Are laboratory-reared populations similar to the ones in the wild? Lab domestication of fathead minnows (Pimephales promelas)
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No matter how the laboratory is set up, rearing conditions will inescapably select for specific traits, producing responses and traits that are different from those in the wild. For the sake of convenience, investigators commonly use constant temperatures when housing organisms, and populations may be adapting to these conditions. If so, applying lab findings to wild organisms may be problematic, especially with the popularity of experiments hoping to predict responses to climate change. I investigated whether exposure to a constant thermal lab environment led a population of fathead minnows, Pimephales promelas, to specialize and become quantitatively different than its wild counterpart. I exposed a wild and a laboratory population of minnows to three temperature regimes (constant 25°C, small fluctuation of 22-28°C, large fluctuation of 19-31°C) and measured their mortality rates, growth rates, upper thermal tolerance, and food consumption. The lab population grew faster under fluctuating temperatures and showed increased food consumption, while the wild population exhibited higher upper thermal tolerance. Interestingly, there was a trade-off between growth and thermal tolerance for the wild population but was absent in the lab population. The observed differences in thermal physiology indicates that we should be cautious about extrapolating results from experiments on domesticated populations.