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Plant Focus

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Gene Flow in the Oak Syngameon and Its Impact on Conservation

By Andrew Hipp | August 13, 2024

An article recently published in Plants, People, Planet investigates patterns of geographic overlap—sympatry—in North American oak species: "Constructing sympatry networks to assess potential introgression pathways within the major oak sections in the contiguous US states" by C.H. Cannon, J. Kartesz, S. Hoban, M.I. Loza, E. Beckman Bruns, and A.L. Hipp. This project, conceived and led by Chuck Cannon of The Morton Arboretum, asks an important question: how can we use our understanding of potential gene flow to inform tree conservation? For it is not individual species that will survive or fail to do so as we change the world around them, but whole suites of species, interconnected by their ecological interactions as well as by gene flow.

Sympatry network in section Quercus (white oaks). The log distribution size of each species in the section is illustrated by the diameter of labeled gray circles. Species connected by orange-colored edges are symmetrically sympatric (less than a 75% ratio of relative sympatry levels) and darker colors indicate greater proportional sympatry. Species connected by purple edges are asymmetrically sympatric (greater than 75% ratio of relative sympatry levels), with the arrow indicating the direction of relationship. Greater levels of asymmetry are indicated by the arrowhead being closer to the embedded species. — _{Sympatry network in section Quercus (White Oaks). The log distribution size of each species in the section is illustrated by the diameter of labeled gray circles. Species connected by orange-colored edges are symmetrically sympatric (less than a 75% ratio of relative sympatry levels) and darker colors indicate greater proportional sympatry. Species connected by purple edges are asymmetrically sympatric (greater than 75% ratio of relative sympatry levels), with the arrow indicating the direction of relationship. Greater levels of asymmetry are indicated by the arrowhead being closer to the embedded species. (Figure 6 from the article. "Constructing sympatry networks to assess potential introgression pathways within the major oak sections in the contiguous US states")}

Oak species can exchange alleles, the gene copies that allow different species to succeed better in one place than another. In this paper, we explore the web of potential pollen movement between species as a tool to ask how we can preserve the interconnections between species. Just as Neanderthal and Denisovan genes live on in modern humans, so extinct oak species may live on, in part, in other species with which they exchange genes. Moreover, hybridization has been key to the success of species as they migrate across landscapes and into new climates and habitats. It becomes all the more important the more rapidly environments change.

_{Heat maps of the total local sympatric effect by county in the United States for (a) white and (b) red oaks. Darker colors indicate a greater total amount of local sympatric effect for all species present in the county. Brewster County, Texas, is shaded in black because it has a total lse of 54, which is twice the value of the next highest in the white oaks. The scale runs from 0 to 30 in both graphs. (Figure 5 from the article "Constructing sympatry networks to assess potential introgression pathways within the major oak sections in the contiguous US states")}

The paper is open-access, free to download, read, and share:

https://nph.onlinelibrary.wiley.com/doi/10.1002/ppp3.10546

Enjoy, and reach out with any questions.

Editor's Note: Chuck Cannon published a summary of this research in International Oaks No. 35, under the title "Conserving Syngameons: Thinking Outside the Species Box". IOS members can access it here.

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