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Productivity increases with species diversity

May 14, 2013

One hundred and fifty years later, research result proves Darwin prediction

TORONTO, ON — Envi­ron­ments con­tain­ing species that are dis­tant­ly relat­ed to one anoth­er are more pro­duc­tive than those con­tain­ing close­ly relat­ed species, accord­ing to new research from the Uni­ver­si­ty of Toron­to Scar­bor­ough (UTSC).

The exper­i­men­tal result from Marc William Cadotte con­firms a pre­dic­tion made by Charles Dar­win in On the Ori­gin of Species, first pub­lished in 1859. Dar­win had said that a plot of land grow­ing dis­tant­ly relat­ed grass­es would be more pro­duc­tive than a plot with a sin­gle species of grass.

Since then, many exper­i­ments have shown that mul­ti-species plots are more pro­duc­tive. Cadotte’s exper­i­ment showed for the first time that species with the great­est evo­lu­tion­ary dis­tance from one anoth­er have the great­est pro­duc­tiv­i­ty gains.

“If you have two species that can access dif­fer­ent resources or do things in dif­fer­ent ways, then hav­ing those two species togeth­er can enhance species func­tion. What I’ve done is account for those dif­fer­ences by account­ing for their evo­lu­tion­ary his­to­ry,” Cadotte says.

Cadotte grew 17 dif­fer­ent plants in var­i­ous com­bi­na­tions of one, two, or four species per plot. As in pre­vi­ous exper­i­ments, he found that mul­ti-species plots pro­duced more plant mate­r­i­al.

But when he ana­lyzed the results he also found that com­bi­na­tions of plants that were dis­tant­ly relat­ed to one anoth­er were more pro­duc­tive than com­bi­na­tions of plants that were close­ly relat­ed. So, for instance, a plot plant­ed with gold­en­rod and the close­ly relat­ed black-eyed susan wasn’t as pro­duc­tive as a plot with gold­en­rod and the more dis­tant­ly relat­ed bluestem grass.

What’s going on isn’t mys­te­ri­ous, Cadotte says. Dis­tant­ly relat­ed plants are more like­ly to require dif­fer­ent resources and to fill dif­fer­ent envi­ron­men­tal nich­es – one might need more nitro­gen, the oth­er more phos­pho­rus; one might have shal­low roots, the oth­er deep roots. So rather than com­pet­ing with one anoth­er they com­ple­ment one anoth­er.

What’s inter­est­ing about his result is that evo­lu­tion­ary dis­tance is all you need to know to pre­dict pro­duc­tiv­i­ty.

The result sug­gests that as plant species dis­ap­pear the Earth will become less pro­duc­tive, and plants will draw even less car­bon from the atmos­phere, pos­si­bly increas­ing the rate of glob­al warm­ing.

On the oth­er hand, the results could give a valu­able tool to con­ser­va­tion efforts. Envi­ron­men­tal­ists try­ing to restore dam­aged habi­tats could use the infor­ma­tion to help them pick which com­bi­na­tions of species to intro­duce.

This research will be pub­lished in the upcom­ing edi­tion of the Pro­ceed­ings of the Nation­al Acad­e­my of Sci­ences of the Unit­ed States (PNAS).


For more infor­ma­tion, con­tact:

Marc W Cadotte
Assis­tant Pro­fes­sor
Depart­ment of Bio­log­i­cal Sci­ences
Uni­ver­si­ty of Toron­to ‑Scar­bor­ough
Office: 416–208-5105