Abstract
Since their origin 160 million years ago, flowering plants have rapidly diversified into more than 300,000 species, adapting to a striking array of habitats and conditions. In this short time, flowering plants have dominated some of the most diverse and extreme environments, harnessed a number of specialized biotic interactions in order to ensure successful pollen and seed dispersal, and adapted to meet the demands of agriculture. Given their diversity and importance, a considerable body of research has been devoted to understanding plant adaptation (Tiffin and Ross-Ibarra, 2014), but the relative importance of the various factors that may impact the process of adaptation are still not well understood. For instance, transitions in polyploidy and mating system have long been considered plausible drivers of flowering plant adaptation (Soltis et al., 2009; Goldberg and Igić, 2012), but both are also associated with evolutionary dead ends (Mayrose et al., 2011; Igic and Busch, 2013). As another example, while the effective size of plant populations is expected to correlate with estimates of the efficiency of natural selection, empirical support for this prediction is mixed (Strasburg et al., 2010; Gossmann et al., 2010). A number of aspects of adaptation have received a degree of theoretical (Hermisson and Pennings, 2017; Ralph and Coop, 2010) or empirical (Strasburg et al., 2012; Anderson et al., 2013; Ågren et al., 2013; Yeaman et al., 2016) support, but it is clear we are far from understanding all of the factors underlying the process of adaptation in flowering plants.
