Pressed Flowers Come Alive by Telling Their Pollination Story -

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by Nathália Susin Streher

Do you ever wonder what made you pursue your dreams in life? When I ask myself this question, it inevitably takes me back to my childhood and the indelible memories that growing up in the most biodiverse country in the world left on me. From the diversity of fruit trees and the tiny animals that crawled them in my backyard to the varied ecosystems in the surrounding areas, living in Brazil has shaped my perception of nature and sparked a singular curiosity about the variety of forms and interactions I could observe. As the little scientist in me grew up, fueled by the fascination with the beautiful mysteries of flowers, it naturally guided me toward the path of studying plants and their interactions.

As I stepped into the world of science, my first paid opportunity as an undergrad in biology was in a small herbarium. There I learned about preserving plant specimens collected from nature and their importance for identification and classification of plant species. What I did not realize back then was that herbaria store more than just names and relations among species; they also provide a means to investigate ecological interactions like the ones that captivated me as a child. I kept that flame of curiosity from my childhood alive and came to the US as a postdoc researcher. My research group at the University of Pittsburgh and I have been incorporating some unconventional uses of herbarium material into our research. In a recent scientific publication, we used herbarium specimens (many sourced from the CMNH herbarium) to explore a crucial ecological mutualism between animals that visit flowers for food and plants that require go-betweens to transport their pollen—a process called pollination.

In pollination biology, it is common to investigate floral characteristics because they play a crucial role in mediating plant interactions with their pollinators. For example, plants with long floral tubes are typically pollinated by morphologically matching long-tongued pollinators. While certain floral traits, such as visible color and scent, may be altered or completely lost during the drying process of plant specimens, many of the other characteristics remain accessible even after years of preservation. Thus, as long as the herbarium sheet contains at least one flower, valuable biological information can be extracted to understand plant-pollinator interactions.

In this study, we used herbarium specimens to reveal the network of past plant-pollinator relationships. Specifically, we sampled a small piece of the flower, the stigma, which is the structure that receives pollen grains delivered by pollinators. As pollinators may visit several plant species flowering together, inspecting stigmas can unveil a plant’s pollination story. By assessing the diversity of pollen grains morphologically distinct from the target species, we gain insights into whether the target species interacted with many or only a few other plant species through pollinator sharing.

Leveraging herbarium specimens for ecological questions offers a unique advantage, as they provide historical, spatial, and long-term perspectives to scientific studies—dimensions that may otherwise be challenging to attain. In studies of plant-pollinator interactions, researchers often rely on direct pollinator observation data, which, while ideal, has limitations such as being time-consuming, costly, and dependent on various conditions. Pollen deposited on stigmas of herbarium specimens arises as a valuable alternative when direct pollinator observation is unfeasible. Herbaria offer scientists a convenient way to compare numerous plant species from around the world. Actively incorporating these specimens into research not only keeps the collections dynamic but also magnifies their overall significance. Much like the plant-pollinator interaction—it’s a win-win scenario. I hope our work inspires others to perceive herbarium collections as guardians of biodiversity and encourages scientists to unlock the hidden potential of their precious specimens.

Beyond the scientific excitement of unraveling the pollination story within herbarium specimens, I once again seemed to have missed yet another potential interaction they could reveal. While going through the cabinets housing the specimens at CMNH, I unexpectedly encountered plants collected from the same region where I was born and raised in Brazil. I never thought that an old, dried plant could make me feel closer to my homeland. Living abroad to pursue the scientific dream is no easy feat—different language, different culture. But that moment was a reminder of my childhood connection with nature that brought me here. Now, I see herbaria not only as guardians of biodiversity but also as promoters of a sense of belonging in us.