XVI International Botanical Congess

What is now South America was part of Gondwana in the Cretaceous, and during the Tertiary remained isolated, which resulted in the evolution of its rich and varied flora. About 3 millions ago, when the Isthmus of Panama was formed, an important exchange of species occurred. This created the phytogeographic pattern that we find today. Venezuela, a neotropical country with a varied geography and climate, reflects in it's flora this evolutionary trend with families originating in Laurasia or Gondwana. This last group includes plants with radiation centers in Amazonia or in the Andes. We analyze the family composition of different forest communities according origin and radiation center. Implications will be discussed. Also, we observe that the families' dominance in an area has a defined pattern, that changes when consider the number of species.