The many elusive pollinators in the genus Amorphophallus

The genus Amorphophallus encompasses some 230 species and is one of the largest genera of the Araceae family. Most species release scents, smelling of carrion, faeces, dung and similar nauseating odours for pollinator attraction and are therefore considered to have evolved a deceptive pollination syndrome. Some of the most iconic members of the genus, such as the A. titanum and A. gigas, are considered to be carrion mimics. Copro-necrophagous insects, beetles and flies in particular, are attracted by these scents and are therefore assumed to act as pollinators. However, many reports and observations on Amorphophallus pollinators are anecdotal in nature or do not distinguish between legitimate pollinators and non-pollinating visitors. Moreover, some published observations are not readily accessible as they are many decades old. Therefore, the available data and information about insect visitors and/or pollinators in the genus Amorphophallus is compiled, reviewed and discussed.

Nectar Production and Spectrum of Insect Visitors in Six Varieties of Highbush Blueberry (Vaccinium corymbosum L.) in SE Poland

The attractiveness of plants to pollinators depends strongly on flower rewards, especially nectar and pollen. Nectar mass, sugar concentration, and sugar mass are known to influence the spectrum and abundance of insect visitors. Respective data on nectar secretion in highbush blueberry ( Vaccinium corymbosum ) under the climatic conditions of Poland are scarce. This study was conducted in 2002–2005 to assess flower abundance, nectar production, and insect visitors in six varieties of V. corymbosum in Niemce, SE Poland. Flower abundance ranged from 1.63 ± 0.64 (‘Darrow’) to 4.07 ± 0.95 in thousands of flowers per shrub (‘Northland’). Nectar mass, sugar concentration, and nectar sugar mass increased with flower age, peaking between the sixth and ninth day. Significant differences in nectar characteristics occurred between years and between varieties. ‘Bluecrop’ and ‘Darrow’ produced the largest nectar mass (19.08 ± 7.09 and 16.60 ± 8.31 mg nectar per flower, respectively) and nectar sugar mass per flower (6.39 ± 1.52 and 5.76 ± 1.51 mg sugar per flower, respectively). The estimated sugar yield in the studied V. corymbosum varieties ranged from 9.4 ± 3.3 to 20.7 ± 3.8 g sugar per shrub (‘Croatan’ and ‘Bluecrop,’ respectively). Regarding insect visitors, only honey bees and bumble bees were observed. Honey bees comprised 81%–98% of the total number of observed insect visitors. Highbush blueberry, due to abundant blooming and high per-flower sugar yield, is thus a good source of nectar sugars for honey bees.

Comparison of floral traits in Calibrachoa cultivars and assessment of their impacts on attractiveness to flower-visiting insects

Ornamental plants are appreciated by humans for their colorfulness, beauty, abundant flowering and long blooming periods. Many ornamental plants can also constitute an additional foraging resource for flower-visiting insects. However, the ability of the popular ornamental plant Calibrachoa to support urban insect communities is not well documented. In this study, 20 different Calibrachoa cultivars were selected and tested in regard to their insect friendliness based on standardized observations (I) in flight tents using the large earth bumble bee Bombus terrestris as a model species and (II) in open field trials. To investigate what floral characteristics might constitute attractiveness to bumble bees, various floral traits were recorded and compared across all tested Calibrachoa cultivars. Over a two-year period, a total of 6,327 foraging bumble bees were recorded in the tent observations. In the open field observations, we counted 4,188 flower-visiting insects. Our results revealed that (I) all Calibrachoa cultivars were visited by insects for foraging, (II) the number of insect visitors varied significantly among the 20 tested cultivars and (III) the cultivars displayed different floral traits. For the morphometric floral traits and the aroma profiles of Calibrachoa, only the mean nectar quantity and a few identified compounds could be correlated with attractiveness to the model species B. terrestris. We also found that the petal color of the tested cultivars had a significant impact on the number of visitors. Therefore, B. terrestris clearly preferred red or blue Calibrachoa cultivars over those with other petal colors. However, as the cultivar preferences in the different insect groups differed, it is highly recommended to use various cultivars in urban plantings. Nevertheless, efforts must be made to explain what additional floral traits make Calibrachoa and other ornamental plants generally attractive to flower visitors. This information can then be used for breeding purposes to increase the insect friendliness of ornamental plants.

