Since today's guest speaker, Juan Armesto, researches seed dispersal mechanisms and mutualisms (among other things), I thought I'd talk about this article on brazil nut regeneration for my New+Hot.
One of the trees that Darwin undoubtedly encountered in his travels in the Amazon was the brazil nut tree, which can grow up to 50 meters high and live 500 years. Nowadays, current agroforestry practices have made the brazil nut an important source of income for communities in the Amazon. However, the harvest of the seeds seems to have an impact on the behavior of the animals that eat them. Agoutis (a type of large rodent) are supposedly the only animals that can actually eat the seeds, in a mutualistic fashion of gnawing through the hard outer shell to access the nuts, which at the same time gives the seeds the chance to grow. But the agoutis' manner of consuming the nuts changes with the availability of the seeds and other food sources. For example, in the wet season, when there is a lot of food around, they tend to cache the seeds for later use, which sometimes results in the seeds' germinating and producing more trees. But in the dry season, when food is less abundant, they tend to just eat the seeds as they find them. Harvesting brazil nuts replicates the conditions the agoutis find in the dry season, so they tend to just eat the seeds; this could explain why intensely-harvested forests tend to have fewer juvenile trees.
Possible conservation implications are that harvesters should make specific efforts to promote regeneration of the trees, by planting seeds in optimum germination locations, rather than leaving their future source of income up to chance-- and rodents.