Defining a regional approach for invasive plant research and management - Invasive Plants: Ecological and Agricultural Aspects - page 128

currently considered invasive can eventually affect ecosystem function. Thus,
it is important to consider the potential impacts of all introduced plants, not
just those already discovered or deemed invasive. Including scientists, conser-
vation managers, and local botanists in defining research and management pri-
orities improves detection of a broad range of introduced plants.
Example research framework: Potentilla recta in the Blue Mountains
Ecoregion of North America
There are many noxious exotic plants presently occurring east of the Cascade
Mountains in the Pacific Northwest (Tab. 1). However, only some of these spe-
cies are considered invasive over large areas, while others are more restricted
in distribution. Managers and policy makers want to know the likelihood of
new plant species becoming prevalent over large areas, but ecologists are only
able to provide after-the-fact explanations for invasions. Predicting which spe-
cies will be invasive and which habitats and ecosystems are invasible remains
difficult [24]. Potentilla recta (Tab. 1) is a relatively recent introduction to the
PNW with many new infestations reaching environmentally severe sizes and
densities [50]. Despite widespread concern about P. recta, we were unaware of
any ongoing studies, and only sparse information was available in the litera-
ture to inform managers about the species.
Potentilla recta (Rosaceae, common name is sulfur cinquefoil) is a herba-
ceous perennial forb native of Eurasia. It was introduced to North America
prior to 1900 [51], and has since spread across the continent. It has been
reported in all states of the USA, except Arizona, Utah and New Mexico. The
ten Canadian provinces also have documented the presence of P. recta . The
plant reproduces only by seed, has a single taproot, and may have several shal-
low, spreading branch roots, but no rhizomes. Potentilla recta has four gener-
al life history stages [52]; viable seed in the soil, seedlings, non-reproductive
rosettes, and reproductive stemmed individuals [53]. Werner and Soule [54]
provide information on the biology of the species from early observations
made in eastern North America where P. recta is a minor agricultural weed.
More recently, P. recta is recognized as increasing in the drier climates of
northwestern North America and is considered a threat to native plant com-
munities where it forms dense populations [50, 55, 56].
Dense and continuous P. recta populations most commonly occur on areas
of soil disturbance (e.g., old fields), but increasingly, populations have been
observed in rangelands and in the understory of open-canopied ponderosa pine
forests. Potentilla recta is unnoticed in many parts of its range because it is
similar in appearance to native co-occurring congeners, particularly Potentilla
gracilis [50]. There are no available biological control agents for P. recta . Due
to the plant's close genetic relationship to native Potentilla species and to cul-
tivated strawberry, finding a host-specific biocontrol agent for P. recta is there-
fore difficult. Potentilla recta was first reported in northeast Oregon in 1969.