Recent Articles from BRMC Newsletters

Invasion

While the land leased by BRMC is protected under a solid deed that prevents development, logging, etc., the number of threats to the preserve remain high. We live in an age when anthropogenic alterations to regional and global ecosystems are severe enough to affect all natural areas whether they are protected on paper or not. What this means is that the concept of forever wild does not generally work for any preserve and especially not for small preserves. If we took a hands-off approach to managing BRMNAP, in time the ecological communities on the Bull Run Mountains would slowly degrade.

We do not have the space here to review all the issues that resource managers must confront to preserve rare species and ecological communities in perpetuity. Instead, I would like to present a concept that is counterintuitive and only recently addressed in a study published in the journal Nature. If a population of species becomes isolated, for example during an introduction, theoretically that population has reduced genetic variability compared to the main population. Combine the reduced variability with a small population size, which has its own increased risk of extinction, and you have to ask: how does an introduced plant or animal become invasive? It would seem the cards are stacked against plants and animals experiencing these conditions from a genetic standpoint. If that is a correct assumption, then how do introduced species persist, expand their ranges, evolve rapidly, and thus become invasive?

To address this question scientists studied the brown anole (Anolis sagrei), a worldwide invasive lizard. Based on genetic analysis, they discovered that there were eight introductions into Florida from across this lizard's native range. The result has been the blending of genetic variation from different geographic source populations and the production of populations that contain substantially more, not less, genetic variation than their native populations. To make matters worse, some recently introduced brown anole populations around the world have originated from Florida and have maintained the elevated levels of genetic variation. In other words, one key to invasion success may be the occurrence of multiple introductions that transform among—population variation in native ranges to within—population variation in introduced areas. In addition, these genetically variable populations may be potent sources for introductions elsewhere (Kolbe et al. 2004).

Invasive species are a growing economic and biological problem. Only a greater understanding of the causes, progression, and consequences of biological invasions can lead to better efforts to mitigate their economic and ecological costs. To learn more about what is negatively impacting our preserve and what we know about minimizing these impacts please join us for our public program "Preserving the Preserve—protecting the Bull Run Mountains from local and regional threats."

Reference: Kolbe, Jason J. et al. Genetic variation increases during biological invasion by a Cuban lizard. Nature. 431, 177-181 (2004).