Scientists have long struggled to explain how tropical forests can maintain their staggering diversity of trees without having a handful of species take over – or having many other species die out.
The answer, researchers say, lies in the soil found near individual trees, where natural “enemies” of tree species reside. These enemies, including fungi and arthropods, attack and kill many of the seeds and seedlings near the host tree, preventing local recruitment of trees of that same species.
Also playing a key role in the tropical forest dynamic are seed dispersers. Seeds from individual trees that are carried a distance away – often by rodents, mammals or birds – have a chance to get established because the fungi and arthropods in the new region target different species. This restriction of tree recruitment near the adult trees creates a long-term stabilizing effect that favors rare species and hinders common ones, the researchers say.
Overturning previous theory, the researchers demonstrate that these interactions with enemies are important enough to maintain the incredible diversity of tropical forests. Results of the study are being published this week in Proceedings of the National Academy of Sciences (PNAS).