Effect of Pollinators and Nectar Robbers on Nectar Production and Pollen Deposition in Hamelia patens (Rubiaceae)1

Nectar in flowers of Epilobium angustifolium was manipulated experimentally to provide enriched versus depleted reward levels to bumblebee pollinators. Bumblebees visited significantly more flowers on inflorescences with high rewards than low ones and stayed longer on individual flowers with high rewards. The greatest pollen deposition occurred in older female flowers having enriched nectar levels. In older female flowers the stigma lobes coil backward, reducing the distance between their receptive surfaces and the nectary site. Younger female flowers, regardless of reward level, only occasionally received more than a few pollen grains per bee visit. Although higher nectar levels are likely to promote pollen receipt over the course of a flower's lifetime, because of changes in stigma configuration with flower development, the number of pollen grains transferred to the stigma at any given time depends on the flower's age as well as its reward status. In this self-compatible plant species, most of the increase in pollen receipt resulting from high nectar production is likely to lead to self-matings since (i) plants are clonal and bees usually fly to nearest neighbor ramets after rewarding visits, (ii) bees visit more flowers on enriched inflorescences than on depleted ones, and (iii) pollen carry-over declines exponentially over the course of an inflorescence visit.

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Pollinators and defence of Stachytarpheta glabra (Verbenaceae) nectar resources by the hummingbird Colibri serrirostris (Trochilidae) on ironstone outcrops in south-east Brazil

Journal of Tropical Ecology ◽

10.1017/s0266467408005051 ◽

2008 ◽

Vol 24 (3) ◽

pp. 301-308 ◽

Cited By ~ 13

Author(s):

Claudia Maria Jacobi ◽

Yasmine Antonini

Keyword(s):

Territory Size ◽

Daily Consumption ◽

Nectar Production ◽

Nectar Source ◽

Mean Size ◽

Vector Insect ◽

Floral Visitors ◽

Pollen Vector ◽

Nectar Robbers ◽

Insect Visitors

Abstract:The production and predictability of nectar resources in a population of Stachytarpheta glabra (Verbenaceae) and their use by insects and hummingbirds on ironstone outcrops in south-east Brazil were investigated. The phenology, density, nectar production, reproductive biology and floral visitors were studied, as well as territory size and daily nectar consumption by its main pollinator, Colibri serrirostris. The plant is abundant in the area, aggregated, and has a long flowering period, with very variable daily flower output. Although it can self-fertilize, it requires a pollen vector. Insect visitors totalled 21 species of bees and lepidopterans, including both pollinators and nectar robbers. Individuals of C. serrirostris defend their territories against other hummingbirds and large insects. Nectar production per hummingbird territory (mean size c. 462 m2) was estimated as 68.6–104 mL d−1 in dense areas at the flowering peak, an amount well above the estimated daily consumption of 13 mL by territory holders. Still, defence of large areas seems necessary to reduce nectar theft and cope with spatial resource unpredictability. Phenological characteristics, high density, and the fact that plants are perennial make S. glabra an attractive resource for nectar-feeders in general, and the main long-lasting nectar source for hummingbirds in the area.

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Assortative Pollination by Red Wattlebirds in a Hybrid Population of Anigozanthos Labill. (Haemodoraceae)

Australian Journal of Botany ◽

10.1071/bt9780335 ◽

1978 ◽

Vol 26 (3) ◽

pp. 335 ◽

Cited By ~ 25

Author(s):

SD Hopper ◽

AH Burbidge

Keyword(s):

Pollen Flow ◽

F1 Hybrids ◽

Hybrid Population ◽

Pollen Deposition ◽

Nectar Production ◽

Selective Pressures ◽

Seasonal Peak ◽

Principal Factors ◽

Foraging Pattern ◽

Foraging Movements

The specificity and spatial pattern of foraging movements of red wattlebirds (Anthochaera carunculata) were studied in a hybrid population of Anigozanthos manglesii D. Don and A. humilis Lindl in the shire cemetery at Gingin, W.A. Differences in phenology, nectar production, stem height and floral dimensions between F1 hybrids and the two parental Anigozanthos species were also documented to assess their influence on foraging behaviour and interspecific pollen flow. The red wattlebirds showed a 97 % fidelity for A. humilis at its seasonal peak in August 1976 and, a month later, an equally strong fidelity (97 %) for A. manglesii at its seasonal peak. Interspecific foraging movements constituted only 1.2% of the total of 925 observed during these two study periods. The spatial distribution of flowering individuals and plant stature appeared to be principal factors determining assortative pollination, presumably because of their influence on the energetics of foraging. It is suggested that the observed nearest-neighbour foraging pattern results in spatial restrictions on pollen flow and may be responsible for the confinement of hybrids to ecotonal zones where the parental species grow intermixed. Gene exchange between species is also restricted by differences in pollen deposition/retrieval sites arising from the divergent floral structures of A. hurnilis and A. rnanglesii. It is proposed that honeyeaters have generated strong selective pressures influencing the stature, floral structure and phenology of these kangaroo paws.

