Evidence for spatial and temporal variation in mating system of Tolpis macrorhiza (Asteraceae), a species endemic to Madeira

Abstract

Abstract There have been many studies of morphological and genetic variation in island plant radiations, but few have shown how the mating system has shaped the patterns of variation. In this study, outcrossing rates and paternity in eight populations of the Madeiran endemic Tolpis macrorhiza were estimated using genome-wide RADseq genotyping. The species is believed to have evolved early in the geological history of the island, and we here examine mating system evolution during colonization and establishment of populations across Madeira. The mating system is highly outcrossing in seven populations and mixed mating in one. Some maternal plants in highly outcrossing populations were inbred, suggesting that mating system varies temporally as well as spatially. This mating system may provide flexibility for establishment of new populations in the dynamic landscapes of oceanic islands while maintaining genetic diversity within populations. Multiple paternity is prevalent in populations, indicating that compatible mates are not limited to a few sires. Our analyses of T. macrorhiza were enabled by several methodological advances included in the v.3 release of the BORICE estimation program. These include SNP filtering programs to generate valid likelihoods and post-processing scripts to partition mating system variation among populations and among maternal plants within populations.