BERND BLOSSEY                                              


Assistant Professor

Department of Natural Resources

122E Fernow Hall, Cornell University

Ithaca, NY 14853

Phone: 607-255-5314

Fax: 607-255-0349




Research Interests

I am an ecological generalist with wide ranging interests (plants, birds, insects, mammals, amphibians) in aquatic and terrestrial systems. My academic training is in ecology, particularly entomology and limnology but with a focus on applied entomology. I am particularly intrigued by potential ecosystem effects associated with increase and decline of invasive plants species in natural areas. Invasive plants are likely to change native species diversity, ecosystem processes, and food webs but for most species we have very little quantitative data to support management and control. The goal of the Ecology and Management of Invasive Plants Program, which I direct, is to assemble multidisciplinary teams of students and other professionals to engage in scientific research and the collection of sound data on the impact of invasive plant species. While the focus of our work are species invasive in the northeastern United States, many of the plants we investigate are widely distributed throughout North America.  Data we generate may ultimately guide management decisions.


An associated goal is the development and improvement of the scientific basis of biological weed control programs. For most of the invasive plant species in North America, chemical, mechanical, or physical measures provide only temporary control. The careful planning and implementation of biological weed control programs offers an ecologically sound alternative control strategy. I believe that by understanding and documenting the long-term impacts of spread and decline (through biocontrol) of invasive plant species on native species and their food webs, important improvements in the safety and success rate of this technology can be achieved. An important aspect of improving adoption and implementation of biocontrol programs are partnerships with agencies and private citizens. We develop standardized monitoring protocols that balance ease of implementation with scientific sophistication but allow citizen participation in scientific data collection (please explore the various opportunities for participation offered through this webpage).


In addition, I am interested in factors contributing to the invasiveness of plant species. Most plant species arriving outside their traditional distributions through human aided transport (accidentally or purposefully) never become establish. Of those that establish, only few (about 10%) escape and naturalize (establish self-sustaining populations without human help). Of those that naturalize about 10% become invasive. In North America about 5000 plant species have naturalized and approximately 500 are recognized as invasive. The intriguing question is: what factors allow certain plant species to become invasive (in fact we know that invasiveness can evolve)? I have proposed the Evolution of Increased Competitive Ability (EICA) hypothesis (Blossey and Nötzold 1995), which explains the invasiveness of certain plant species through interaction of herbivores with their host plant. Plants that were under high herbivore pressure in their native range experience enemy-free space in their new range. This absence of natural enemies allows introduced plants to shift resource from herbivore defense to increased vegetative growth or seed output, allowing them to outcompete native plants. The importance of natural enemies is highlighted by the fact that invasiveness of plants can be reversed through the release of biological control agents (but not always).




In general, we use a combination of long-term monitoring (often at invasion fronts) and experiments. I strongly believe that reliable predictions about behavior of organisms or natural systems can only be derived at through field or common garden experiments and field observations. While the ability to manipulate large systems is limited, concerns over appropriateness of spatial and temporal scales when investigating invasions need to be paramount. Long-term monitoring can be a powerful (but greatly underutilized and underfunded) tool to understand potential ecosystem impacts of non-indigenous plants.



1. Biological control of garlic mustard (Alliaria petiolata). Funded since 1998 through support by various state Departments of Natural Resources, Native Plant Societies, private donors, the Strategic Environmental Research and Development Program, and the US Forest Service.


2. Impact of invasive plants on abundance and fitness of woodland salamanders. Funded through IL Department of Natural Resources and US EPA.


3. Developing biological control of Phragmites australis. Funded since 1998 through grants from NY, RI and National Sea Grants, The US Fish and Wildlife Service, The US Bureau of Reclamation, and the New Jersey Public Service Enterprise Group. A frequent PI or Co-Pi on these grants is Richard Casagrande and his team from the University of Rhode Island.


4. Morphological differences and herbivore resistance in native and introduced genotypes of P. australis. (with R. Casagrande as PI) Funded by RI and National Sea Grants and the US Fish and Wildlife Service.


5. Evaluating the success of biological control of purple loosestrife. Various projects funded through US Bureau of Reclamation and NY Department of Environmental Conservation, Bureau of Wildlife


6. Impact and development of biological control of Japanese knotweed. Funded through US Forest Service.



Key References


Blossey, B. 1999. Before, during, and after: the need for long-term monitoring in invasive plant species management. Biological Invasions 1:301-311.

Blossey, B., and T. R. Hunt-Joshi. 2003. Belowground herbivory by insects: influence on plants and aboveground herbivores. Annual Review of Entomology 48:521-547.

Blossey, B., and R. Nötzold. 1995. Evolution of increased competitive ability in invasive nonindigenous plants: a hypothesis. Journal of Ecology 83:887-889.

