From Swiss Federal Institute of Technology in Zürich [ETH Zürich] [Eidgenössische Technische Hochschule Zürich] (CH): “Geologically vibrant continents produce higher biodiversity” 

From Swiss Federal Institute of Technology in Zürich [ETH Zürich] [Eidgenössische Technische Hochschule Zürich] (CH)

Peter Rüegg

Using a new mechanistic model of evolution on Earth, researchers at ETH Zürich can now better explain why the rainforests of Africa are home to fewer species than the tropical forests of South America and Southeast Asia. The key to high species diversity lies in how dynamically the continents have evolved over time.

The tropical forests of South America are much more species-​rich compared to those of Africa. The Andean Cock-​of-the Rock (Rupicola peruvianus) is a particularly striking representative of South America’s diversity. Photograph: ondrejprosicky/ AdobeStock.

Tropical rainforests are the most biodiverse habitats on Earth. They are home to a huge number of different plants, animals, fungi and other organisms. These forests are primarily spread over three continents, concentrated in the Amazon Basin in South America, the Congo Basin in Central Africa, and the vast archipelago of Southeast Asia.

One might assume that all tropical rainforests are about equally diverse due to their stable warm and humid climate and their geographical location around the equator – but this is not the case. Compared to South America and Southeast Asia, the number of species in Africa’s humid tropical forests is significantly lower for many groups of organisms.

Palms with few species

A good illustration of this uneven distribution – what researchers refer to as the pantropical diversity disparity (PDD) – is palm trees: of the 2,500 species worldwide, 1,200 occur in the Southeast Asian region and 800 in the tropical forests of South America, but only 66 in African rainforests.

Why this should be so is debated among biodiversity researchers. There is some evidence that the current climate is the cause of the lower species diversity in Africa’s tropical forests. The climate in Africa’s tropical belt is drier and cooler than that in Southeast Asia and South America.

Other evidence suggests that the different environmental and tectonic histories of the three tropical forest regions over tens of millions of years had an impact on the differing levels of biodiversity. Such environmental changes include, for example, the formation of mountains, islands, or arid and desert areas.

However, it is difficult to distinguish between the two factors of current climate and environmental history.

Mountain building brings up diversity

Led by Loïc Pellissier, Professor of Landscape Ecology, researchers at ETH Zürich have now investigated this question with the help of a new computer model that allows them to simulate species diversification over millions of years of evolution. They conclude that the current climate is not the main reason why biodiversity is lower in the rainforests of Africa. Rather, biodiversity has emerged from the dynamics of mountain building and climate change. The results of the historical simulations largely coincide with the patterns of biodiversity distribution observable today.

“Our model confirms that differences in palaeoenvironmental dynamics produced the uneven distribution of biodiversity, rather than current climatic factors,” says Pellissier. “Geological processes as well as global temperature fluctuations determine where and when species emerge or go extinct.”

One factor in particular is crucial to high biodiversity on a continent: geological dynamics. Active plate tectonics promote both the formation of mountains such as the Andes in South America and the emergence of archipelagos as in Southeast Asia. These two processes result in many new ecological niches, which in turn give rise to numerous new species. Africa’s rainforest belt has had less tectonic activity over the past 110 million years. It is also relatively small because it is bordered by drylands in the north and south, limiting its spread. “Species from humid regions can hardly adapt to the dry conditions of the surrounding drylands,” Pellissier points out.

Geologically vibrant continents produce higher biodiversity

The “gen3sis” model developed by ETH researchers was only recently presented in the journal PLoS Biology. It is a mechanistic model in which the primary constraints such as geology and climate are represented together with biological mechanisms and from which biodiversity patterns can materialise. To simulate the emergence of biodiversity, the most important processes to integrate into the model are ecology (i.e. each species has its own limited ecological niche), evolution, speciation and dispersal.

“With these four basic rules, we can simulate the population dynamic of organisms over shifting environmental conditions and offer a very good explanation for how the organisms came about,” Pellissier says.

By building their model on these basic evolutionary mechanisms, the researchers can simulate species diversity without having to input (distribution) data for each individual species. However, the model requires data on the geological dynamics of the continents under consideration, as well as humidity and temperatures from climate reconstructions.

The researchers are now refining the model and running simulations to understand the emergence of biodiversity in other species-​rich regions, such as the mountains of western China. The model’s code and the palaeoenvironmental reconstructions are open source. All interested evolutionary and biodiversity researchers can use it to study the formation of biodiversity in different regions of the world.

See the full article here .


