PARENT SESSION
Poster Session # 16: Invasive Species.

Wednesday, August 6 Presentation from 5:00 PM to 6:30 PM. SITCC Exhibit Hall B.

Reproductive life history traits and competition as explanations for the success of the invasive perennial Rubus phoenicolasius.

Innis, Anne^{*,1, 2}, Forseth, Irwin¹, Whigham, Dennis², ¹ University of Maryland, College Park, MD² Smithsonian Environmental Research Center, Edgewater, MD

ABSTRACT- There is a growing presence of invasive species in global ecosystems. Invasive species displace native species, threaten biodiversity and alter the function of ecosystems. Determining both the characteristics of invasive species and those of the invaded habitat will enhance management and prevention of further invasions. The most effective studies of invasive species involve a comparison of closely related invasive and native species. This study used two perennial Rubus congeners, an invasive species, wine raspberry (Rubus phoenicolasius), and a native species, sawtooth blackberry (Rubus argutus). Rubus phoenicolasius is invading fields and successional forests, R. argutus habitat, along the Atlantic Coast of the United States. In 2002 two studies were conducted at the Smithsonian Environmental Research Center, Edgewater, MD. In the study of reproductive life history traits, 40 individuals of each Rubus species were examined for self-pollination by excluding pollinators, with pollen bags, and recording fruit set. R. phoenicolasius was shown to self-pollinate more than R. argutus. During the growing season, 901 individuals of R. phoenicolasius and 1159 individuals of R. argutus were surveyed for age and reproductive effort. Of the mature individuals, R. phoenicolasius were more likely than R argutus to be reproductive. R. phoenicolasius produced greater numbers of fruit with more seeds per fruit than R. argutus. Self-pollination, high fruit and seed set of R. phoenicolasius may drive rapid population growth. In the competition study, 72 1m² plots with existing populations of Duchesnea indica were used to determine the impacts of R. phoenicolasius and R. argutus on local species. Planned comparisons between the two Rubus treatments showed no significant difference in the response of D. indica. The drought that was in effect in Maryland may have suppressed growth of the three species, thus masking any competitive interactions. With the worldwide problem of invasive species, it is necessary to understand what characteristics define invasive species and quantify the effects of invasive species on plant communities.

Key words: competition, Rubus , invasive species, reproduction