Blossey, B., V. Nuzzo, H. Hinz, and E. Gerber. 2001a. Developing biological control of Alliaria petiolata (M. Bieb.) Cavara and Grande (garlic mustard). Natural Areas Journal 21:357-367.

Blossey, B., L. C. Skinner, and J. Taylor. 2001b. Impact and management of purple loosestrife (Lythrum salicaria) in North America. Biodiversity and Conservation 10:1787-1807.

Byers, J. E. 2002. Impact of non-indigenous species on natives enhanced by anthropogenic alteration of selection regimes. Oikos 97:449-458.

Callaway, R. M., and E. T. Aschehoug. 2000. Invasive plants versus their new and old neighbors: a mechanism for exotic invasion. Science 290:521-523.

Chapin, F. S., E. S. Zavaleta, V. T. Eviner, R. L. Naylor, P. M. Vitousek, H. L. Reynolds, D. U. Hooper, S. Lavorel, O. Sala, S. E. Hobie, M. C. Mack, and S. Diaz. 2000. Consequences of changing biodiversity. Nature 405:234-242.

Crawley, M. J. 1987. What makes a community invasible? Pages 429-453 in A. J. Gray, M. J. Crawley, and P. J. Edwards, editors. Colonization, Succession and Stability. Blackwell Scientif Publications, Oxford.

Davis, M. A., J. P. Grime, and K. Thompson. 2000. Fluctuating resources in plant communities: a general theory of invasibility. Journal of Ecology 88:528-534.

Ellstrand, N. C., and K. Schierenbeck. 2000. Hybridization as a stimulus for the evolution of invasiveness in plants? Proceedings of the National Academy of Sciences 97:7043-7050.

Farnsworth, E. J., and D. R. Ellis. 2001. Is purple loosestrife (Lythrum salicaria) an invasive threat to freshwater wetlands? Conflicting evidence from several ecological metrics. Wetlands 21:199-209.

Gray, A. J. 1986. Do invading species have defineable genetic chracteristics? Philosophical Transactions  of the Royal Society of London B 314:655-674.

Hendrix, P. F., and P. J. Bohlen. 2002. Exotic earthworm invasions in North America: ecological and policy implications. BioScience 52:801-811.

Keane, R. M., and M. J. Crawley. 2002. Exotic plant invasions and the enemy release hypothesis. Trends in Ecology and Evolution 17:164-170.

Kennedy, T. A., S. Naeem, K. M. Howe, J. M. H. Knops, D. Tilman, and P. Reich. 2002. Biodiversity as a barrier to ecological invasion. Nature 417:636-638.

Klironomos, J. N. 2002. Feedback with soil biota contributes to plant rarity and invasiveness in communities. Nature 417:67-70.

Kolar, C. S., and D. M. Lodge. 2002. Ecological predictions and risk assessment for alien fishes in North America. Science 298:1233-1236.

Kourtev, P. S., J. G. Ehrenfeld, and M. Häggblom. 2002. Exotic plant species alter the microbial community structure and function in the soil. Ecology 83:3152-3166.

Lee, C. E. 2002. Evolutionary genetics of invasive species. Trends in Ecology & Evolution 17:386-391.

Levine, J. M., M. Vilà, C. M. D'Antonio, J. S. Dukes, K. Grigulis, and S. Lavorel. 2003. Mechanisms underlying the impacts of exotic plant invasions. Proceedings of the Royal Society of London B DOI 10.1098/rspb.2003.2327.

Lonsdale, W. M. 1999. Global patterns of plant invasions and the concept of invasibility. Ecology 80:1522-1536.

Mack, R. N., D. Simberloff, W. M. Lonsdale, H. Evans, M. Clout, and F. A. Bazzaz. 2000. Biotic invasions: causes, epidemiology, global consequences, and control. Ecological Applications 10:689-710.

Maron, J. L., and M. Vilà. 2001. When do herbivores affect plant invasions? evidence for the natural enemies and biotic resistance hypotheses. Oikos 95:361-173.

Mitchell, C. E., and A. G. Power. 2003. Release of invasive plants from fungal and viral pathogens. Nature 421:625-627.

National Research Council. 2002. Predicting invasions of nonindigenous plants and plant pests. National Academy Press, Washington D. C.

Saltonstall, K. 2002. Cryptic invasion by non-native genotypes of the common reed, Phragmites australis, into North America. Proceedings of the National Academy of Sciences 99:2445-2449.

Schmidt, K. A., and C. J. Whelan. 1999. Effects of exotic Lonicera and Rhamnus on songbird nest predation. Conservation Biology 13:1502-1506.

Torchin, M. E., K. D. Lafferty, A. P. Dobson, V. J. McKenzie, and A. M. Kuris. 2003. Introduced species and their missing parasites. Nature 421:628-630.

Yela, J. L., and J. H. Lawton. 1997. Insect herbivore loads on native and introduced plants: a preliminary study. Entomologia Experimentalis et Applicata 85:275-279.