Pollination networks summarize interactions between plants and pollinators, providing insight into ecosystem stability. An unplanned fire provided the opportunity to assess network structure following disturbance in the Tall Grass Prairie Preserve in southern Manitoba. I established transects in sites burned <1 year, 5-6 years, or 10+ years ago. I assessed species richness, diversity, abundance, and phenology of insects and flowering plants. I created interaction matrices by recording plant-insect interactions, and sampled pollen loads from insects. Network structure was assessed by connectance, nestedness, and interaction strength. Flowers were more abundant and bloomed two weeks earlier in newly burned sites in 2010. Bees showed responses to fire based on nesting habitat, however visits by syrphids were related to precipitation. Network structure showed that tall grass prairie pollination networks were resilient to disturbance and variable environmental conditions, and management of prairie by fire did not negatively impact plant-pollinator interactions within the community overall. / February 2016

Thesis (MScAgric)--University of Stellenbosch, 2000. / ENGLISH ABSTRACT: Ineffective pollination of the main cultivar with the pollinator cultivar is due to either an incompatibility problem between the main and pollinator cultivar, or because the flowering times of the main and pollinator cultivars do not overlap adequately. Three trials were conducted to try and find a more effective way to determine cultivar compatibility and to group cultivars together according to their budburst reaction to chilling. Most apple cultivars are self-incompatible and need cross-pollination for fruit set. Due to differences in the genetically defined fertilisation compatibility between the pollen from the male parent (pollinator) and the egg cell of the female parent, various apple pollinators differ in their ability to set fruit with viable seed. Fruit weight and size are positively correlated with seed set although it has been found that the pollinator can have a direct influence on fruit quality. 'African Red' apple trees on M7 rootstock in an evaluation block on a commercial farm in the Koue Bokkeveld region (32°55'N 19°27'E, Mediterranean climate, ;::::1060Utah chill units, and ;::::530mm rainfall annually; altitude 966 m) were used to assess the influence of 5 pollinators ('Granny Smith', 'Winter Banana', 'Cripps' Pink', 'Cripps' Red' and 'Simpson Crab') on fruit set, fruit weight and length and diameter. The degree to which 'African Red' is self-compatible was also assessed and the effect of flowering position ("king" vs. lateral) on fruit quality was determined. None of the pollinators showed a significantly higher fruit set. No differences in fruit set were found between the "king" and lateral flowering positions. No significant differences were found in the average number or weight of well developed seeds between pollinators. In both years fruit weight was significantly correlated to seed number for all five pollinator cultivars. In 1998 'Simpson crab' gave fruit that were significantly more elongated than those of 'Cripps' Pink'. 'African Red' is highly self incompatible. Compatibility assessments that are based on the number of fruit that develop after the flowers ofthe main cultivar had been hand pollinated in field trials are a time-consuming process. Allele-specific PCR amplification for some of the known S-alleles of the incompatibility S-gene (S2, S3, S5, S7 and S9) was carried out to successfully predict the compatibility of genotypes. The results compared well with that found in literature. For all the Malus domestica cultivars tested at least one, but in some instances both alleles of the S-gene were determined. 