A single plant with a large distribution: Phylogenetic relationships of South American populations of Pteridium esculentum (Dennstaedtiaceae)

The bracken fern (Pteridium, Dennstaedtiaceae) is a cosmopolitan fern genus, perhaps best known as weedy, disturbance colonizers. Bracken is also toxic to many livestock animals, and the control of this species is of agricultural interest. The taxonomy of Pteridium has been described in multiple schemes, ranging from one to four species with numerous subspecies and varieties. Recent work has focused on the world wide distribution and systematics of the bracken fern. South American species, however, have so far been poorly sampled in such work. Here, we present the first continent-wide sampling and analysis of Pteridum esculentum, a primarily southern hemisphere diploid species. Within South America, P. esculentum has several morphotypes, currently described as subspecies based on morphology alone. We use double digest restriction site-associated DNA sequencing (ddRADSeq) to assess the phylogenetic relationships of P. esculentum subspecies. The identification of patterns of morphological and molecular variability in P. esculentum will lay the foundations for studying variations in its behavior as a weed, as well as its impact on the production of agricultural livestock in South America.