Winter restricts innovation—A new model for tropical plant biodiversity is based on the 'storage effect'

Tropical forests are home to many more species than

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forests to the north. For example, almost 1,200 tree species inhabit the 4.2 million square kilometers of temperate and boreal forests in the Northern Hemisphere, while an astonishing 1,440 tree species inhabit just 0.25 square kilometers of tropical forest near Manaus, Brazil. How can so many tree species coexist in such small areas in the tropics?

Ecologists have never been able to answer that question. To coexist, species must differ from one another so that two individuals of the same species (conspecifics) share more requirements and therefore have a greater negative impact on one another than do two individuals of different species (heterospecifics). This prevents any one species from becoming dominant because more and more of its neighbors are conspecifics with identical requirements. Meanwhile, rare species may be saved because more and more of their neighbors are heterospecifics with different resource requirements.

Many mechanisms lead to this outcome. The problem has been that all mechanisms known to promote species coexistence have appeared to operate with similar efficacy at all latitudes.Usinowicz et al. provide the first evidence that a mechanism that enables the stable coexistence of species is stronger in the Tropics and becomes steadily weaker at higher latitudes. The mechanism is called the storage effect and works for species, like trees, that have recurrent reproduction and long-lived adults that ensure population persistence over many reproductive opportunities. If the timing of successful reproductive events differs among species, new recruits will be more likely to have conspecific neighbor

Read more at: https://phys.org/news/2017-09-winter-restricts-innovationa-tropical-biodiversity.html#jCp