Pollinator Visitation Frequency Research Articles

Effects of ecological factors on the pollination biology and seed production of Salvia daiguii: A critically endangered ornamental species from China

Salvia constitutes one of the largest genera in the Lamiaceae, with approximately 1,000 species found worldwide, and is recognized for its high ornamental and medicinal value. Salvia daiguii is a multipurpose perennial herb that grows on cliffs in the Zhangjiajie City, Hunan Province, China. Nevertheless, the pollination biology of vulnerable plants on cliffs, specifically the effects of abiotic factors on flower visitation and seed set, remains poorly understood. In this study, we observed the effects of biotic factors: flowering phenology and flower characteristics, flower longevity, nectar volume and concentration, pollen viability and stigma receptivity, pollinator visitation frequency, pollen remaining and deposition, and breeding systems, as well as abiotic factors: habitat fountain, temperature, and humidity, on the pollination and seed production of S. daiguii in two populations in Zhangjiajie City. The pollination biology results reveal that S. daiguii has a mixed mating system that depends on pollinators. The flower visitation and seed set of S. daiguii in the absence of natural fountain areas in Tianmenshan National Forest Park was scarcely affected by biotic factors. However, we observed a significant reduction in pollinator types, visitation frequency, and natural seed set of this population owing to abiotic factors, including the presence of a fountain habitat and increased humidity. Further, seed set in the Zhangjiaxi Ecological Forest Reserve was affected by both biotic (serious pollen limitation) and abiotic (higher population temperature) factors. We considered that pollinators types, flower visitation frequency, and natural seed set are vulnerable to the influence of ecological factors in fragmented habitats. Our results reveal the mechanisms contributing to the endangerment of species exemplified by S. daiguii and underscore the significance of conservation efforts for the sustainable use of other endangered species.

High toxin concentration in pollen may deter collection by bees in butterfly-pollinated Rhododendron molle.

The hypothesis that plants evolve features that protect accessible pollen from consumption by flower visitors remains poorly understood. To explore potential chemical defenses against pollen consumption, we examined the pollinator assemblage, foraging behaviour, visitation frequency and pollen transfer efficiency in Rhododendron molle, a highly toxic shrub containing Rhodojaponin III. Nutrient (protein and lipid) and toxic components in pollen and other tissues were measured. Overall in the five populations, floral visits by butterflies and bumblebees were relatively more frequent than visits by honeybees. All foraged for nectar but not pollen. Butterflies did not differ from bumblebees in the amount of pollen removed per visit, but deposited more pollen per visit. Pollination experiments indicated that R. molle was self-compatible, but both fruit and seed production were pollen limited. Our analysis indicated that the pollen was not protein-poor and had a higher concentration of the toxic compound Rhodojaponin III than petals and leaves, which compound was undetectable in nectar. Pollen toxicity in Rhododendron flowers may discourage pollen robbers (bees) from taking the freely accessible pollen grains, while the toxin-free nectar rewards effective pollinators, promoting pollen transfer. This preliminary study supports the hypothesis that chemical defense in pollen would be likely to evolve in species without physical protection from pollinivores.

Pollinator-mediated connectivity in fragmented urban green spaces—tracking pollen grain movements in the city center

Cities are expanding rapidly and emerging as complex ecosystems. This expansion of urbanized areas has resulted in the alteration and fragmentation of several natural habitats. Recent studies have shown that cities support a significant level of biodiversity. This unexpected role of cities holds promise for advancing knowledge of urban ecosystems and promoting their conservation. In particular, the connectivity of plant populations through pollen transfer is crucial for the long-term persistence of insect-pollinated plant species. In this study, we tracked pollen movement areas in four isolated patches of urban greenery in urbanized area using quantum dots. We studied Fritillaria imperialis (spring) and Hemerocallis sp. (mid-summer). Our research revealed frequent pollen transfer between small, isolated flowering patches, even when these locations were not connected by green corridors. Common elements found in urban ecosystems, such as streets, trails, and pavements, do not stop the dispersion of pollen grains. Moreover, the migration pathways of pollen grains vary for each species according to different factors. For F. imperialis, we identified the proportion of green areas in proximity to the study location as a key factor in shaping pollen transfer. For Hemerocallis, we discovered that the proportion of green areas, the distance between study sites, and the frequency of pollinator visits are influential factors. Our study demonstrates that small isolated plant populations exchange pollen due to pollinator movement, indicating that these small populations may serve as stepping stones for pollinators among larger populations.

