Tracing the history of angiosperm systematics through Liliales and Asparagales

Emily Humphreys, Cody Coyotee Howard, Carrie Tribble

The field of systematics is central to how we understand, classify, and discuss organisms and their evolution. Systematics directly or indirectly touches every branch of biology. Over the last 50 years, methods in the field have been continually reshaped by advancing technologies, transitioning from primarily relying on morphological data to utilizing genomic-scale data sets. As the methods systematists use have changed, so too has our understanding of deep evolutionary relationships among flowering plants. In this primer, we illustrate advances in systematic methods using two closely related botanical orders, Liliales and Asparagales. Members of these orders were once both considered part of the same family, Liliaceae. Molecular data steered us towards a more refined understanding, validating the decision to split Liliaceae into several currently recognized orders including Liliales and Asparagales. In early molecular studies primarily using chloroplast data, Liliales was most closely related to the group containing Asparagales and another lineage, commelinids. Over the past decade though, the increasing availability of large-scale nuclear data across non-model plants has made possible several studies that demonstrate a direct sister clade relationship between Liliales and Asparagales. Here, we summarize the history of angiosperm systematics and demonstrate how advances in theory and practice have shaped the relative placements of Liliales and Asparagales in the monocot phylogeny. We further discuss the impact of a sister relationship among Liliales and Asparagales on our understanding of monocot trait evolution, and the implications of current and advancing methodologies for the future of plant systematics.