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Ecological and evolutionary responses to climate change

"That climate acts in main part indirectly by favoring other species, we may clearly see in the prodigious number of plants in our gardens which can perfectly well endure our climate, but which never become naturalized, for they cannot compete with our native plants, nor resist destruction by our native animals." -- Darwin

People sometimes ask whether wild species can evolve fast enough, or migrate fast enough, to keep up with global warming. I've always thought the answer would depend on how their competitors were faring. If the competitors are just as stressed by higher temperatures as they are, both might survive a moderate increase in temperature. But if the competitors are moving in from a warmer region, so they're already adapted to hotter temperatures, the locals may be doomed.

This week's paper, "Eco-evolutionary responses of biodiversity to climate change" modeled evolution, migration, and competition as climate warms. Their analysis predicted that:

"high dispersal did not reduce extinctions, because the shifting ranges of some species hastened the decline of others... no extinctions occurred without competition"
Relative to displacement by better-adapted migrants, evolution was particularly important in the tropics and near the poles. Species in the warmest areas (e.g., in the tropics) aren't threatened by migration of species already adapted to warmer climates.

The evolution of high-temperature tolerance in temperate species is slowed by maladaptive gene flow from cooler climates, balancing adaptive gene flow from warmer climates, so displacement by other species may trump evolution.

Near the poles, however, gene flow only comes from warmer climates, so it's more consistently adaptive in a warming climate. If penguins from the South Pole mated with penguins from South Georgia, they'd introduce cold-adapted genes, slowing evolution to warmer temperatures -- but there aren't any penguins at the South Pole.
Evolution therefore plays a larger role in responses to warming climate in polar than in temperate regions.

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