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The floral and pollination biology of jujubes (Ziziphus mauritiana) and longans (Dimocarpus longan) were studied near Hanoi, Vietnam. Jujube is a protandrous species with three phases of flowering. After a brief asexual phase, anthers dehisce and release pollen in the afternoon of the day of anthesis. Stigmas become most receptive the following day when flowers are actively secreting nectar. Both jujube and longan flowers are visited during the day by insects of many families, particularly honeybees and flies (syrphids, calliphorids, and muscids). Honeybees, Apis cerana, made up 84% of floral visitors to jujube flowers and 47 – 95% to longan inflorescences. Bagging experiments revealed that diurnal insect visitors are very important in fruit production of both jujubes and longans. In jujubes, no fruits were set during the first pollination trial early in the flowering period. Fruit set increased to 0.17% midway through flowering and 2.21% for the trial conducted late in the flowering period. Fruit set recorded one week after anthesis suggested that all types of pollination may result in fruits, but 7 weeks after anthesis only open pollination (unbagged flowers) and diurnal pollination treatments yielded fruits. Most fruits (~97%) were estimated to result from honeybee visits to flowers. Longans are also predominantly pollinated by diurnal insects (~84%), but with minor contributions from wind pollination (8.4%) and self-pollination (7.7%). A. cerana was estimated to contribute 67% of longan pollination. Pollination requirements for 39 Vietnamese crops were reviewed. Most benefit from insect pollination. For 8 crops important in Vietnamese agriculture for which there were sufficient data, crop yields and values were estimated. Honeybee pollination resulted in ~50% of yields of these 8 crops, contributing ~900 millionion USD of their total values. This analysis indicates that the pollination service provided by honeybees is enormous. / Association of Universities and Colleges of Canada (AUCC) and Canadian International Development Agency (CIDA): Tier 2 CIDA-UPCD Project.

In this thesis I investigated the importance of plant-animal mutualisms to the reproductive success of three West African mistletoe species in two genera, Globimetula braunii, Agelanthus brunneus and A. djurensis, in Ngel Nyaki Forest Reserve, Nigeria. The flowers of all three mistletoes were visited by 3 - 4 species of sunbird. Agelanthus flowers were also visited by honeybees (Apis mellifera) and a small social wasp species (Vespinae). A. mellifera appeared to be robbing nectar from the flowers of A. brunneus. To investigate the relative role of pollinators, I compared flower opening and fruit set amongst bagged, caged, natural, hand-selfed and hand-crossed treatments. The flowers of G. braunii were able to selfopen on average 66% of the time when pollinators were excluded, whereas pollinators were essential to the flower opening mechanism of both Agelanthus spp. Insects were as effective at opening the flowers of Agelanthus spp. as sunbirds. However, flower opening ability did not translate directly into pollination effectiveness, as insect access alone did not result in significantly higher fruit set than that observed under the bagged condition. There was no significant evidence for autonomous selfing within any of the three mistletoes and thus reproduction was almost entirely reliant on 3 – 4 species of sunbird. Hand-pollinations of all three species indicated a high level of self-compatibility, and in one species, G. braunii, pollen limitation was evident (PLI = 0.504). To investigate dispersal mutualisms amongst the three mistletoe species, fruit ripening and removal were monitored. The fruits of all three mistletoe species appeared to be removed rapidly from plants as they ripened, with few ripe or overripe fruits present on the branches at any time. Dispersal efficiency, or the total proportion of fruit crop removed across the fruiting season, was also very high (>90%) for the Agelanthus spp. but lower in G. braunii, for which almost a third of the total fruit crop was recorded undispersed in fruit nets beneath plants. Mistletoes are an important component of West African montane forests. Disruption to mistletoe reproductive mutualisms may affect not only mistletoes and their mutualists directly, but also an entire network of species, all linked within a web of interactions. To protect these ecosystems from further degradation, increased community involvement and greater enforcement of laws set out to manage montane forest habitat across the region is essential. Without this support, the future of these ecosystems and the web of interacting species within remains tenuous.

Thesis (Ph. D.)--University of Adelaide, Dept. of Horticulture, Viticulture and Oenology, 1995? / Includes bibliographical references (leaves 186-209).

The Neotropical cloud forest inhabiting orchid Dracula felix has long been postulated to be a fungal mimic due to the form of its lower labellum and attraction to it by drosophilid flies that are often found feeding on fungal fruiting bodies in the surrounding area. The low number of co-occurring flowers in the area combined with the high number of fruiting fungi appears to have driven the evolution of the orchid genus Dracula to mimic these co-occurring fungi so that pollinators may be recruited. Over several years of working with these orchids we have noticed a particular lapping behavior by the pollinating flies on the labella and sepals of the Dracula flowers. In this study we have first surveyed floral yeasts and molds associated with Dracula flowers and then investigated the role of these fungi in attracting pollinators and offering a food reward to retain them for pollination purposes. In addition to the floral yeasts, leaf endophytes and root associated fungi were cultured and identified, and their frequencies were determined.

