A few weeks ago, the web site CO2Science posted a review of a recent study by Idaho researchers Shawn R. Narum and Nathan R. Campbell of the Columbia River Intertribal Fish Commission (CRTFC) evaluating thermal adaptability of desert redband trout (RBT; Oncorhynchus mykiss gairdneri). This was a genetic study of adaptability comparing desert populations, where conditions are highly variable, to montane populations where conditions are more stable. Essentially, it is a study of evolutionary changes over the short term rather than adaptation over several generations. The CO2Science review and the original paper are worth reading and point to how animal populations may be able to respond to environmental changes, especially climate, relatively quickly.
Early in my career I worked with a variety of desert Lahontan cutthroat trout (LCT; O. clarki henshawi) endmic to the high desert of northeastern Nevada under environmental conditions very similar to desert RBT. Both of these trout subspecies were intriguing to trout biologists because their habitats, especially with respect to summer temperatures, would normally be considered unsuitable for trout*. However, these fishes thrived. In fact, conditions were such that stocking of hatchery rainbow trout (O. m. irrideus) that are generally produced from coastal stocks, inevitably failed in the HCT streams we studued; typically, stocking rainbow trout either out-compete cutthroat trout or form hybrid swarms when they are put together.
Most of the fish we studied were members of local populations in small, sometimes intermittent, streams, but larger fish also occurred in larger streams like the Mary's and Humboldt Rivers. It was known that there was very high degree of genetic differentiation among populations of HCT, suggesting limited reproductive interaction, though it was also assumed that larger migratory individuals moved into these streams in spring to spawn.
These were the early days of genetic taxonomy, but the genetic variability of these eastern populations suggested they may have been an independent subspecies of cutthroat trout; we accepted this distinction and called them Humboldt cutthroat trout (HCT)**. Our studies were directed at physical habitat conditions and population dynamics, not genetic, but in two papers we proposed "genetic flexibility" or "plasticity" (for which we had no precise definition) was responsible; that is, we thought it likely that these fish were genetically capable of tolerating a wide range of unpredictable and extreme environmental conditions absent specific evolutionary change.
In the first paper, titled “Population Fluctuations and Genetic Differentiation in the Humboldt Cutthroat Trout of Gance Creek, Nevada,” published in 1983***, we theorized that HCT had evolved sufficient adaptive flexibility to respond properly to variable local conditions and was indirectly expressed in the high genetic diversity among local populations of these fish demonstrated by other researchers (see here). The second publication was entitled “Evidence for Variability in Spawning Behavior of Interior Cutthroat Trout in Response to Environmental Uncertainty” and dealt with response of HCT in a small stream to extreme streamflow conditions. In this case we thought we might have detected two spawning events in response to an early freshet followed by sustained spring runoff. This may have been driven by spawning events that included migrants tuned into basin-scale triggers and some among resident individuals responding to local cues.
While these two papers may not have represented earth-shaking research, they have been used in developing management strategies to help recover LCT, a subspecies of cutthroat trout listed as "Threatened" under the Endangered Species Act. In addition, and most relevant in the context of this post, they hypothesized a genetic component to the ability of HCT to tolerate extreme and variable environmental conditions, including stream temperature. With the Narum's and Campbell's work, it would seem that such a genetic component has been demonstrated.
It is experience like this that has helped lead me to question the "consensus" view of dire environmental and social consequences of a changing climate. Climate, of course, is constantly changing in response to natural cycles and the human influence on them. A reductionist approach to such complex systems is quite likely to lead to oversimplification of cause and effect relationships. It seems to me that climate alarmists embrace this narrow view of climate system dynamics and environmental response to change. Environmental variability happens, habitat conditions change, ecosystems naturally change as climate changes and organisms must be flexible or evolve to maintain viable populations. Even though people naturally favor environmental conditions that they perceive as normal, changes in organism ranges and even extinctions occur naturally over time as well as in response to human action; but no given state is inherently superior any other, just different. To me, it seems likely that some ecosystems may change and some organisms may be displaced, but many will be able to cope with whatever climatic changes occur over the next few decades, whether those changes are anthropogenically derived or natural or both.
Most of the fish we studied were members of local populations in small, sometimes intermittent, streams, but larger fish also occurred in larger streams like the Mary's and Humboldt Rivers. It was known that there was very high degree of genetic differentiation among populations of HCT, suggesting limited reproductive interaction, though it was also assumed that larger migratory individuals moved into these streams in spring to spawn.
These were the early days of genetic taxonomy, but the genetic variability of these eastern populations suggested they may have been an independent subspecies of cutthroat trout; we accepted this distinction and called them Humboldt cutthroat trout (HCT)**. Our studies were directed at physical habitat conditions and population dynamics, not genetic, but in two papers we proposed "genetic flexibility" or "plasticity" (for which we had no precise definition) was responsible; that is, we thought it likely that these fish were genetically capable of tolerating a wide range of unpredictable and extreme environmental conditions absent specific evolutionary change.
In the first paper, titled “Population Fluctuations and Genetic Differentiation in the Humboldt Cutthroat Trout of Gance Creek, Nevada,” published in 1983***, we theorized that HCT had evolved sufficient adaptive flexibility to respond properly to variable local conditions and was indirectly expressed in the high genetic diversity among local populations of these fish demonstrated by other researchers (see here). The second publication was entitled “Evidence for Variability in Spawning Behavior of Interior Cutthroat Trout in Response to Environmental Uncertainty” and dealt with response of HCT in a small stream to extreme streamflow conditions. In this case we thought we might have detected two spawning events in response to an early freshet followed by sustained spring runoff. This may have been driven by spawning events that included migrants tuned into basin-scale triggers and some among resident individuals responding to local cues.
While these two papers may not have represented earth-shaking research, they have been used in developing management strategies to help recover LCT, a subspecies of cutthroat trout listed as "Threatened" under the Endangered Species Act. In addition, and most relevant in the context of this post, they hypothesized a genetic component to the ability of HCT to tolerate extreme and variable environmental conditions, including stream temperature. With the Narum's and Campbell's work, it would seem that such a genetic component has been demonstrated.
It is experience like this that has helped lead me to question the "consensus" view of dire environmental and social consequences of a changing climate. Climate, of course, is constantly changing in response to natural cycles and the human influence on them. A reductionist approach to such complex systems is quite likely to lead to oversimplification of cause and effect relationships. It seems to me that climate alarmists embrace this narrow view of climate system dynamics and environmental response to change. Environmental variability happens, habitat conditions change, ecosystems naturally change as climate changes and organisms must be flexible or evolve to maintain viable populations. Even though people naturally favor environmental conditions that they perceive as normal, changes in organism ranges and even extinctions occur naturally over time as well as in response to human action; but no given state is inherently superior any other, just different. To me, it seems likely that some ecosystems may change and some organisms may be displaced, but many will be able to cope with whatever climatic changes occur over the next few decades, whether those changes are anthropogenically derived or natural or both.
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* A review of the state of the knowledge by Dr. Robert Behnke on western trouts in the 1970s-80s is available here.
** Information supporting the logic behind this reasoning can be found here and here.
*** Note that the title on the paper contains a typographic error using the word “Generic” instead of “Genetic.”
** Information supporting the logic behind this reasoning can be found here and here.
*** Note that the title on the paper contains a typographic error using the word “Generic” instead of “Genetic.”
