Plenty
of Space to Invade
University of Massachusetts Amherst, Science Daily
A new study, the first comprehensive assessment of native vs.
non-native plant distribution in the continental United States, finds
non-native plant species are much more widespread than natives, a finding that
lead author Bethany Bradley at the University of Massachusetts Amherst called
"very surprising."
"Ecologists typically think of invasive species as being
introduced in one spot and gradually spreading out from there. But, we found
that even species with only a handful of occurrences were distributed all
across the U.S.," she says. "The future may already be here."
The international team the biogeographer led explored the
geographic distributions of over 13,000 plant species, comparing those that are
native and non-native to the continental United States, to identify differences
in their overall geography. The work, which appears in the current online issue
of Global Ecology and
Biogeography, is co-authored with Regan Early of the University of Exeter,
U.K., and Cascade Sorte of the University of California, Irvine.
Their comparative analysis highlights the fact that native
plants are strongly limited in their distributions compared to non-native
plants, probably because they have a harder time dispersing into suitable
climates. That is, people aren't moving them around as much, Bradley says.
The authors believe that this pattern is a result of widespread
human introduction of non-native and invasive plants. Regionally, the
ornamental plant trade and other human activities like planting of seeds with
weed contaminants help non-natives overcome dispersal barriers that limit the
distribution of native species.
"One silver lining for biological conservation is that
native species are not so strongly limited by climate as once assumed,"
she adds. In other words, native species' distributions aren't defined by their
climate tolerances. Instead, other, non-climate-related dispersal barriers or
interactions with other species can prevent native species from moving into
environments where they could otherwise exist.
"With this study, we're showing that inability to disperse,
not climate tolerance, is likely stopping some species from inhabiting a
broader range. This could mean that many species predicted to go extinct with
climate change could persist for longer than previously anticipated under novel
climates."
But, Bradley warns, "Dispersal barriers aren't going away,
so even if native species can survive a little longer with climate change, most
are clearly not going to be able to shift into newly suitable climate without
our help."
The researchers analyzed the distributions of 13,575 plant
species (9,402 native, 2,397 endemic, 1,021 alien and 755 invasive) across the
U.S. For each species, they recorded the total number of grid cells (roughly
county-sized) occupied, calculated potential range based on climatic
conditions, and measured their latitudinal and longitudinal extents. They then
used the number of occupied and potential grids to calculate occupancy of
potential range (range infilling) for each.
Bradley says although non-native and invasive species are much
more widespread than natives, they have "filled in" much less of
their potential range. Native species on average occupied about 50 percent more
of their potential range than non-native species. For managers dealing with
invasive species, Bradley says, "watch out."
She adds, "We're likely to see more problems from invasive
species ahead as they continue to expand locally into suitable
environments." As the paper title states, invasive plants have plenty more
space to invade.
This research was initiated during a working group supported by
the National Center for Ecological Analysis and Synthesis (NCEAS) and supported
by the Department of Defense's Strategic Environmental Research and Development
Program.
Story
Source:
The above story is based on materials provided by University of Massachusetts Amherst. Note: Materials may be edited for
content and length.
Journal
Reference:
Bethany A. Bradley, Regan Early, Cascade J. B. Sorte. Space to invade? Comparative
range infilling and potential range of invasive and native plants. Global
Ecology and Biogeography, 2015; DOI: 10.1111/geb.12275
Cite
This Page:
University of Massachusetts Amherst. "Non-Native Plants
Widespread, Plenty of Space to Invade." Science Daily,
20 January 2015.
<www.sciencedaily.com/releases/2015/01/150120085609.htm>.