HURRICANE DORIAN is the latest example of a frightening trend. Extreme weather events are becoming more frequent, more severe and more widespread as a consequence of climate change. New research from Washington University in St Louis provides important new insights into how different species may fare under this new normal.

Faced with unprecedented change, animals and plants are scrambling to catch up — with mixed results. A new model developed by Carlos Botero, assistant professor of Biology in Arts & Sciences, and Thomas Haaland, formerly a graduate student at the Norwegian University of Science and Technology, helps to predict the types [ihc-hide-content ihc_mb_type=”show” ihc_mb_who=”2,3″ ihc_mb_template=”1″ ] of changes that could drive a given species to extinction.

The study, published Sept 27 in the journal Ecology and Evolution, challenges the idea that species previously exposed to more variable conditions are more likely to survive extreme events.

“It is difficult to predict how organisms will respond to changes in extreme events because these events tend to be, by definition, quite rare,” Botero said. “But we can have a pretty good idea of how any given species may respond to current changes in this aspect of climate — if we pay attention to its natural history, and have some idea of the climatic regime it has experienced in the past.”

Unexpected vulnerabilities

Researchers in the Botero laboratory use a variety of tools from ecology and evolutionary biology to explore how life — from bacteria to humans — copes with and adapts to repeated environmental change.

For the new study, Botero worked with his former student Haaland, now a postdoctoral fellow at the University of Zurich in Switzerland, to develop an evolutionary model of how populations respond to rare environmental extremes. (Think: 500-year floods.) These rare events can be tricky for evolution because it is difficult to adapt to hazards that are almost never encountered.

Through computer simulations, Haaland and Botero found that certain traits and experiences emerged as key indicators of vulnerability.

Specifically, they found:

• Species that breed a single time in their lifetime tend to evolve conservative behaviors or morphologies, as if they were expecting to experience an environmental extreme every time.

• In contrast, species in which a single individual can reproduce multiple times and in different contexts (say, a bird that nests several times in a season and in different trees), evolution favors behaving as if environmental extremes simply never happen.

The key insight of this new model is that species belonging to the former, “conservative” category can easily adapt to more frequent or widespread extremes but have trouble adjusting when those extremes become more intense. The opposite is true of species in the latter, “care-free” category. Haaland and Botero also found that factors speeding up trait evolution are generally likely to hinder – rather than favor – adaptation to rare selection events. Part of the reason: High mutation rates tend to facilitate the process of adaptation to normal conditions during the long intervals in between environmental extremes.

“Our results challenge the idea that species that have been historically exposed to more variable environments are better suited to cope with climate change,” Botero said. [/ihc-hide-content]