Effect of climate, anther morphology and pollination syndrome on pollen availability in Penstemon

Traditionally, pollen presentation is thought to be a function of pollinator type and visitation frequency. However, despite the repeated observation that pollen presentation is influenced by flower morphology and abiotic factors, these aspects have been little studied in the wild. Here, we evaluated the effect of climate, anther morphology, and pollination syndrome on anther dehiscence time (the length of time an anther takes to fully dehisce after a flower opens). We recorded anther dehiscence time in twelve species of Penstemon including the four major anther types and the two most common pollination syndromes. We also conducted an experiment to measure the effect of humidity and temperature on anther dehiscence. We found that anther morphology was correlated with anther dehiscence time. Anthers with wide openings take the longest time to dehiscence. These results provide some support for the hypothesis that anther dehiscence time has evolved to decrease pollen wastage. Contrary to the assumption that bird-pollinated species have simultaneous pollen presentation, hummingbird-pollinated species had longer anther dehiscence time than most bee-pollinated species. The experiment revealed that high humidity and low temperature increase anther dehiscence time. Our results suggest that pollen presentation is influenced by anther morphology, pollination syndrome, and the physical environment. Optimal pollen presentation presumably maximizes conspecific pollen transfer and reduces pollen thieving.

Reproductive biology and pollination ecology of Ipomoea triloba L. (Convolvulaceae): An alien invasive species of the Indo‐Burma biodiversity hotspot

AbstractIpomoea triloba L., an annual twining herb, is considered an alien invasive species and is distributed all around the globe including tropical Asia. It affects the yield of various economically important crops. Studies on floral phenology and reproductive biology are fundamental for the development of management strategies and the conservation of plants. Hence, we investigated the phenology, floral biology, pollen viability, stigma receptivity, pollination mechanism, and reproductive success of I. triloba at two different locations in one of the global biodiversity hotspots. Floral anthesis was diurnal, starting at 6:30 a.m. and lasting until 7:00 a.m. Pollen viability and stigma receptivity were found to coincide, thus suggesting the species was homogamous. The flowers were mostly visited and pollinated by sweat bees (Halictidae), blue‐banded bees (Amegilla sp.), flies (Mesembrius sp.), and butterflies (Appias olferna, Pelopidas agna, and Zizina otis). Further, the pollinator visitation frequency showed a moderately positive correlation with the number of open flowers in both study populations. The plant produced fruits in the absence of pollinators in self‐pollination treatments, indicating a self‐compatible breeding system and dependency on insect pollination for reproductive success. Further, pollen supplementation significantly enhanced the fruit setting and mean seed per fruit at both study sites, suggesting pollen limitation. Additionally, pollen production and pollen/ovule ratio also indicated the facultative autogamous breeding system in I. triloba. Overall, these reproductive characteristics such as mixed mating systems and generalist insect visitation may allow the invasive I. triloba to establish new populations from low numbers of propagules.

Floral Aroma and Pollinator Relationships in Two Sympatric Late-Summer-Flowering Mediterranean Asparagus Species.

This research delves into plant-pollinator relationships within the Mediterranean region, focusing on two synchronous and sympatric asparagus species: A. acutifolius and A. albus. For the first time, the floral scents of the genus Asparagus are reported. We investigate the volatile organic compounds (VOCs) present in their floral scents and their impact on pollinator attraction. Captured flower-emitted VOCs underwent solid-phase microextraction of headspace (SPME-HS) and gas chromatography and mass spectrometry (GC-MS) analysis. The investigation confirms distinctive aroma profiles for each species. A. albus predominantly emits benzene derivatives and sesquiterpenes, while A. acutifolius is characterized by carotenoid derivatives, monoterpenes, and sesquiterpenes. The only shared compounds between the two species are the sesquiterpenes (Z,E)-α-farnesene and (E,E)-α-farnesene. A positive correlation links peak floral aroma intensity (benzenoids in A. albus and ionones in A. acutifolius) with a higher pollinator visit frequency, emphasizing the critical role of intense floral scents in pollinator attraction. The study of reproductive aspects reveals almost complete gynodioecy in A. acutifolius, influencing unique dynamics for the two species. These adaptations hold significant importance within the Mediterranean ecosystem, particularly during the late dry summer period, when a limited number of plant species vie for a shared primary pollinator.

