Format: ORAL

Sarah K. Morris1, Weston L. Testo1, Michael A. Sundue2

1 Pringle Herbarium, Department of Plant Biology, University of Vermont, Burlington, VT, USA 2 Royal Botanic Garden Edinburgh, UK

Nearly one-third of fern speciation events involve ploidy changes, compared to 15% in angiosperms, highlighting the unparalleled importance of reticulate evolution in fern diversification. Despite fern diversity peaking in the tropics, few studies have addressed hybridization and polyploidy in tropical fern lineages. Pleopeltis is a group of about 100, mostly epiphytic species found throughout the American tropics. Species of Pleopeltis occur in a broad spectrum of ecosystems, ranging from pluvial lowlands to dry alpine zones and with a great diversity of morphologies. Hybridization appears to be frequent throughout the group, challenging the delimitation of species and application of names. Evolutionary investigations have been hampered by several polytomies, recalcitrant nodes and short branch lengths in the backbone of the phylogeny, suggesting a possible rapid speciation event. Here, we focus on the Andean Pleopeltis species complex, a clade of pinnately divided species found in mid to upper elevations in the northern and central Andes and the putative hybrids between them. Using an integrative approach including geography, morphometrics, spore size and admixture analyses, we developed the first hypothesis of reticulate relationships within this complex and tested this hypothesis using recently developed phylogenomic techniques. Sourced from herbarium specimens and silica gel dried material, we produced DNA sequence data for all members in the Andean Pleopeltis species complex using the ?Genealogy of Flagellate Plants (GoFlag) target capture probe set, and we used a suite of newly developed allele-phasing bioinformatic tools to infer relationships between allopolyploid species and their diploid progenitors in this clade and elucidate the role of introgression and incomplete lineage sorting. This is the first phylogenomic investigation of this genus as well as one of the first investigations of polyploid speciation in a tropical fern clade using modern sequencing and bioinformatic techniques.