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Asymmetrical legitimate pollination in distylous Palicourea demissa (Rubiaceae): the role of nectar production and pollinator visitation

Journal of Tropical Ecology ◽

10.1017/s0266467411000150 ◽

2011 ◽

Vol 27 (4) ◽

pp. 393-404 ◽

Cited By ~ 7

Author(s):

Hamleth Valois-Cuesta ◽

Pascual J. Soriano ◽

Juan Francisco Ornelas

Keyword(s):

Cloud Forest ◽

Pollen Deposition ◽

Nectar Production ◽

Pollinator Visitation ◽

Visitation Rate ◽

Floral Visitor ◽

Floral Visitors ◽

Floral Visitation ◽

Nectar Availability

Abstract:We investigated morph differences in attributes that contribute to rewarding floral visitors of the distylous shrub Palicourea demissa at La Mucuy cloud forest in Venezuela. In both morphs, we measured nectar production from flowers subjected to repeated removals at 2-h intervals (10 plants per morph) and flowers that accumulated nectar for 24 h (10 plants per morph). In both cases, floral visitors were excluded. In addition, we quantified nectar availability (30 plants per morph), floral visitation (10–12 plants per morph) and legitimate pollination (30 plants per morph) throughout the day. We explored morph differences in the variables mentioned above using analyses of variance, and the effects of nectar variation on floral visitation and legitimate pollination using regression models. We observed 1205 floral visits, grouped into six hummingbird (94.7%) and three insect species (5.3%), across observations (264 h). Coeligena torquata was the most frequent floral visitor (34%) in both morphs (1.4–1.7 visits per plant h−1). Nectar production and availability, and visitation rate were similar between morphs. Visitation rate and legitimate pollen deposition increased with the nectar production in both morphs, but levels of legitimate pollination were higher on short-styled flowers than long-styled flowers. These results show that short-styled and long-styled flowers reward floral visitors equally, but frequency and foraging behaviour of long-billed pollinators can promote asymmetrical legitimate pollination.

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Flower mites and nectar production in six hummingbird-pollinated plants with contrasting flower longevities

Canadian Journal of Botany ◽

10.1139/b02-109 ◽

2002 ◽

Vol 80 (11) ◽

pp. 1216-1229 ◽

Cited By ~ 13

Author(s):

Carlos Lara ◽

Juan Francisco Ornelas

Keyword(s):

Species Interactions ◽

Field Experiments ◽

Nectar Production ◽

Nectar Volume ◽

Hummingbird Pollination ◽

Multiple Species ◽

Floral Morph ◽

Flower Mites ◽

Nectar Robbers ◽

Nectar Availability

Hummingbird flower mites and hummingbirds may compete intensely for the nectar secreted by their host plants. Here, we present the results from field experiments in which flower mites were excluded from flowers of six hummingbird-pollinated plants with contrasting flower longevities. Nectar measurements were taken on flowers from which mites were excluded and those without mite exclusion over their lifespans. The exclusion of mites had a significant positive effect on the amount of nectar available in plants with long-lived flowers. In contrast, nectar availability in short-lived flowers was not significantly reduced after mite exclusion. The significance of the mite-exclusion treatment was independent of floral morph and flower age. Results also suggest that the magnitude of the mite-exclusion treatment depends on the volume of nectar produced by the flower throughout its lifetime. The treatment effect was detected when nectar consumption, presumably by flower mites, exceeded 13% of the nectar produced by the flowers; nectar availability was not significantly reduced when nectar volume was < 7 µL per flower. It appears that flower mites consume proportionately more nectar in long-lived flowers than in short-lived flowers. Parasitic hummingbird flower mites seem to be preferentially taking advantage of plant-pollinator interactions in which flowers last several days and produce large volumes of nectar. The consequences of this finding concerning planthummingbirdmite interactions await further investigation. As a working hypothesis, we propose that nectar production has increased over evolutionary time not only by the selective pressures imposed by the pollinators, but also to compensate for the reduction they suffer after exploitation by nectar robbers and thieves such as flower mites.Key words: Ascidae, flower longevity, hummingbird pollination, multiple-species interactions, mutualism exploitation, nectar theft.

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Corolla Abscission Triggered by Nectar Robbers Positively Affects Reproduction by Enhancing Self-Pollination in Symphytum officinale (Boraginaceae)

Biology ◽

10.3390/biology10090903 ◽

2021 ◽

Vol 10 (9) ◽

pp. 903

Author(s):

Qin-Zheng Hou ◽

Nurbiye Ehmet ◽

Da-Wei Chen ◽

Tai-Hong Wang ◽

Yi-Fan Xu ◽

...

