Contribution Of Pollinators Research Articles

Status and trends of pollination services in Amazon agroforestry systems

With the growing demand for food production worldwide, natural landscapes are increasingly being replaced by agricultural areas, which directly affects biodiversity and local ecosystem services. Agroforestry systems, which are the intentional integration of trees and shrubs into crop and animal farming systems, are a more sustainable production approach that has been increasing in several forested areas around the globe. Here, we examine the trends of agroforestry in the Brazilian Legal Amazon and estimate the associated value of ecosystem services mediated by pollinators. Using data from 2006 and 2017, we detected an increase in agroforestry activity in the Amazon, both in the number (3.27%) and in the area (23.18%) of establishments. Crop production in forested areas increased by 45.61% in the same period, and the main products cultivated in both years were native products from the Amazon, such as açaí , Brazil nut and babassu. Although the crop data are from forested areas, all the five crops with the highest production value are associated with agroforestry in the Amazon. Pollination services also increased during the same period from US$73.3 to US$156.7 million (113.76%). In 2006, the value of pollination services corresponded to 44% of the total crop production, and it jumped to 64.43% in 2017. Bees and beetles were the two main groups of pollinators quoted for the analysed crops. Our estimates show the important contribution of pollinators to crop production in the Amazon forest. However, a growing loss of Amazon forest has been observed, and this can jeopardize pollinators and have detrimental consequences on food production in the near future. Public policies are urgently needed to encourage crop production in harmony with natural areas, combining the protection of forests and pollinators with food production.

Bees forage on bahiagrass spikelets

Bahiagrass (Paspalum notatum Flüggé; Poaceae) is primarily a pasture grass in the southern US. It is also lawn grass found in residential settings, public parks, and planted in golf courses. Bahiagrass is principally wind-pollinated, but the pollination contribution of insect pollinators is not documented. A survey was conducted on bahiagrass patches in central Georgia, USA, to determine the visitation of foraging pollinators. The results showed that European honey bees, bumblebees, and sweat bees forage on bahiagrass spikelets. Of the total bees observed, 10.6% (n = 94) were foraging on bahiagrass, compared to 46.8% on white clover, 27.7% on dandelion, and 14.8% on buckhorn plantain. This is the first report showing bee foraging on bahiagrass. The results suggest that bahiagrass spikelets may be a supplemental resource for bees and essential for bee conservation programs in rural and suburban areas. More research is warranted to determine how bahiagrass spikelets play a role in meeting the nutritional needs of bees to help sustain their colony and provide pollination service.

Sacred church forests as sources of wild pollinators for the surrounding smallholder agricultural farms in Lake Tana Basin, Ethiopia

Remnant natural forests act as a source of wild pollinators that are potentially relevant for crop pollination for sustaining the food production system of smallholder farms. In the Ethiopian highlands, sacred forests scattered within agricultural landscapes harbour wild pollinators. The contribution of wild pollinators to crop pollination services to surrounding smallholder agricultural farms is largely unknown. In this study, we empirically assessed the effects of Ethiopian church forest habitats on crop flower visitation by pollinators on smallholder farms in Lake Tana basin, Ethiopia. Crop flower visitation rates were recorded in 72 crop fields along distance gradients within a 1500 m buffer zone around 15 church forest patches. We constructed cross-validated generalized additive mixed models (GAMMs) to fit the crop flower visitation rates with fixed effect explanatory variables (distance from forest, forest patch size, forest age, forest functional diversity index, forest proximity index and crop type) that are known to potentially influence pollinator visitation in crop fields. Total flower visitation rates decreased with distance to the forest patches across an agricultural landscape. Visitation rates increased with increasing forest patch size, functional richness, proximity index, and age of church forest patches. Overall, we found that the rate of crop flower visitation varies with pollinator-dependent crop types and wild pollinator groups. An in-depth understanding of the forest biodiversity, cultural value, food security nexus enables the promotion of ongoing church forest stewardship in local and regional policies.

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.

Pollinator-mediated facilitation alleviates pollen limitation in a plant-hummingbird network.

