DOI: 10.5061/dryad.th441
title: Data from: Reproduction in flame azalea (Rhododendron calendulaceum, Ericaceae): a rare case of insect wing pollination

description: Although many angiosperms are serviced by flying pollinators, reports of
 wings as pollen vectors are rare. Flame azalea (Rhododendron
 calendulaceum) is visited by diverse insects, yet previous observations
 suggested that only butterfly wings may transfer pollen to stigmas. We
 used an experimental approach to determine whether butterfly wings are the
 primary vehicle of pollination in flame azalea. Over two seasons of
 observations, only butterflies (Papilio glaucus and Speyeria cybele)
 contacted both anthers and stigmas, yet because of differences in
 wing-flapping behavior, P. glaucus transferred pollen most efficiently. In
 contrast, bee species specialized either on pollen or nectar but did not
 contact both anthers and stigmas. A field experiment revealed that flowers
 excluding butterflies experienced almost complete fruit failure, whereas
 fruit set in open flowers did not differ from those that were hand
 pollinated. Additionally, butterflies had 56-fold more azalea pollen on
 their wings than bodies, while azalea stigmas bore both pollen and wing
 scales. These results suggest that plants with many visitors contacting
 reproductive organs may still specialize on a single guild of visitors for
 pollination and that wing-borne pollen transfer is a key mode of flame
 azalea pollination.
description: Butterfly pollen
 loadsPollen carried on wings
 and bodies of butterflies collected in the field near R. calendulaceum
 plants in June of 2011 and 2014 (data in separate tabs). Individual pollen
 grains counted for 2011 butterflies and half of 2014 butterflies before
 switching to categorical ranges for 2014 butterflies (data for both ranges
 and counts shown here, in separate tabs).Butterfly pollen load
 data.xlsx2011 wings v body
 dataData from observations
 of _Papilio glaucus_ butterflies foraging on _Rhododendron calendulaceum_
 flowers in the field. Showing contact between butterfly wings and an
 anther & stigma versus contact between butterfly's body and an
 anther & stigma. Observed contact = 1, absence of contact = 0. Note
 that these data should not be used to draw any conclusions about which
 visits had BOTH wings and bodies contact anthers and stigmas. Data
 collected June 2011.Flower visitor
 observationsObservations of flower
 visitors on _Rhododendron calendulaceum_ and flower parts contacted; taken
 June 2014.Papilio glaucus v.
 Speyeria cybele on flame azaleaField observations of
 contact between a butterfly and anthers versus stigmas during visits to
 _Rhododendron calendulaceum_ flowers by the butterflies _Papilio glaucus_
 and _Speyeria cybele_. Contact with flower part during a flower visit = 1,
 absence of contact with a flower part = 0.Pollen & wing scale
 load on stigmas from naturally visited flowersAfter observing a visit
 by a butterfly in the field, stigmas from R. calendulaceum flowers were
 clipped and attached to a microscope slide in the field. Data show
 presence/absence (=Y/N) of pollen and butterfly wing scales on stigmas as
 scored after examining stigmas under the microscope.Pollen & Scale load on
 stigmas from naturally visited
 flowers.xlsxPollinator exclusion
 experiment dataData from experimental
 exclusion of flower visitors to _Rhododendron calendulaceum_. Treatments
 applied 6/12/14 - 6/13/14 and fruit set scored 8/4/14-8/7/14. Treatments
 defined as follows: A = flowers open to all visitors; B = mesh + cage (all
 visitors excluded); C = cage (only large visitors, e.g. big butterflies,
 excluded); D = maximum fruit set (unopened flwrs covered with ziplock
 until open, then pollinated by hand with outcrossed
 pollen).Stigma load from single
 butterfly visits on emasculated flowers_Rhododendron
 calendulaceum_ twigs bearing budding inflorescences were cut in the field
 and kept in water in the lab. Flowers were emasculated upon anthesis, and
 emasculated inflorescences were attached to the end of a pole and
 presented to foraging _Papilio glaucus_ butterflies near flowering _R.
 calendulaceum_ plants in the field. Stigmas of emasculated flowers were
 removed and attached to a microscope slide in the field following a visit,
 and scored for the presence/absence (=Y/N) of pollen grains and butterfly
 wing scales upon inspection under the microscope.