The relationship between niche breadth and adaptive traits is central to studies of diversification. Field observations indicate that species of the fern genus Pleopeltis (Polypodiaceae) tend to exist in two ends of the environmental spectrum ranging from hyper-humid to arid. Two innovative traits in this clade likely facilitated opposing niche selection: absorptive laminar scales appear to be an adaptation to dry habitats and green spores appear to be an adaptation to wet habitats. The species found at the ends of the ecological spectrum tend towards having a more extreme version of the two traits. Is the evolutionary history of Pleopeltis a result of traits responding to the exploration of new ecological niches or the exaptation of morphological traits that already existed? Based on extensive observations of these species in the field at various climatic and elevational zones in Mexico, Costa Rica, Colombia, and Ecuador, we hypothesize that absorptive laminar scales and achlorophyllous spores represent adaptations of Pleopeltis to habitats with significant water stress, and that chlorophyllous spores and fewer scales are adaptations to wetter habitats. We further hypothesize that these innovative adaptations allowed this lineage to diversify into new habitats with less competition. Using phylogenetic comparative methods, we evaluated the interplay between evolution of adaptive traits, movement into new ecological niches, and speciation.