The influence of variation in style length on pollen flow and seed set was examined in six populations of Menyanthes trifoliata in southwestern British Columbia to evaluate Ganders' hypothesis that morphological distyly increases the fecundity of a diallelic self-incompatible plant. In five populations, Menyanthes was distylous and self-incompatible. The sixth population consisted of pins and morphological homostyles (thrums with unusually long styles). In each population morph frequency, pollen frequency, the composition of stigmatic pollen loads and seed set were estimated. Results from the six populations demonstrate that the size and composition of stigmatic pollen loads fluctuates erratically during the flowering season. Pins and thrums experienced disassortative pollination, assortative pollination and random pollination at different times during the season. Homostyles were always assortatively pollinated. Among populations there was a high correlation between morph frequency (pollen frequency) and the composition of stigmatic pollen loads. However, in anisoplethic populations of Menyanthes morphological distyly seems to compensate for the rarity of one floral form, by increasing the proportion of compatible pollen received by the opposite floral form. Comparison of the composition of stigmatic pollen loads of homostyles with those of thrums revealed that the separation of stigmas and anthers in distylous flowers of Menyanthes reduces the number of incompatible pollen grains received, and the reciprocal placement of stigmas and anthers appears to increase the number of compatible pollen grains received. Seed set in the six populations of Menyanthes was always below the potential maximum. Among populations there was a high correlation between the number of compatible pollen grains received and seed set. In at least one population, pollen availability was a major factor limiting seed set, but other factors are probably influencing seed set in Menyanthes as well. Thrums set significantly more seeds per capsule than homostyles. In populations of Menyanthes, the reciprocal placement of stigmas and anthers in distylous flowers (compared to homostylous flowers) increases the amount of compatible pollen deposited on stigmas, and this increase is associated with greater fecundity. / Science, Faculty of / Botany, Department of / Graduate

The plant nectar microbiome (NMB) primarily composed of fungi and bacteria can qualitatively and quantitively affect floral rewards and ultimately impact plant-pollinator interactions and plant reproductive success. Evidence suggests that changes in microenvironmental conditions across spatial gradients can induce changes in the floral nectar microbiome, leading to microbiome variation within species. Specifically, changes in biotic and abiotic conditions across an elevation gradient (i.e. pollinator community composition, temperature, UV exposure, nutrient availability) have the potential to induce variation NMB composition and abundance. However, this has been little explored. For instance, we could expect that the diversity and abundance of the NMB will decrease with elevation as the growing conditions become less favorable (e.g. lower temperatures). In this study, we evaluate spatial variation in nectar microbiome composition, diversity, and abundance in populations of Rhododendron catawbiense at high (H) and low (L) elevations separated by over 1000ft in Roan Mountain, TN. Nectar samples were collected, plated, quantified and isolated. Fungal ITS sequences were obtained from individual colonies by Sanger sequencing and directly from nectar samples by Nanopore NGS. Preliminary results suggest that elevation can affect fungal abundance and composition in the NMB. We found 10 fungal species inhabiting the nectar of R. catawbiense (H= 4; L= 9). We also observed variation in nectar yeast abundance with more than 30x as many CFUs (colony forming units) (H= 1.89 ±10.64; L=38.43 ±1.39.12) and twice as many RPKMs (reads per kilobase matched) (H= 2.8x107 ± 2.46x107; L=5.5x107 ±3.6x107) on average at the lower elevation. Interestingly, R. catawbiense NMB in the lower elevation had a broader diversity of species (Simpson Diversity Index: H= 0.52; L= 0.95), perhaps as a result of more favorable growing conditions. This trend is largely associated with higher abundance of Metschnikowiaceae yeast OTUs and lower abundance of potentially pathogenic Basidyomycete OTUs. Overall, results indicate that elevation can mediate changes in the composition and abundance of microorganisms in the NMB, which in turn can lead to differences in pollinator community composition and plant reproductive success. These results highlight the need evaluate within-species variation in NMB at large spatial scales and its potential consequences for plant reproductive success, plant-pollinator interactions and plant community dynamics. This is particularly important in the face of human-mediated environmental disturbances that can alter plant-microbe interactions.