Opsin Evolution in Flower-Visiting Beetles

Flowers have evolved signals that exploit the sensory systems of insect visitors. In the case of visual cues, color signals are thought to have been shaped in large part by the spectral sensitivity of key pollinators, such as hymenopterans. Beetles were some of the first plant pollinators, pre-dating the angiosperm radiation but with the exception of a few well-studied species, the evolution of flower-visiting beetle visual systems is poorly understood. Thus, the ability of beetles to detect and distinguish flower color signals and perhaps their potential role in shaping flower coloration is not well understood. Traditional models of pollinator visual systems often assume a putative tri- or tetrachromatic flower-visitor, as is found in bees, flies and butterflies. Beetles are unique among modern pollinators as ancestrally they did not possess the machinery for trichromatic vision, lacking the blue-sensitive photoreceptor class. Research on the evolution of visual genes responsible for wavelength sensitivity (opsins) has revealed that beetles with putative tri- and tetrachromatic visual systems have evolved independently, along multiple lineages. We explore the evolution of beetle visual genes using newly generated and publicly available RNA-seq data from 25 species with flower associations, including previously unexplored key flower-visitor groups and 20 non-flower visiting relatives. Our findings serve as a resource to inform and guide future studies on beetle-flower interactions, where insight from both signal and receiver is needed to better understand these poorly explored systems.

Pollination Studies on Both Floret and Capitulum Levels in an Oil Seed Crop,Guizotia abyssinica(L.f.) Cass.

Niger,Guizotia abyssinica(L.f.), is an important oilseed crop widely grown in Ethiopia and India, but poor pollination is one of the major constraints in achieving the yield potential of the crop. Our aim was to understand better the pollination biology and role of flower insect visitors in reproduction success. Results indicated that full anthesis occured in the morning between 06.00 and 08.00 h and pollen dehiscence eight to eleven hours after anthesis. Stigma receptivity commenced nine hours after anthesis and lasted for the next 24 h. A total of eighteen insect species representing six families visited Niger flowers, and among these,Apis floreaandA. ceranawere dominant. The flowers were self-incompatible as there was no seed set upon the selfing of floret and selfing of capitulum. The maximum seed set (78.33±0.14%) was noticed when flowers were allowed for open pollination and the lowest was recorded when the whole plant was caged to exclude pollinator visits (0.33±0.67). The time spent byA. ceranaandA. floreawas 1.35±0.48 and 1.83±0.12 seconds per floret, respectively and 9.63±0.69 and 14.9±0.94 seconds per capitulum, respectively.A. ceranaandA. floreawere found to be more efficient pollinators ofG. abyssinica.Introducing bee colonies might greatly improve the yield, and it is also important to conserve bees in the vicinity ofG. abissynicafields during the flowering period. Hence, introducing bee colonies might greatly improve the yield of Niger.

New records of pollinators and other insects associated with Arizona milkweed, Asclepias angustifolia, at four sites in Southeastern Arizona

Asclepias angustifolia is a Mexican milkweed that barely enters the U.S.A. Its pollinators and other insect visitors have not been investigated. During 2018 and 2019, insect visitors were photographed at a native population and three gardens in and near the Huachuca Mountains, Southeastern Arizona. A total of 216 site visits produced at least 369 species of insects in seven orders. Images revealed 140 potential pollinators with a preponderance of Hymenoptera, Lepidoptera, and Diptera. Orders of insects are discussed, as are flowering phenology, potential pollinators in functional groups, introduced insects, and the value of A. angustifolia for monarch butterflies and other insects in pollinator gardens and in planting palettes created for restoration sites. NOTE: Supplementary files can be found in the left menu.

Inflorescence morphology and development of suweg (Amorphophallus paeoniifolius (Dennst.) Nicolson

Hanfayani T, Yuzammi, Hadiah JT. 2020. Inflorescence morphology and development of suweg (Amorphophallus paeoniifolius (Dennst.) Nicolson. Biodiversitas 21: 5835-5844. Inflorescence of Amorphophallus paeoniifolius (Dennst.) Nicolson consists of two main parts: spathe and spadix. Detailed information on its development, however, is not yet available. This study aimed to investigate the development and morphology of suweg’s inflorescence, to reveal the anthesis of male and female flowers, and to observe its insect visitors. The study observed 46 inflorescences, ten of which were measured for detailed developments. Inflorescences were observed from bud emergence to withering during one flowering cycle. The results showed that the flowering process included six phases which altogether required 22 to 36 days, namely the developments of inflorescence bud, cataphyll, spathe and spadix, appendix, fully bloomed inflorescence, and flowers anthesis. The inflorescence height including peduncle was 48–75 cm, spathe 19–50 cm long, spathe circle 65–176 cm, appendix 13–33 cm long, and appendix circle 45–80 cm. Three appendix forms were observed: ovate (43.48%), triangular conic (41.30%), and rounded (15.22%). Female flower anthesis occurred one day prior to male flower anthesis. Insect visitors found during anthesis were Lucilia sericata (Calliphoridae), Sarcophaga sp. (Sarcophagidae), and Trigona speciosa (Apidae).