PARENT SESSION
Oral Session #66: Invasions: Plants. Mechanisms, patterns, controls. Presiding: R. Mack.
Thursday, August 9, 2001. 1:00 PM to 4:45 PM. Hall of Ideas E.
Fitness and phenotypic plasticity among European, North American, and New Zealand populations of Bromus tectorum.
Kinter, Cecilia1, Mack, Richard1, 1
ABSTRACT- Within 40 years of introduction in the late 1800s, the Eurasian grass Bromus tectorum (cheatgrass) was abundant across western North America. This grass arrived in New Zealand at least 100 years ago, and has yet to become invasive. We hypothesized that known high levels of phenotypic plasticity and fitness of B. tectorum contributed to the invasive character of North American populations, while low levels of plasticity and fitness have precluded a New Zealand invasion. In a common greenhouse, we compared 62 B. tectorum populations from widely separated locales in western North America, New Zealand, and western Europe under low temperature, low nutrient, low moisture, and a control. We assessed 15 phenotypic traits (e.g. height, tiller number, days to flowering, seed biomass). Significant differences (p<0.0001, ANOVA) among source locations were evident 30 days after emergence. For example, 30-day heights averaged across all environments for North American, European, and New Zealand populations were 21.72, 19.00, and 14.98 cm, respectively. North American populations were consistently most vigorous, followed by European and lastly New Zealand populations. Additionally, phenotypic plasticity levels--assessed using reaction norms and ANOVA--differed significantly: North American populations ranked highest, New Zealand populations lowest. Differences in levels of phenotypic plasticity and fitness between source populations for B. tectorum in North America and New Zealand have likely contributed to the radically different histories of this grass in two of its new ranges.
KEY WORDS: invasions, weeds