Study Finds Climate Change Accelerates Hybridization Between Native, Invasive Trout
MISSOULA – A new article by researchers from the University of Montana, the U.S. Geological Survey and Montana Fish, Wildlife & Parks asserts that climate warming is increasing the hybridization of trout – interbreeding between native and non-native species – in the interior western United States.
Clint Muhlfeld, a research assistant professor in the UM Division of Biological Sciences’ Flathead Lake Biological Station and research ecologist with the USGS Northern Rocky Mountain Science Center in Glacier National Park, is the lead author of the article, titled “Invasive hybridization in a threatened species is accelerated by climate change,” which was published in the latest issue of Nature Climate Change. Co-authors are Ryan Kovach, a postdoctoral scholar at UM’s Flathead Lake Biological Station, and Leslie Jones, a UM doctoral student who works with Muhlfeld and USGS.
Specifically, rapid increases in stream temperature and decreases in spring flow over the past several decades contributed to the spread of hybridization between native westslope cutthroat trout and the introduced rainbow trout – the world’s most widely introduced invasive fish – across the Flathead River system in Montana and British Columbia, Canada.
Experts have hypothesized that climate change could decrease worldwide biodiversity through cross-breeding between invasive and native species, but this study is the first to directly and scientifically support this prediction. The study was based on 30 years of research by scientists with UM, USGS and Montana FWP.
Hybridization has contributed to the decline and extinction of many native fishes worldwide, including all subspecies of cutthroat trout in western North America, which have enormous ecological and socioeconomic value. The researchers used long-term genetic monitoring data coupled with high-resolution climate and stream temperature predictions to measure whether climate warming enhances interactions between native and non-native species through hybridization.
“Climatic changes are threatening highly prized native trout as introduced rainbow trout continue to expand their range and hybridize with native populations through climate-induced ‘windows of opportunity,’ putting many populations and species at greater risk than previously thought,” Muhlfeld said.
“The study illustrates that protecting genetic integrity and diversity of native species will be incredibly challenging when species are threatened with climate-induced invasive hybridization,” he said.
Westslope cutthroat trout and rainbow trout both spawn in the spring and can produce fertile offspring when they interbreed. Over time, a mating population of native and non-native fish will result in only hybrid individuals with substantially reduced fitness because their genomes have been altered by non-native genes that are maladapted to the local environment. Protecting and maintaining the genetic integrity of native species is important for a species’ ability to be resilient and better adapt to a rapidly changing climate.
Historical genetic samples revealed that hybridization between the two species was largely confined to one downstream Flathead River population. However, the study noted, during the past 30 years, hybridization rapidly spread upstream, irreversibly reducing the genetic integrity of native westslope cutthroat trout populations. Genetically pure populations of westslope cutthroat trout are known to occupy less than 10 percent of their historical range.
The rapid increase in hybridization was associated with climatic changes in the region. From 1978 to 2008, the rate of warming nearly tripled in the Flathead basin, resulting in earlier spring runoff, lower spring flooding and flows, and warming summer stream temperatures. Those locations with the greatest changes in stream flow and temperature experienced the greatest increases in hybridization.
Relative to cutthroat trout, rainbow trout prefer these climate-induced changes and tolerate greater environmental disturbance. These conditions likely have enhanced rainbow trout spawning and population numbers, leading to massive expansion of hybridization with westslope cutthroat trout.
“The evolutionary consequences of climate change are one of our greatest areas of uncertainty because empirical data addressing this issue are extraordinarily rare,” Kovach said. “This study is a tremendous step forward in our understanding of how climate change can influence evolutionary process and ultimately species biodiversity.”
Overall, aquatic ecosystems in western North America are predicted to experience earlier snowmelt in the spring, reduced late spring and summer flows, warmer and drier summers, and increased water temperatures – all of which indicate increased hybridization between these species.
Additional UM-affiliated authors are UM Wildlife Biology Program Director Winsor Lowe, UM Associate Professor of Conservation Ecology Gordon Luikart and Regents Professor Emeritus Fred Allendorf. Authors not affiliated with UM are Robert Al-Chokhachy with the USGS Northern Rocky Mountain Science Center, Matthew Boyer with Montana FWP in Kalispell and Robb Leary with Montana FWP in Missoula.