Plants at population edges enjoy longer mating distances: Implications for conservation practice

Habitat fragmentation and population declines have led to increased population edges, exposing higher proportions of plants to ecotones. However, it remains a challenging question how edge plants perform compared with interior ones, as they usually experience dissimilar abiotic and biotic interactions. To address this question, we performed experiments on a monoecious herb (Sagittaria trifolia) focusing on the reproductive fitness and mating patterns of individuals at the edge of two common gardens established under varied light conditions (open vs. understory) with natural pollination. Plant female fitness was determined by seed production, whereas male fitness and mating patterns were resolved by paternity analysis employing eight microsatellite markers. Results showed that edge plants had lower pollinator visitation frequency than interior ones in both gardens. However, there was no significant reduction in female or male reproductive success of edge plants. Instead, edge plants enjoyed longer distances of effective pollen dispersal when reproduced as males, as well as longer distances of sires when reproduced as females. This pattern was consistent across habitats and years. Together, the results indicate that edge plants not only maintained a comparable level of reproduction as interior ones but also enjoyed greater mating distances, which would likely bring about higher genetic diversity in their offspring. This further implies that edge effects may play an important role in promoting gene exchange and encouraging population recovery.

Effect of grazing disturbance on floral display, pollen limitation and plant pollination efficiency in the desert steppe

BackgroundGrazing disturbance usually affects floral display and pollination efficiency in the desert steppe, which may cause pollen limitation in insect-pollinated plants. Effective pollination is essential for the reproductive success of insect-pollinated plants and insufficient pollen transfer may result in pollen limitation. Caragana microphylla Lam is an arid region shrub with ecological importance. Few studies have been conducted on how grazing disturbance influences pollen limitation and pollination efficiency of C. microphylla. Here, we quantify the effect of different grazing intensities on floral display, pollinator visitation frequency and seed production in the Urat desert steppe.ResultsIn C. microphylla, supplemental hand pollination increased the seed set, and pollen limitation was the predominant limiting factor. As the heavy grazing significantly reduced the seed set in plants that underwent open-pollination, but there was no significant difference in the seed set between plants in the control plots and plants in the moderate grazing plots. Furthermore, there was a higher pollinator visitation frequency in plants in the control plots than in plants in the heavy grazing plots.ConclusionsWe found that pollinator visitation frequency was significantly associated with the number of open flowers. Our findings also demonstrated that seed production is associated with pollinator visitation frequency, as indicated by increased seed production in flowers with higher pollinator visitation frequency. Therefore, this study provides insight into the effect of different grazing intensities on floral display that are important for influencing pollinator visitation frequency and pollination efficiency in desert steppes.

Pollinator efficiency of avocado (Persea americana) flower insect visitors

Abstract Pollination services from insects are important for higher yield and better fruit quality in avocado (Persea americana Mill.). Measuring pollinator effectiveness is significant for capturing the relative contributions of different insect taxa to pollination services and for identification of the most important pollinators of this globally important crop. In the present study, we tested pollinator efficiency of avocado in Kenya based on pollen deposition after single visits of flowers by different pollinator species and visitation frequency. We monitored the pollination frequency during the flowering period replicated across six farms. Three trees were selected per farm, each with five flower panicles. Out of the 14 observed insect flower visitor species, pollen deposition efficiency was highest in the Western honey bee (Apis mellifera L.), followed by the hover fly species (Phytomia incisa W.). These two species had both the highest pollen deposition and pollen grain loads on their bodies. Furthermore, A. mellifera was the most frequent avocado flower visitor followed by Diptera except hoverflies. Our results imply that A. mellifera can be managed to achieve adequate pollination services for avocado, particularly in areas lacking efficient wild pollinators.

The effects of inbreeding depression and pollinator visitation on the maintenance of herkogamy in Oxalis corniculata, a species derived from a heterostylous ancestor

