinations and selective pollinator exclusions in two populations in central Norway. In both populations, the exclusion of diurnal pollinators significantly reduced seed production compared to open pollination, whereas the exclusion of nocturnal pollinators did not. There was significant selection on traits expected to influence pollinator attraction and pollination efficiency in both the diurnal and nocturnal pollination treatment. The relative strength of selection among plants exposed to diurnal and nocturnal visitors varied among traits and populations, but the direction of selection was consistent. The results suggest that diurnal pollinators are more important than nocturnal pollinators for seed production in the study populations, but that both categories contribute to selection on floral morphology. The study illustrates how experimental manipulations can link specific categories of pollinators to observed selection on floral traits, and thus improve our understanding of how species interactions shape patterns of selection.     

Evolution of polyploidy and the diversification of plant-pollinator interactions

One of the major mechanisms of plant diversification has been the evolution of polyploid populations that differ from their diploid progenitors in morphology, physiology, and environmental tolerances. Recent studies have indicated that polyploidy may also have major effects on ecological interactions with herbivores and pollinators. We evaluated pollination of sympatric diploid and tetraploid plants of the rhizomatous herb Heuchera grossulariifolia (Saxifragaceae) along the Selway and Salmon Rivers of northern Idaho, USA, during four consecutive years. Previous molecular and ecological analyses had indicated that the tetraploid populations along these two river systems are independently derived and differ from each other in multiple traits. In each region, we evaluated floral visitation rate by all insect visitors, pollination efficacy of all major visitors, and relative contribution of all major pollinators to seed set. In both regions, diploid and tetraploid plants attracted different suites of floral visitors. Most pollination was attributable to several bee species and the moth Greya politella. Lasioglossum bees preferentially visited diploid plants at Lower Salmon but not at Upper Selway, queen Bombus centralis preferentially visited tetraploids at both sites, and worker B. centralis differed between sites in their cytotype preference. Hence, diploid and autotetraploid H. grossulariifolia plants act essentially as separate ecological species and may experience partial reproductive isolation through differential visitation and pollination by their major floral visitors. Overall the results, together with recent results from other studies, suggest that the repeated evolution of polyploidy in plants may contribute importantly to the structure and diversification of ecological interactions in terrestrial communities.     

Floral scents: their roles in nursery pollination mutualisms

Mutualisms are interspecies interactions in which each participant gains net benefits from interacting with its partner. In nursery pollination mutualisms, pollinators reproduce within the inflorescence they pollinate. In these systems, each partner depends directly on the other for its reproduction. Therefore, the signal responsible for partner encounter is crucial in these horizontally transmitted mutualisms, in which the association between specific partners must be renewed at each generation. As in many other interspecies interactions, chemical signals are suspected to be important in the functioning of these mutualisms. We synthesized and compared the published data available on the role of floral scents in the functioning of the 16 known independently evolved nursery pollination mutualisms. So far, attraction of pollinators to their specific hosts has been investigated in only seven of these systems, and the majority of the studies have been conducted on one of them, fig/fig wasp interactions. While such unevenness of the information limits the potential for meta-analysis, some patterns emerge from this review concerning the role of flower volatiles in maintaining the specificity of pollinator attraction, in signaling the appropriate phenological stage for pollinator visit, in attracting the pollinator toward the rewardless sex in dioecious plant species and in aiding the location and exploitation of resources by parasites and predators associated with these mutualisms. Finally, we highlight new perspectives on the evolution of signals in these diversified systems depending on the age and the degree of specificity of the interaction, and on the effect of phylogenetic inertia on the evolutionary dynamics of plant signals.     

Caveats to quantifying ecosystem services: fruit abortion blurs benefits from crop pollination.

The recent trend to place monetary values on ecosystem services has led to studies on the economic importance of pollinators for agricultural crops. Several recent studies indicate regional, long-term pollinator declines, and economic consequences have been derived from declining pollination efficiencies. However, use of pollinator services as economic incentives for conservation must consider environmental factors such as drought, pests, and diseases, which can also limit yields. Moreover, "flower excess" is a well-known reproductive strategy of plants as insurance against unpredictable, external factors that limit reproduction. With three case studies on the importance of pollination levels for amounts of harvested fruits of three tropical crops (passion fruit in Brazil, coffee in Ecuador, and cacao in Indonesia) we illustrate how reproductive strategies and environmental stress can obscure initial benefits from improved pollination. By interpreting these results with findings from evolutionary sciences, agronomy, and studies on wild-plant populations, we argue that studies on economic benefits from pollinators should include the total of ecosystem processes that (1) lead to successful pollination and (2) mobilize nutrients and improve plant quality to the extent that crop yields indeed benefit from enhanced pollinator services. Conservation incentives that use quantifications of nature's services to human welfare will benefit from approaches at the ecosystem level that take into account the broad spectrum of biological processes that limit or deliver the service.     

