Contacts:Eric LonsdorfDepartment of Ecology, Evolution and Behavior, (612) 624-6711
Deane MorrisonUniversity News Service[email protected](612) 624-2346
ANOTHER CONSEQUENCE OF LANDSCAPE FRAGMENTATION: INBRED PLANTS USE NITROGEN LESS EFFICIENTLY
MINNEAPOLIS / ST. PAUL--The fragmentation of landscapes by human activities creates "islands" of plants, some of which must breed only with a small number of near neighbors. This leads to inbreeding, which has been shown to reduce seed-bearing and productivity and even cause extinction. Now, a study by University of Minnesota ecology graduate student Eric Lonsdorf has indicated that in some plant species, inbreeding reduces efficiency with which the plants use nitrogen. Lonsdorf presented his work Aug. 9 at the Ecological Society of America annual meeting in Madison, Wis.
As landscapes are carved up, their makeup changes; they do not remain simple miniatures of the original landscapes. Lonsdorf said his study shows that fragmentation changes the genetic makeup of species, which in turn alters the species' interactions with their environments. Fragmentation, then, influences the course of evolution, and inbreeding is a major route.
To study the effects of inbreeding on nitrogen use efficiency, Lonsdorf worked with Nemophila menziesii, or baby blue eyes, a vinelike ground plant found in the grasslands of California. He compared the carbon-to-nitrogen ratio (C/N) of tissue from plants that had been outcrossed (the parent plants were unrelated) to C/N in inbred plants (from parents that were self-pollinated). 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. Also, outcrossed plants had higher C/N ratios under low nutrient conditions than in nutrient-rich conditions. Inbred plants, however, showed little or no response to nutrient conditions.
His findings have implications for the restoration of fragmented landscapes, Lonsdorf said.
"There's a debate about whether to use local seed or seed from far away when restoring," he said. "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." Also, he said, the fact that fragmentation affects different plants in different ways will change plant communities. Ecological relationships that existed when landscapes were undisturbed may be absent following fragmentation and restoration. For example, inbreeding that results from habitat fragmentation may alter the response of plants to competitors and other stressors.
A goal of Lonsdorf's research is to link genetic changes in populations to ecological changes. He is now studying the variation among species in their responses to fragmentation.
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