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.

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.

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.