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An international research team led by a 91社区 researcher used a simple experiment that mimics how plants and animals interact with each other鈥攍eaving seeds out for 24 hours to see how many get eaten. Seven thousand seed beds were deployed across a huge geographic scale, with 70 sites cutting across 18 mountains from Alaska to the equator.

鈥淭heory predicts that interactions among species鈥攍ike predation and competition鈥攚ill be strongest in the warm, productive, biodiverse ecosystems of the tropics and low elevations,鈥� says lead author Anna Hargreaves, an evolutionary ecologist in 91社区鈥檚 Department of Biology. 鈥淔or example, the spectacular diversity of tropical trees is thought to result partly from stronger interactions between plants and the animals that prey on their seeds, which shapes how and where plants grow and adapt,鈥� adds Hargreaves, who launched the project while at the University of British Columbia鈥檚 (UBC) Biodiversity Research Centre.

Until recently, however, evidence for this key ecological theory was inconclusive and came from small-scale studies that used different methods.

Using consistent methods and seeds from the Arctic to equator, this new study shows that seed predation increased by 17 percent from the Arctic to the Equator and by 17 percent from 4,000 metres high in the Andes down to sea level. The research team replicated the 24-hour experiment several times during each latitude鈥檚 natural seed-producing period.

鈥淭hese interactions form the basis of how ecosystems function and the direct benefits of those ecosystems to human society,鈥� says Santiago David, a PhD student at UBC who ran one of the study sites in Colombia. 鈥淯nderstanding global patterns in key interactions between species, such as seed predation, is essential when we think about managing or restoring the ecosystems, especially in the face of climate change."

Predation driven by insects and other invertebrates

听By protecting some seeds from mammals, the researchers showed that the study鈥檚 large-scale patterns are being driven by the smallest seed predators: insects and other invertebrates.

The only other standardized experiment of comparable scale used clay model caterpillars and found that attack rates on the model caterpillars increased toward low latitudes鈥攁n interaction also driven largely by invertebrates.

鈥淭aken together, these experiments suggest that invertebrates play an outsized role in the community dynamics and evolution of tropical and lowland ecosystems,鈥� says Hargreaves. 鈥淎nd yet we know relatively little about invertebrates, for example, how climate change is affecting their populations.鈥�

The researchers are now extending the project inland to mountains with very different climates and ecosystems at the same latitudes, to test what drives the stronger interactions.

Photo 1: High latitude (Yukon) low elevation.听A Hargreaves听

Photo 2: Seed predator banana slug. Southern BC, Canada. A. Hargreaves

The study, 鈥淪eed predation increases from the Arctic to the Equator and from high to low elevations,鈥� involving researchers from 13 institutions across the Americas, was published today in Science Advances.

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Contact:
Anna Hargreaves
Department of Biology
91社区
anna.hargreaves [at] mcgill.ca

Chris Chipello
91社区 Media Relations Office
514-398-4201
christopher.chipello [at] mcgill.ca

http://www.mcgill.ca/newsroom/