More than 60% of plant populations experience low pollen availability which limits seed production (pollen limitation). Pollen limitation occurs due to low quantity or quality of pollen delivered to stigmas. Despite its ubiquity in nature, to date we still have limited understanding of the drivers of pollen limitation in plant communities. Plants typically occur in diverse communities where pollinator sharing is common and can influence quality and quantity aspects of pollen limitation. Co-flowering species can attract larger numbers of pollinators or they can compete for pollinators affecting pollen loads on stigmas. Pollinator competition may also lead to higher rates of self-pollination, reducing pollen quality. Knowledge on the relative contribution of pollen quantity and quality to overall pollen limitation, and how it varies with increasing co-flowering diversity, is central for understanding the factors that determine plant reproductive success. Here, we used populations of four Clarkia species to evaluate how changes in co-flowering community diversity impact the contribution of pollen quantity and quality in limiting plant reproduction. We sampled twenty-five communities of 1-4 species. We collected 29-100 styles per site/species (2400 total). Styles were processed and the amount of pollen grains and pollen tubes were counted under a microscope. Differences in the amount of pollen grains received (pollen quantity) and proportion of pollen tubes produced (pollen quality) were estimated across species and populations. The amount of pollen received increased with increasing number of co-flowering species only for C. unguiculata, suggesting pollinator facilitation. The proportion of pollen tubes was not affected by the number of co-flowering species present. All Clarkia species differ in the amount of pollen grains received and the proportion of pollen tubes produced. C. xantiana, received the least amount of pollen but produced the highest amount of pollen tubes. C. speciosa received the highest amount of pollen grains but produced the fewest number of tubes. Pollen quantity and quality varied widely among individuals within a population compared to individuals across populations or species. Pollen quality and quantity are limiting factors in the reproductive success of Clarkia species, however their relative contribution depends on species identity. Overall, differences in pollen limitation may depend on intrinsic species characteristics rather than aspects of the surrounding co-flowering community. Specifically, quantity and quality components of pollen limitation may vary depending on differences in pollinator community composition, level of specialization and efficiency, and differences in plant mating system (self vs outcrossed). This study emphasizes the need to fully evaluate all aspects of pollen limitation and how these vary across space and species. This knowledge is key to understand the processes that mediate plant reproductive success in nature and how plants will respond to human disturbances.

Like orchids, the complexity of flowers found in asclepiads (Asclepiadoideae, Apocynaceae) and the fact that pollen is presented as pollinaria, offers excellent opportunities to study various aspects of plant-pollinator interactions. In this thesis I investigated two broad themes: ecological aspects of the pollination biology of hymenopteran and fly-pollinated asclepiads as well as the degree of specialization to certain pollinators in these species. Colonizing plants often reproduce through self-pollination, or have highly generalized pollination systems, or both. These characteristics facilitate establishment in small founding populations and generates the prediction that reproductive success should be independent of population size in these species. Chapter one examines the pollination biology of Gomphocarpus physocarpus, an indigenous, weedy species and investigates the relationship between reproductive success and population size. In this species, there is no evidence of an Allee effect and reproductive success is not correlated with population size. In addition G. physocarpus is not capable of self-pollination, suggesting it is completely reliant on pollinators for seed set. The lack of a relationship between pollination success and population size is therefore likely explained by the generalized wasp pollination system of this species. Several milkweeds are invasive outside of their native ranges. Invasive species either need to co-opt native pollinators in order to reproduce or reduce their reliance on pollinators through having the ability to self-pollinate. Co-opting native pollinators is expected to be easier in species that have generalized pollination systems, alternatively species with specialized flower morphologies need to rely on similar functional groups of pollinators to be present within the invaded range. Chapter two investigates the pollination biology and pollination success of the invasive milkweed, Araujia sericifera, and finds that in South Africa, this species is visited mainly by native honeybees and nocturnal moths. Moths however contribute little to pollen removal, and deposition. Based on the apparent morphological mismatch between the flower of A. sericifera and native honeybees, I propose that the native pollinators of this species are likely to be larger Hymenoptera (e.g. Bumblebees). Data from a breeding system study, indicated that this species is not capable of automatic self-pollination, but could set fruit from geitonogamous self-pollinations pointing to the importance of native pollinators for successful reproduction. The pollinaria of milkweeds can accumulate on pollinators to form pollen masses large enough to physically interfere with the foraging behaviour of pollinating insects. In chapter three I describe the pollination biology of Cynanchum ellipticum and find that this species is mainly pollinated by honeybees although this species is visited by several other members of Hymenoptera, Lepidoptera and Diptera. Due to the structure of the pollinaria, these chain together relatively efficiently and frequently form large pollinarium loads on the mouthparts of honeybees. However there is little evidence that these pollinarium loads influence the foraging times of pollinators and only a few individual honeybees exhibited longer foraging times and most honeybees were unaffected by the presence of large pollinarium loads. Within the genus Cynanchum there is large variation in the gynostegium structure that may influence the pattern of pollinarium loading on pollinators as well as pollen reception as shown in chapter three. In Chapter four, the pollination biology of Cynanchum obtusifolium is examined, and like that of C. ellipticum, this species is visited by a wide diversity of pollinators but honeybees appear to be the primary pollinators. More importantly this species is shown to be andromonoecious and produces two morphologically different flower types, that may be distinguished based on differences in the gynostegium structure. These two types of flower could mainly be distinguished by the length of the anther wings. I found that flowers with short anther wings function as male flowers by only exporting- and rarely receiving pollinia. Flowers with longer anther wings function as hermaphrodite flowers and can both export and receive pollinia. The ratio of male to hermaphrodite flowers varied at different times during the flowering season, but preliminary data suggested that this was not related to levels of pollination success. The genera Stapelia and Ceropegia are well known for their intricate floral adaptations that mimic the brood and feeding substrates of pollinating flies. Despite several studies that have documented the various adaptations to fly pollination in different species, there is a lack of natural history studies documenting different flower visitors, pollen loads and long term levels of pollination success in these species. In Chapter six I document the pollination biology of Ceropegia ampliata by documenting different pollinators and quantifying average levels of pollination success and the nectar reward. I also experimentally manipulated the trapping hairs of this species to determine whether trapping hairs influence average levels of pollen export and receipt. I show that Ceropegia ampliata is pollinated by a generalist guild of flies (mainly Tachinidae, Sarcophagidae, Muscidae and Lauxaniidae) and produces minute quantities of relatively dilute nectar as a reward. Pollination success was generally low in this species and increases periodically suggesting that the abundance of pollinators is patchy. I found that flowers with trapping hairs that had already wilted had higher levels of pollinarium removal than flowers with erect hairs, however experimentally removing the hairs had no significant effect on pollen export and receipt. In Chapter seven, I document the pollinators, pollen loads and long term levels of pollination success in Stapelia hirsuta var. bayllissi, a rare sapromyiophilous stapeliad. I find that, in contrast to C. ampliata, this species was specialized to pollination by small flies of the family Anthomyiidae. Similar to the results from Chapter seven, I find that long term levels of pollination success were typically low but could increase periodically, although such increases were generally unpredictable. There are currently very few records documenting pollinator interactions in the Periplocoideae. Many species within this subfamily exhibit open-access flowers suggestive of pollination by short-tongued insects. I investigated the pollination biology of Chlorocyathus lobulata, a rare species with a highly localized distribution. I aimed to determine the pollinators, average levels of pollination success and demography of this species in order to determine whether this rare species is suffering from the collapse of a highly specialized pollinator mutualism. I also quantified the high incidence of flower herbivory caused by larvae of the moth, Bocchoris onychinalis. I find that C. lobulata has a highly generalized fly pollination system and average levels of pollination success suggested that a large proportion of flowers had pollen removed and deposited suggesting that this species is not experiencing pollination failure. The large numbers of juveniles present also indicated that recruitment is taking place.

