Floral morphology and pollination in Gastrodia elata,a mycoheterotrophic orchid

Pollination biology in Gastrodia elata was investigated on Rebun Island, Japan. The flowers have an urceolate perianth chamber whose opening is constricted by the column and labellum. This structure plays a crucial role in the selection of small‐bodied bees from flower visitors of various body sizes. In addition, the furrow on the ventral side of the column possibly contributes to the admission of sweat bee pollinators, whose thoracic widths match the width of the furrow. Sweat bees receive the pollinarium on their thorax while escaping head first from the chamber. No pollinator rewards, such as previously reported harvestable spongy tissue, are likely to be produced by the orchid. The flowers, however, have a glossy area reminiscent of nectar secreted into the chamber that likely acts as a deceptive signal for pollinators. Fruit‐set ratios were found to vary spatiotemporally; the values were higher under bright light conditions, probably reflecting the presence of sweat bees for sunny places.     

Happy to breed in the city? Urban food resources limit reproductive output in Western Jackdaws

Urban areas expand worldwide, transforming landscapes and creating new challenging habitats. Some bird species, mainly omnivorous feeding on human waste and cavity nesters, commonly breed in these habitats and are, therefore, regarded as urban‐adapted. Although urban areas may provide new nesting sites and abundant human waste, the low breeding success found in some of these species suggests that the poor protein content in human waste might limit breeding parameters. We investigated whether the breeding success of a cavity nester and omnivorous species commonly breeding in urban areas, the Western Jackdaw (Corvus monedula), depended on the availability of good‐quality non‐urban food. We approached the objective by combining a literature review and experiments in the field. With the literature review, we compared jackdaw populations in different habitats across Europe and found that clutch size and number of fledglings per pair decreased with distance to non‐urban foraging grounds, even after controlling for the effect of colony size, latitude, and climate. In two experiments, we tested whether the breeding success of urban pairs could be increased by supplementing high‐quality food, first only during egg formation and second also until chick fledging. Food supplementation during egg formation led to larger eggs and higher hatching success than in urban control nests, but this did not result in higher chick survival. However, when food supplementation was prolonged until fledging in the second experiment, we observed a significant increase of nestling survival. These findings highlight that research and management actions should not only focus on species displaced by urbanization, but also on “urban‐adapted” species, as they might be suffering from a mismatch between availability of nesting sites in buildings and adequate non‐urban food resources. In these cases, nest sites should be provided in or close to adequate food resources.     

Does acoustic priming ‘sweeten the pot’ of floral nectar?

A recent claim that evening primrose flowers adaptively secrete nectar in response to vibrations from hovering bees lacks supporting evidence. The authors fail to demonstrate that bees can access the concealed nectar and that their visits enhance plant fitness. Reanalysis of the authors’ data raises additional concerns about their conclusions.