Reclassifying Earth’s tropical forests: Bayreuth scientist researching Kilimanjaro contributes to international study
Universität Bayreuth, Press release No. 019/2018, 6 February 2018
Researchers from 159 universities and research institutes around the world have, for the first time, systematically investigated how Earth’s tropical forests are related to each other in terms of their evolutionary history. Dr. Andreas Hemp of the University of Bayreuth also contributed to this major project by investigating forest areas in East Africa, especially on Mount Kilimanjaro. Phylogenetic analyses demonstrated that two regions of the world can be distinguished in which the forests exhibit a particularly high degree of relatedness: Africa and the Americas on the one hand, and the Indo-Pacific on the other. The findings have been published in the academic journal PNAS.
How can the tropical forests of South America be related to those that stretch from the Congo in Central Africa to Guinea in West Africa? The scientists believe it is due to evolutionary history: around 100 million years ago, South America broke off from the southern supercontinent of Gondwana and drifted west while what is now Africa emerged from the rest of the continent. In the further course of evolution, both continents eventually developed their own species of plants and vegetation. However, the tropical forests have not diverged very far, at least at the genus level of the tree species present. Nowadays, scientists may thus refer to an American-African cluster when speaking from a phylogenetic perspective. In particular, the African forests from the Congo to Guinea exhibit strikingly few differences with regard to species composition. According to the researchers, this unusual uniformity could be related to repeated ice ages and the dry periods that went along with them in this large area.
The tropical forests in East Africa, Madagascar, India, Southeast Asia, Australia, and on the Pacific Islands also exhibit a strong evolutionary relationship despite the great distances separating them. One explanation could be a common evolutionary origin in eastern Gondwana. Over the past two decades, biologists have also shown that there have been several significant instances of the biological exchange of plant species in the greater area surrounding what is now the Indian Ocean. The researchers believe that the tropical forests were also involved in such interrelationships allowing them to become a vast Indo-Pacific Cluster. Even the forests of Madagascar and New Guinea belong to this cluster although they differ considerably with respect to species composition.
“The analyses we carried out in close international collaboration have, for the first time, made it possible to develop a biogeographical mapping of the tropical forests that is solely based on evolutionary history – or to be more precise – on phylogenetic similarities between the forests,” explained Dr. Andreas Hemp, research associate in plant systematics at the University of Bayreuth.
Dr. Hemp’s research on vegetation on Mount Kilimanjaro and other regions of East Africa over the past several years has helped explain the diversity and evolutionary development of the forests in these areas. In the context of the new worldwide study, he played a key role in demonstrating that these tropical forests are not to be attributed to the greater region of Africa and the Americas but rather comprise the western tip of the Indo-Pacific Cluster. “Phylogenetic similarities are known to influence how tropical forests react, for example, to extreme events resulting from global climate change. For this reason, they can give us important clues as to how likely it is that changes in the global climate will affect vast regions of Earth’s forests in the long term,” Hemp said.
J.W. Ferry Slik, Janet Franklin, et al.: Phylogenetic classification of the world’s tropical forests, Proceedings of the National Academy of Sciences of the United States of America (PNAS), February 2018, DOI: 10.1073/pnas.1714977115.
PD Dr. Andreas Hemp
University of Bayreuth
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