The study was supported by the Great Northern Landscape Conservation Cooperative, the U.S. Department of the Interior’s Northwest Climate Science Center, the National Climate Change and Wildlife Science Center, the National Science Foundation and Bonneville Power Administration.
The article can be viewed online at http://dx.doi.org/10.1038/nclimate2252. For more information call Muhlfeld at 406-600-9686 or email cmuhlfeld@usgs.gov.
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* The Warm List – seen here: http://www.numberwatch.co.uk/warmlist.htm
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Do they taste the same? We have some brown and rainbow trout in Oz, but the brown don’t seem to thrive as well and they actually breed rainbow trout in farms then release them in the wild.Depends if they are in a lake or in fast running cold creeks. We have a trout season in NSW, and no trout fishing is allowed as it is their breeding season. June until early October. I like trout next to Tasmanian salmon, so long as they don’t smoke it. Then it tastes like kippers to me.
Do they marry Bonos?
My question is, did Clint Muhlfeld apply for a grant to study trout, get turned down? And then did he apply again – this time mentioning climate change- and then got money? Oh, and the resulting paper got publicity …
TobiasN yes good question. It was stated many years ago, if you mention climate change in your thesis, you will get a grant. Otherwise No.
All the global warming believers are half breed – part human, part Martian. Seriously? What a farce.
What does climate change have to do with it? There are always consequences when you introduce new species into an ecosystem. When will they ever learn?
They use to call that natural selection on which fish adapts to the environment better. Adapt or die even if your offspring become a new bread of fish.
It just goes to show that horny salmon are like horny male humans – they like hot foreign chicks that wiggle their butts at them. It’s a story as old as animals…
So what?
Good heavens. Must we have issues with black trout marrying white trout???? Really????? What a load of hooey. At issue here are the earlier attempts to introduce non-native fish into streams and rivers whose native population was severely diminished. So who came up with putting non-native fish in these rivers? The guvmnt did that. So live with it. The same thing will happen between coyotes and non-native wolves in Oregon. When will we understand that in terms of nature, it is best we leave well enough alone. Native fish population down? Then stop fishing. If a state doesn’t want the consequences of that, let the state decide to stock with non-native fish and live with the consequences of cross breeding. If part of that drainage system is federal land (an oxymoron in a Union of states), let them keep the federal land pristine. As for the river part that is state land, county land, private land, whatever, they that owns it should get to choose. And if migration happens, well sh** happens.
If evolution is good and climate change causes faster evolution, isn’t climate change good?
That’s what happens when you introduce a non native species. Look at the cane toad in Oz. At one town the stupid people killed all the black snakes the only species that can kill them. Look at the shark that has invaded fresh water the Bull Shark, it adapted to salt and fresh water.
Hybridized trout are stocked in lakes and rivers all over the world. The offspring or the initial eggs they lay are typically not fertile. Most trout taste very similar so it doesn’t make much difference. Salmon are a closely related species so can also be cross-bred. Fish stocking stations can make this an easy business but you probably don’t want to know how it is done.
There were two larger lakes where I grew up that were stocked with Splake. Splake is a cross-breed between a brook trout and lake trout and it is a hardy trout that grows quickly and can reach 20 pounds.
Any native species trout that CAN cross-breed, WILL cross-breed and HAVE cross-bred and it has ALWAYS happened in nature and it has nothing to do with global warming.
I am speechless. Ok,,,, my fingers just quit!
Oh the pain!
Xerox Pamela’s comment here>
These statements don’t make logical sense. If the non-native fish genes are maladapted to the local environment, how can these fish be successful breeders? Assuming native species are highly adapted to local environments, then how can they be more resilient when the environment changes rapidly?
Fishermen prize the native cutthroat trout for their challenge and rarity. Introducing rainbows was a mistaken attempt to expand fishing opportunities. Temperature changes only add to the problem.
“It’s worse than we thought!” On and on they go. Doom and gloom and oh-how-naughty-we are. Message to alarmists – Give it an effing rest!
