How and why do bees buzz? Implications for buzz pollination

Buzz pollination encompasses the evolutionary convergence of specialised floral morphologies and pollinator behaviour in which bees use vibrations (floral buzzes) to remove pollen. Floral buzzes are one of several types of vibrations produced by bees using their thoracic muscles. Here I review how bees can produce these different types of vibrations and discuss the implications of this mechanistic understanding for buzz pollination. I propose that bee buzzes can be categorised according to their mode of production and deployment into: (1) thermogenic, which generate heat with little mechanical vibration; (2) flight buzzes, which combined with wing deployment and thoracic vibration, power flight, and (3) non-flight buzzes in which the thorax vibrates but the wings remain folded, and include floral, defence, mating, communication, and nest-building buzzes. I hypothesise that the characteristics of non-flight buzzes, including floral buzzes, can be modulated by bees via modification of the biomechanical properties of the thorax through activity of auxiliary muscles, changing the rate of activation of the indirect flight muscles, and modifying flower handling behaviours. Thus, bees should be able to fine-tune mechanical properties of their floral vibrations, including frequency and amplitude, depending on flower characteristics and pollen availability to optimise energy use and pollen collection.

Moths sense, but do not learn flower odors with their proboscis during flower investigation

Insect pollinators, like the tobacco hawkmoth Manduca sexta, are known for locating flowers and learning floral odors by using their antennae. A recent study revealed, however, that the tobacco hawkmoth additionally possesses olfactory sensilla at the tip of its proboscis. Here, we ask whether this second “nose” of the hawkmoth is similarly involved in odor learning as are the antennae. We first show that Manduca foraging efficiency at Nicotiana attenuata flowers increases with experience. This raises the question whether olfactory learning with the proboscis is playing a role during flower handling. By rewarding the moths at an artificial flower, we show that – while moths learn an odor easily when they perceive it with their antennae – experiencing the odor just with the proboscis is not sufficient for odor learning. Furthermore, experiencing the odor with the antennae during training does not affect the behavior of the moths when they later can detect the learned odor with the proboscis only. Therefore, there seems to be no cross-talk between antennae and proboscis and information learnt by the antennae cannot be retrieved by the proboscis.

Efisiensi Penyerbukan oleh Penyerbuk Liar dan Lebah Tetragonula laeviceps pada Bunga Ranti dan Kacang Panjang

Penyerbukan serangga merupakan salah satu upaya peningkatan efisiensi produksi tanaman berbuah pada lahan terbatas. Penelitian bertujuan mengamati aktivitas dan efisiensi penyerbukan serangga liar dan Tetragonula laeviceps pada tanaman ranti dan kacang panjang dengan sistem tanam tumpang sari di Desa Sukawangi, Kabupaten Sumedang pada bulan September hingga Januari 2020. Pengamatan dilakukan pada pukul 08:00-15:00 WIB selama periode perbungaan. Pengamatan dilakukan pada perlakuan aplikasi T. laeviceps, open-pollination, dan self-pollination, masing-masing perlakuan terdiri atas 100 bunga ranti dan 100 bunga kacang panjang dan dianalisis menggunakan one way analysis of variance (α = 0.05). Aktivitas serangga diukur berdasarkan flower handling time, foraging rate, visitation rate, dan fruit set. Kualitas buah diukur berdasarkan diameter, bobot, panjang, dan oBrix. Hasil penelitian ditemukan masing-masing tiga serangga pengunjung berpotensi polinator pada ranti dan kacang panjang dengan pola kunjungan bervariasi pada open-pollination. Efisiensi fruit set tertinggi ranti terjadi pada perlakuan aplikasi T. laeviceps dan kacang panjang pada perlakuan open-pollination. Terdapat perbedaan nyata pada oBrix buah ranti dan kacang panjang, sedangkan self-pollination hanya menghasilkan buah yang secara signifikan lebih panjang pada kacang panjang. Dengan demikian, T. laeviceps dapat dijadikan salah satu alternatif serangga penyerbuk terdomestikasi dalam upaya efisiensi fruit set dan kualitas buah tanaman ranti dan kacang panjang. Kata kunci: aktivitas serangga, fruit set, kualitas buah

Inbreeding and competition, but not abiotic stresses, increase fluctuating asymmetry of Mimulus guttatus flowers

Genetic and environmental disturbances are expected to increase developmental instability, which may result in higher fluctuating asymmetry (FA), i.e. small random deviations from symmetry. Plant leaves often do not show this pattern, possibly due to high phenotypic plasticity of leaf shape and low adaptive significance of leaf symmetry. In contrast, symmetry in many animal traits but also in flower shape is considered to be under selection, and FA in such traits may better reflect developmental instability. Using geometric morphometrics, I analysed the symmetry of flowers of inbred and outbred Mimulus guttatus (Phrymaceae) plants grown under five stress treatments with and without grass competition. Flower FA was not increased by abiotic stress, but by inbreeding and competition. As inbreeding and competition affected different principal components of flower FA, different mechanisms may be involved in their effects on FA. FA decreased with individual biomass particularly in selfed offspring, which suggests that inbreeding increased FA particularly when growth was limited by environmental or genetic constraints. Increased flower FA of inbred offspring may explain increased flower handling time and reduced pollinator preference for inbred plants in other M. guttatus studies, and could thus have important consequences for plant demography and plant–pollinator interactions.