Keyword(s):

Reproductive Success ◽

Pollen Viability ◽

Pollen Grains ◽

Pollen Deposition ◽

Nectar Robbing ◽

Positive Effects ◽

Symphytum Officinale ◽

Self Pollination ◽

Nectar Robbers ◽

The Impact

Nectar robbers, which affect plant fitness (directly or indirectly) in different degrees and in different ways, potentially constitute a significant part of mutualistic relationships. While the negative effects of nectar robbing on plant reproductive success have been widely reported, the positive effects remain unknown. The target of our study was to evaluate the effects of nectar robbers on the reproductive success of Symphytum officinale (Boraginaceae). We observed the behavior, species and times of visitors in the field, and we assessed the effect of nectar robbers on corolla abscission rate and time. To test the fitness of corolla abscission, we detected the changes in stigma receptivity, pollen viability, pollen amount and appendage opening size along with the time of flower blossom. The flowering dynamics and floral structure were observed to reveal the mechanism of self-pollination. Finally, pollen deposition seed set rate and fruit set rate were determined to estimate the effect of nectar robbers on reproduction success. We observed 14 species of visitors and 2539 visits in 50 h of observation; 91.7% of them were nectar robbers. The pressure and nectar removal of nectar robbers significantly promoted corolla abscission during a period when pollen grains are viable and the stigma is receptive. In addition, corolla abscission significantly increased the pollen deposition and seed setting rate. Our results demonstrate that nectar robbing contributes to enhancing seed production and positively and indirectly impacts the reproductive success of S. officinale. This mechanism involved the movement of anthers and indirect participation by nectar robbers, which was rarely investigated. Considering the multiple consequences of nectar robbing, understanding the impact of nectar robbers on plant reproduction is essential to comprehend the evolutionary importance of relationships between plants and their visitors.

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Influence of Phenotype, Season, and Time‐of‐day on Nectar Production in Cotton 1

Crop Science ◽

10.2135/cropsci1981.0011183x002100040007x ◽

1981 ◽

Vol 21 (4) ◽

pp. 507-511 ◽

Cited By ~ 4

Author(s):

Gordon D. Waller ◽

F. D. Wilson ◽

Joseph H. Martin

Keyword(s):

Time Of Day ◽

Nectar Production

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Roles of nectar robbers in reproduction of the tropical treelet Quassia amara (Simaroubaceae)

Oecologia ◽

10.1007/bf00379850 ◽

1985 ◽

Vol 66 (2) ◽

pp. 161-167 ◽

Cited By ~ 48

Author(s):

David W. Roubik ◽

N. Michele Holbrook ◽

German V. Parra

Keyword(s):

Nectar Robbers ◽

Quassia Amara

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Linking modern pollen accumulation rates to biomass: Quantitative vegetation reconstruction in the western Klamath Mountains, NW California, USA

The Holocene ◽

10.1177/0959683620988038 ◽

2021 ◽

pp. 095968362098803

Author(s):

Clarke A Knight ◽

Mark Baskaran ◽

M Jane Bunting ◽

Marie Champagne ◽

Matthew D Potts ◽

...

Keyword(s):

Mean Squared Error ◽

Plant Biomass ◽

Source Area ◽

Pollen Deposition ◽

Accumulation Rates ◽

Klamath Mountains ◽

Plant Abundance ◽

Circular Area ◽

Value Analysis ◽

Pollen Accumulation Rates

Quantitative reconstructions of vegetation abundance from sediment-derived pollen systems provide unique insights into past ecological conditions. Recently, the use of pollen accumulation rates (PAR, grains cm−2 year−1) has shown promise as a bioproxy for plant abundance. However, successfully reconstructing region-specific vegetation dynamics using PAR requires that accurate assessments of pollen deposition processes be quantitatively linked to spatially-explicit measures of plant abundance. Our study addressed these methodological challenges. Modern PAR and vegetation data were obtained from seven lakes in the western Klamath Mountains, California. To determine how to best calibrate our PAR-biomass model, we first calculated the spatial area of vegetation where vegetation composition and patterning is recorded by changes in the pollen signal using two metrics. These metrics were an assemblage-level relevant source area of pollen (aRSAP) derived from extended R-value analysis ( sensu Sugita, 1993) and a taxon-specific relevant source area of pollen (tRSAP) derived from PAR regression ( sensu Jackson, 1990). To the best of our knowledge, aRSAP and tRSAP have not been directly compared. We found that the tRSAP estimated a smaller area for some taxa (e.g. a circular area with a 225 m radius for Pinus) than the aRSAP (a circular area with a 625 m radius). We fit linear models to relate PAR values from modern lake sediments with empirical, distance-weighted estimates of aboveground live biomass (AGLdw) for both the aRSAP and tRSAP distances. In both cases, we found that the PARs of major tree taxa – Pseudotsuga, Pinus, Notholithocarpus, and TCT (Taxodiaceae, Cupressaceae, and Taxaceae families) – were statistically significant and reasonably precise estimators of contemporary AGLdw. However, predictions weighted by the distance defined by aRSAP tended to be more precise. The relative root-mean squared error for the aRSAP biomass estimates was 9% compared to 12% for tRSAP. Our results demonstrate that calibrated PAR-biomass relationships provide a robust method to infer changes in past plant biomass.

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