Are ecologists blind to small things? The missed stories on non-tropical seed predation on feces

Authors


P. Manzano, TEG, Depto Ecología, Univ. Autónoma de Madrid, ES–28049 Madrid, Spain. E-mail: pablo.manzano@uam.es

Abstract

Seed dispersal involves several complex stages that can be affected by multiple peripheral processes. Thus, a major dispersal event can be followed by secondary dispersal, which can reduce density-dependent mortality and consolidate the dispersal phase. But predation events can also follow, and predation of seeds in feces is particularly interesting because it can heavily alter the fate of seeds dispersed through vertebrate guts. Our review of 20 cases involving this kind of interaction found that research has chiefly been in tropical and subtropical areas (85% of cases), suggesting that it is a minor phenomenon at higher latitudes. However, the small size of both the seeds and predators involved may have caused this process to go unnoticed outside the tropics. We tested the presence of predation of seeds in feces at a temperate, semi-arid and small-seed dominated ecosystem and found that it can be as important as in tropical latitudes, affecting up to 80% of feces in mid-summer. Moreover, it may influence endozoochory in a way whose significance could have been strongly underestimated, as it affects 35% of the seeds dispersed by sheep during the year. Our results may encourage scientists to pay attention to other interactions that may be widespread globally but go unnoticed. The study of seed dispersal, especially, may be suffering from the researchers’ difficulty in handling processes that are difficult to observe because of the small size of the organisms involved.

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