'Simpson crab' (Malus baccata) did, however, not possess any of the tested S-alleles. One-year-old, ca. 40 mm long shoots of various apple cultivars were selected from commercial orchards in both the Elgin [34°S, 305 m, ca. 750 chill units (CU) (Richardson et al., 1974)] and Koue Bokkeveld (33°S, 945 m, ca. 1300 CU) regions of the Western Cape, South Africa in two consecutive years (1998 and 1999). Shoots were forced at a constant 25°C with continuous illumination after receiving their allocated chill units. The effect of chilling period on the budburst of each cultivar in both regions was estimated by determining, 1) the total proportion of budburst (%Bb), 2) the proportion of shoots with terminal budburst (%TBb), and 3) the rate of budburst [lI(days to 25% budburst)]. It was found that these indices differed significantly between cultivars, and within cultivars between areas, as far as budburst patterns, in reaction to chilling, were concerned. The rate of budburst was the most consistent in describing the reaction of buds to different chilling periods and could be used to group cultivars together according to their budburst reaction to chilling. / AFRIKAANSE OPSOMMING: KRUISBESTUIWINGSBIOLOGIE VAN APPELS MET SPESIALE VERWYSING NA 'AFRICAN RED'. Oneffektiewe kruisbestuiwing III die boord kan toegeskryf word aan Of onverenigbaarheid tussen die hoof- en bestuiwingskultivar Of as gevolg van die blomtyd van die kruisbestuiwer wat nie genoegsaam oorvleuel met die van die hoofkultivar nie. Drie proewe is uitgevoer om 'n meer effektiewe proses daar te stel vir die toets van kultivarverenigbaarheid en om kultivars te probeer groepeer na gelang van hul reaksie op bepaalde hoeveelhede koue. Meeste appelkultivars is selfonverenigbaar en benodig kruisbestuiwing vir genoegsame vrugset. As gevolg van verskille III die geneties gedefinieerde bevrugtingsverenigbaarheid tussen die stuifmeel van die manlike ouer (bestuiwer) en die eiersel van die vroulike ouer (hoofkultivar), verskil bestuiwers in hul vermoë om vrugte met sade te set. Vruggrootte en -massa is positief gekorreleerd met saadset alhoewel dit al gevind is dat die bestuiwer op sig self ook 'n invloed op vrugkwaliteit kan hê. 'African Red' appelbome op M7 onderstamme, in 'n evaluasie blok op 'n kommersiële plaas in die Koue Bokkeveld (32°55'N 19°27'E, Meditereense klimaat, ::::1060 Utah koue eenhede, en ::::530mmjaarlikse reënval; ligging 966 m), is gebruik om die invloed van 5 bestuiwers ('Granny Smith', 'Winter Banana', 'Cripps' Pink', 'Cripps' Red' and 'Simpson Crab') op vrugset, vrugmassa, -lengte en -deursnee oor twee seisoene te bepaal. Die mate waartoe 'African Red' self onverenigbaar is en die effek van blomposisie ("king" vs laterale blom) op vrugkwaliteit is ook bepaal. Geen een van die bestuiwers het vrugset beduidend beïnvloed nie. Ook is daar geen verskille gevind tussen die "king" en laterale blomposisies t.o.v. vrugset nie. Geen beduidende verskille is tussen bestuiwers gevind in die gemiddelde aantal of gewig van volsade geset nie .. In albei jare was die vrugmassa beduidend gekorreleerd met saadset vir al vyf bestuiwerkultivars. In 1998 het 'Simpson Crab' vrugte geset wat beduidend langer was as vrugte wat geset het toe 'Cripps' Pink' as bestuiwer gebruik is. Daar is ook gevind dat 'African Red' hoogs selfonverenigbaar is. Verenigbaarheidstoetse wat gebaseer is op die aantal vruggles wat ontwikkel nadat blomme van die hoofkultivar met die hand bestuif is, is 'n tydsame proses. Allele spesifieke PCR amplifikasie vir bekende S-allele van die onverenigbaarheids S-geen (S2, S3, S5 S7en S9) is suksesvol uitgevoer om die verenigbaarheid van genotipes vooraf te bepaal. Die resultate het goed vergelyk met wat in literatuur gevind is. Vir al die Malus domestica spesies wat getoets is, is ten minste een, en in sommige gevalle twee, van die S-allele gevind. Die blomappel 'Simpson' (Malus baccata) het egter nie een van die vyf S-allele opgelewer nie Een-jaar-oue, 40 mm lang lote van verskeie appelkultivars, is in twee opeenvolgende jare (1998 en 1999) vanuit kommersiële boorde in beide die Elgin [34°S, 305 m, ca. 750 koue eenhede (CU) (Richardson et al., 1974)] and Koue Bokkeveld (33°S, 945 m, ca. 1300 CU) areas van die Wes Kaap gsny. Die lote is geforseer om te bot by 'n konstante temperatuur van 25°C met deurlopende beligting, nadat elke groep lote aan 'n bepaalde hoeveelheid koue blootgestel is. Die effek van koue op bot van elke kultivar in beide areas is bepaal deur, 1) die totale persentasie knoppe wat gebot het, 2) die persentasie terminale knoppe wat gebot het, en 3) die tempo van bot [l/(dae tot 25% bot)] te meet. Daar is gevind dat bo-genoemde parameters beduidend tussen kultivars, en binne kultivars tussen areas, verskil. As 'n beskrywing van die reaksie van knoppe op koue het die tempo van bot die mees konstante resultate oor die twee opeenvolgende seisoene gelewer en kon hierdie parameter gebruik word om kultivars in groepe, na gelang van hul reaksie op koue, in te deel.