Floral temperature patterns can function as floral guides

Floral guides are signal patterns that lead pollinators to floral rewards after they have located the flower, and increase foraging efficiency and pollen transfer. Patterns of several floral signalling modalities, particularly colour patterns, have been identified as being able to function as floral guides. Floral temperature frequently shows patterns that can be used by bumblebees for locating and recognising the flower, but whether these temperature patterns can function as a floral guide has not been explored. Furthermore, how combined patterns (using multiple signalling modalities) affect floral guide function has only been investigated in a few modality combinations. We assessed how artificial flowers induce behaviours in bumblebees when rewards are indicated by unimodal temperature patterns, unimodal colour patterns or multimodal combinations of these. Bees visiting flowers with unimodal temperature patterns showed an increased probability of finding rewards and increased learning of reward location, compared to bees visiting flowers without patterns. However, flowers with contrasting unimodal colour patterns showed further guide-related behavioural changes in addition to these, such as reduced reward search times and attraction to the rewarding feeder without learning. This shows that temperature patterns alone can function as a floral guide, but with reduced efficiency. When temperature patterns were added to colour patterns, bees showed similar improvements in learning reward location and reducing their number of failed visits in addition to the responses seen to colour patterns. This demonstrates that temperature pattern guides can have beneficial effects on flower handling both when alone or alongside colour patterns.

The cost of fidelity: foraging oligolectic bees gather huge amounts of pollen in a highly specialized cactus–pollinator association

Plant–pollinator interactions vary along a specialization–generalization continuum. Advances in understanding the evolutionary and ecological consequences of different degrees of specialization depend on precise data on plant–pollinator interdependency. We studied the association of Parodia neohorstii (Cactaceae) and its bee pollinators focusing on pollinator foraging behaviour, flower functioning, female and male reproductive success, and pollen fate. Parodia neohorstii showed synchronized flower opening and pollen presentation but discontinuous blooming. The apparently generalized flowers partition pollen through thigmonastic stamen movements that function as a mechanical filter against generalist bees by restricting access to the major pollen reservoir to bees that show flower handling ‘know-how’, thereby favouring the oligolectic bee Arhysosage cactorum. This pollinator adjusted its pollen foraging to flower opening, removed pollen hurriedly, and promoted maximal fruit and seed set, which was minimal in its absence. Estimates of pollen fate revealed that a huge amount of pollen flows to specialized pollinators (86.5%), and only 0.9% reaches conspecific stigmas. The specialized interaction between P. neohorstii and Arhysosage cactorum, both threatened species, is efficient but fragile. Any environmental modification that causes a mismatch between the partners is likely to result in reproductive failure.

Peranan Lebah Trigona laeviceps (Hymenoptera: Apidae) dalam Produksi Biji Kailan (Brassica oleracea var. alboglabra)

Kale (Brassica oleraceae) has small and compound floral-type and usually visited by bees, including Trigona laeviceps (Apidae: Melliponini) as pollinator which can increase fruit and seed production of many species of agricultural crops. Aims of the research were to study foraging activity and the role of T. laeviceps in seed production of kale. Three treatments were used i.e., caged crop with one colonies of T. laeviceps, open crop with one colonies of T. laeviceps and caged crop without bee. Foraging activities of T. laeviceps were observed during the flowering by using a focal sampling method and visual method. Measuring the amount of pollen was done by using glycerol and alcohol (70%) with a ratio 4:1 and pollen viability was observed in Brewbaker and Kwack solutions. Result showed that flower handling time of T. laeviceps was highest during 09.00-10.00 (36.3 seconds/flower) with foraging rate was 8.26 flowers per 5 minutes. Flower handling time was lowest during 15.00-16.00 (10.6 seconds/flower) with foraging rate was 28.6 flowers per 5 minutes. Pollen load of T. laeviceps in the caged crop (8125 grain) was higher than in open crop (3000 grain). Viability of the pollen in the caged crop (80.8%) was higher than that of open crop (31.4%). Pollination by T. laeviceps increased 141% number of pods per plant, 48% number of seeds per pod, 204% of seed weight per plant, and 177% of seed germination. <br /><br />Keywords: foraging activity, pollination, fruit set, pollen viability<br /><br />