Herbivory-mediated pollinator limitation: negative impacts of induced volatiles on plant-pollinator interactions

Although induced plant responses to herbivory are well studied as mechanisms of resistance, how induction shapes community interactions and ultimately plant fitness is still relatively unknown. Using a wild tomato, Solanum peruvianum, native to the Peruvian Andes, we evaluated the disruption of pollination as a potential ecological cost of induced responses. More specifically, we tested the hypothesis that metabolic changes in herbivore-attacked plants, such as the herbivore-induced emission of volatile organic compounds (VOCs), alter pollinator behavior and consequentially affect plant fitness. We conducted a series of manipulative field experiments to evaluate the role of herbivore-induced vegetative and floral VOC emissions as mechanisms by which herbivory affects pollinator behavior. In field surveys and bioassays in the plants' native habitat, we found that real and simulated herbivory (methyl jasmonate application) reduced attractiveness of S. peruvianum flowers to their native pollinators. We show that reduced pollinator preference, not resource limitation due to leaf tissue removal, resulted in reduced seed set. Solitary bee pollinators use floral plant volatiles, emitted in response to herbivory or methyl jasmonate treatment, as cues to avoid inflorescences on damaged plants. This herbivory-induced pollinator limitation can be viewed as a general cost of induced plant responses as well as a specific cost of herbivory-induced volatile emission.     

Mimics and magnets: the importance of color and ecological facilitation in floral deception

Plants that lack floral rewards can attract pollinators if they share attractive floral signals with rewarding plants. These deceptive plants should benefit from flowering in close proximity to such rewarding plants, because pollinators are locally conditioned on floral signals of the rewarding plants (mimic effect) and because pollinators are more abundant close to rewarding plants (magnet effect). We tested these ideas using the non-rewarding South African plant Eulophia zeyheriana (Orchidaceae) as a study system. Field observations revealed that E. zeyheriana is pollinated solely by solitary bees belonging to a single species of Lipotriches (Halictidae) that appears to be closely associated with the flowers of Wahlenbergia cuspidata (Campanulaceae), a rewarding plant with which the orchid is often sympatric. The pale blue color of the flowers of E. zeyheriana differs strongly from flowers of its congeners, but is very similar to that of flowers of W. cuspidata. Analysis of spectral reflectance patterns using a bee vision model showed that bees are unlikely to be able to distinguish the two species in terms of flower color. A UV-absorbing sunscreen was applied to the flowers of the orchid in order to alter their color, and this resulted in a significant decline in pollinator visits, thus indicating the importance of flower color for attraction of Lipotriches bees. Pollination success in the orchid was strongly affected by proximity to patches of W. cuspidata. This was evident from one of two surveys of natural populations of the orchid, as well as experiments in which we translocated inflorescences of the orchid either into patches of W. cuspidata or 40 m outside such patches. Flower color and location of E. zeyheriana plants relative to rewarding magnet patches are therefore key components of the exploitation by this orchid of the relationship between W. cuspidata and Lipotriches bee pollinators.     

Anther-mimicking floral guides exploit a conflict between innate preference and learning in bumblebees (<Emphasis Type="Italic">Bombus terrestris</Emphasis>)

Bee-pollinated plants are frequently dichogamous: e.g. each flower has a discernable male and female phase, with only the male phase offering a pollen reward. Pollen-collecting bees should therefore discriminate against female-phase flowers to maximise their rate of pollen harvest, but this behaviour would reduce plant fitness due to inferior pollination. Here, we test the hypothesis that flowers use pollen-mimicking floral guides to prevent flower-phase discrimination. Such floral guides resemble pollen in spectral reflection properties and are widespread among angiosperm flowers. In an array of artificial flowers, bumblebees learned less well to discriminate between flower variants simulating different flowering phases when both flower variants carried an additional pollen-yellow guide mark. This effect depended crucially on the pollen-yellow colour of the guide mark and on its spatial position within the artificial flower. We suggest that floral guides evolved to inhibit flower-phase learning in bees by exploiting the innate colour preferences of their pollinators.     