Facilitation and competition among plants sharing pollinators have contrasting consequences for plant fitness. However, it is unclear whether pollinator-mediated facilitation and competition may affect pollen limitation (potential contribution of pollination to fitness) in pollination networks. Here, we investigated how pollinator sharing affects pollen limitation in a tropical hummingbird-pollinated community marked by facilitation. We employed indices describing how much a plant species potentially affects the pollination of other co-flowering species through shared pollinators (acting degree) and is affected by other co-flowering species (target degree) within the plant-hummingbird network. Since facilitation often increases pollination quantity but not necessarily quality, we expected both indices to be associated with reductions in pollen limitation estimates that depend on pollination quantity (fruit set and seed number) rather than estimates more strictly related to quality (seed weight and germination). We found that both indices were associated with reductions in pollen limitation only for seed weight and germination. Thus, facilitation occurred via qualitative estimates of pollen limitation. Our results suggest that facilitation may enhance plant fitness estimates even if quantitative components of plant fecundity are already saturated. Overall, we showed that pollinator-mediated indirect effects in a multispecies context are important drivers of plant fitness estimates with consequences for coexistence in diverse communities.

Contribution of animal pollination to food nutrient production in Benin-West Africa

BackgroundPollinators play a key role in human food production by improving the yield and quality of crops. Several studies assessed the economic value of pollination services delivered by animals through yield improvement. However, little is known about the contribution of animal pollinators to nutrient production. This study assessed the contribution of animal pollination to nutrient production in Benin. Food and Agriculture Organization data on crop production and United States Department of Agriculture crop composition data of 37 leading crops were used. These crops were categorized into five classes, depending on their degree of dependence on animal pollinators for fruit production.ResultsThe study showed that more than half of the studied crops (56.75%) relies at different levels on animal pollination for fruit production. Minerals, namely fluoride (83.92%) and selenium (52.62%), were the most delivered by animal-pollinated crops. Roughly 50% of lipids outputs and 24% of proteins outputs were obtained from pollinator-dependent crops. Significant outputs of fat-soluble vitamins up to 65% were also attributed to animal pollination. A low contribution of animal pollination (up to 8%) was reported for water-soluble vitamins.ConclusionAnimal-pollinated crops significantly contribute to the supply of nutrients and consequently to nutritional and food security in Benin. Conservation of pollinators should be considered as an important component of food security programs in the country.

Importance of Insect Pollinators for Florida Agriculture: A Systematic Review of the Literature

Insect pollinators contribute significantly to global food production impacting both crop yields and quality, but the dependence of specific crops on insect pollinators can vary across production regions and cultivars. The state of Florida has a unique agroecosystem that supports temperate and tropical fruits, vegetables, and nuts, and these specialty crops likely have a high dependence on pollinators. We conducted a systematic review to quantify the role of insect pollinators for Florida agriculture, and to identify crops and cultivars for which recent research on pollination is lacking. For all crops, we determined the average yield losses incurred without insect pollination (“pollinator contribution value”) by synthesizing previously reported values. We found that insect pollinators are required or beneficial for 47 different crops in Florida, or 43% of all plant crop species grown in the state. Major crops in the state with complete to high dependence on insect pollinators include blueberries, mangoes, melons, squashes, and tangelos; for these crops, insect pollinators contribute 75 to 100% of crop productivity. Other major crops in Florida that are moderately to highly dependent on pollinators include avocadoes, cucumbers, field tomatoes, grapefruits, green beans, oranges (select cultivars), peppers, southern peas, and strawberries, with pollinator contributions ranging from 30 to 74%. The contribution of insect pollinators exceeds $50 million per crop per yr in Florida for 7 of its most valuable crops. Using production data at the county level, we found that pollinators contribute to agriculture in almost all Florida counties. Our review identified a number of crops for which little information on pollination requirements exists, especially for modern cultivars. We discuss gaps in our knowledge of crop pollination requirements and recommendations for future research. Estimates of pollinator contributions are invaluable for farm management and policy decisions around pollinator conservation.

Temporal Trends in Pollination Deficits and Its Potential Impacts on Chinese Agriculture.

