Montana Lake study reveals how invasive species affect native food webs


Date:
November 4, 2021
Source:
The University of Montana
Summary:
Invasive species cause biodiversity loss and about $120 billion
in annual damages in the U.S. alone. Now, thanks to a new
collaborative study, there is greater insight into how invasive
species progressively affect native food webs in mountain lakes.



FULL STORY ========================================================================== Invasive species cause biodiversity loss and about $120 billion in annual damages in the U.S. alone. Despite plentiful evidence that invasive
species can change food webs, how invaders disrupt food webs and native
species over time has remained unclear.


==========================================================================
Now, thanks to a new collaborative study, there is greater insight into
how invasive species progressively affect native food webs. The research
was conducted by the University of Montana's Flathead Lake Biological
Station, the U.S. Geological Survey and Montana Fish, Wildlife & Parks.

"This study provides new details about how invasive lake trout affect
entire lake food webs," said U.S. Fish and Wildlife fish biologist
Charles Wainright, who recently completed his graduate student work at
UM's biological station.

"The findings will be important for conserving native species and
ecosystems in Montana and elsewhere." The study, recently published
in the journal Proceedings of the National Academy of Sciences, used
long-term fisheries monitoring records to determine the timing of invasion
by a nonnative fish predator, lake trout, in 10 northwestern Montana
lakes. It also analyzed food webs from those lakes to determine how they changed and impacted native communities as the invasions progressed.

The research team showed that lake trout disrupted food webs by forcing
native fishes to feed on suboptimal food sources in different habitats, eventually causing the loss of the native predator, bull trout, a
threatened species protected under the U.S. Endangered Species Act.

"Native bull trout populations have drastically declined in many lakes
across western Montana due to competitive interactions with invasive
lake trout," said Clint Muhlfeld, a USGS aquatic ecologist and FLBS
associate research professor.

"For the first time, we show what happens not only to bull trout but
entire food webs supporting them as lake trout invade and upset lake
ecosystems over time." The study also showed the food-web effects of
lake trout invasion were especially pronounced as lake trout abundance increased rapidly 25 to 50 years after colonization. After 50 years, lake
trout were the dominant apex predator in these food webs. The study shows
that, given enough time, invasive lake trout can disrupt and replace a
native fish species -- like bull trout -- and create divergent biological communities that are vastly different than uninvaded ecosystems.

This study adds to a body of evidence showing that invasive species
have affected western Montana. For example, until the late 1800s,
about 10 native species of fish patrolled the waters of Flathead Lake, including abundant westslope cutthroat trout and bull trout. Beginning
in 1905, fisheries managers began introducing nonnative species to the
food web as a means to improve Flathead Lake tourism and generate more recreational fishing appeal. Today, there are more than 20 species of
fish in Flathead Lake, and introduced species like lake trout, lake
whitefish, and Mysis shrimp dominate the food web in Flathead Lake,
so much so that native species -- including bull trout and westslope
cutthroat, Montana's state fish -- have declined dramatically.

"This has been a truly collaborative effort," said FLBS lake ecologist
Shawn Devlin. "The work leverages the rather bleak history of introduction
and invasion of nonnative species in northwest Montana lakes into an
ecological experiment built on the power of long-term data and a deeper understanding of lake ecology." The study's results stress the importance
of protecting entire landscapes from biological invasions. The use of innovative biosurveillance monitoring techniques, like environmental DNA,
also are critical to increasing the likelihood of detecting invaders
before they become established. For ecosystems that already have been
invaded, this study's findings can inform proactive control efforts
during the early stages of invasion to avoid food web disruptions that
may be difficult to reverse.

The study, led by Wainright, was co-authored by Muhlfeld, Devlin,
FLBS Director Jim Elser and Samuel Bourret of Montana Fish, Wildlife &
Parks. The research was supported by the USGS Biological Threats Program,
FLBS and philanthropic gifts.

========================================================================== Story Source: Materials provided by The_University_of_Montana. Note:
Content may be edited for style and length.


========================================================================== Journal Reference:
1. Charles A. Wainright, Clint C. Muhlfeld, James J. Elser, Samuel L.

Bourret, Shawn P. Devlin. Species invasion progressively disrupts
the trophic structure of native food webs. Proceedings of the
National Academy of Sciences, 2021; 118 (45): e2102179118 DOI:
10.1073/ pnas.2102179118 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2021/11/211104140129.htm

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