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ETH Zurich campus
Swiss Federal Institute of Technology in Zürich [ETH Zürich] [Eidgenössische Technische Hochschule Zürich] (CH) is a public research university in the city of Zürich, Switzerland. Founded by the Swiss Federal Government in 1854 with the stated mission to educate engineers and scientists, the school focuses exclusively on science, technology, engineering and mathematics. Like its sister institution Swiss Federal Institute of Technology in Lausanne [EPFL-École Polytechnique Fédérale de Lausanne](CH) , it is part of the Swiss Federal Institutes of Technology Domain (ETH Domain)) , part of the Swiss Federal Department of Economic Affairs, Education and Research [EAER][Eidgenössisches Departement für Wirtschaft, Bildung und Forschung] [Département fédéral de l’économie, de la formation et de la recherche] (CH).

The university is an attractive destination for international students thanks to low tuition fees of 809 CHF per semester, PhD and graduate salaries that are amongst the world’s highest, and a world-class reputation in academia and industry. There are currently 22,200 students from over 120 countries, of which 4,180 are pursuing doctoral degrees. In the 2021 edition of the QS World University Rankings ETH Zürich is ranked 6th in the world and 8th by the Times Higher Education World Rankings 2020. In the 2020 QS World University Rankings by subject it is ranked 4th in the world for engineering and technology (2nd in Europe) and 1st for earth & marine science.

As of November 2019, 21 Nobel laureates, 2 Fields Medalists, 2 Pritzker Prize winners, and 1 Turing Award winner have been affiliated with the Institute, including Albert Einstein. Other notable alumni include John von Neumann and Santiago Calatrava. It is a founding member of the IDEA League and the International Alliance of Research Universities (IARU) and a member of the CESAER network.

ETH Zürich was founded on 7 February 1854 by the Swiss Confederation and began giving its first lectures on 16 October 1855 as a polytechnic institute (eidgenössische polytechnische Schule) at various sites throughout the city of Zurich. It was initially composed of six faculties: architecture, civil engineering, mechanical engineering, chemistry, forestry, and an integrated department for the fields of mathematics, natural sciences, literature, and social and political sciences.

It is locally still known as Polytechnikum, or simply as Poly, derived from the original name eidgenössische polytechnische Schule, which translates to “federal polytechnic school”.

ETH Zürich is a federal institute (i.e., under direct administration by the Swiss government), whereas the University of Zürich [Universität Zürich ] (CH) is a cantonal institution. The decision for a new federal university was heavily disputed at the time; the liberals pressed for a “federal university”, while the conservative forces wanted all universities to remain under cantonal control, worried that the liberals would gain more political power than they already had. In the beginning, both universities were co-located in the buildings of the University of Zürich.

From 1905 to 1908, under the presidency of Jérôme Franel, the course program of ETH Zürich was restructured to that of a real university and ETH Zürich was granted the right to award doctorates. In 1909 the first doctorates were awarded. In 1911, it was given its current name, Eidgenössische Technische Hochschule. In 1924, another reorganization structured the university in 12 departments. However, it now has 16 departments.

ETH Zürich, EPFL (Swiss Federal Institute of Technology in Lausanne) [École polytechnique fédérale de Lausanne](CH), and four associated research institutes form the Domain of the Swiss Federal Institutes of Technology (ETH Domain) [ETH-Bereich; Domaine des Écoles polytechniques fédérales] (CH) with the aim of collaborating on scientific projects.

Reputation and ranking

ETH Zürich is ranked among the top universities in the world. Typically, popular rankings place the institution as the best university in continental Europe and ETH Zürich is consistently ranked among the top 1-5 universities in Europe, and among the top 3-10 best universities of the world.

Historically, ETH Zürich has achieved its reputation particularly in the fields of chemistry, mathematics and physics. There are 32 Nobel laureates who are associated with ETH Zürich, the most recent of whom is Richard F. Heck, awarded the Nobel Prize in chemistry in 2010. Albert Einstein is perhaps its most famous alumnus.

In 2018, the QS World University Rankings placed ETH Zürich at 7th overall in the world. In 2015, ETH Zürich was ranked 5th in the world in Engineering, Science and Technology, just behind the Massachusetts Institute of Technology(US), Stanford University(US) and University of Cambridge(UK). In 2015, ETH Zürich also ranked 6th in the world in Natural Sciences, and in 2016 ranked 1st in the world for Earth & Marine Sciences for the second consecutive year.

In 2016, Times Higher Education World University Rankings ranked ETH Zürich 9th overall in the world and 8th in the world in the field of Engineering & Technology, just behind the Massachusetts Institute of Technology(US), Stanford University(US), California Institute of Technology(US), Princeton University(US), University of Cambridge(UK), Imperial College London(UK) and University of Oxford(UK) .

In a comparison of Swiss universities by swissUP Ranking and in rankings published by CHE comparing the universities of German-speaking countries, ETH Zürich traditionally is ranked first in natural sciences, computer science and engineering sciences.

In the survey CHE ExcellenceRanking on the quality of Western European graduate school programs in the fields of biology, chemistry, physics and mathematics, ETH Zürich was assessed as one of the three institutions to have excellent programs in all the considered fields, the other two being Imperial College London(UK) and the University of Cambridge(UK), respectively.