PARENT SESSION
Oral Session #63: Invasive Species: Terrestrial.
Presiding: D. Larson
Wednesday, August 7. 1:00 PM to 4:45 PM. Graham Meeting Room, TCC.

Invasive Bromus tectorum in North America shows higher fitness than native and introduced populations elsewhere.

Kinter, Cecilia^*,1, Mack, Richard¹, ¹ Washington State University, Pullman, Washington

ABSTRACT- The Eurasian grass Bromus tectorum was introduced into arid shrublands and grasslands of New Zealand and North America over 100 years ago, but has strikingly different histories in these ranges. In the southern part of New Zealand's South Island, it persists at low levels, while in western North America, it dominates vast areas. We hypothesized that inherent high fitness contributed to the invasive character of North American populations, while low fitness in founder populations precluded a New Zealand invasion. In four common greenhouse environments, we compared 62 Bromus tectorum populations from western North America, New Zealand, and western Europe. We assessed 15 phenotypic and fitness traits (e.g. height, days to flowering, vegetative biomass, seed biomass). Significant differences (p<0.0001, ANOVA) among source locations were evident for most traits assessed. For example, vegetative biomass/plant averaged across all environments was 10.1, 9.4, and 8.7 g for North American, European, and New Zealand populations, respectively. North American populations were consistently most vigorous, followed by European and lastly New Zealand populations. Canonical Correspondence Analysis of phenotypic traits grouped North American populations with those from Austria, Slovakia, and eastern Germany, and New Zealand populations with those from the Netherlands and western Germany. Differences in fitness between source populations have likely contributed to radically different histories of Bromus tectorum in two of its new ranges.

KEY WORDS: invasion, genetics, Bromus tectorum