110
East Coast populations. The distribution of B. tectorum across NA suggests that the
grass could have spread westward with European settlers. Alternatively, the species’
occurrence throughout NA may stem from separate introductions. These two
hypotheses were tested through genetic analysis of populations of B. tectorum
across the USA and Canada.
Fig. 4.2 Multilocus genotypes for 38 populations of Bromus tectorum in the Eastern USA. Pie
diagrams illustrate the proportions of each multilocus genotype in each population. (Sizes of the
pie diagrams and any offset segments here and in Figs. 4.3 – 4.8 vary only to enhance legibility.)
Lines accompanying pie diagrams indicate locations of the populations. Numbers are population
designations from Bartlett et al. ( 2002 )
S.J. Novak and R.N. Mack