Research in the Sessa lab focuses broadly on plant systematics and understanding the evolutionary and ecological processes that shape plant diversity. Lab members work on a number of projects around this central theme, with phylogenetics as the unifying conceptual framework. Phylogenies inform our research in a number of related areas, including understanding basic relationships among taxa, patterns of reticulate evolution, diversification rates and biogeographic history of organisms, community phylogenetics, and trait evolution using comparative methods. Organismally, we have a strong focus on the seed-free vascular plants: ferns and lycophytes (traditionally collectively called pteridophytes). Our work, whether on ferns, lycophytes, or other systems, uses data collected in field and experimental studies and generated via Sanger and next-generation sequencing. We integrate techniques from several disciplines, including computational and evolutionary genomics, phylogenetic systematics, physiological ecology, and traditional specimen-based botany. There are many ongoing projects in the lab, including those listed below.

Flagellate Plants

This is a collaborative effort to build phylogenies for flagellate plants: gymnosperms, ferns, lycophytes, mosses, liverworts, and hornworts.

African ferns

Little is known about phylogenetic relationships or historical biogeography of African ferns and we are working to rectify this.

Community Phylogenetics

We are using phylogenetics and niche modeling to study community assembly of Florida ferns and south Florida’s endangered Pine Rocklands.

Dryopteris and Asplenium

We study phylogenetics, biogeography, and reticulate evolution of the Dryopteris and Asplenium, the woodferns and rockferns.

Fern genomics

Ferns are the only major lineage of land plant without a nuclear genome reference sequence; we are part of collaborative efforts to change this.

Fern mating systems

Ferns are capable of an extreme form of inbreeding, and we are interested in the implications for fern ecology and evolution.


The OneKP project has sequenced transcriptomes for more than 1,400 species of plants, from algae to angiosperms.


Goodeniaceae is a family of flowering plants that is diverse in Australia and related to the sunflowers.