The genus Erica is the most species rich in the Cape Floristic Kingdom, yet there are limited data on the various flower-pollinator interactions and breeding systems for the majority of these species. Until recently research has focussed on predictive floral traits, including flower shape, length of corolla and corolla opening to identify likely pollinators in this genus. Field observations provide an empirical test of such predictions. This study investigated three species of Erica and compared their pollination and breeding systems and floral biology. Research, including field experiments and pollinator observations was undertaken in the Vogelgat Private Nature Reserve, Maanschynkop Nature Reserve and Boskloof farm in the vicinity of Hermanus in the Western Cape Province of South Africa. Field observations were conducted to determine what flower- visitor interactions occurred, while nectar volumes and sugar concentrations were measured to determine the value of the reward to the different visitors. Selective exclusion and breeding system experiments were carried out to determine whether these Erica species were capable of autonomous self-fertilization or whether they are pollinator dependent for breeding success. The unusual morphology of Erica lanuginosa suggested rodent-pollination. Field observations, including photographs of visits to plants in the field, the presence of pollen in scat sample and selective exclusion and breeding system experiments identified rodents, primarily Acomys subspinosus to be the primary pollinator. Long-proboscid flies of the family Nemestrinidae were found, on the basis of field observations to be responsible for pollination of the endemic Erica aristata. This was supported by with nectar volume and sugar concentration samples which are consistent with other long-proboscid fly-pollinated plant species. Selective exclusion and breeding system experiments undertaken confirmed that Erica aristata required a pollinator to set seed. Observations and breeding trials revealed bird-pollination in Erica sessiliflora. Nectar volume and sugar concentrations in Erica sessiliflora were in line with other sunbird-pollinated plant species, providing the necessary rewards for sunbirds visiting this species. Specialised pollination by single pollinators was found in all three species and results from breeding system experiments show that out-crossing is important. Further research into pollinator-flower interactions in the genus Erica is necessary, not least to understand more fully the conservation importance of specific pollinators.