My research aims to uncover the evolution and functional implications of phenotypic diversity across the plant kingdom. The techniques I use to address these major issues integrate structure, function, and evolution, using both large-scale phylogenetic analyses across thousands of species and small-scale anatomical and physiological analyses narrowing in on single organisms. With each study, I aim to understand the evolutionary history of particular phenotypic traits and how this relates to the diversification of the clade. My current research program aims to understand the hydraulic implications and evolution of the water transport system (xylem) in ferns, a species rich clade with a roughly 400-million-year history. Some of the questions I ask include: How does diversity in the construction of vascular tissues affect water movement in fern stems? How has this variation in vascular architecture evolved across fern evolutionary history? What are the ecological and developmental drivers of structural variation in the vascular system? In addition to my specific focus on vascular tissues, I am also interested in a variety of other topics including biogeography, sterile-fertile leaf dimorphism, and lycopsid evolution.

The Hydraulic Implications of Primary Vascular Construction

Ferns exhibit remarkable structural diversity of their vascular systems. However, little is understood about the functional consequences of this variation. In this project, I explore the hydraulic implications of the impressive structural diversity of primary vasculature in fern rhizomes. Check out our paper here.

Rhizome cross section of the Hay Scented Fern (Dennstaedtia Punctilobula) showing the primary vasculature. Xylem cells are autoflourescing purple

The Evolution of Primary Vascular Architecture

The defining feature of all vascular plants is the production of primary vascular tissues (xylem and phloem). The arrangement of vascular tissues within the stem (stelar architecture) has interested botanists for over 200 years, however we lack a clear understanding of how this structural variation evolved. Using neobotanical and paleobotanical data in combination with phylogenetic comparative methods, I am able to unveil the macroevolutionary processes responsible for the evolution of stelar architecture.

Reconstruction of the evolutionary history of vascular architecture across the fern phylogeny

Movement Without Muscle: The Sensitive Fern

Propagule dispersal is important for the persistence of species and populations. In plants, the focus is largely on brightly colored fruit and vertebrate dispersers. However, there are many ways for plants to disperse without animal assistance. For example, wind dispersed seeds are abundant and adaptations to wind dispersal are found all around us. One group that relies almost entirely on wind for their dispersal is ferns. A unique species of this lineage is the sensitive fern, that produces a tough/woody fertile leaf in the summer, but does not disperse its spores until the following spring. Here, I aim to understand how the leaflets of this fern open and what environmental signals dictate its phenology.

A young, developing fertile frond of the Sensitive Fern (Onoclea sensibilis)

Global Fern Biodiversity

With over 11,000 species, ferns are one of the most species rich lineages of land plants. Where are all these species found? How have these species evolved? What are the drivers of this diversification? These are the types of questions I ask and answer in order to better understand the evolution and diversification of ferns on a global scale. Check out our paper here.

Hunting for ferns at the Continental Divide, Costa Rica

Selected Publications

Suissa, J.S., and Friedman, W.E. Rapid diversification of vascular architecture underlies the Carboniferous fern radiation. (PDF available upon request).

Suissa, J.S., Kinosian, S.P., Schafran, P.W., Bolin, J, Taylor, W.C., Zimmer, E.A. (in review) Revealing the origins of a reticulate complex in the genus Isoëtes. Molecular Phylogenetics and Evolution. PDF

Suissa, J.S., and Friedman, W.E. (2021). From cells to stems: the effects of primary vascular construction on drought-induced embolism resistance in fern rhizomes. New Phytologist. DOI: 10.1111/nph.17629. PDF

Presentation link here!

Suissa, J.S., Sundue, M.A., Testo, W.L. (2021). Mountains, Climate and Niche Heterogeneity Explain Global Patterns of Fern Diversity. The Journal of Biogeography. DOI: 10.1111/jbi.14076. PDF

Presentation link here!

Suissa, J.S., Sundue, M.A. (2020). Diversity Patterns of Neotropical Ferns: Revisiting Tryon’s Centers of Richness and Endemism. The American Fern Journal. 110(4), 211-232. PDF

Suissa, J.S. (2020) Polycyclic solenostele, a new synapomorphy for Pteris sect. Litobrochia. The American Fern Journal. 110(3), 127-138. PDF

Suissa, J.S., and Green, W.A. (2020). CO2 starvation experiments provide support for the carbon-limited hypothesis on the evolution of CAM-like photosynthesis in Isoëtes. Annals of Botany. 127(1), 135-141. PDF.

Presentation link here!

Kinosian, S.P., and Suissa, J.S. (2020) The mothers of Pteridology. The American Fern Journal. 110 (1), 3-19. PDF

Suissa, J.S., and Barton, K.E. (2018). Intraspecific and interspecific variation in prickly poppy resistance to non-native generalist caterpillars. Botanical Sciences. 96 (2), 168-179. PDF