Influence of plant domestication on plant-pollinator interactions: Floral attributes and floral visitor communities in wild and cultivated squash plants

Premise

Domestication of plant species results in phenotypic modifications and changes in biotic interactions. Most studies have compared antagonistic plant-herbivore interactions of domesticated plants and their wild relatives, but little attention has been given to how domestication influences plant-pollinator interactions. Floral attributes and interactions of floral visitors were compared between sister taxa of the genus Cucurbita (Cucurbitaceae), the domesticated C. moschata, C. argyrosperma ssp. argyrosperma and its wild progenitor C. argyrosperma ssp. sororia in the place of origin.

Methods

We conducted univariate and multivariate analyses to compare floral morphological traits and analyzed floral reward (nectar and pollen) quantity and quality between flowers of wild and domesticated Cucurbita taxa. Staminate and pistillate flowers of all three taxa were video recorded, and visitation and behavior of floral visitors were registered and analyzed.

Results

Most floral morphological characteristics of flowers of domesticated taxa were larger in both staminate and pistillate flowers. Staminate and pistillate flowers presented distinct correlations between floral traits and integration indices between domesticated and wild species. Additionally, pollen quantity and protein to lipid ratio were greater in domesticated species. Cucurbit pollen specialists, Eucera spp., had the highest probability of visit for all Cucurbita taxa.

Conclusions

We provide evidence that floral traits of domesticated and wild Cucurbita species experienced different selection pressures. Domesticated Cucurbita species may have more resources invested towards floral traits, thereby increasing attractiveness to pollinators and potentially plant reproductive success. Wild ancestor plant populations should be conserved in their centers of origin to preserve plant-pollinator interactions.     

The effects of predation risk from crab spiders on bee foraging behavior

Recent studies have suggested that top–down effects ofpredation on plant–pollinator interactions may not be,as previously thought, rare and/or weak. In this paper, we explorethe effects of crab spiders (Araneae: Thomisidae) on the behaviorof 2 species of bee (Hymenoptera: Apidae) foraging for nectarand pollen on 3 different plant species in central Portugal.In 2 experiments, we found that the eusocial bee Apis melliferawas significantly less likely to inspect and accept a floweror inflorescence if it harbored a spider. In contrast, we foundno such effects of spiders on the behavior of the solitary beeEucera notata. Further experiments showed that the effects ofenvironmental cues associated with predators on flower visitationby A. mellifera were detectable even when no spider was presentat the moment a flower was encountered. Such indirect effectswere only identified, however, in bees foraging on 1 of 2 plantspecies studied. In a final experiment, A. mellifera was shownto respond negatively to the presence of the corpses of conspecificsglued to flowers. This suggests that prey corpses left exposedon petals or bracts by spiders provide an obvious cue that beescan use to avoid predators. These results add to a growing bodyof evidence that plant–pollinator interactions are notimmune to the effects of predation and suggest that the strengthof such effects vary both between and within species.     

Records of bees (Hymenoptera: Apoidea) new to both Georgia and Transcaucasia revealed by DNA barcoding

Community composition of local pollinator assemblages, population dynamics and distribution patterns of many species are still poorly known, especially in little studied regions like Transcaucasia. We generated a total of 189 DNA barcodes from bees collected in 14 apple orchards in central and eastern Georgia to extend our knowledge of their distribution. Sequences (ca. 700 bp of the mitochondrial cytochrome oxidase I gene) were compared to the NCBI nucleotide database. Using a threshold of 98% similarity, analyses suggested that the sampled bees belong to 36 species of Apidae, Andrenidae, Halictidae, and Megachilidae. We report five bee species for the first time for Georgia: Andrena alfkenella Perkins, 1914, Halictus cochlearitarsis Dours, 1871, Nomada goodeniana (Kirby, 1802), Nomada ruficornis (Linnaeus, 1758) and Eucera nigrescens Pérez, 1879, four of which are also new for the Transcaucasia region. With these additions, the number of bee species known to occur in Georgia increases to 371.     

Floral and pollination biology of the critically endangered insular orchid Calanthe amamiana: Implications for in situ conservation

Calanthe amamiana is a terrestrial orchid that thrives on the shady forest floors of broad-leaved forests on Amami Island, central Ryukyus, Japan. Here, I report on the floral and pollination biology of this critically endangered orchid based on a 7-year study conducted in the species' natural habitats. As the nectarless flowers are probably self-compatible but are unable to autonomously self-pollinate, they need to attract pollen vectors by deceit for pollination. To advertise themselves, the flowering inflorescences, which comprise a few to dozens of flowers, use whitish floral colors that are comparatively conspicuous against the shaded background. The exclusive pollinator was the long-horned bee Eucera okinawae, which nests in soils of the forest floor, although bee abundance varied considerably among study years. Natural fruit-set ratios were generally low but showed interannual variation. The annual fruit-set ratios were positively correlated with annual bee abundance, thereby suggesting that under natural conditions, the orchid is pollinator-limited. Given that C. amamiana is dependent exclusively on E. okinawae for pollination and is also probably pollinator-limited, conservation plans for this orchid should take into consideration the welfare of long-horned bees. In particular, as nectariferous flowers were unavailable within broad-leaved forests, to satisfy the foraging requirements of long-horned bees, conservation managers should be cognizant of conservation values of flowering plants distributed in sun-lit sites near orchid habitats, and manage those in an appropriate manner.     

Rôle des abeilles sauvages et domestiques (Hymenoptera : Apoidea) dans la pollinisation de la fève (Vicia faba L. var. major) (Fabaceae) en région de Constantine (Algérie)

Résumé. Les insectes pollinisateurs des cultures de Vicia faba L. en région de Constantine (Algérie) ont été étudiés pendant trois périodes de floraisons (2000, 2001 et 2002). Huit espèces d’abeilles ont été inventoriées. L’abeille sauvage Eucera numida Lepeletier et l’abeille domestique Apis mellifera L. en sont les butineurs les plus abondants. Eucera numida est probablement le pollinisateur le plus efficace car toutes ses visites peuvent être pollinisantes. A l’inverse, un tiers des visites de l’abeille domestique sont consacrées au “vol de nectar” à travers des trous faits par les bourdons à la base des corolles. Ces visites sont non pollinisantes. Les visites d’ Eucera numida sont également plus rapides (m = 10 visites par minute) et son aptitude à déclencher les fleurs de fève est plus grande que celle de l’abeille domestique. Les plants accessibles aux pollinisateurs produisent plus de gousses, les gousses contiennent plus de graines et les graines sont plus grosses et mieux formées que sur les plants encagés.