Nectar secondary compounds affect self-pollen transfer: implications for female and male reproduction

Pollen movement within and among plants affects inbreeding, plant fitness, and the spatial scale of genetic differentiation. Although a number of studies have assessed how plant and floral traits influence pollen movement via changes in pollinator behavior, few have explored how nectar chemical composition affects pollen transfer. As many as 55% of plants produce secondary compounds in their nectar, which is surprising given that nectar is typically thought to attract pollinators. We tested the hypothesis that nectar with secondary compounds may benefit plants by encouraging pollinators to leave plants after visiting only a few flowers, thus reducing self-pollen transfer. We used Gelsemium sempervirens, a plant whose nectar contains the alkaloid gelsemine, which has been shown to be a deterrent to foraging bee pollinators. We found that high nectar alkaloids reduced the total and proportion of self-pollen received by one-half and one-third, respectively. However, nectar alkaloids did not affect female reproduction when we removed the potential for self-pollination (by emasculating all flowers on plants). We then tested the assumption that self-pollen in combination with outcrossed pollen depresses seed set. We found that plants were weakly self-compatible, but self-pollen with outcrossed pollen did not reduce seed set relative to solely outcrossed flowers. Finally, an exponential model of pollen carryover suggests that high nectar alkaloids could benefit plants via increased pollen export (an estimate of male function), but only when pollinators were efficient and abundant and plants had large floral displays. Results suggest that high nectar alkaloids may benefit plants via increased pollen export under a restricted set of ecological conditions, but in general, the costs of high nectar alkaloids in reducing pollination balanced or outweighed the benefits of reducing self-pollen transfer for estimates of female and male reproduction.     

Facilitation in an insect-pollinated herb with a floral display dimorphism

Population context should influence pollination success and selection on floral display in animal-pollinated plants because attraction of pollinators depends not only on the characteristics of individual plants, but also on the attractiveness of co-occurring conspecifics. The insect-pollinated herb Primula farinosa is polymorphic for inflorescence height. Natural populations may include both long-scaped plants, which present their flowers well above the soil surface, and short-scaped plants, with their flowers positioned close to the ground. We experimentally tested whether seed production in short-scaped P. farinosa varied with local morph frequency and surrounding vegetation height. In tall vegetation, short-scaped plants in polymorphic populations produced more fruit and tended to produce more seeds than short-scaped plants did in monomorphic populations. In low vegetation, population composition did not significantly affect fruit and seed output of short-scaped plants. The results suggest that long-scaped plants facilitate short-scaped plants in terms of pollinator attraction and that the facilitation effect is contingent on the height of the surrounding vegetation. The documented facilitation should contribute to the maintenance of the scape length polymorphism in ungrazed areas where litter accumulates and vegetation grows tall.     

Higher soybean production using honeybee and wild pollinators, a sustainable alternative to pesticides and autopollination

This is the first report showing that using honeybee (Apis mellifera) and wild pollinators complementary pollination can enhance soybean productivity (Glycine max). Current industrial production of soybean involves autopollination and high loads of pesticides. Therefore, growers have neglected possible biotic pollination despite suggestions that soybean benefit from insect pollinators. Reports advocating possible biotic pollination are based on experiments where bees are caged with flowering plants and the absence of pesticides, thus not in field conditions. Therefore, here we compared in field conditions soybean yield produced (1) independently of biotic pollinators, (2) with wild pollinators and (3) with honeybee colonies. Results showed an increase of +6.34 % of soybean yield in areas where wild pollinators had free access to flowers. The introduction of honeybee colonies further raised the yield of +18.09 %. Our findings therefore show that, though soybean is autogamous, allowing pollination by wild pollinators leads to higher yields. Moreover, adding honeybee mitigates pollination deficits and improves yield compared to current practices.     