AbstractThe evolutionary transition from outcrossing in heterostylous morphs to selfing in homostylous morphs has occurred in many plant lineages. Homostylous variants with a low degree of herkogamy may increase the reproductive advantage of autonomous self‐pollination when there is little inbreeding depression and/or low pollinator visitation. Oxalis corniculata, a self‐compatible perennial herb derived from a tristylous ancestor, is reported to have two floral morphs. Homostyled plants are broadly distributed in Japan, whereas long‐styled plants are reported to occur only in coastal areas. We examined the hypothesis that a reproductive advantage in avoiding inbreeding depression and/or frequent pollinator visits enables long‐styled plants to live in some areas. Studies on floral variation revealed that the degree of herkogamy varied widely and continuously within and among populations. Homostyled and long‐styled morphs were functionally defined based on the ability of autonomous self‐pollination. Homostyled plants were widely distributed, whereas long‐styled plants were found in and around the two coastal populations and relatively inland populations. Pollination experiments provided no evidence of inbreeding depression in either homostyled or long‐styled plants. Pollinator visitation frequency was higher in the two coastal populations than in the other populations. Thus, reproductive disadvantage in long‐styled plants lacking autonomous self‐pollination has reduced in the two coastal populations, and long‐styled plants may be maintained due to a competitive advantage of large seed size. In contrast, we recorded no comparable frequencies of pollinator visitation in other populations containing long‐styled plants, indicating that there are other factors contributing to the maintenance of long‐styled plants in these areas.

Defensive mutualists affect outcross pollen transfer and male fitness in their host plant

Ant guards can increase plant fitness by deterring herbivores, but they may also reduce it by interfering with pollination. While ant impacts on herbivory have been well‐studied, much less is known about their impacts on pollinators and associated consequences for plant pollination, particularly pollen transfer dynamics and outcrossing/selfing rates. We used field experiments to quantify the effect of ant guards on pollinator community composition, frequency and duration of flower visits, and cascading effects on outcrossing pollen transfer and pollen exports in Turnera velutina (Passifloraceae). Although ant patrolling did not affect pollinator community composition or visitation frequency, it decreased flower visit duration and the time pollinators spent foraging inside flowers. Such behavioural changes resulted in reduced pollen deposition on stigmas, decreased pollen exports (a proxy for male fitness) and significantly doubled outcross pollen transfer. This study contributes to our understanding of how non‐pollinator mutualists can shape plant reproductive processes. We discuss the downstream effects that variation in biotic defences, such as rewards for guarding ants, can have on plant pollen transfer patterns and fitness.In conclusion, guarding ants influence pollen transfer patterns in Turnera velutina, increasing outcrossing in a self‐compatible species at the cost of male fitness. We show how non‐pollinators, such as defensive ant mutualists, can shape plant reproductive traits and discuss the consequences these interactions may have for plant mating systems.

Visual function of red staminal filaments in a bee-pollinated plant

ABSTRACT Background Floral colour is a primary signal in plant-pollinator interactions. Presumably because bees lack red receptors, bee-pollinated flowers are rarely red. Hypericum (Hypericaceae) is a genus, with yellow flowers and filaments, mainly pollinated by bees. However, one species, H. ascyron exhibits unique red filaments. Aims We tested whether the red filaments influence pollinator visitation frequency and colour perception. Methods We examined whether H. ascyron require pollinators for seed set and compared insect visitation rates of H. ascyron with those of a sympatric yellow-filamented congener. Colour perception by bees was also estimated. Results Pollinator visitation substantially enhanced seed set under natural conditions and flowers of H. ascyron had similar rates of visitation by bees as their yellow-filamented congener. Red filaments per se absorbed ultraviolet light and therefore should not be perceived as a chromatic colour by bees. The chromatic contrasts between filaments and petals as perceived by pollinators was similar between species, whereas achromatic contrasts were higher in H. ascyron. Conclusions Pure-red staminal filaments work as well in attracting potential pollinators as the yellow filaments of congeners. Based on our findings, we suggest that the evolution of red filament colour may have been driven by factors other than pollinator attraction.

Floral Patches and Their Impact on Pollinator Attraction and Yield Production on Cucurbita maxima Var. Paine in Central Chile

In recent decades, it has been shown that pollination deficit can significantly affect crop production. Moreover, now it is known that the appropriate management of pollination can increase the quantity and quality of yields. Therefore, pollination appears to be a key component in modern agriculture. This study aimed to determine the impact of floral patch addition on the quality and quantity of Cucurbita maxima fruit production. To this end, we manually added a set of ornamental plant species to the edge of the crop and monitored the pollinator diversity and visit frequency, as well as the seed set and sugar content of the pumpkin yield, in treatment and control parcels. The results showed that there was a higher visit rate in the treated parcel. Only the sugar content, and not the seed set, was affected by the addition of ornamental species and the pollinator visit rate. These findings indicate that the addition of flowering plants can favor different components of the crop yield of this species, but future studies should sample on a broader spatial and temporal scale in order to certify the generalizability of our results.

