One of Darwin's many ideas was that interactions between species – like competition and predation – are stronger and therefore more important in tropical and lowland ecosystems. Until recently however, evidence for large-scale patterns in the intensity of species interactions was contradictory, and cobbled together from many small-scale studies using different methods.

 

The goal of the BIG experiment is to test geographic patterns in the intensity and effects of species interactions using simple, standardized experiments conducted at massive geographic scales. To do this I collaborate with a network of fantastic biologists working in >10 countries spanning the Americas.

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For Phase 1 of the BIG experiment, we set out more than 7000 small piles of seeds along 18 mountains from Alaska to Ecuador, and checked them the next day to see how many were eaten.

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We showed that even after only 24 hours, seed predation more than doubles from the arctic to equator and from 4000 meters elevation (high in the Andes) to sea level:

Seed predation increases from the Arctic to Equator and from high to low elevations. Science Advances.

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We also showed that these large-scale patterns are driven by the smallest seed predators: high predation in the tropics and lowlands is caused mostly by insects and other invertebrates. Thus a relatively underappreciated group of animals likely plays an outsized role in the ecology and evolution of our most biodiverse ecosystems.

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Media coverage:

ScienceTrends summary

Radio Canada article (french)

Prince George Daily News article

Phys.org article

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In BIG experiment #2 we tested whether latitudinal gradients in seed predation are flattened in urban environments, as one might expect given urbanization's homogenizing effect on local habitats. This work was recently published:

Latitudinal gradients in seed predation persist in urbanized environments. Nature Ecology & Evolution

 

BIG experiment #3 extended to mountains farther inland in the Americas and down toward the south pole, exploring the factors that drive the strength of species interactions. Results in Antonio's thesis here.

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Media coverage:

McGill tribune article

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Phase 4 is looking at evolutionary effects. Collaborators from any continent are welcome - please get in touch if you would like to be involved!