In montane forests plant species are predicted to migrate upslope to track changing temperatures and avoid extinction. Central to predictions of species responses to climate change is an understanding of species distributions along environmental gradients. Biotic interactions can play important roles in setting species distributions and abundances, but despite their potential to influence species responses to climate change, biotic interactions remain mostly unquantified along elevational gradients. An important interaction long studied in tropical forests is post-dispersal seed predation which has been shown to affect the population dynamics, community structure, and diversity of plant species in time and space. We quantify variation in seed predation from a comparative seed predation study of 23 species of tropical trees across a 2.5 km elevation gradient in the Peruvian Andes. We then combine measured seed survival with previously published transition matrices of tropical plants to assess the effects of the observed variation in seed predation on population growth rates.

Results/Conclusions

We found marked variation among species in total seed survival depending on the major seed predator of the species and also consistent changes in seed survival rates across the elevation gradient. There was a significant increase in seed survival with increasing elevation, resulting in a 9-fold increase in effective fecundity for trees at high elevation.  This potential increase in seed crop size at least doubles modelled plant population growth, greatly increasing population migration potential in the face of climate change.  These results also indicate that species interactions can have effects on par with climate in species responses to global change.