Data and analysis scripts for: Asymmetrical reproductive barriers in sympatric Jewelflowers: are floral isolation, genetic incompatibilities, and floral trait displacement connected?

Floral visitors influence reproductive interactions among sympatric plant
species, either by facilitating assortative mating and contributing to
reproductive isolation, or by promoting heterospecific pollen transfer,
potentially leading to reproductive interference or
hybridization.  We assessed preference and constancy of floral
visitors on two co-occurring Jewelflowers (Streptanthus breweri and S.
hesperidis, Brassicaceae) using field arrays, and quantified two floral
rewards potentially important to foraging choice – pollen production and
nectar sugar concentration – in a greenhouse common garden. 
Floral visitors made an abundance of conspecific transitions between S.
breweri individuals, which thus experienced minimal opportunities for
heterospecific pollen transfer from S. hesperidis.  In contrast,
behavioral isolation for S. hesperidis was essentially absent due to
pollinator inconstancy.  This pattern emerged across multiple
biotic environments and was unrelated to local density
dependence.  S. breweri populations that are sympatric with S.
hesperidis had higher nectar sugar concentrations than their sympatric
congeners, as well as allopatric conspecifics.  Previous work
shows that S. breweri suffers a greater cost to hybridization than S.
hesperidis, and here we find that it also shows asymmetrical floral
isolation and floral trait displacement in sympatry.  These
findings suggest that trait divergence may reduce negative reproductive
interactions between sympatric but genetically incompatible relatives.