The evolution of birds on the Galápagos Islands, the cradle of Darwin's theory of evolution, is a two-speed process. Most bird species are still diversifying, while the famous Darwin's finches have already reached an equilibrium, in which new species can only appear when an existing one becomes extinct. This finding expands the classical theory on island evolution put forward in the 1960s. The study is published online on June 23 in Ecology Letters.
Islands are seen as natural laboratories for the study of evolution. They form isolated ecosystems with barriers to migration. Classical Island Theory predicts that a dynamic equilibrium will occur between immigration and extinction of species. Recent theory adds that as species diversity increases, ever more ecological niches become occupied, which has a negative effect on immigration (new immigrants from outside of the Galápagos cannot settle) and diversification (radiation into new species is blocked).
'However, this has never been tested in detail, for lack of data and the right analytical tools', explains Rampal Etienne, Associate Professor of Theoretical and Evolutionary Community Ecology at the University of Groningen, the Netherlands. Together with Luis Valente (University of Potsdam, Germany) and Albert Phillimore (University of Edinburgh, UK), he developed DAISIE, a mathematical model that uses phylogenetic data on living species to reconstruct evolutionary dynamics. DAISIE stands for Dynamic Assembly of Islands by Speciation, Immigration and Extinction, and was named after famous radiations of daisy-like plants on Hawaii.
DAISIE was fed with the phylogenetic trees of existing bird species on the Galápagos Islands. These were constructed with genomic data that has become available in recent years. DAISIE then estimates diversity limits and rates of immigration, speciation and extinction per lineage.
'The analysis shows that for the finches, diversity does indeed have a negative effect. There is no more room for new species, unless one of the existing species becomes extinct, so the islands are saturated regarding finch-type species', Etienne explains. This does not mean the radiation is static. 'We found that the rates of both evolution and extinction are very high for Darwin's finches. That is probably why these birds have reached an equilibrium.'
Other species like mockingbirds have not yet reached equilibrium, which contrasts sharply with the current view that oceanic islands are at equilibrium. 'Our data shows that they are evolving more slowly and are still diversifying.' In a million years or so, more mockingbird species may have appeared - granted that conditions on the islands remain the same.
The study shows that the DAISIE model - which the authors have made available as a library* in the free and widely used R software environment - is a valuable tool for the study of evolutionary dynamics on islands. It includes speciation and thus extends existing island theory, which is based on immigration and extinction. Etienne: 'And of course, it works for all isolated ecosystems, not just islands but also lakes or mountain tops.'
Apart from explaining evolutionary history, DAISIE also predicts future diversity. 'This could be interesting from a conservation point of view: we are not just conserving existing species, but also future diversity.'
*Link to the DAISIE programme: http://cran.
Rene Fransen | EurekAlert!
Conservationists are sounding the alarm: parrots much more threatened than assumed
15.09.2017 | Justus-Liebig-Universität Gießen
A new indicator for marine ecosystem changes: the diatom/dinoflagellate index
21.08.2017 | Leibniz-Institut für Ostseeforschung Warnemünde
Plants and algae use the enzyme Rubisco to fix carbon dioxide, removing it from the atmosphere and converting it into biomass. Algae have figured out a way to increase the efficiency of carbon fixation. They gather most of their Rubisco into a ball-shaped microcompartment called the pyrenoid, which they flood with a high local concentration of carbon dioxide. A team of scientists at Princeton University, the Carnegie Institution for Science, Stanford University and the Max Plank Institute of Biochemistry have unravelled the mysteries of how the pyrenoid is assembled. These insights can help to engineer crops that remove more carbon dioxide from the atmosphere while producing more food.
A warming planet
Our brains house extremely complex neuronal circuits, whose detailed structures are still largely unknown. This is especially true for the so-called cerebral cortex of mammals, where among other things vision, thoughts or spatial orientation are being computed. Here the rules by which nerve cells are connected to each other are only partly understood. A team of scientists around Moritz Helmstaedter at the Frankfiurt Max Planck Institute for Brain Research and Helene Schmidt (Humboldt University in Berlin) have now discovered a surprisingly precise nerve cell connectivity pattern in the part of the cerebral cortex that is responsible for orienting the individual animal or human in space.
The researchers report online in Nature (Schmidt et al., 2017. Axonal synapse sorting in medial entorhinal cortex, DOI: 10.1038/nature24005) that synapses in...
Whispering gallery mode (WGM) resonators are used to make tiny micro-lasers, sensors, switches, routers and other devices. These tiny structures rely on a...
Using ultrafast flashes of laser and x-ray radiation, scientists at the Max Planck Institute of Quantum Optics (Garching, Germany) took snapshots of the briefest electron motion inside a solid material to date. The electron motion lasted only 750 billionths of the billionth of a second before it fainted, setting a new record of human capability to capture ultrafast processes inside solids!
When x-rays shine onto solid materials or large molecules, an electron is pushed away from its original place near the nucleus of the atom, leaving a hole...
For the first time, physicists have successfully imaged spiral magnetic ordering in a multiferroic material. These materials are considered highly promising candidates for future data storage media. The researchers were able to prove their findings using unique quantum sensors that were developed at Basel University and that can analyze electromagnetic fields on the nanometer scale. The results – obtained by scientists from the University of Basel’s Department of Physics, the Swiss Nanoscience Institute, the University of Montpellier and several laboratories from University Paris-Saclay – were recently published in the journal Nature.
Multiferroics are materials that simultaneously react to electric and magnetic fields. These two properties are rarely found together, and their combined...
19.09.2017 | Event News
12.09.2017 | Event News
06.09.2017 | Event News
22.09.2017 | Life Sciences
22.09.2017 | Medical Engineering
22.09.2017 | Physics and Astronomy