The Herbarium: Invasive Migrations

September 26, 2017
Dr. J,

Bonnie mentioned going into the field to collect plants in the near future.  I’m sure the process of pressing plants isn’t very complex or exciting, but I am excited to learn about it.

I met a gentleman named Allison who worked as the curator of the state herbarium of Ohio.  He’s retired, but clearly can’t stop picking and pressing plants.  He pulled some green-fringed clump from a ziplock sandwich bag and placed it on a white paper.  He stared at a strand of his clump under a low magnification scope that is normally covered with a pink teapot cozy.  After about five minutes, he called Bonnie over excitedly.  His clump of green may be an invasive species that is new to the area—previously recorded in Philadelphia, but not in western PA.  The best part is that his finding came from a seam in the sidewalk along Fifth Avenue.  He turned to me—I was rather obviously eavesdropping—and remarked at how most people, even botanists, might step right over the plant.  I was interested in how it came here.  He suggested the shoes of college students as a delivery method for the seeds.

Later that day, I considered how the herbarium plays a role in findings such as these.  The herbarium is home to many type specimens, which serve as templates for how a species is described, as well as historic distribution data from the entire collection and a variety of botanical resources.  Having access to the herbarium provides collectors an opportunity to add to knowledge about species distributions and phenology.  Allison claims that many botanists are interested in the conservation of rare and endangered species, but that invasive species are just as important to study now.  It didn’t occur to me before that by looking for new introductions of invasive species botanists can track plant migration from an earlier point.  This data can help scientists learn about what makes invasive species particularly effective and what might prevent the migration of a plant species.

As for the progress of my ongoing project of sorting plants, I finished the extensive genus Eriogonum—most of the specimens were from the western US.  I still have a way to go, but it is interesting to see the results of taxonomists’ lumping and splitting.

Regards,
Aaron

Postscript:  Invasive species are a hot topic in ecology, with research focusing on what makes invasive species so successful.  Plants that migrate to new regions and become prevalent, often dominating their new habitat, are considered invasive.  A good example of an invasive species is Japanese knotweed, which can be found growing on roadsides and in moist soils near streams and rivers.  Because invasive species become known after they have already colonized their new habitat, studying the initial introduction is almost impossible.  This is one way that herbarium collections can provide historical data on invasive species migrations.  Additionally, research on species that were unsuccessful at introduction could provide insights into invasive species, but these introductions are not well-documented.

By identifying features that make an invasive species successful, conservation measures can predict species that might pose a threat to foreign habitats.  Australia in particular, which suffers from a myriad of invasive plants and animals, has very strict regulations regarding the import of living organisms in order to prevent potentially devastating species introductions.

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