Pollination and Floral Biology of a Rare Morning Glory Species Endemic to Thailand, Argyreia siamensis

Argyreia siamensis is extremely rare, and very little is known about its reproduction. The species has colorful flowers that seem likely to attract pollinators, but population sizes are typically small (<30 individuals). To determine whether poor reproduction contributes to its rarity, we investigated its mating system and potential pollinators in two populations. We also examined the staminal trichomes and floral nectary to investigate their role in pollinator attraction. The mating system was assessed with a bagging experiment and pollinator visits were recorded with action cameras. Additionally, we tested the staminal trichomes and floral nectary for terpenes and flavonoids and examined floral nectary micromorphology via scanning electron microscope and compound light microscope. Our results reveal that A. siamensis is self-incompatible and dependent on pollinators; the western population was pollinated by bees (Meliponini and Amegilla), while the eastern population was mainly pollinated by skipper butterflies (Hesperiidae). Both staminal trichomes and the floral nectary appear to contribute to pollinator attraction through the presence of terpenes and flavonoids (in both secretory structures) and nectariferous tissue and nectarostomata (in the nectary). Our results indicate that A. siamensis has reliable and effective pollinators and that insufficient pollination is likely not a primary cause of its rarity.

Pollination in the Rainforest: Scarce Visitors and Low Effective Pollinators Limit the Fruiting Success of Tropical Orchids

A single plant might be visited by many flower visitors but not all might act as pollinators. Legitimate pollinators might also differ considerably in their efficiency, limiting pollination success. Unsuitable climatic conditions such as rain also affect pollinator activity. However, in the evergreen rainforest there is no prolonged dry season and flowering occurs usually under rain. Here, we explore the dependence on pollinators and the efficiency of flower visitors for the fruiting success of 10 Andean rainforest orchids. All species were self-compatible but strictly pollinator-dependent. Overall, we found low levels of fruit set in control flowers while experimental geitonogamous and cross-pollinations increased fruit set, revealing extensive pollination limitation in all populations. Seed viability dropped considerably after self and geitonogamous pollinations suggesting the possibility of early-acting inbreeding depression. Even though we monitored flower visitors on an extensive survey, few visitors were seen in these species and even fewer acted as legitimate pollinators. Thus, even though orchid pollination might be extremely diversified, these results show that few visitors are pollinating these species, explaining the low levels of fruit set recorded in the area studied.

Nocturnal Bees as Crop Pollinators

Bees are typically diurnal but around 1% of described species have nocturnal activity. Nocturnal bees are still poorly studied due to bias towards studying diurnal insects. However, knowledge concerning their biology and role as crop pollinators has increased. We review the literature on nocturnal bees’ traits and their host plants, and assess the crop pollination effectiveness of this neglected group. Nocturnal bees have visual adaptations to cope with low light intensities, and floral scents are a key sensory cue used to find their host flowers. Nocturnal bees generally show high flower constancy, the ability to vibrate flowers, and high transfer rates of pollen grains to stigmas. The flowers visited by nocturnal bees range from small radial and zygomorphic flowers to large brush blossoms; moreover, they visit plants with different flowering strategies. Nocturnal bees are effective pollinators of regional fruit crops in Brazil, such as cambuci (Campomanesia phaea), guaraná (Paullinia cupana), cajá (Spondias mombin), and in North America of cultivated pumpkins (Cucurbita species). However, they most likely are pollinators of several other crops. Strategies to host high numbers of nocturnal bees around cropping areas should be taken, such as preserving adjacent native forests, restricting soil management, providing food resources beyond crop flowers, and avoiding light pollution.

Landscape Enhancements in Apple Orchards: Higher Bumble Bee Queen Species Richness, but No Effect on Apple Quality

Bumble bees are among the most effective pollinators in orchards during the blooming period, yet they are often threatened by the high levels of pesticide use in apple production. This study aimed to evaluate the influence of landscape enhancements (e.g., hedgerows, flower strips) on bumble bee queens in apple orchards. Bumble bee queens from 12 orchards in southern Québec (Canada) were marked, released, and recaptured in the springs and falls of 2017 to 2019. Half of the 12 orchards had landscape enhancements. Apples were harvested in 2018 and 2019 to compare their quality (weight, diameter, sugar level, and seed number) in sites with and without landscape enhancements. Species richness, as well as the occurrence of three species out of eight, was higher in orchards with landscape enhancements than in orchards without such structures. The occurrence of Bombus ternarius was lower in orchards with high levels of pesticide use. Apples had fewer seeds when collected in orchards with landscape enhancements and were heavier in orchards that used more pesticides. Our work provides additional evidence that landscape enhancements improve bumble bee presence in apple orchards and should therefore be considered as a means to enhance pollination within farms.

Floral and reproductive biology and pollinators of Campomanesia guazumifolia (Cambess.) O. Berg., neglected species

Studies on the Myrtaceae family are mainly distributed in floristic surveys, reproductive studies of plant communities or related to family taxonomy. Based on this, the objective of the present study was to elucidate aspects of floral and reproductive biology and, of floral visitors from Campomanesia guazumifolia (Cambess.) O. Berg., a neglected species. Information was obtained on floral morphology and morphometry, anthesis, nectary, and structures attractive to pollinators, characterization of pollinators, receptiveness of stigma and maturing of the androecium components, and characterization of the reproductive system. Sete-capote tree has hermaphrodite flowers, and the floral opening occurs mainly during the daytime. Pollen grains was the main resource offered to pollinators. The flowers had mellow sweet odor, attracting mainly native bees and Apis melifera, which was characterized as effective pollinators. The species presents high reproductive efficiency and could be considered self-compatible; however, fertilization also occurs by cross-pollination.