Relying on wild bees for pollination services has become necessary as the global demand for crops dependent on animal pollination increases. If wild bee populations are to establish and persist in agricultural landscapes, there must be sufficient floral resources over time and space. This study examines the relationship between bee visits in agroecosystems and the spatiotemporal availability of floral resources over one season. I expected that landscapes with greater floral resources earlier in the season would subsequently experience more bee visits than landscapes with fewer early-season floral resources, and that the spatiotemporal scale of this effect would differ among taxa. I measured bee visitation rate and floral resource density over three spatial scales and during four time-periods spanning one season, in 27 agricultural sites across Ontario and Québec, Canada. The present abundance of floral resources at a local scale positively influenced bee visits across all sampling periods. However, differences in the temporal scale of bees’ response to floral resources were observed at landscape scales. Past and present floral resources were positively or negatively associated with bee visits depending on the time of season and which taxon was examined. The number of visits by Andrenidae, honey bees, and bumble bees increased with floral resource abundance in previous time-periods, while other taxa exhibited a negative association with past floral resources, suggesting possible dilution of bee populations at a landscape scale. Understanding the scales at which bee taxa are influenced by floral resources can allow development of land management strategies that could enhance crop pollination and conserve species threatened by agricultural intensification.

A range of fairly common plants were investigated in Darling in the Western Cape, to determine their pollinator syndromes, and to evaluate the relative importance of monkey beetles (Scarabaeidae: Rutelinae: Hopliini) and relatively short-tongued horseflies (Tabanidae) in their pollination. Detailed observations showed that all the plants investigated are visited by more than one insect species. Visitation rates and pollen loads of all insects found on the plants were used to assess their pollination efficiency. For all plants investigated, only a subset of the visitor-suite was found to contribute to the plant's reproductive success. Geissorhiza radians (Thunb.) Goldblatt and Wachendorfia paniculata L. seem to have specialized pollinator systems, both relying on tabanids for their pollination, while Heliophila coronipifolia, L. Monsonia speciosa, L.f. Ornothogalum thyrsoides, Jacq. Romulea hirsuta (Klatt) Baker and Ursinia anthemoides (L.) Poir. appear to have more generalized pollinator syndromes. Monkey beetles were the predominant and generally the most efficient pollinators for all these species. It is therefore concluded that these two insect groups are important pollinators of the plants investigated and probably play a part in the pollination of several other plants in the community. An evaluation of the larval requirements of pollinators revealed that although some species show clear patterns in terms of what types of soil conditions they prefer, successful emergence of insect species is generally not limited by a shortage of suitable habitats. Environmental variability may therefore play the largest role in determining the emergence and abundance of pollinators. This has implications for plants reliant on insects for their pollination, especially for species with specialized pollinator syndromes. Fluctuations in the environment may be a partial explanation for the prevalence of the generalized pollination syndromes observed.

Human encroachment on ecosystems is one of the key environmental stressors facing natural habitats. Understanding how individual species are affected by these disturbances is therefore fundamental to preserving the stability of vital ecosystem services, such as pollination. Roughly 87.5% of plants are animal pollinated, with pollination contributing over $175 billion to the global economy each year. Despite its ecological and economic importance, studies that have comprehensively evaluated how multiple components of pollination success are impacted by human disturbances are limited. Here we evaluate how different aspects of pollination success, including patterns of pollinator visitation, pollen removal (male fitness), and deposition, fruit and seed production (female fitness) vary across an urbanization gradient in populations of Asclepias syriaca (Common Milkweed). Preliminary data was collected on four naturally occurring Asclepias syriaca sites (Watauga Lake, Warrior’s Path, Lake Ridge, Jacob’s Nature Park) in Northeast Tennessee. Urbanization around each site was quantified using ArcGIS and the National Land Cover Database. Sites were visited every other day (5-12 visits per population) during the flowering season and data was collected on male reproductive success (proportion of pollinaria removed), female reproductive success (proportion of flowers receiving pollinaria), pollinator visitation rate and composition, fruit production, and seed set. Preliminary data on four Asclepias syriaca populations shows large among-site variation in male and female reproductive success, pollinator visitation rate, pollinator community composition, fruit abundance, and seed set. Specifically, the quantity and quality of pollen received varies between all four sites. Pollen quality was highest at Lake Ridge (mean 2.57 fruits per plant and 278 seeds per fruit), and lowest at Warrior’s Path (mean 1.54 fruits and 199 seeds), the most agricultural site. Male success was highest at Warrior’s Path (0.492) and lowest at Watauga Lake (0.308). Female success was approximately equal between three of the sites (between 0.208 and 0.179), but lower at Jacob’s Nature Park (0.072). There was significant among-site variation in pollinator community, not only in terms of composition, but also visitation rate. Visitation rate was highest at Warrior’s Path and Lake Ridge (0.214 and 0.283, respectively), and lowest at Watauga Lake and Jacob’s Nature Park (0.126 and 0.123, respectively). Interestingly, Jacob’s Nature Park and Watauga Lake represent the most and least developed sites, respectively, though the Watauga Lake population was adjacent to a major road. Among-site variation in pollination success is likely due to variation in pollinator community across the sites.