That warmlist you supplied at the end of the post is getting mighty long. I share it with people to give them a laugh. The Earth listing alone is hilarious! Check it out.
http://www.numberwatch.co.uk/warmlist.htm
“Protecting and maintaining the genetic integrity of native species is important for a species’ ability to be resilient and better adapt to a rapidly changing climate.”
Say what? Why exactly is that true? It seems to me that if the native cutthroat trout were more resilient and better able to adapt to a rapidly changing climate, then they would not be being bred out of existence by the Rainbow Trout hybrid. It is precisely because they are NOT more resilient and able to adapt that they are being displaced by the hybrid trout – who apparently ARE more resilient and better able to adapt than the Cutthroat. If they weren’t the native cutthroat trout would displace them and would be expanding their range.
If my eyes aren’t deceiving me, things look a little different and not nearly so worrisome if we look at 100+ years of data…
Max raw temp and precipitation charts from USHCN for Great Falls, which is a large city not so far from the study area:
http://cdiac.ornl.gov/cgi-bin/broker?id=243751&_PROGRAM=prog.gplot_meanclim_mon_yr2013.sas&_SERVICE=default¶m=TMAXRAW&minyear=1891&maxyear=2013
http://cdiac.ornl.gov/cgi-bin/broker?id=243751&pvar=CPRECIP&_PROGRAM=prog.gplot_totalclim_mon_yr2013.sas&_SERVICE=default&minyear=1892&maxyear=2013
Both from here: http://cdiac.ornl.gov/cgi-bin/broker?_PROGRAM=prog.climsite_monthly.sas&_SERVICE=default&id=243751&_DEBUG=0
If someone finds a closer station, please post.
Last time I looked “biodiversity” meant “more species” which means that biodiversity increased with interbreeding, not decreased. The whole claim that “more diversity is better” is mostly meaningless, anyway.
The guy does sound a lot like a White (or Black, or Brown, or Yellow) supremist, doesn’t he?
Climate change has become the modern ‘god of gaps.’ We can’t explain our findings therefore it is caused by climate change. I always find it amusing to replace ‘climate change’ or any other synonym with ‘the Gods are [angry]’ which makes for far more entertaining reading.
Mod : Should be ‘the Gods are angry’ in my post…
Take a page from the history of the Mennonites. Marrying close cousins is not all it’s cracked up to be. Our native breeding stock is likely severely genetically weak exactly because of the lack of bedding down with that sexy young “different” thing wagging her tail at the stock of males ogling her.
Mennonites now ship their potential breeding stock of young male and female almost adults clear across the country. I wonder why.
[snip – don’t post this racist crap on my blog- Anthony]
“Over time, a mating population of native and non-native fish will result in only hybrid individuals with substantially reduced fitness because their genomes have been altered by non-native genes that are maladapted to the local environment.”
I agree with Gary. Having bred animals for a long time, there is a thing called “hybrid vigour” that suggests that cross-breeding improves hardiness and improves fitness, not the other way. I don’t care if we are talking cattle, horses, dogs or cats, it is demonstrable. I would think that it is the same in fish. By introducing new genes, there is more chance of producing hardiness in the end as any that breed the other direction soon disappear.
Further, since Rainbow Trout are spreading rapidly, according to this article, they must be HIGHLY adaptable in converse to the statements in this article. Further, assuming the hybrids can breed, the hybridized group will be even stronger.
Cutthroat trout are less adaptable. They require clear cold water and generally prefer the headwaters so they don’t have to compete with other species. There are 13 sub-species of Cutthroat Trout. It may be that restricted fishing as we have in Alberta has allowed them to expand their range in addition to intrusion to the “mixing” region by Rainbow Trout. We have catch and release in many Cutthroat areas. In the Bow River that runs through Calgary, Alberta there are five species of fish: Bull, Brown, Rainbow, Cutthroat and Brook trout – AND Cut-Bow HYBRIDS!!
http://www.thebowriver.com/trout_identification.htm
Nothing new here. Move along.
Going down to my trout pond next to the house to catch a Rainbow for supper.
Are they strong, adapted to their environment and taste good? Hey we are mixing the world’s humans too and we call this homogenization process “diversity” (for some reason) don’t we.