Mutualismos Extremos de Polinização: História Natural e Tendências Evolutivas

Abstract

Mutualistic interactions are spread in all ecossystems and are being increasingly regarded important in creating and maintaining the biodiversity in different environments. Our revision aims to discuss about specialization and evolution in pollination systems in the context of mutualism theory. We illustrate this discussion with four of the most well-studied examples of specialized pollination. The concept of mutualism has changed through history, being nowadays considered as an exploitation relationship with net benefits to all interacting species. In this scenario, the mutualistic interactions can be grouped into two categories: (1) facultative - when there is no exclusive dependence between species; and (2) obligatory - when the interacting species cannot survive outside of the relationship. Some interactions under the obligatory mutualism seem to have high degree of specialization and exclusivity between partners, being called extreme mutualisms. Here, we discuss the following potentially extreme pollination mutualism: (I) long corolla flowers and the hawk moths of Sphingidae family, (II) figs and fig-wasps, (III) yuccas and yucca-moths, and (IV) malesof Euglossini bees and orchids. Then, we discuss the underlying possible evolutionary process leading to the current scenario of such specialized relationships is presented. Although some high specialized species-specific pollination interaction can potently exist, in general, in the discussed exemples, these relationships seem to have evolved under diffuse selection pressure. Such pattern lead to functional group formation that, although highly dependent on the interaction allow its components to vary across time and space. Finally, we suggest that further studies on pollination mutualistic interactions should consider scales (space and time) and the context investigated, which mean whether they are using a taxonomic, functional or evolutionary point of view, or even a combination of them.