A meta-analysis of single visit pollination effectiveness

Many animals provide essential ecosystem services in the form of plant pollination. A rich literature documents considerable variation in the single visit pollination effectiveness of different plant visitors, but this literature has yet to be comprehensively synthesized. We conducted a hierarchical meta-analysis of 193 studies and extracted 1716 single visit effectiveness (SVE) comparisons for 252 plant species. We paired SVE data with visitation frequency data for 75 of these studies. Given the global dominance of honeybees in pollinator communities, we used these data to ask: 1) Do honeybees (Apis mellifera) and other floral visitors vary in their SVE?; 2) To what extent do plant and pollinator attributes predict the difference in SVE between honeybees and other visitors?; and 3) Is there a correlation between floral visitation frequency and SVE? We found that honeybees were significantly less effective than the most effective non-honeybee pollinator. Although not significantly different, honeybees also tended to be less effective than the mean community effectiveness. Honeybees were less effective as pollinators of crop plants and when compared to birds and other bees. Visitation frequency and pollination effectiveness were positively correlated, but this trend was largely driven by data from communities where honeybees were absent, suggesting that honeybees generally combine high visitation frequency and lower SVE. Our study demonstrates that non-honeybee floral visitors are highly effective pollinators of many crop and non-crop plants. While the high visitation frequency typically displayed by honeybees undoubtably makes them important pollinators, we show that honeybees are slightly less effective than the average pollinator and rarely the most effective pollinator of the plants they visit. As such, honeybees may be imperfect substitutes for the loss of wild pollinators and safeguarding global crop production will benefit from conservation of non-honeybee taxa.

Island Invasions by Introduced Honey Bees: What Can Be Expected for Puerto Rico and the Caribbean?

Apis species are a major component of pollinator faunas in their native and introduced habitats. A widespread concern is that non-native Apis mellifera may have negative effects on native pollinators and on plant reproduction. This is based on the assumptions that natural communities are at capacity, resource competition structures communities, native pollinators are more effective pollinators of native species, yet A. mellifera are superior competitors. The latter two assumptions are often true, but evidence from the Neotropics indicates that tropical communities are not tightly structured, and the foraging flexibilities of native bees maintain their populations. However, the less diverse and disharmonic biotas of islands may limit the buffering capacity of flexible behaviors. While few studies address these assumptions or the ecological and evolutionary consequences of A. mellifera to the flora and fauna of tropical islands, an accumulation of taxon-specific studies are suggesting that such effects run the spectrum from subtle and indirect to obvious and direct. A concerted research effort is needed to address the multitude of issues to develop strategies to ameliorate or enhance honey bee effects, or just let nature take its course.

Pollination by hummingbirds of Vriesea gigantea (Bromeliaceae) populations in Southern Brazil

The pollination syndrome hypothesis usually does not successfully apply to the diversity of floral phenotypes or help predict the pollinators of most plant species. In Bromeliaceae, there is a wide range of floral visitors, making its species ideal to test for a correlation between nectar and floral traits with pollination syndrome. In this study, we analyzed the floral features, nectar production patterns, pollinators and floral visitors of Vriesea gigantea, and discussed its potential adaptive and ecological significance. We study three natural populations from the Atlantic Forest, Southern Brazil. The species presented protogyny and herkogamy, and its anthesis occurred at different periods among different populations. Vriesea gigantea has a relatively constant rate of nectar production during the day that continues overnight but at a reduced rate. Newly opened flowers already have around 80.0 μl of nectar. Although classified as chiropterophilous, based on flower morphology and pollinator observations, our results show that hummingbirds are effective pollinators in the studied populations of V. gigantea.

Reproductive Biology and Fruit Setting of Passiflora quadrangularis L. (Giant Granadilla) in East Malaysia

Passiflora quadrangularis L., also known as giant granadilla, belongs to the family Passifloraceae together with the well-known species Passiflora edulis Sims. This species has received attention from growers in recent years due to its aromatic flowers, unique and excellent fruit flavor and phytotherapeutic properties. Despite the numerous health benefits of this Passiflora species, information on their agronomical features and production is scarce. Therefore, the objective of this study was to examine the reproductive biology and fruit setting of P. quadrangularis cultivated in Sarawak, Malaysia. The findings revealed that the giant granadilla was a steady-state species that produced flowers lasting for only one day. Passiflora quadrangularis started to produce flowers 3 months after transplantation, followed by fruiting two months after anthesis. In East Malaysia, the flowers started blooming at dawn (0625±0.17 hours) followed by anthesis at 0806±0.23 hours and remained open until sunset. In contrast to P. edulis which flowered all year round, this species only exhibited two peaks, with a minor peak recorded from January-March and a major peak from September-December, coinciding with warm temperatures and moderate rainy season. Good fruit yields were recorded which was attributed to the ability for self-pollination due to autogamy and geitonogamy, in addition to the presence of effective pollinators. The yearly production of P. quadrangularis, produced relatively larger fruit with weights ranging from 884.4-2892.7 g, was 20,151.36 kg ha-1 (8993 fruits). Detailed information on the reproductive behavior of P. quadrangularis growing in local climates can be used for commercial cultivation and future breeding studies.