Experimental Demonstration of an Allee Effect in American Ginseng

Abstract: Harvesting of wild American ginseng (   Panax quinquefolius ) for the herbal trade has lowered natural population sizes. We tested for reproductive limitation due to small population size (a form of the Allee effect) by experimentally planting "natural" populations numbering 4, 16, and 64 using 4-year-old cultivated plants. Plant size traits and reproductive traits ( bud, flower, green fruit, and mature fruit) were recorded through the ensuing summer. Fruit production per flower and per plant increased in proportion to flowering population size (  p = 0.0063 and p = 0.0017, respectively), strongly suggesting that an Allee effect occurs in very small populations. The increase in fruit production was not explained by either plant or inflorescence size differences. Although population size-dependent pollination, through insufficient pollinator visitation rate or pollen transfer rate, seems the most likely cause of the observed effects, our limited observations of pollinators were not sufficient to demonstrate a change in pollination rates as a function of population size. Knowledge of the presence as well as the mechanism underlying this Allee effect may be especially useful for management and determination of minimum viable population size of the species in the wild.     

Work division of floral scent compounds in mediating pollinator behaviours

Floral scents are known as an olfactory signal for attracting pollinators, but why the flowers pollinated by highly specialised pollinators emit scents consisting of mixtures of many compounds and dominated by one or a few compounds is still poorly understood. We supposed that each (especially characteristic) chemical in floral scents may play a specific role in mediating pollinator behaviours and tested this supposition in a fig-fig wasp mutualism. Ficus curtipes is obligately pollinated by an undescribed Eupristina species. In the scent of F. curtipes receptive figs, over 50 compounds have been identified, and the scent is dominated by two compounds, 6-methyl-5-hepten-2-ol (OL) and 6-methyl-5-hepten-2-one (NE). We therefore tested the roles of the two major chemicals in mediating the pollinator behaviours. Our results show that OL and NE, respectively, act as a long-distance attractant and a fig-entry behaviour stimulant to the obligate pollinator wasp. Namely, OL attracts the wasps to the figs and NE guides the wasps into the figs. This finding on the work division of floral scent compounds partially explains the maintenance mechanism of the fig-fig wasp mutualism and the significance of the chemical diversity of floral scent in plant–pollinator interactions, especially in specialised pollination systems.     

Predispersal seed herbivores, not pollinators, exert selection on floral traits via female fitness

Herbivores that oviposit in flowers of animal-pollinated plants depend on pollinators for seed production and are therefore expected to choose flowers that attract pollinators. This provides a mechanism by which seed herbivores and pollinators could impose conflicting selection on floral traits. We measured phenotypic selection on floral traits of Lobelia siphilitica (Lobeliaceae) via female fitness to determine the relative strength of selection by pollinators and a specialist predispersal seed herbivore. We were able to attribute selection on flowering phenology to the herbivores. However, no selection could be attributed to pollinators, resulting in no conflicting selection on floral traits. Unlike pollinators, whose preference for certain floral traits does not always translate into higher fitness, any discrimination by seed herbivores is likely to decrease fitness of the preferred floral phenotype. Thus predispersal seed herbivores may be a significant agent of selection on floral traits.     

Geographic structure of pollinator communities, reproductive assurance, and the evolution of self-pollination

Reproductive assurance is often invoked as an explanation for the evolution of self-fertilization in plants. However, key aspects of this hypothesis have received little empirical support. In this study, I use geographic surveys of pollinator communities along with functional studies of floral trait variation to examine the role of pollination ecology in mating system differentiation among populations and subspecies of the annual plant Clarkia xantiana. A greenhouse experiment involving 30 populations from throughout the species' range indicated that variation in two floral traits, herkogamy and protandry, was closely related to levels of autofertility and that trait variation was partitioned mainly among populations. Emasculation experiments in the field showed that autonomous selfing confers reproductive assurance by elevating fruit and seed production. Surveys of pollinator communities across the geographic range of the species revealed that bee pollinator abundance and community composition differed dramatically between populations of the outcrossing subspecies xantiana and the selfing subspecies parviflora despite their close proximity. Specialist bee pollinators of Clarkia were absent from selfing populations, but they were the most frequent visitors to outcrossing populations. Moreover, within the outcrossing subspecies xantiana, there was a close correspondence between specialist abundance and population differentiation in herkogamy, a key mating system trait. This spatial covariation arose, in part, because geographically peripheral populations had reduced herkogamy, higher autofertility, and lower pollinator abundance compared to central populations of xantiana. Finally, I detected strong spatial structure to bee communities both across the range of the species and within the outcrossing subspecies. In both cases, spatial structure was stronger for specialist bees compared to generalist bees, and pollinator communities varied in parallel with population variation in herkogamy. These results provide evidence that mating system differentiation parallels spatial variation in pollinator abundance and community composition at both broad and more restricted spatial scales, consistent with the hypothesis that pollinator abundance and reproductive assurance are important drivers of plant mating system evolution.     