Worldwide, there is increasing evidence that shows a decline in pollinators, limiting crop pollination and production. However, it is unclear to what extent Chinese agriculture could be impacted by pollinator deficits. Data for 84 major crops in China between 1961 and 2018 were analyzed for the temporal trends in crop area and production, agricultural economic contribution of pollination, crop yield deficits, and honey bee pollination demand. We found a rapid increase in agricultural dependence on insect pollinators: both the cultivated area and total production of pollinator-dependent crops increased faster than those of pollinator-independent crops during 1961-2018. The total economic value of pollination amounted to US$ 106.08 billion in 2010, representing 19.12% of the total production value of Chinese agriculture, approximately twice the 9.5% value estimated for global agriculture. Crops with higher pollinator dependence showed greater mean growth in cultivated area than those with lower dependence, but lower mean growth of crop production and yield. Crop yield growth was also more unstable with increasing pollinator dependence. The minimum pollination demand for honey bee colonies was about three times the stock of honey bee colonies available in 2018. Furthermore, we found a decline in crop yield deficit with the increase in honey bee colony pollination service capacity. We considered that the shortage of pollinators resulted in the yield deficits for pollinator-dependent crops. Future increase in the area of pollinator-dependent crops will increase the need for more pollinators, suggesting the importance of implementing measures to protect pollinators to ensure a better-secured future for agricultural production in China.

No Tradeoff in Fiber Quality with Increased Cotton Yield Due to Outcross Pollination

The societal and economic benefits of ecosystem services are both immense and multi-faceted. To holistically quantify the contribution of pollinators to agriculture requires measuring multiple indices of crop production beyond crop yield. Here, we conduct a field-based hand pollination experiment to measure the effects of self and outcross pollen on fiber yield and quality in conventionally managed cotton crops. First, we determine how different pollination treatments affect specific indices of fiber yield and fiber quality, including fiber length and fineness. Second, we investigate the suggested tradeoff between fiber yield and quality. We find that flowers receiving outcross pollen produce larger, heavier bolls than either self-crossed or non-crossed flowers. However, contrary to expectation, flowers of different treatments are indistinguishable in terms of fiber quality. Overall, we find that pollination treatment has no discernable effect on either fiber length or fiber fineness. Understanding the contribution of ecosystem services across multiple axes provides growers with information concerning potential tradeoffs or synergies, and offers insight into management decisions.

Economics of Pollination

Many food crops rely on pollination by animals. Historically, wind and wild organisms provided pollination as an ecosystem service that varied across agroecological zones, cropping systems, and time. The value of these pollination services is likely substantial but has not been estimated reliably. More recently, pollination services in major crop-producing regions have been provided through organized markets, primarily the rental of honey bees. The sustainability of commercially provided pollination services is being challenged by parasites, diseases, pesticide exposures, poor nutrition, and Colony Collapse Disorder. Economic analyses indicate that honey bee rental markets have been able to adjust to those challenges, at least to date. Understanding the future sustainability of rental markets requires greater knowledge of the contributions of wild pollinators, optimal management of pollination services from wild and managed organisms, and the value of pollination services provided by wild and managed organisms.

Pollination Contribution Differs among Insects Visiting Cardiocrinum cordatum Flowers

(1) Background: Cardiocrinum cordatum (Thunb.) Makino (Liliaceae) is a forest perennial herb distributed in East Asia. Although flower visitors for this plant species have been well reported, their contribution to pollination remains unknown. (2) Methods: We evaluated pollination contribution for visitors of C. cordatum flowers in a natural cool temperate forest. We investigated visiting frequency, the number of pollen grains per body surface, fruit set, and the mean number of seeds per fruit produced after a single visit of each visiting species. Combining the results of these experiments, we determined the most important pollinators of this species. (3) Results: For the population investigated in the study, the three most essential pollinators were the bumblebee (Bombus diversus tersatus) (Apidae), sweat bee (Halictidae sp.), and marmalade hoverfly (Episyrphus balteatus) (Syrphidae). Additionally, we found that the contribution of a flower-visiting ant species (Myrmica ruginodis Nylander (s.l.)) (Formicidae) is small. (4) Conclusions: Pollinator contributions differed among flower visitors. Our results underscore the insufficiency of current information about flower-visiting species to evaluate pollination contribution.

