DOI: 10.5061/dryad.8cz8w9gmp
title: Darwin’s vexing contrivance: A new hypothesis for why some flowers have two kinds of anther

description: Heteranthery, the presence of two or more anther types in the same flower,
 is taxonomically widespread among bee-pollinated angiosperms, yet has
 puzzled botanists since Darwin. We test two competing hypotheses for its
 evolution: the longstanding “division of labour” hypothesis, which posits
 that some anthers are specialized as food rewards for bees whereas other
 are specialized for surreptitious pollination, and our new hypothesis that
 heteranthery is a way to gradually release pollen that maximizes pollen
 delivery. We examine the evolution of heteranthery and associated traits
 across the genus Clarkia (Onagraceae) and study plant-pollinator
 interactions in two heterantherous Clarkia species. Across species,
 heteranthery is associated with bee pollination, delayed dehiscence and
 colour crypsis of one anther whorl, and movement of that anther whorl upon
 dehiscence. Our mechanistic studies in heterantherous species show that
 bees notice, forage on, and export pollen from each anther whorl when it
 is dehiscing, and that heteranthery promotes pollen export. We find no
 support for division of labour, but multifarious evidence that
 heteranthery is a mechanism for gradual pollen presentation that likely
 evolved through indirect male-male competition for siring success.
description: File name
 BombusTrials2018.R contains the scripts to analyze pollen export
 data from dosing v. no dosing C. unguiculata flowers exposed to Bombus
 impatiens in the greenhouse. 
 ClarkiaPhyloHeteranthery.R contains the analysis scripts for
 comparative phylogenetic analyses of heteranthery in Clarkia, including
 ancestral reconstructions of characters, correlated evolution of
 heteranthery and pollination, correlated evolution of heteranthery and
 anther movement, differences in anther timing separation between
 heterantherous and non-heterantherous species, and comparisons of colors
 of flower parts Color.R contains the scripts that take
 raw reflectance data from flower parts and interpret it in bee vision
 models. cylindrica.R contains the analysis script for
 analyzing pollen fates from inner v outer anthers in Clarkia
 cylindrica. FieldManipulationsCung.R contains the
 scripts for analyzing visitation data to Clarkia unguiculata flowers with
 phenotypic manipulations. BombusColorPosition.csv
 contains a summary of the visitation data for captive bumblebees exposed
 to manipulated C. unguiculata flowers. R = filaments painted red, Y =
 filaments painted yellow, I = anthers drawn together in an erect position,
 O = anthers left reflexed
 BombusColorPosition1stVisit.csv contains the visitation data for
 captive bumblebees exposed to manipulated C. unguiculata flowers. R =
 filaments painted red, Y = filaments painted yellow, I = anthers drawn
 together in an erect position, O = anthers left reflexed, N = nectaring
 behavior, P = pollen-collecting behavior
 BombusTrials2018.csv is the data of pollen exported to stigmas
 and collected by bees from dosing v. no dosing C. unguiculata flowers
 exposed to Bombus impatiens in the greenhouse. It is the input file for
 BombusTrials2018.R. CLABIL.csv is the reflectance data
 from various flower parts of Clarkia biloba. It is reported as percent
 reflectance by wavelength. CLACYL.csv is the
 reflectance data from various flower parts of Clarkia cylindrica. It is
 reported as percent reflectance by wavelength.
 CLADUD.csv is the reflectance data from various flower parts of
 Clarkia dudleyana. It is reported as percent reflectance by
 wavelength. CLALIN.csv is the reflectance data from
 various flower parts of Clarkia lingulata. It is reported as percent
 reflectance by wavelength.
 Clarkia_Phenotype_Heteranthery.csv contains phenotype data for
 phylogenetic comparative analyses and is called by
 ClarkiaPhyloHeteranthery.R. ClarkiaITS.nex is the tree
 file (posterior distribution) from the Clarkia phylogenetic analysis
 published in supplement of Briscoe Runquist R, Grossenbacher D, Porter S,
 Kay K, Smith J. 2016. Pollinator-mediated assemblage processes in
 California wildflowers. Journal of Evolutionary Biology 29(5):1045-58.
 doi: 10.1111/jeb.12845 CLAUNG.csv is the reflectance
 data from various flower parts of Clarkia unguiculata. It is reported as
 percent reflectance by wavelength. CLAXAN.csv is the
 reflectance data from various flower parts of Clarkia xantiana. It is
 reported as percent reflectance by wavelength.
 CungManipulative.csv is the input file for
 FieldManipulationsCung.R and contains the visitation data for C.
 unguiculata flowers. CungSeeds.csv contains the seed
 set data (viable seeds) and proportion of ovules fertilized (viable seeds
 out of the total ovules observed) for the Clarkia unguiculata flowers
 included in the field flower manipulations.
 D65_Poppy_paper.txt is illuminance data from van der Kooi CJ,
 Elzenga JTM, Staal M, Stavenga DG. 2016. How to colour a flower: on the
 optical principles of flower coloration. Proceedings of the Royal Society
 B: Biological Sciences 283: 20160429. Green
 Contrasts_All.csv is the output file from the pavo color analyses of
 flower parts and is used as input for comparisons in
 ClarkiaPhyloHeteranthery.R leaf_average_8spp.csv is
 background reflectance data from van der Kooi CJ, Elzenga JTM, Staal M,
 Stavenga DG. 2016. How to colour a flower: on the optical principles of
 flower coloration. Proceedings of the Royal Society B: Biological Sciences
 283: 20160429. name_change.csv is a translation file
 for taxon names in Clarkia_Phenotype_Heteranthery.csv to match the tip
 names in the phylogeny pollen_available.csv presents
 measurers (mm) of exposed pollen on dosing v. no dosing C. unguiculata
 flowers exposed to Bombus impatiens in the greenhouse. It is an input file
 for BombusTrials2018.R. pollen_data.csv is the input
 file for cylindrica.R and contains counts of pollen from inner v outer
 anthers for bee scopae and plant stigmas.
 sensitivity-normalised.txt is is bee photoreceptor data from
 Peitsch D, Fietz A, Hertel H, de Souza J, Ventura DF, Menzel R. 1992 The
 spectral input systems of hymenopteran insects and their receptor-based
 colour vision. J Comp Physiol A 170, 23–40.
 time_lapse_data.csv contains the data on anther dehiscence timing
 for species grown in the greenhouse. It was used to plot Fig 3.