Do rewardless orchids show a positive relationship between phenotypic diversity and reproductive success?

Among rewardless orchids, pollinator sampling behavior has been suggested to drive a positive relationship between population phenotypic variability and absolute reproductive success, and hence population fitness. We tested this hypothesis by constructing experimental arrays using the rewardless orchid Dactylorhiza sambucina, which is dimorphic for corolla color. We found no evidence that polymorphic arrays had higher mean reproductive success than monomorphic arrays for pollinia removal, pollen deposition, or fruit set. For pollinia removal, monomorphic yellow arrays had significantly greater reproductive success, and monomorphic red the least. A tendency for yellow arrays to have higher pollen deposition was also found. We argue that differential population fitness was most likely to reflect differential numbers of pollinators attracted to arrays, through preferential long-distance attraction to arrays with yellow inflorescences. Correlative studies of absolute reproductive success in 52 populations of D. sambucina supported our experimental results. To our knowledge this is the first study to suggest that attraction of a greater number of pollinators to rewardless orchids may be of greater functional importance to population fitness, and thus ecology and conservation, than are the behavioral sequences of individual pollinators.     

Collapse of a pollination web in small conservation areas

A suspected global decline in pollinators has heightened interest in their ecological significance. In a worst-case scenario, the decline of generalist pollinators is predicted to trigger cascades of linked declines among the multiple specialist plant species to which they are linked, but this has not been documented. I studied a portion of a pollination web involving a generalist pollinator, the oil-collecting bee Rediviva peringueyi, and a community of oil-secreting plants. Across 27 established conservation areas located in the Cape Floral Region, I found substantial variation in the bees' occurrence in relation to soil type and the successional stage of the vegetation. Anthropogenic declines were detectable against this background of naturally occurring variation: R. peringueyi was absent from small conservation areas (< 385 ha) in an urban matrix. In the absence of the bee, seed set failed in six specialist plant species that are pollinated only by R. peringueyi but remained high in a pollination generalist, which had replacement pollinators. The findings are consistent with theoretical predictions of the importance of generalist pollinators in maintaining the structure of pollination webs.     

Modeling scale up of anthropogenic impacts from individual pollinator behavior to pollination systems

Understanding how anthropogenic disturbances affect plant–pollinator systems has important implications for the conservation of biodiversity and ecosystem functioning. Previous laboratory studies show that pesticides and pathogens, which have been implicated in the rapid global decline of pollinators over recent years, can impair behavioral processes needed for pollinators to adaptively exploit floral resources and effectively transfer pollen among plants. However, the potential for these sublethal stressor effects on pollinator–plant interactions at the individual level to scale up into changes to the dynamics of wild plant and pollinator populations at the system level remains unclear. We developed an empirically parameterized agent-based model of a bumblebee pollination system called SimBee to test for effects of stressor-induced decreases in the memory capacity and information processing speed of individual foragers on bee abundance (scenario 1), plant diversity (scenario 2), and bee–plant system stability (scenario 3) over 20 virtual seasons. Modeling of a simple pollination network of a bumblebee and four co-flowering bee-pollinated plant species indicated that bee decline and plant species extinction events could occur when only 25% of the forager population showed cognitive impairment. Higher percentages of impairment caused 50% bee loss in just five virtual seasons and system-wide extinction events in less than 20 virtual seasons under some conditions. Plant species extinctions occurred regardless of bee population size, indicating that stressor-induced changes to pollinator behavior alone could drive species loss from plant communities. These findings indicate that sublethal stressor effects on pollinator behavioral mechanisms, although seemingly insignificant at the level of individuals, have the cumulative potential in principle to degrade plant–pollinator species interactions at the system level. Our work highlights the importance of an agent-based modeling approach for the identification and mitigation of anthropogenic impacts on plant–pollinator systems.     

