Mating system of Datura inoxia: association between selfing rates and herkogamy within populations

Plant mating system determines, to a great extent, the demographic and genetic properties of populations, hence their potential for adaptive evolution. Variation in plant mating system has been documented between phylogenetically related species as well between populations of a species. A common evolutionary transition, from outcrossing to selling, is likely to occur under environmental spatial variation in the service of pollinators. Here, we studied two phenotypically (in floral traits) and genetically (in neutral molecular markers) differentiated populations of the annual, insect-pollinated, plant Datura inoxia in Mexico, that differ in the service of pollinators (Mapimi and Canada Moreno). First, we determined the populations' parameters of phenotypic in herkogamy, outcrossing and selling rates with microsatellite loci, and assessed between generation (adults and seedlings) inbreeding, and inbreeding depression. Second, we compared the relationships between parameters in each population. Results point strong differences between populations: plants in Mapimi have, on average, approach herkogamy, higher outcrossing rate (t(m) = 0.68), lower primary selling rate (r = 0.35), and lower inbreeding at equilibrium (F-e = 0.24) and higher inbreeding depression (delta = 0.25), than the populations of Canada. Outcrossing seems to be favored in Mapimi while selling in Canada. The relationship between r and F-e were negatively associated with herkogamy in Mapimi; here, progenies derived from plants with no herkogamy or reverse herkogamy had higher selfing rate and inbreeding coefficient than plants with approach herkogamy. The difference F-e-F is positively related to primary selling rate (r) only in Canada Moreno which suggests inbreeding depression in selfing individuals and then genetic purging. In conclusion, mating system evolution may occur differentially among maternal lineages within populations of Datura inoxia, in which approach herkogamy favors higher outcrossing rates and low levels of inbreeding and inbreeding depression, while no herkogamy or reverse herkogamy lead to the evolution of the selfing syndrome following the purge of deleterious alleles despite high inbreeding among individuals.

Automated summary

This study investigated the genetic and phenotypic differences between two populations of the annual insect-pollinated plant Datura inoxia in Mexico. The results showed significant variations in outcrossing and selfing rates between the two populations, with Mapimi population favoring outcrossing and Canada Moreno population favoring selfing. Additionally, the study found a relationship between inbreeding depression and primary selfing rate in the Canada Moreno population.