Character displacement is a potentially important process driving trait evolution and species diversification. Floral traits may experience character displacement in response to pollinator-mediated competition (ecological character displacement) or the risk of forming hybrids with reduced fitness (reproductive character displacement). We test these and alternative hypotheses to explain a yellow-white petal color polymorphism in Leavenworthia stylosa, where yellow morphs are spatially associated with a white-petaled congener (L. exigua) that produces hybrids with complete pollen sterility. A reciprocal transplant experiment found limited evidence of local adaptation of yellow color morphs via increased survival and seed set. Pollinator observations revealed that Leavenworthia attract various pollinators that generally favor white petals and exhibit color constancy. Pollen limitation experiments showed that yellow petals do not alleviate competition for pollination. Interspecific pollinator movements were infrequent and low hybridization rates (∼0.40% - 0.85%) were found in each morph, with natural rates likely being lower. Regardless, hybridization rates were significantly higher in white morphs of L. stylosa, yielding a small selection coefficient of s = 0.0042 against this phenotype in sympatry with L. exigua. These results provide support for reproductive character displacement as a mechanism contributing to the pattern of petal color polymorphism in L. stylosa.
Pollinator Observations Data
This workbook contains the raw data from observations of pollinators in both two-species (sheet 1) and one-species (sheet 2) arrays. It also includes the visitation rates (visits/flower/hour) of pollinators for each observation session (sheet 3) given the number of open flowers at the time. This data was used to evaluate heterogeneity of preference between pollinator groups, differences in pollinator assemblages between yellow and white sites, differences in visitation to white and yellow flowers across sites, and floral constancy both within and between species.
Local Adaptation Data
This workbook has data regarding the fitness characters of plants from one-species arrays (# seeds, # siliques, # total flowers). This data was used to assess the hypothesis of local adaptation by comparing the total number of seeds and mortality of white and yellow L. stylosa individuals in white and yellow populations.
Leavenworthia spatial data
This workbook contains the population locales for L. stylosa (sheet 1), L. exigua (sheet 2), and L. torulosa (sheet 3). These raw data were utilized to estimate nearest neighbor distances from L.stylosa populations (sheet 4) and to estimate levels of geographic isolation of white and yellow L. stylosa populations from L. exigua (sheet 5) and L. torulosa (sheet 6).
C code for Geographic Isolation
This document contains the code (written in C and compiled and executed in Microsoft Codeblocks) used to sample Leavenworthia population locality data to produce estimates of geographic isolation between white and yellow populations L. stylosa and either L. exigua or L. torulosa.
Pollen Supplementation Data
This workbook contains information on seed production (# siliques, # total seeds, proportion unsuccessful fruits) for both pollen supplemented and open pollinated L. stylosa plants grown in sympatry with either L. torulosa (sheet 1) or L. exigua (sheet 2). This data was used to test whether white or yellow L. stylosa plants alleviated pollen limitation in sympatry with these two congenerics.
Hybridization Rate Data
This workbook contains the raw data used to identify hybrid seeds from L. stylosa plants in two-species arrays (sheet 1). Individuals were considered to be hybrids if they exhibited PCR bands for both an L. stylosa and L. exigua specific allele at the Lal2 locus. This data was used to estimate hybridization rates between white L. stylosa and L. exigua (sheet 2) and yellow L. stylosa (sheet 3) through the use of maximum likelihood inference.
Migration-Selection Balance Data
This workbook contains the calculations used to determine the coefficient of selection against white L. stylosa in sympatry with L. exigua, the sterility of L. stylosa x L. exigua hybrid individuals, and the frequency of white L. stylosa in sympatry with L. exigua at migration-selection balance and in Hardy-Weinberg equilibrium. These parameters were estimated using information from our hybridization rate estimates, greenhouse crossing experiments, and migration estimates from Dixon et al 2013.
Greenhouse hybridization data
This workbook contains information on the number of adhering pollen grains, number of germinating pollen, and number of pollen tubes for different types of crosses between L. stylosa, L. exigua, and L. stylosa x L. exigua hybrid individuals. This data was used to identify the extent of pre-zygotic isolation between L. stylosa and L. exigua and to help quantify the sterility of hybrid offspring.