Pollination increases white and narrow-leaved lupin protein yields but not all crop visitors contribute to pollination

Global biodiversity is declining under pressure of agricultural intensification and land-use change. Two-thirds of the agricultural lands is directly or indirectly devoted to the production of animal products. Replacing animal-based proteins by plant-based proteins can be an important step to a more sustainable agricultural system. Lupins (Lupinus sp.) are promising crop species due to a high protein content of up to 40 %, but crop yields are unstable in both quantity and quality. This might be due to a lack of effective pollinators, but the contribution of insect pollination to lupin crop yield is unknown. Here we studied for five varieties of two common lupin crop species (L. albus and L. angustifolius) which pollinators visit lupin flowers, whether this depends on nectar production, and what the contribution of insect pollination is to crop yield. We used a semi-experimental setup and placed bagged and open-pollinated plants in pots along an expected gradient of insect visitors and determined several yield parameters. We recorded 1355 pollinator visits of only eight bee species. None of the varieties tested produced nectar. Compared to bagged plants, protein yield increase of open-pollinated plants ranged from 3 to 11% depending on variety. Yield of open-pollinated plants was only consistently related to visitation of the large-bodied buff-tailed bumblebee (B. terrestris group; 59 % of all pollinators) with impact on seed set related yield parameters (number of seeds and pods) being generally larger than on seed filling related yield parameters (g/plant). Within the observed range, higher visitation rate of buff-tailed bumblebees increased protein yield of open-pollinated plants with 10–40 %. Visitation rates of the smaller common carder bee (B. pascuorum; 33 % of all pollinators), or all pollinators combined, were not significantly related to protein crop yield. This could indicate that only relatively large species are effective lupin pollinators. Lupins are generally considered self-pollinating, and therefore growers do not actively manage for insect pollination. Our results show that insect pollination, and in particular buff-tailed bumblebees, can contribute substantially to the crop yield, which suggests that management aimed at enhancing effective pollinator species can help to make lupin crop cultivation more profitable. Amongst others, such management should make sure that ample nectar is available in the surroundings of lupin crops, as lupin does not produce nectar.

Indirect effect of pesticides utilization towards diversity of pollinator insects in chili plantation

The contribution of insect pollinators to the ecology and production of food crops is threatened by excessive use of pesticides. Pesticides have an impact on reducing the presence of pollinators in agricultural land. The diversity of pollinators depends on food availability and habitat quality. This research emphasizes the diversity of insect pollinators by the application of pesticides in chili plantations in Muaro Jambi, Sumatra. Insect observations were conducted on April-May 2018 using the scan sampling method. Specimen collection is carried out from 08.00-16.00. Data analysis used Shannon-wiener diversity index (H’), Simpson’s index (D), and Pielou evenness index (E). The results of the study were 498 collected individuals consisting of 9 species. Apis melífera, Apis cerana, and Eurema hecabe are the most dominant insect pollinators. Whereas Apis mellifera showed two peaks of flower visitation (an intense first one between 08.00 until 11.00 a.m. and a second less intense one after 14.00 p.m.). Pollinator insect diversity index in the medium category. Our observations also show that the application of pesticides, anthesis and dehiscence to flowers as well as the activity of pollinating insects which together cause low diversity index values.

Pollinator effectiveness in the mixed-pollination system of a Neotropical Proteaceae, <i>Oreocallis grandiflora</i>

In pollination systems with a diverse community of floral visitors, qualitative and quantitative variations in pollination effectiveness can lead to a system in which higher effectiveness results from the synergetic contribution of multiple pollinators. By employing a series of field and laboratory experiments in the south Andes of Ecuador, we compared the effectiveness of hummingbirds and nocturnal mammals visiting Oreocallis grandiflora, an Andean member of the Proteaceae. Pollinator effectiveness was measured with a quantitative component that assessed visitation rates to inflorescences and number of contacted stigmas per visit, and with a qualitative component that counted the number of deposited pollen grains in stigmas. Effectiveness estimates were complemented with controlled pollination experiments that contrasted fruit and viable seed set among flowers exposed to either diurnal or nocturnal pollination, self-pollinated flowers, and a control group with flowers exposed to naturally occurring pollination. Four species of hummingbirds and two species of nocturnal mammals visited the flowers of O. grandiflora. Hummingbirds outperformed nocturnal mammals in the quantitative components of pollination, while mammals were more effective than hummingbirds in the qualitative component. Pollination success was higher for the control group than for the other treatments, while hummingbirds and mammals performed similarly. Our findings suggest a case of functional complementarity in pollination: hummingbirds’ quantitative effectiveness complements nocturnal mammals’ qualitative effectiveness. Furthermore, our study demonstrates that pollination success in plants can be greater when flowers are visited by the whole diversity of pollinators.

