My graduate
students and I are primarily interested in biological invasions,
particularly plant invasions. Throughout
much of my career, I have investigated the causes and epidemiology
of invasions. As a result, I have investigated the events
that surround the accidental or deliberate introductions of species
into new ranges, the circumstances that facilitate or thwart their
persistence in the new range, and the reasons for an introduced
species becoming invasive in a new range and consequently becoming
highly damaging to the natural environment, national economies
and even human health.
In the course of this research my graduate students
and I have included studies in plant demography, ecological genetics
(in both the native and introduced ranges of the species), ecophysiology,
dendrochronology, and the community consequences of invaders, such
as through competition. Reconstructing the historical events
associated with the species’ entry into a new range has also
provided an illuminating source of information. In addition,
I have investigated the means by which we can predict potentially
invasive species (as an aid to erecting more effective quarantine
protocols) and finally in devising effective means for the eradication
of introduced species that appear likely to become invasive. This
latter work has allowed me to advise and comment on an array of
legislative and regulatory issues dealing with invasive species,
both in the U.S. and overseas.
Current Research
Current research in my lab includes the following
topics.
The invasive grass, Bromus tectorum. The
population biology of Bromus tectorum (cheatgrass) is
a topic that has long attracted me. Cheatgrass is a small,
annual grass that was accidentally and repeatedly introduced into
the U.S. as early as the late 18th century. Its spread in
the Intermountain West (the Great Basin) has been the spark for
a huge transformation of the communities and ecosystems within
this region. (See my publication list to best review our
prior research on this important invader.) Our current research
examines the genetic variation among populations of cheatgrass
in its introduced U.S. range and well in its native range in Europe
and Central Asia. This exciting area of research will continue,
and there is much more we need to know about this grass’s
ecological genetics across its large introduced and immense native
ranges.
Predicting the identity of future plant
invaders is a daunting task that has obvious
practical implications. Any nation’s success in
providing broad-spectrum biosecurity is well served by knowing
in advance which species could cause harm if introduced inside
its borders. Quarantine regulations, national and international,
are necessary expressions of these concerns, yet our ability
to predict the next invader (aside from a species having a “track
record” of destruction elsewhere) is poor.
The majority of vascular plants are introduced
deliberately into a new range. Consequently, their identity
may be known before arrival, even if little or nothing is known
of their response in a new range. My students and I have
become increasingly interested in the likelihood of native species
in eastern temperate Asia (primarily China) being introduced to
the U.S. and subsequently becoming invasive. Consequently,
we are examining floristic and functional groups of temperate Asian
species in experimental protocols for evidence of their ability
to thrive in natural communities in the Pacific Northwest. Clearly
the number and volume of plant introductions to the U.S. from eastern
Asia is increasing, thereby giving our research much relevance
to the growth of international trade.
The role of environmental stochasticity
in plant naturalizations. For any taxonomic
group, the likely fate of immigrants is extinction, i.e., the
odds against naturalization, much less invasion, are extraordinarily
high. My students and I are investigating experimentally
the role of stochasticity for immigrant populations of different
sizes. In addition, I am continuing my long-term interest
in the effect on introduced species of natural enemies in a
new range, i.e., cases in which biotic agents act as control
agents.
Eradication of unwanted plant immigrants. Short
of blocking the entry of unwanted non-native species at the border,
the most effective means to minimize their effect is through their
total destruction (eradication). Achieving total eradication
can be daunting, and I explore effective means to cause eradication,
mainly through developing step-by-step protocols that land managers
and others can readily employ. |
|
