Simberloff discusses invasive species, biodiversity

Managing invasive species is incredibly important to biodiversity conservation efforts, said Daniel Simberloff, professor of environmental science at the University of Tennessee, Knoxville, in his lecture “Managing Biological Invasions: What’s Worked, What Hasn’t, and Some Controversial New Prospects.”

Invasive species are living organisms that are not native to an ecosystem, and can thus cause harm to global biodiversity, explained Simberloff. He added that there are two methods by which invasive species have traditionally been managed: eradication, or the complete elimination of the population from a region, and maintenance management, which aims to maintain invasive populations at low levels.

Simberloff explained that novel genetic techniques for managing exotic invasive species are quickly garnering interest in the field.

One such genetic technique uses Trojan sex chromosomes, in which genetically male organisms exposed to female hormones appear physically female, and vice versa. Simberloff noted that this interrupts reproduction in the population, eventually driving it to extinction. He explained that although this method is not very quick on its own, it can be the death knell for an invasive species when combined with more traditional chemical and biological methods of population management. Simberloff added that this was not just a hypothetical model, but has been tested with designer mosquitoes to battle dengue in Brazil.

Even though invasive plants can often have more extensive impacts than invasive animal species, traditional management methods have targeted animals far more than they have plants and their pathogens because of the difficulty in controlling entire plant species, Simberloff explained. Some genetic techniques hope to address this problem.

RNA interference, for example, binds to the single-stranded RNA molecules in cells and prevents them from making protein. Simberloff said that RNAi is being used against plant pathogens such as insects, and has been labeled “dsRNA [double-stranded RNA] insecticide” because of its effectiveness in removing insects.

In addition to new genetic technologies, traditional mechanical, chemical, and biological methods of management have been successful in many organisms, Simberloff explained. Some of these techniques include prescribed fires that reduce Australian paperbark, lipid-coated biological toxins called BioBullets that manage zebrafish, and dams built against lampreys.

Simberloff noted that these methods could have severe off-target effects on species native to the ecosystem. He noted that in such cases, field observations have led scientists to ingenious solutions. For example, researchers saw that lampreys preferred some streams over others, so they were able to isolate a compound in these streams that attracted the lampreys.

Eradication as important as maintenance management, and is often used to eliminate invasive species in discrete geographical regions such as islands, Simberloff explained. He noted that of the 1,100 attempts to eradicate invasive island species, 900 have been successful. However, the challenges of eradication include eliminating multiple invasive species while doing no harm to local populations and conducting eradication efforts on human-inhabited islands.

Simberloff provided some historical background for the research on invasive species management by introducing the United Nations Scientific Committee on Problems of the Environment project. Since SCOPE’s establishment in 1969, several avenues of research into invasive species have taken off, including ecosystem-wide and evolutionary research.

He said that ecosystem-wide studies, for example, explored the impact of rats on islands, which demonstrated the impact of a single invasive species on both above-ground and below-ground food webs. Additionally, Simberloff said that research on the evolutionary impact of invasive species showed that invasion was not a one-time event but hybridization over multiple invasions. He explained that this has answered the genetic paradox of invasions: How does a small invasive population remain unthreatened by elimination through genetic drift?

Simberloff’s lecture was part of the William L. and Jane H. Fortune Distinguished Lecture Series in Conservation Biology and included in the EEB 522 Seminar Series: Colloquium on the Biology of Populations. The lecture took place in Guyot 10 at 12:30 p.m. on Thursday and was attended by about 60 people.