Location problem of Osmia cornuta nesting aids for optimum pollination

The economic contribution of insect pollinators is evident as they contribute to higher crop yield quantity and quality. The management of bee species is key to crop production, especially where wild and domesticated bees are in low abundance. Several bee species have been identified as possible candidates for replacing, or at least supplementing, the decreasing number of honey bees. Our research seeks to address the location problem as regards nesting aids for Osmia cornuta bees in orchards using mathematical programming models for determining the optimal location of nesting aids and optimizing the management of solitary bees. A differential evolution algorithm is used to solve a location model of Osmia cornuta nesting aids for optimum pollination. Instead of a random ad hoc location of nesting aids in an orchard, or at the edge of an orchard, we utilize an effective optimization tool to determine locations which will optimize pollination by alternative pollinators, and increase the economic output of an agricultural business. The importance of this proposed model is likely to increase with agricultural intensification, and the decrease of the numbers of wild pollinators.

Economics of Pollination

Many food crops rely on pollination by animals. Historically, wind and wild organisms provided pollination as an ecosystem service that varied across agroceological zones, cropping systems, and time. The value of these pollination services is likely substantial but has not been estimated reliably. More recently, pollination services in major crop producing regions have been provided through organized markets, primarily the rental of honey bees. The sustainability of commercially provided pollination services is being challenged by parasites, diseases, pesticide exposures, poor nutrition, and Colony Collapse Disorder. Economic analyses indicate that honey bee rental markets have been able to adjust to those challenges, at least to date. Understanding future sustainability of rental markets requires greater knowledge of contributions of wild pollinators, of optimal management of pollination services from wild and managed organisms, and of the value of pollination services provided by wild and managed organisms.

Relative importance of diurnal and nocturnal pollinators for reproduction in the early spring flowering shrub Stachyurus praecox (Stachyuraceae)

AbstractGeneralized pollination systems may be favored in early spring flowering plants, as during this period pollinator activity is unpredictable. Many previous studies have concentrated on the importance of diurnal visitors in pollination, and consequently, information on the contribution of nocturnal visitors to pollination in early spring is limited. This study was conducted to evaluate the relative importance of diurnal and nocturnal pollinators in the early spring flowering dioecious shrub Stachyurus praecox (Stachyuraceae), in two temperate forests in central Japan. Visitors to the female and male flowers were observed during day and night, and their relative contributions to seed set were compared. The pollinator observations revealed that the diurnal and nocturnal insects visited both male and female flowers, and that the main flower visitors were diurnal small bees and flies as well as nocturnal settling moths. The diurnal and nocturnal flower visitors also acted as pollinators, as the pollen grains of S. praecox were attached to the insects collected from the female flowers. Pollination experiments demonstrated that the contributions of diurnal pollinators to the seed set were higher than those of the nocturnal pollinators. The results of this study indicate that S. praecox has a generalized pollination system, comprising both diurnal insects and nocturnal settling moths. Although the roles of diurnal insects are more important in the pollination of S. praecox, nocturnal settling moths may have a complementary role in early spring.

