Pollination Efficiency of <i>Ceratina cyanea</i>(Hymenoptera: Apidae) on <i>Helianthus annuus</i>(Asteraceae) Flowers at Dang (Ngaoundere, Cameroon)

To evaluate the impact of Ceratina cyanea on fruit and seed yields of sunflower, experimental field was set up from June to July in 2016 and 2017 at Dang. Observations were done on 540 capitula divided in four treatments: two treatments differentiated according to the presence or absence of protection on capitula regarding Ceratina cyanea and other flowering insects’ visits;the third with capitula protected and uncovered when florets were opened, to allow C. cyanea visits and flowers bagged uncovered and rebagged without the visit of insects or any other organisms. Bee’s daily rhythm of activity, its foraging behavior on florets and its pollination efficiency were evaluated. Bee’s daily rhythm of activity, its foraging behavior on flowers and its pollination efficiency were evaluated. Results show that, C. cyanea foraged on Helianthus annuus flowers throughout its whole blooming period. Among 32 insect species recorded on H. annuus capitula, C. cyanea ranked second accounting for 10.79% all visits, after Apis mellifera (76.06%). On florets, individual bees intensely harvested nectar and slightly collected pollen. The mean duration of a visit per floret was 3.62 sec for nectar harvest and 9.58 sec for pollen collection. For the two years, through its pollination efficiency on H. annuus, C. cyanea has increased the fruiting rate by 65.90%, the percentage of fruit with seed by 63.56% and the percentage of normal seeds by 76.11%. Based on these results, we recommend the protection of C. cyanea nests at the vicinity of sunflower fields to increase its fruit and seed yields in the Adamaoua Region of Cameroon.

Pollination Efficiency of <i>Amegilla calens</i>(Hymenoptera: Apidae) on <i>Gossypium hirsutum</i>L. (Malvaceae) Variety L457 Flowers at Meskine (Maroua, Cameroon)

Animal pollination is a key of reproduction of more plants species including Gossypium hirsutum. This Malvaceae is the best cultivated oilseed plant in tropical and subtropical regions in the world. This research evaluates the interaction between Amegilla calens and Gossypium hirsutum from 2018 to 2019 based on the activities of the solitary bee on the flowers of this plant and their productive impact in field. The experiment was focused on four repeated treatments during the flowering phase: the first two were characterised by the existence or absence of protection of the flowers regarding all insects and the other two made up of flowers designed for the exclusive visit of A. calens or open then protected again without a visit from an insect or any other organism. Daily rhythm of activity, behavioural ecology, the pollination efficiency, the fruiting rate, the number of seeds per capsule and the percentage of normal seeds were evaluated. Among twenty insects species recorded A. calens is the most abundant with 30.72% of 655 visits and the most efficient pollinator. Amegilla calens is active on G. hirsutum flowers from 6 a.m. to 5 p.m. with a maximum activity situated from 8 a.m. to 9 a.m. All visits of this solitary bee are able to fertilize the flowers of Malvaceae. The mean duration of a visit per flower for pollen harvest is also more important (23.57 ± 0.96 sec) than nectar collection (13.69 ± 0.72 sec). For the two years, through its pollination efficiency, A. calens increased the fruiting rate by 20.30%, as well as the percentage of normal seeds by 32.39%. Therefore, we concluded that A. calens is the important pollinator and increases the fecundity and number of normal seeds of G. hirsutum.

Impact of <i>Amegilla calens</i>and <i>Apis mellifera</i>Pollination on <i>Gossypium hirsutum</i>var. QR₁302 Flowers at Tchabbal-Mounguel (Ngaoundéré, Cameroon)

