185in their native ranges that have been introduced into North America. Thus, their
ecology in their native ranges forecasts their behavior in an introduced range.
Additional information on invasive species such as B. hordeaceus , B. rubens , and
B. japonicus would inform their management. Data for other less invasive annual
species in section Bromus is limited, but could shed light on reasons for lack of
invasiveness and invasiveness alike.
Research on perennial Bromus grasses has focused on breeding and cultivation
of species used for hay and forage. More research about the relationship between
invasion and human use of perennial Bromus species for animal feed and revegeta-
tion could help to encourage the development of varieties that are less likely to
escape from cultivation and to damage natural habitats and could also contribute to
a better understanding of invasion. The history of Bromus inermis in North America
is an important case study.
Research that focuses on climatic factors is becoming increasingly important.
Changes in temperature and rainfall patterns could affect the current ranges of intro-
duced Bromus grasses. Some invasive species such as B. tectorum and B. arvensis
may become less common in parts of their current ranges, but could expand into
new areas. Other Bromus species could also move into new areas or become more
serious invaders (Zelikova et al. 2013 ; Sherry et al. 2012 ; Bradley and Wilcove
2009 ; Hobbs et al. 2007 ).
A number of patterns revealed by our analyses could be studied in greater depth.
For example, our analyses showed that species that were described and named early
are more likely to be widely distributed and weedy than species that were named
and described more recently. If this pattern also occurs in other taxa and to better
understand the underlying factors, it could be used to predict and prevent future
invasions. We also showed that polyploidy is associated with weediness, especially
for perennial Bromus. Exploration of this pattern could reveal important mecha-
nisms of plant invasions.
Finally, while many Bromus grasses are invasive, some are rare and others are
likely to be threatened by changes in agricultural and land management practices,
habitat loss, and climate change. A number of species grow in limited areas,
sometimes at high elevations or in other areas with extreme environmental condi-
tions. Information about these grasses is diffi cult to fi nd and in some cases their
current status is unknown.
References
Acedo C, Llamas F (2001) Variation of micromorphological characters of lemma and palea in the
genus Bromus (Poaceae). Ann Bot Fenn 38:1–14
Ainouche ML, Bayer RJ (1997) On the origins of the tetraploid Bromus species (section Bromus ,
Poaceae): insights from internal transcribed spacer sequences of nuclear ribosomal
DMA. Genome 40:730–743
Andersson L, Milberg P, Schütz W, Steinmetz O (2002) Germination characteristics and emergence
time of annual Bromus species of differing weediness in Sweden. Weed Res 42:135–147
6 Attributes That Confer Invasiveness and Impacts Across the Large Genus Bromus...