Habitat fragmentation decreases plants’ ability to take up nitrogen

The increasing size and isolation of habitats is changing the genetic make-up of plants, affecting different species in different ways, so altering communities, says Eric Lonsdorf, a graduate student from the University of Minnesota, who carried out the research. Ecological relationships that existed when landscapes were undisturbed may be absent following fragmentation and restoration, altering factors such as the relationships between competing species. Studies in the past have found that seed-bearing and productivity are reduced, even causing extinction under such conditions.

Using Nemophila menziesii, or baby blue eyes, a vine-like ground plant found in the grasslands of California, Lonsdorf compared the carbon-to-nitrogen ratio (C/N) of tissue from plants that had been outcrossed – where the parent plants were unrelated – to C/N in plants from self-pollinated parents. He found higher C/N ratios in the outcrossed plants, indicating that the plants needed less nitrogen to store a given amount of carbon than did the inbred plants, with the ratios even higher for outcrossed plants in areas of nitrogen stress.

“There’s a debate about whether to use local seed or seed from far away when restoring,” said Lonsdorf. “If inbreeding is a concern, I’d expect you should use seed from far away. A counter argument is that seed and pollen from the local area are more adapted to the environment. To decide, you should know how your plants will be affected by inbreeding because genetic changes caused by inbreeding will affect ecological relationships.”

Lonsdorf is now studying the variation among species’ reaction to fragmentation, with the ultimate aim of linking genetic changes in a population to ecological changes.