Up to 96% of angiosperms are dependent on animal pollinators for successful reproduction thus providing a key ecosystem service. Recent studies however, have indicated that micro-organisms inhabiting floral nectar can influence interactions between plants and their pollinators with consequences for plant fitness. Specifically, floral nectar provides suitable habitat for fungal and bacterial species i.e., the nectar microbiome (NMB), which can alter the amount and quality of nectar, floral volatile composition and impact pollinator preference and plant reproductive success. While the extent and consequences of these interactions are well understood for one or few plant species, community-level studies on the structure, drivers and fitness consequences of interactions between plants and nectar inhabiting microorganism are scarce. Community-level of studies of the drivers and consequences of interactions between plants and nectar microorganisms can help advance our understanding of the mechanisms that mediate the structure of plant-pollinator networks and mediate plant community assembly. In this study, we describe the structure of a plant-nectar microbiome network in a serpentine plant community in Northern California. We further evaluate how the structural properties of such network are mediated by the abundance and diversity of floral visitors and its effects on plant reproductive success. Nectar samples were collected from 15 plant species and cultured on agar plates until isolated. Fungal ITS and bacterial 16s DNA sequences were used for identification by Sanger sequencing. We further explored the effects pollinator visitation on of plant-microbiome network properties and the effects of the latter on pollen deposition and pollen tube production. Plant-nectar microbiome network was composed of 52 fungal and 27 bacterial morphospecies (79 total cultured CFU). Filamentous fungi (i.e. molds) comprise 80% of all fungal colonies. Network analysis also revealed network connectance and specialization were lower (0.07 and 0.39 respectively) than reported for plant-pollinator networks in the same community. On average, individual plants have 2.32 links with modularity and nestedness values of 0.36 and 0.32, respectively, which are comparable to plant-pollinator network values. An increase in diversity of insect visitors species significantly increased NMB richness. Furthermore, increased NMB species richness seemed to have a marginal positive effect on conspecific pollen deposition but nor on pollen tube production. Our results suggest that community-level patterns of NMB composition can be determined by the diversity and abundance of the pollinator community, with potential consequences for plant reproductive success.

No description available.

Thesis (Ph. D.)--University of Wisconsin, 1965. / Includes bibliographical references.

Hedgerow fruits provide a food resource for several UK farmland bird species from late summer, through winter and into spring. This project aims to develop the understanding of the interactions between fruit-bearing hedgerow flowers, their pollinators, hedgerow fruits and frugivorous birds. Experiments revealed that flowers of blackthorn, hawthorn and ivy all benefited from insect visits in order to develop fruit. The flowers of bramble and dog rose showed little requirement for insect pollination, and produced fruit when insects were excluded. There was evidence that for the hedges under study, the pollination service provided by insects to blackthorn and hawthorn flowers was inadequate since the flowers of these plants were pollen limited. The relative abundance of different insect groups foraging on blackthorn flowers was highly variable between hedges, suggesting that the contribution of a particular insect group to blackthorn pollination may vary according to their local density. Bumblebees, bristly flies and solitary bees were considered to have the greatest value for pollinating blackthorn flowers, based on foraging attributes (bumblebees and solitary bees), and abundance (bristly flies), but their activity did not correlate with the proportion of flowers that set fruit. Solitary bee activity correlated with hawthorn pollination, and there was strong evidence that social wasps were the best pollinators of ivy flowers on the hedges studied. Environmental factors such as hedge aspect did not significantly affect the activity of most pollinators (with the exception of solitary bees) or the proportion of blackthorn flowers that set fruit. Equally, the presence of the mass-flowering, attractive forage source, oilseed rape in fields adjacent to hedgerows, did not significantly influence the activity of most pollinators or the proportion of hawthorn flowers that set fruit. The abundance of some frugivorous birds, in particular the migratory thrushes (redwings and fieldfares) was positively related to the yield of fruits, including sloes and haws in hedges. So the evidence suggests that on these farms, pollinator communities are important for ensuring some hedgerow shrubs provide copious fruit, which may be vital for birds during winter months when invertebrate food is scarce. These links between flowers, pollinators, fruits and birds are discussed, alongside suggestions for safeguarding the fruit supply for farmland birds in the future.

Thesis (M.S.)--Oregon State University, 2007. / Printout. Includes bibliographical references (leaves 44-52). Also available on the World Wide Web.