Thursday, 2 April 2020

About the distribution of biodiversity on our planet


Date: April 1, 2020
Source: University of Bern

Since Charles Darwin, biologists have been using the so-called "biotic interactions" hypothesis to explain, at least in part, why the tropics around the equator are so species rich. The hypothesis focuses on the importance of interactions between species for biodiversity. The geneal idea is that species interactions increase towards the species-rich equator. Such interactions may include interactions such as between parasites and host, or between a predator and its prey. The intuitively appealing hypothesis is: The stronger the interactions between species, the faster evolutionary change, thus resulting in increased species diversity. Strong species interactions should further help maintain a high level of biodiversity. Testing this long-standing hypothesis has proven extremely difficult in the past, and the results from past studies aiming to test the "biotic interactions" hypothesis are mixed.

A new publication in Nature Communications now further challenges the general validity of the "biotic interactions" hypothesis. The study suggests that a specific but fundamental interaction between species -- predation by large fish such as tunas or sharks -- is stronger in the temperate zone than near the equator. According to the "biotic interactions" hypothesis, stronger interactions should be accompanied by a higher diversity of fish species -- a pattern that is also not born out by the study. The study is headed by Dr. Marius Roesti, who began the research work at the University of British Columbia in Vancouver and is now working at the Institute of Ecology and Evolution at the University of Bern.

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