Insect pollination is important in a smallholder bean farming system

BackgroundMany crops are dependent on pollination by insects. Habitat management in agricultural landscapes can support pollinator services and even augment crop production. Common bean (Phaseolus vulgaris L.) is an important legume for the livelihoods of smallholder farmers in many low-income countries, particularly so in East Africa. While this crop is autogamous, it is frequently visited by pollinating insects that could improve yields. However, the value of pollination services to common beans (Kariasii) yield is not known.MethodsWe carried out pollinator-exclusion experiments to determine the contribution of insect pollinators to bean yields. We also carried out a fluorescent-dye experiment to evaluate the role of field margins as refuge for flower-visitors.ResultsSignificantly higher yields, based on pods per plant and seeds per pod, were recorded from open-pollinated and hand-pollinated flowers compared to plants from which pollinators had been excluded indicating that flower visitors contribute significantly to bean yields. Similarly, open and hand-pollinated plants recorded the highest mean seed weight. Extrapolation of yield data to field scale indicated a potential increase per hectare from 681 kg in self-pollinated beans to 1,478 kg in open-pollinated beans indicating that flower visitors contributed significantly to crop yield of beans. Our marking study indicated that flower-visiting insects including bees, flies and lepidopterans moved from the field margin flowers into the bean crop. Overall, these results show that insect pollinators are important for optimising bean yields and an important food security consideration on smallholder farms. Field margin vegetation also provides habitat for flower-visiting insects that pollinate beans. Hence, non-crop habitats merit further research focusing on establishing which field margin species are most important and their capacity to support other ecosystem services such as natural pest regulation or even pests.

Forest fragments influence pollination and yield of soybean crops in Chaco landscapes

Habitat remnants act as a source of pollinators potentially relevant for crop pollination and yield. This work analyzes how habitat loss influences pollinators, effective pollination and yield of soybean crops. The study area comprises ten sites adjacent to forest patches surrounded by a soybean matrix in central Argentina (eight sites in the season 2014–2015 and two sites in the season 2015–2016). Pollination was estimated by pollen deposition and frequency of flower visitors. Pollen deposition on stigmas and seed set were measured comparing open plants and plants with pollinator exclusion. These response variables were compared considering increasing distance to the forest edge and an increasing gradient of forest patch size. Bees were the most frequent visitors of soybean flowers, especially honeybees, but also at least three native bee species were recorded. Open plants showed higher rates of stigmatic pollen deposition than plants with pollinator exclusion, but seed set was similar. Total insect visitation rates, especially of native insects, decreased with distance to the forest edge and so did pollen deposition. Pollen deposition and seed set increased with increasing forest patch size for plants located near and far from the forest edge, respectively. Overall, our results suggest that the contribution of native pollinators from local forest patches is important for effective pollination across the landscape. Small patches of forest (approximately 1 ha.) guarantee pollinators to ensure plant yields similar to the yields of plants growing close to large patches, but only at short distances; while larger forest patches provide better pollination services for the crop at larger distances from the forest edge. However, we encourage further studies because results suggest that other factors may also influence soybean pollination and production.

Breeding systems of floral colour forms in the Drosera cistiflora species complex.

Variation in plant breeding systems has implications for pollinator-mediated selection on floral traits and the ecology of populations. Here we evaluate pollinator contribution to seed production, self-compatibility and pollen limitation in different floral colour forms of Drosera cistiflora sensu lato (Droseraceae). These insectivorous perennial plants are endemic to fynbos and renosterveld vegetation in the Cape Floristic Region of South Africa, and the species complex includes five floral colour forms (pink, purple, red, white and yellow), some of which are known to be pollinated by beetles. Controlled hand-pollination experiments were conducted in 15 populations of D. cistiflora s.l. (two to four populations per floral colour form) to test whether the colour forms vary in their degree of self-compatibility and their ability to produce seeds through autonomous self-fertilization. Yellow-flowered forms were highly self-incompatible, while other floral colour forms exhibited partial self-compatibility. Seed set resulting from autonomous selfing was very low, and pollinator dependence indices were high in all populations. Since hand cross-pollination resulted in greater seed set than open pollination in 13 of the 15 populations, we inferred that seed production is generally pollen-limited. Drosera cistiflora s.l. typically exhibits high levels of pollinator dependence and pollen limitation. This is unusual among Drosera species worldwide and suggests that pollinators are likely to mediate strong selection on attractive traits such as floral colour and size in D. cistiflora s.l. These results also suggest that the floral colour forms of D. cistiflora s.l. which are rare and threatened are likely to be vulnerable to local extinction if mutualisms were to collapse indefinitely.