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201312Dec21:32

Darwin’s inva­sive species the­ory challenged

Infor­ma­tion
pub­lished 12 Decem­ber 2013 | mod­i­fied 03 Novem­ber 2014
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For more than a cen­tury and a half, researchers inter­ested in inva­sive species have looked to Charles Dar­win and what has come to be called his “nat­u­ral­i­sa­tion conun­drum.” If an invader is closely related to species in a new area, he wrote in his land­mark “The Ori­gin of Species,” it should find a more wel­com­ing habi­tat. On the other hand, it could expect to com­pete with the related species and be vul­ner­a­ble to its nat­ural ene­mies. Or as Michael Ren­ton, plant biol­o­gist at Uni­ver­sity of West­ern Aus­tralia, explained Darwin’s the­ory: “If the species is more dis­tantly related to species within the com­mu­nity, it will be more likely to be inva­sive, because it will have dif­fer­ent nat­ural enemies.”

DarwinSpecies vs. details
But a paper that is pub­lished online on 2 Decem­ber in the Pro­ceed­ings of the National Acad­emy of Sci­ences says the relat­ed­ness of new and estab­lished species is not as impor­tant as the details of how they go about doing their business.

We thought we under­stood how things hap­pened, but maybe they hap­pened for another reason
« Emily Jones, lead author, Depart­ment of Ecol­ogy and Evo­lu­tion­ary Biol­ogy, Rice Uni­ver­sity, Hous­ton, USA

Jones started pon­der­ing Darwin’s conun­drum while a post-​doctoral researcher in the Wash­ing­ton State Uni­ver­sity lab of Richard Gomulkiewicz.

Darwin’s logic doesn’t pan out
“Dar­win put out a lot of inter­est­ing ideas back in the day but he didn’t have the means to check them with rigour,” says Gomulkiewicz, co-​author and a pro­fes­sor in WSU’s School of Bio­log­i­cal Sci­ences. “That’s what we did with our math­e­mat­i­cal model, and we found that Darwin’s logic on this issue doesn’t quite pan out.”

The model Jones and her col­leagues have devel­oped in analysing Darwin’s conun­drum could lead to a new way of gaug­ing the poten­tial of inva­sive species, a major eco­log­i­cal and eco­nomic con­cern as plants and ani­mals have spread into new habi­tats around the planet.

Genet­ics alone a weak pre­dic­tor
Dar­win focused on phy­logeny, species’ relat­ed­ness or genetic sim­i­lar­ity. But the research team focused on species’ phe­no­types, char­ac­ter­is­tics that emerge as a plant or animal’s genes inter­act with the envi­ron­ment. In the process, they found that genetic rela­tion­ships alone are a weak pre­dic­tor of an invaders success.

To be sure, says Jones, researchers will want to see what species an invader is related to and what inter­ac­tions that species has that are impor­tant for under­stand­ing its sur­vival. But then, she says, “you’d want to look at how those inter­ac­tions depend on traits and affect births and deaths in the invad­ing species.”

So, the new research sug­gests degree of rela­tion­ship is not the most impor­tant fac­tor, but the invad­ing species’ inter­ac­tion with its new envi­ron­ment. William Feeney, PhD can­di­date at Aus­tralian National Uni­ver­sity, said: “It’s sug­gest­ing that these things may be more com­pli­cated than we have given them credit for. Basi­cally it’s show­ing that the evo­lu­tion­ary his­tory of the inter­ac­tions between species in a pop­u­la­tion could affect the like­li­hood of that pop­u­la­tion being suc­cess­fully invaded by a new species. If there’s a lot of com­pe­ti­tion between species in a pop­u­la­tion, an inva­sive species could be at a dis­ad­van­tage upon arrival and not do too well, com­pared to an ecosys­tem with less competition.”



(Source: Wash­ing­ton State Uni­ver­sity press release, 03.12.2013; The Con­ver­sa­tion, 02.12.2013)


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