The upside of invasion

Most people will agree that invasive species are, generally, not good things. Especially people who have ever sat down in a patch of star thistle, or been slapped in the face by an Asian carp. However, invaders are quite fascinating (terrible yet fascinating, like your drunk uncle’s dance moves at a wedding), and can be used to address fundamental issues in ecology and evolution.  One of my personal favorites is the question of how species adapt to new environments. There are many examples of invasive species rapidly adapting to novel habitats, but we’re not entirely sure how this happens. We are also concerned about the evolutionary potential of all species in the face of global change—i.e. whether species will be able to rapidly adapt to changing environments. So it seems that invaders make pretty convenient study systems: if we can figure out how and why invaders adapt quickly, we could gain some insight into how other species are going to deal with adapting to habitats altered as a result of global change.

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Fun fact: Lactuca serriola is the diploid progenitor or lettuce

In a recent study, Jake M. Alexander examined the limits of adaptive evolution in the face of global change using an invasive plant, Lactuca serriola, as a model system. Using molecular markers, a common garden experiment, and climatic niche modeling, he addressed the following questions:

(1) What was the native-range source of invasive-range populations of L. serriola?

(2) Is there evidence of rapid evolution in L. serriola’s invasive range?

(3) Has L. serriola expanded its climatic niche in its invasive range (i.e. has it adapted to environmental conditions totally different from those in its native range)?

Here’s a brief summary of what he found:

(1) Although L. serriola is native to Europe and western Asia, invasive range populations of L. serriola likely originated from European populations.

(2) Invasive range L. serriola flower earlier on average than ancestral European plants, suggesting selection for earlier flower time has driven rapid evolution following introduction.

(3) Invasive-range L. serriola has expanded its climatic niche compared to that of European populations. However, the invasive climatic niche is no different than the climatic niche across the entire native range (including Asia).

So what does all this mean? Alexander’s results suggest that, within this species, populations have the ability to rapidly adapt, but only to conditions that are within L. serriola’s climate envelope. In terms of invasion, this can be considered a good thing—this suggests that the invasive potential of a species can be predicted by its native range climate niche. In terms of a species’ ability to rapidly adapt to habitats altered by global change, this isn’t necessarily great. Populations at the core of a species’ range will likely be able to adapt to new conditions, as long as those conditions are similar to those that already exist at the edge of a range. But populations at a range edge (already at the extreme end of a climate envelope) might not be able to rapidly adapt to more extreme conditions. Overall, this study was a super-cool example of how looking at invasions can give insight into conservation!

Alexander, JM (2013) Evolution under changing climates: climatic niche stasis despite rapid evolution in a non-native plant. Proc R Soc B: 208

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