Mutualism between a leguminous tree and large African monkeys as pollinators

Observations of a monkey community in a forest of the Zaire Basin show that four species intensively lick the nectar of Daniellia pynaertii (Caesalpinoideae) for 5 months of the year; nectar makes up a mean of 20% and a maximum of 50% of monthly plant feeding records (Fig. 3). Such intensive nectar-feeding by monkeys of up to 8 kg body weight probably developed in these basically frugivorous primates as an alternative strategy to cope with a shortage of fleshy fruits. This would have been possible due to the high density of the plant species, the synchrony and abundance of its flowering (Fig. 2), and the large size of the nectar drop and its nutritional value. Patterns of monkey movements among Daniellia trees show that one flowering tree may receive up to 10 species visits and 30 individual visits per day, for a total of up to 141 min. (Table 1). A monkey troop can visit 12 trees in succession over less than 3 h (Fig. 4). This suggests that monkeys are able to promote pollen transfer both among flowers of the same tree and between conspecific trees. The individual tree fruiting index is positively correlated with its flowering index and with the amount of visits by monkeys, indicating at least that monkeys do not inhibit the reproductive ability of flowers (Fig. 5). These results suggest that monkeys can be considered as a guild of effective pollinators. Long-term coevolution between the plant and its present-day pollinators seems unlikely, and we suggest that monkeys replaced other pollinators, such as Lepidoptera. This hypothesis is supported by the fact that tubular flowers adapted for pollination by Lepidoptera are found in affine species of the same genus and of affine genera, the latter being known to be pollinated by these insects. In contrast, D. pynaertii flowers typically meet the pollination syndrome currently defined for attracting large mammals: notably conspicuousness and open morphology of the flowers, nectar colour and abundance. These characteristics suggest that coadaptation between monkeys and plant or at least one-sided adaptation has operated. Correspondence to: A. Gautier-Hion     

Bee community shifts with landscape context in a tropical countryside.

The ongoing scientific controversy over a putative "global pollination crisis" underscores the lack of understanding of the response of bees (the most important taxon of pollinators) to ongoing global land-use changes. We studied the effects of distance to forest, tree management, and floral resources on bee communities in pastures (the dominant land-use type) in southern Costa Rica. Over two years, we sampled bees and floral resources in 21 pastures at three distance classes from a large (approximately 230-ha) forest patch and of three common types: open pasture; pasture with remnant trees; and pasture with live fences. We found no consistent differences in bee diversity or abundance with respect to pasture management or floral resources. Bee community composition, however, was strikingly different at forest edges as compared to deforested countryside only a few hundred meters from forest. At forest edges, native social stingless bees (Apidae: Meliponini) comprised approximately 50% of the individuals sampled, while the alien honeybee Apis mellifera made up only approximately 5%. Away from forests, meliponines dropped to approximately 20% of sampled bees, whereas Apis increased to approximately 45%. Meliponine bees were also more speciose at forest edge sites than at a distance from forest, their abundance decreased with continuous distance to the nearest forest patch, and their species richness was correlated with the proportion of forest cover surrounding sample sites at scales from 200 to 1200 m. Meliponines and Apis together comprise the eusocial bee fauna of the study area and are unique in quickly recruiting foragers to high-quality resources. The diverse assemblage of native meliponine bees covers a wide range of body sizes and flower foraging behavior not found in Apis, and populations of many bee species (including Apis), are known to fluctuate considerably from year to year. Thus, the forest-related changes in eusocial bee communities we found may have important implications for: (1) sustaining a diverse bee fauna in tropical countryside; (2) ensuring the effective pollination of a diverse native plant community; and (3) the efficiency and stability of agricultural pollination, particularly for short-time-scale, mass-flowering crops such as coffee.     

Orchid bees don't need orchids: evidence from the naturalization of an orchid bee in Florida

Almost 200 species of orchid bees are the exclusive pollinators of nearly 700 specialized orchids in the neotropics. This well-known mutualism involves orchids, called perfume orchids, which produce species-specific blends of floral fragrances, and male orchid bees, which collect and use these fragrance compounds during their courtship. We report here the naturalization of an orchid bee, Euglossa viridissima, in southern Florida, USA, where perfume orchids are absent. Chemical analysis of the contents of the fragrance storage organs in the hind tibias of 59 male bees collected in Florida identified 55 fragrance compounds, including 27 known from the perfumes of nine species of E. viridissima's orchid mutualists in Mesoamerica. Aromatic leaves, such as basil, were found to be important surrogate sources of needed fragrance compounds in Florida. The bee's ability to live and become abundant in the absence of its orchid mutualists suggests that the orchid bee-perfume orchid mutualism may be facultative for the bees, even though it is obligatory for the orchids. This invasive bee visits and potentially pollinates the flowers of many plants in Florida, behavior that could promote the abundance of selected exotic and native species.