Comparative effects of pollen limitation, floral traits and pollinators on reproductive success of Hedysarum scoparium Fisch. et Mey. in different habitats

BackgroundReproduction in most flowering plants may be limited because of the decreased visitation or activity of pollinators in fragmented habitats. Hedysarum scoparium Fisch. et Mey. is an arid region shrub with ecological importance. We explored the pollen limitation and seed set of Hedysarum scoparium in fragmented and restored environments, and examined whether pollen limitation is a significant limiting factor for seed set. We also compared floral traits and pollinator visitation between both habitats, and we determined the difference of floral traits and pollinators influenced reproductive success in Hedysarum scoparium.ResultsOur results indicated that supplementation with pollen significantly increased seed set per flower, which is pollen-limited in this species. Furthermore, there was greater seed set of the hand cross-pollination group in the restored habitat compared to the fragmented environment. More visits by Apis mellifera were recorded in the restored habitats, which may explain the difference in seed production between the fragmented and restored habitats.ConclusionsIn this study, a positive association between pollinator visitation frequency and open flower number was observed. The findings of this study are important for experimentally quantifying the effects of floral traits and pollinators on plant reproductive success in different habitats.

Diversity of pollinators in marigold (Tagetes erecta L.) in a core area of Kathmandu Valley, Nepal

Insect pollinators provide crucial ecosystem services in the urban environment but are under threat and lack comprehensive study and Pollinators’ interaction to change urban land use. Marigold is an important nectar provider for many insects, plays a major role in ecosystem services, and holds a strong cultural and economic value. Therefore, it is important to learn the diversity of insect pollinators in marigolds in an urban environment and assess the impact of urbanization on pollinators. This study aimed to study pollinator diversity, visit frequency, and shift-wise distribution in the core urban area of Kathmandu valley. A total of 21 species of pollinators were recorded from fourteen families and four orders: Hymenoptera, Diptera, Lepidoptera and Coleoptera. Lepidoptera accounted for the highest diversity index of 1.87 followed by Diptera. Furthermore, the study recorded the highest species diversity and abundance during the daytime compared to the morning and the evening hour. The highest diversity of Diptera and Lepidoptera suggests that the urban area is a suitable foraging area whereas, the absence of wild bees further suggests the urbanization as a threat to the wild bee population and demand urgent policy or action for the conservation of pollinators for the conservation of biodiversity and growth in agricultural production.

Pollinator Visitation Frequency Associated with Native and Non-native Plants in a Mid-Atlantic Piedmont (USA) Urban Garden

Pollinator Visitation Frequency Associated with Native and Non-native Plants in a Mid-Atlantic Piedmont (USA) Urban Garden

Impact of floral characters, pollen limitation, and pollinator visitation on pollination success in different populations of Caragana korshinskii Kom

Caragana korshinskii Kom. has a significant function in desert-grassland revegetation in arid regions. Plant reproduction in arid regions can be restricted due to inadequate pollen receipt and reduced pollen transfer. An assessment of pollination success as a result of pollen limitation and pollinator visitation in various C. korshinskii populations is presently lacking. We thus tested three different treatments (pollen addition, control, and procedural control) to elucidate how pollen limitation affects seed numbers per flower in C. korshinskii. We also determined the effect of pollinator visit frequency on seeds per flower. Our results demonstrated that there was a higher proportion of open flowers and mature fruits in the managed population than in the natural population. Pollen addition significantly increased seed number per flower, and pollen limitation was determined to be a significant limiting factor in seed production. Furthermore, Apis mellifera was determined to be the principal pollinator, and pollinator visitation frequency was significantly correlated with open flower number. Our findings also demonstrated that pollinator visitation rate and seed production were positively correlated. Management and pollinator visitation could affect seed production, which may explain the higher seeds per flower in the managed population compared with the natural population.

