Skip to main content
U.S. flag

An official website of the United States government

Assisted diversification for an era of habitat extinction

Informally Refereed

Abstract

How do we conserve tree diversity in a rapidly changing world, dominated by intensive human impact on the landscape? The Anthropocene is a useful term to describe a new era in Earth’s history, where we dominate the globe’s resources so completely that our activities alter basic nutrient, water, climate, and energy cycles. These rapid environmental changes and the substantial decline in available and appropriate habitat for many organisms has led to predictions of a sixth global extinction event, where a large fraction of the world’s species are lost. These mass extinctions clearly impacted animal species more than they did plant species. Recent studies suggest that plant speciation may have actually increased at the end of the Cretaceous Period when the dinosaurs largely vanished. Plants must have life histories and reproductive strategies that allow them to persist through times of rapid environmental change.
In addition to being autotrophic and capable of remaining dormant as seed for many years, most plants in diverse genera remain inter-fertile among closely related species. Early evolutionary botanists described these suites of inter-fertile species that retain the ability to exchange genes at a diminished rate as a syngameon. Numerous examples have been identified and documented in the scientific literature and this reproductive strategy has also been termed “diversification with gene flow”. Oaks (Quercus spp.) are famous for being promiscuous across species boundaries and numerous examples of hybrid offspring, genetic introgression, and cytoplasmic organelle capture exist. I would argue that oaks are not at all unusual among trees, but instead are representative of diverse tree genera, particularly in the tropics. The oaks are one of the few examples of a temperate tree group that has diversified in the same way that many tropical genera have. I would further suggest that participation in a syngameon is a critical aspect for trees to adapt to environmental change and novel environments.

Parent Publication

Citation

Cannon, Charles H. 2017. Assisted diversification for an era of habitat extinction. In: Sniezko, Richard A.; Man, Gary; Hipkins, Valerie; Woeste, Keith; Gwaze, David; Kliejunas, John T.; McTeague, Brianna A., tech. cords. 2017. Gene conservation of tree species—banking on the future. Proceedings of a workshop. Gen. Tech. Rep. PNW-GTR-963. Portland, OR: U.S. Department of Agriculture, Forest Service, Pacific Northwest Research Station. p. 71.
https://www.fs.usda.gov/research/treesearch/55174