Exotic Brome-Grasses in Arid and Semiarid Ecosystems of the Western US

© Springer International Publishing Switzerland 2016 155 M.J. Germino et al. (eds.), Exotic Brome-Grasses in Arid and Semiarid E ...

156 6.1 Introduction The grass family ( Poaceae ) contains a number of species that are of exceptional importance to humans, inc ...

157 Several studies have investigated invasiveness in annual Bromus grasses. Hulbert ( 1955 ) studied ten species that have been ...

Table 6.1 Taxonomy of the tribe Bromeae Genus Methods of subdividing Bromus grasses Life span No. species Ploidy Native distribu ...

159 about invasiveness in Bromus grasses. We evaluated the data in the database to identify factors for which information for ma ...

160 Table 6.2 Hypotheses evaluated in this chapter, based on factors that are commonly listed as contributing to invasiveness in ...

161 Factor Hypothesis Basis/rationale Independent variables Comments based on analyses 6 Ploidy level Polyploid chromosome count ...

162 Table 6.2 (continued) Factor Hypothesis Basis/rationale Independent variables Comments based on analyses 11 Climate Ability ...

163 we looked for species that are listed as a weed in one or more of three categories: crop weed (weeds of crops), ruderal weed ...

16 4 All temperature and precipitation data used in the analyses were based on cli- mate data collected from 1961 to 1990 that w ...

165 6.3 Results and Discussion 6.3.1 Summary of Results Based on the data we collected in the database, we categorized 24 specie ...

Table 6.3 Results of univariate logistic regressions Independent variable No. Values Is widely introduced Is a crop weed Is a ru ...

(continued) Life span 147 22.827 <0.0001 38.9695 <0.0001 37.5581 <0.0001 20.5218 <0.0001 Medium vs. long 31.333 (5.7 ...

Table 6.3 (continued) Cultivars available 147 21.0028 <0.0001 16.856 (5.036–56.414) 10.5678 0.0012 6.491 (2.092–19.693) 9.588 ...

169 Table 6.4 Results of two multiple logistic regressions with a backward stepwise elimination conducted for each of the four d ...

170 Neobromus reached North America and eventually South America by the end of the Pliocene, with diploid and tetraploid Ceratoc ...

171 at least 18 species are widely introduced, 11 (or more) are crop weeds, 11 (or more) are ruderal weeds, and at least eight a ...

172 Vahl (rescue brome), a valuable forage species with many cultivars, has become an invasive environmental weed in some areas ...

173 Hypothesis 5 (Table 6.2 ) states that species with low mean seed mass are more likely to be invasive. Our analyses did not s ...

174 Fig. 6.3 Frequency distribution of species’ maximum awn lengths by taxonomic section in the Bromus genus, for introduction o ...