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The Hype about Ecotypes

This article by Shannon Kingsley first appeared in WildfloraRI, Spring 2023
Shannon Kingsley is the botanist for ReSeeding RI

A plastic tray of seedlings of Achillea millefolium

Ecoregion 59 seedling tray of common
yarrow (Achillea millefolium) being grown for ReSeeding RI. photo, Shannon Kingsley

For the ReSeeding Rhode Island Initiative—RIWPS’s five-year plan to amplify native, ecotypic plants and seeds across the state—the concept of “ecotypes” is paramount. For native plant enthusiasts, it is exciting to see the availability and popularity of ecotypic seeds and plants increase. Yet, an ecotype is still a complex and oftentimes baffling concept. For starters, what exactly is an ecotype? What makes a population ecotypic? Does planting ecotypic seed increase regional biodiversity? Here, we hope to address some of these persistent questions and demystify some key evolutionary concepts to aid in our collective understanding of ecotypes.

An Ecotype is Born

In a groundbreaking paper in 1922, Swedish evolutionary botanist Göte Turesson coined the term “ecotype.” Turesson noted how environmental factors such as climate, soil, and light exposure play significant roles in establishing genetically distinct populations in a variety of plant populations. He advocated the use of a new word, ecotype, to describe these unique populations. He states that an ecotype is “an ecological unit to cover the product arising as a result of the genotypical response of an ecospecies to a particular habitat.” Simply put, Turesson thought of an ecotype as a population that is genetically adapted to a specific environment.

Over the next 100 years, scientists have expanded, shifted, and interrogated the ecotype concept within fields from ecology and evolution to genetics and virology. Today, the ecotype concept is still complex, and there does not seem to be any straight-forward guidelines for its application in scientific inquiry. Some studies apply genetic analyses to gauge ecotypic differentiation, while other studies purely focus on tracking changes in phenotypic (observable) traits over time.

Evolution and Ecotypes

The concept of an ecotype is intrinsically tied to evolution and the mechanisms that drive evolutionary change. One of the major drivers of evolutionary change is natural selection, or the process through which adaptation to environmental factors favors survival and reproduction. These adaptations are typically phenotypic (observable) traits that are inheritable, or genetically passed down to offspring.

As populations adapt and change, evolutionary change is at play. Ecotypic differentiation, or the process through which populations diverge ecotypically, is a form of natural selection. Ecotypes give rise to morphologically and genetically distinct populations of the same species so as to aid them in survival and reproduction.

For example, when we observe the salt-laden leaf blades of Spartina alterniflora (smooth cordgrass), we observe the species’ phenotypic adaptation to its saline environment. This adaptation, expressed by its genetic makeup, allows the species to expel salt from its system, thus helping it to survive in its specific environment. Now, say we find a population of Spartina alterniflora growing in a dry-mesic forest. To adapt to its drier environment, this population might have thicker leaf blades to allow for greater water storage. We may wonder whether these two populations are ecotypic. Of course, this is an extreme scenario because Spartina alterniflora does not grow in dry-mesic forests. However, the principles remain the same: ecotypes arise when populations of the same species exhibit distinct adaptive responses to varying environmental conditions.

Exploring the Ecotype

How do we know whether the population we find is truly ecotypic? Well, the truth is — we don’t, not without conducting extensive research. When we say “ecotypic seed,” we broadly refer to seeds originating from wild populations in a certain locality (or from plants whose seeds are wild-derived). For ReSeeding Rhode Island, we define an ecotype as “a population of a species that is adapted to a local environment.” We do not engage in rigorous scientific research to determine whether, for example, one population of Pycnanthemum muticum (broad-leaved mountain mint) possesses distinct genetic variation from another population of P. muticum based on environmental differences (although wouldn’t that be cool?). Instead, we operate under the assumption that Rhode Island wild-collected seeds will be best adapted to local environmental conditions and therefore have higher rates of survival when planted back into the RI landscape.

The United States Environmental Protection Agency outlines 182 “Level III Ecoregions” across North America, geographic areas grouped by factors such as topography, soil composition, and biodiversity. Ecoregion 59, or the “Northeastern Coastal Zone,” spans Rhode Island, Connecticut, Massachusetts, and southern Maine and New Hampshire. Ecoregion 59 is characterized by nutrient-poor soils, oak-pine forests, continental glacial lakes, and irregular plains. Over the last year, we collected the seeds of thirty native species from wild populations across Ecoregion 59, guided by our understanding that this ecoregion is home to ecotypic plants and therefore these seeds may possess adaptive genetic diversity.

Year 2: What’s Next for ReSeeding Rhode Island?

Wavy-leaved aster (Symphyotrichum undulatum) seedlings sown in 2022, the first year of the ReSeeding Rhode Island Initiative. Photo by Shannon Kingsley

After one year of learning, growing, and yes—adapting!—we head into the 2023 growing season with a reinvigorated

vision for ReSeeding Rhode Island. We seeded nineteen species in early January and our horticulturist, Barbara Shaughnessy, has carefully tended to these plants through the winter. In early March, a couple seedlings poked their green heads out of the chilly soil, an exciting occurrence for our eager Steering Committee members! Dave Vissoe and Brenda Woodward continue to work with RI farmers to establish founder plots where we will plant these seeded species.

This season, we plan to collect many of the same species we collected in 2022, while increasing our collection of spring-blooming species. In addition, we hope to collect the seeds of several native shrubs, including Vaccinium sp. (blueberry) and Viburnum sp. (arrowwood). We are currently expanding our educational and outreach efforts. In the meantime, follow our Instagram page (@reseedingri) to stay up-to-date on ReSeeding Rhode Island. See our ReSeedingRI homepage for more general information.

Why ReSeeding Rhode Island?

As native plant enthusiasts, we have long advocated the importance of native plants to create ecologically biodiverse habitats, ones that will support the local bugs, bees, and butterflies, the beasts and birds that depend on them — even the microbes and fungi dwelling in the soil.

Not all plants labeled “native,” however, contribute equally to this rich and intricate web of interdependent relationships that are a function of the coevolution of our local flora and fauna. Ecotypic plants, plants sourced from historically local native plant populations in an ecoregion, are uniquely suited to the biotic and abiotic environments of their particular region. These ecotypic plants, however, are not readily available in the current supply chain. Reseeding RI aims to amplify their availability, envisioning corridors of thriving biodiverse landscapes in Rhode Island.