The investigations were carried out from September 10 through October 13, 2017 at Tchabbal-Mounguel. On Gossypium hirsutum flowers, investigations were done on many aspects of the pollination services of Amegilla calens and Apis mellifera. G. hirsutum flowers were observed to study the activity of A. calens and A. mellifera and to evaluate their impacts on fruits and seed yields of this Malvaceae. The treatments consisted of 120 flowers left for free pollination, 120 flowers protected from insects using gauze bag nets, 200 protected flowers and visited exclusively by A. calens and A. mellifera and 100 protected flowers then opened and closed without any visit of insects or any other organisms. The results show that on cotton flowers, foragers of A. calens and A. mellifera highly collect nectar and pollen on its flowers. The highest mean number of individuals simultaneously active per 1000 flowers is 587 for A. calens and 526 for A. mellifera. Through their pollinating efficiency, A. calens and A. mellifera caused a significant increase in the fruiting rate by 7.00% and 17.33%, the number of seeds per fruit by 44.20% and 18.32% and the normal seeds by 47.78% and 5.66% respectively. Therefore, the conservation of the nests of A. calens and colonies of A. mellifera around G. hirsutum plantations are to be recommended to improve the fruit and seed yields of this Malvaceae.

Effects of distinct pollinators on the mating system and reproductive success in Incarvillea sinensis,an annual with large floral displays

Aims Most flowering plants engage in mutualisms with animals to move pollen between individuals,and it is expected that pollinators play an essential role in the evolution of selfing,yet few studies have deter-mined how distinct pollinator types affect a plant’s mating system and reproductive success differentially.We investigated the effect of two different pollinators on the reproductive success of Incarvillea sinensis,an annual with showy,insect-pollinated,one-day flowers.Methods We marked flowers after a single visit from both pollinator species(Bombus patagiatus and Amegilla quadrifasciata)and calculated the number of pollen grains deposited on the stigma and pollen left in the anthers,the fruit and seed set,the outcrossing rate and the cor-relations of paternity.Important Findings There was no significant difference in the number of pollen grains deposited on the stigma,or in the seed and fruit set between the two pollinators in both years.The mean number of pollen grains removed by B.patagiatus was significantly higher than that removed by A.quadrifasciata.The outcrossing rate of flowers pollinated by B.patagiatus was significantly higher than that of flowers pollinated by A.quadrifasciata.The correlation of paternity of flowers pollinated by B.patagiatus was significantly lower than that of flowers polli-nated by A.quadrifasciata.For I.sinensis,B.patagiatus may exhibit larger pollen wastage,thus reducing the male reproductive success of the plant,but it causes higher female reproductive success because of its higher outcrossing rate and the lower correlation of paternity.Our findings highlighted that different animal pollinators could indeed cause differential mating systems and reproductive success.

Weak correlation of flower color and nectar-tube depth in temperate grasslands

Aims Nectar is one of the most common floral rewards offered to pol-linators by plants.Depending on the plant species,nectar is offered openly or in tubes of various lengths restricting accessibility of this resource for flower visitors with short mouthparts.if attract-ing pollinators that match floral morphology increases pollination efficiency,flowers could profit from signaling nectar-tube depth to pollinators.Since flower colors are important signals in plant-pol-linator communication,we investigated whether and which differ-ent chromatic or achromatic aspects of flower color might indicate nectar-tube depth or whether flower colors facilitate the differen-tiation between flowers with long nectar tubes by means of high chromatic uniqueness.Methods To this end,we collected flower reflectance spectra of 135 grassland plant species.We analyzed flower colors as raw reflectance spectra in principal component analysis(PCA)and in the color space of honeybees.Important Findings The correlation between flower colors and tube depths was weak.From the bee’s point of view,blue flowers had on average deeper tubes than green,blue-green and UV-green flowers potentially allow-ing insects to predict tube depths based on blue color.Spectral purity did not correlate with nectar-tube depth,nor did the chromatic uniqueness of flower colors in the honeybee color space.Dominant wavelength showed a significant but very weak correlation with tube depth.The achromatic green contrast decreased with increasing tube depth as did brightness;thus deep tubes were less conspicuous than shallow tubes.Chromatic components resulting from PCA did not or only slightly correlate with tube depth.Our results illustrate that flower colors may have a certain potential to indicate tube depth,i.e.nectar accessibility,from a bee’s perspective.