Evolution was famously depicted by Darwin in The Origin of Species as a branching tree. However, we now know that the tree of life doesn’t just consist of ever-finer splitting branches, but that many of these branches join back together in a process known as reticulate evolution. Ferns are notorious for their species complexes, clouds of closely related species with many reticulate relationships between hybrids and their parent taxa. Such complexes have frustrated many a taxonomist trying to draw clear lines between species.
With next-generation DNA sequencing, we finally have the tools to resolve relationships within these difficult groups. I am currently applying two such methods, amplicon sequencing using long-read PacBio technology, and sequence capture of hundreds of low-copy nuclear loci, to untangle relationships within the Thelypteris angustifrons species complex.