My research aims to uncover the evolution and functional implications of diverse phenotypic traits across the plant kingdom. The techniques I use 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 key organisms. Some of the questions I ask include: How are diverse traits constructed? How does the structure of these traits relate to their function? How has this variation in evolved? What are the ecological and developmental drivers of structural variation?

Research Topics

The evolution nectaries in non-flowering plants

Plant-animal interactions are fundamental components of biology. Pollination, for instance, leads to proper fruit and seed development and can serve as a driver of species diversification. Underpinning these interactions is a reward for the pollinators—usually, a sugary liquid secreted from a structure called a nectary. Nectaries are common in flowers, but also occur on leaves, where instead of attracting pollinators, they attract insects to secondarily defend against herbivory. Surprisingly, ferns have also evolved nectaries, where they serve a similar functional role. To gain a more holistic view on the origin and evolution of nectaries, it is crucial to focus on non-flowering plants. As part of my current research, I am using anatomical, molecular, and phylogenetic approaches to explore the convergent origins and evolution of nectaries in non-flowering plants.

Ant visiting a nectar-gland of Bracken fern (Pteridium aquilinum).

The evolution and functional implications of vascular patterning

Nearly 425 million years ago land plants evolved novel tissues to move water and sugar more efficiently through their body. These conducting tissues, xylem and phloem, greatly amplified mass flow rates, allowing plants to increase photosynthetic capacity, grow larger, and alter aspects of the terrestrial ecosystem including carbon dioxide modulation and increased oxygenation, in turn, profoundly affecting the course of evolution for life on land. These vascular plants now account for over 90% of Earth’s terrestrial flora and are the foundational components of nearly every ecosystem. Throughout geologic time the evolution of vascular tissues led to a striking display of structural and physiological variation. In this pillar of my research program I explore how these integral vascular tissues evolved over geologic time and function in a whole-plant context.

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

The evolution of fertile-sterile leaf dimorphism

Propagule dispersal is important for the persistence of species and populations. Across all vascular plants propagules (seeds or spores) are developed on leaves. Within the ferns, the majority of species produce spores on the same leaves which they use for photosynthesis, this is termed monomorphic. However, certain species are dimorphic, meaning they produce partially or completely distinct vegetative and reproductive leaves. This modification reaches an exceptional stage in extant seed plants, where reproductive leaves are utterly distinct from vegetative ones. In almost all cases they are modified to the point of unfamiliarity with their homologous leafy counterparts (i.e., the extremely modified seed-bearing leaf: the carpel). The presence of a gradient between monomorphism and dimorphism within the ferns allows us to explore the developmental, functional, and evolutionary consequences of fertile-sterile leaf dimorphism.

Humidity-driven movement In the leaflets of the Sensitive Fern (Onoclea sensibilis)

Patterns of global fern biodiversity

With over 11,000 species, ferns are one of the most species rich lineages of land plants. They occur all over the world from desert outcrops to alpine peaks. As part of this pillar of my research program I explore where fern species are found, how they have evolved, what drives their diversification.

Hunting for ferns at the Continental Divide, Costa Rica


  1. Suissa, J.S., Agbleke, A.A., and Friedman, W.E. (in review). The hydraulic implications of rhizomatous growth and the homorhizic habit. American Journal of Botany. PDF available upon request.

  1. Suissa, J.S., and Friedman, W.E. (2022). Rapid diversification of vascular architecture underlies the Carboniferous fern radiation. Proceedings of the Royal Society B. 289: 20212209. PDF

Presentation link here!

  1. Suissa, J.S. (2022) Fern fronds that move like pine cones: humidity-driven motion of fertile leaflets governs the timing of spore dispersal in a widespread fern species. Annals of Botany. 129(5), 519–528. PDF

  1. Suissa, J.S., Kinosian, S.P., Schafran, P.W., Bolin, J, Taylor, W.C., Zimmer, E.A. (2022) Homoploid hybrids, allopolyploids, and high ploidy levels characterize the evolutionary history of a western North American quillwort (Isoëtes) complex. Molecular Phylogenetics and Evolution.166 (107332). PDF

  1. 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. 232(6), 2238-2253. PDF

Presentation link here!

  1. Suissa, J.S., Sundue, M.A., Testo, W.L. (2021). Mountains, Climate and Niche Heterogeneity Explain Global Patterns of Fern Diversity. Journal of Biogeography. 48(6), 1296-1308. PDF

Presentation link here!

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

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

  1. 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!

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

  1. 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