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Invasive Plants in Galapagos May Really Be Native

For years, conservationists have been concerned about the impact of invasive plant species in the Galápagos Islands. Hundreds of species have been identified as being nonnative, introduced through human contact. The idea is to remove these plants to help keep the archipelago ecologic

ally pristine.

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That’s a worthy goal. But there’s just one problem, according to a study in Science: some of these pariah plants turn out to be native after all. They predate humans in the Galápagos by thousands of years.

The evidence for this is in the form of fossilized pollen grains found in sediment cores from bogs on Santa Cruz island in the heart of the archipelago. Jacqueline F.N. van Leeuwen of the University of Bern in Switzerland and Cynthia A. Froyd of Oxford University in England and colleagues identified pollen of six species that earlier studies had concluded were probably nonnative. Pollen was found in samples up to 8,200 years old; it is generally agreed that the first humans to reach the Galápagos were Europeans, in 1535.

Among the species revealed to be native are billy goat weed (Ageratum conyzoides) and swamp hibiscus (Hibiscus diversifolius). Swamp hibiscus appears to be spreading on Santa Cruz, which had been seen as evidence of its invasiveness, but instead it may just be reclaiming habitat that was lost over time.

Most of these plants are widespread throughout the Pacific, so the researchers suggest that similar paleoecological studies on other islands will help determine whether these species, and perhaps many others, have wrongly been categorized as well.

By José Miguel Gumucio