Ecological role of a flower-dwelling predator in a tri-trophic interaction in northwestern Patagonia

Flower-dwelling predators may play several ecological roles depending on their effects on the reproductive success of the plants that they use to forage. However, tri-trophic interactions often are context-dependent highlighting the importance of assessing both the overall top-down effect on plant fitness and predator behavioral and physiological attributes that shape that outcome. We studied the effect of the flower-dwelling crab spider Misumenops pallidus on the perennial herb Anemone multifida in a low-thicket in Northwestern Patagonia. We measured pollinator visitation frequency, florivory rate, plant fitness, spider abundance, and spider's physiological (e.g. camouflage) and behavioral attributes (e.g. host selection, fidelity) that aid to define its possible ecological role. Misumenops pallidus showed a generalist diet (mostly pollinators), camouflage strategies, and intraspecific selection for plants bearing higher number and longer trichomes. Additionally, it displayed host-fidelity with long periods of permanence in the selected host plant, occupying ∼25% of plant population. However, the presence of these spiders did not affect pollinator visitation rate, florivory or plant fitness, indicating a commensalism role. Our findings suggested that the asymmetric benefit in this plant-spider association may be attributed to a combination of factors. In particular, the low-to-moderate spider abundance, generalist diet and cryptic camouflage; all of which weaken the top-down effect on pollinators and plant fitness, especially whenever ecological redundant pollinators are present. However, temporal and/or spatial variation on spider population might enhance this asymmetric benefit for the spider, potentially changing its role from commensalism to antagonism.

Temperature-driven changes of pollinator assemblage and activity of Megaleranthis saniculifolia (Ranunculaceae) at high altitudes on Mt. Sobaeksan, South Korea

BackgroundTemperature-driven variation in pollinator assemblage and activity are important information, especially at high altitudes, where rising temperature trends exceed global levels. Temporal patterns of pollinators in a flowering season can be used as a proxy to predict the changes of high-altitude plants’ mutualistic relationships. We observed a spring temperature change in one population of a high-altitude endemic species, Megaleranthis saniculifolia on Mt. Sobaeksan, and related it to pollinator assemblage and activity changes.MethodsThis study was conducted at two sites, each facing different slopes (NE and NW), for two times in the spring of 2013 (early-flowering, April 27–28, vs. mid-flowering, May 7–8, 2013). We confirmed that the two sites were comparable in snowmelt regime, composition of flowering plants, and flower density, which could affect pollinator assemblage and activity. Pollinator assemblage and activity were investigated at three quadrats (1 m2 with 5-m distance) for each site, covering a total of 840 min observation for each site. We analyzed correlations between the temperature and visitation frequency.ResultsTwelve pollinator species belonging to four orders were observed for M. saniculifolia at both sites during early- and mid-flowering times. Diptera (five species) and hymenopteran species (four species) were the most abundant pollinators. Pollinator richness increased at both sites toward the mid-flowering time [early vs. mid = 7 (NE) and 3 (NW) vs. 9 (NE) and 5 (NW)]. Compared to the early-flowering time, visitation frequency showed a fourfold increase in the mid-flowering time. With the progression of spring, major pollinators changed from flies to bees. Upon using data pooled over both sites and flowering times, hourly visitation frequency was strongly positively correlated with hourly mean air temperature.ConclusionsThe spring temperature change over a relatively brief flowering period of M. saniculifolia at high altitudes can alter pollinator assemblages through pollinator dominance and visitation frequency changes. Thus, this study emphasizes information on intra- and inter-annual variations in the mutualistic relationship between pollinators and M. saniculifolia to further assess the warming impacts on M. saniculifolia’s reproductive fitness.

Comparative pollen limitation and pollinator activity of Caragana korshinskii Kom in natural and fragmented habitats

In many flowering plants, fragmented habitats may affect pollen limitation, pollinator behavior, and plant-pollinator interactions. Pollen limitation may decrease plant reproduction due to low levels of pollen transfer and inadequate pollen receipt. However, how fragmented habitats affect the pollen limitation and pollinator activity of Caragana korshinskii Kom. still needs further study. We designed a pollen supplementation treatment to understand how pollen limitation affects seed set. We calculated the visiting patterns and frequency of pollinators in different habitat types (natural and fragmented) to determine the effect of fragmented habitats on pollinator activity and on the pollination success of a desert-grassland shrub. Our results demonstrated that pollen supplementation was found to significantly increase seed set per flower, which is pollen-limited in the studied species. Moreover, the pollen limitation index in fragmented habitats was increased compared to that of natural habitats. Apis mellifera was found to be the dominant pollinator, with more pollinators and a higher visitation frequency of A. mellifera found in natural habitats compared to fragmented habitats. Our results showed that pollen limitation intensity was significantly correlated with the pollinator visitation frequency in the both habitats. Outcrossing was dominant in the breeding system, and insect pollination played a critical role in outcrossing. We found that fragmented habitats could affect pollinator activity, which might reduce pollen dispersal among flowers and the probability of outcrossing in the studied habitats.