Researchers in Lund, Copenhagen, and Norwich have shown that harmful mutations present in the DNA play an important – yet neglected – role in the conservation and translocation programs of threatened species.

“Many species are threatened by extinction, both locally and globally. For example, we have lost about ten vertebrate species in Sweden in the last century. However, all these species occur elsewhere in Europe, which means that they could be reintroduced into Sweden. Our computer simulations show how we could theoretically maximize the success of such reestablishments”, says Bengt Hansson, a biologist at Lund University. 

In a new study published in Science, the researchers investigated which individuals might be most suited for translocation to new populations. To date, conservation geneticists have opted to select the most genetically variable individuals. However, the authors argue that is important to consider what type of genetic variation is being moved around. Using supercomputer simulations, they showed that harmful mutations present in the genome of translocated individuals can cause problems in future generations. This so-called “mutation load” could jeopardize the viability of the new population in the long run and eventually led to extinction.

According to Hansson and van Oosterhout, a geneticist at the University of East Anglia, Norwich, who led the study, the best choice is to exclude individuals with many harmful mutations while selecting individuals from multiple different source populations.

“Active translocation of animals between localities is sometimes the last option available to conservation biologists. By carefully selecting individuals based on their low mutation load, we can minimize the loss of fitness that is normally associated with inbreeding in small populations”, says Bengt Hansson.

Huge advances have been made in DNA sequencing technologies, and the whole genomes of individuals can now be sequenced for relatively little costs. This opens up new possibilities to improve the conservation management of threatened species.

“For many species of mammals and birds, we now know which mutations are harmful. Similar mutations are also found in humans, so we understand what they do, and hence, we know what to look out for when analyzing the sequence data of those species. The advantage of using DNA sequencing is that we can see these mutations in the genome, even if an individual carries just a single copy of the mutant gene. This means we can select against those bad mutations even before they cause a problem. Our computer model shows that at least theoretically, this ensures the best probability for population survival. This could help conservation managers in picking the optimal individuals of a threatened species for translocation into a new habitat”, says van Oosterhout.

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So-called quantum dots are a new class of materials with many applications. Quantum dots are realized by tiny semiconductor crystals with dimensions in the nanometre range. The optical and electrical properties can be controlled through the size of these crystals. As QLEDs, they are already on the market in the latest generations of TV flat screens, where they ensure particularly brilliant and high-resolution color reproduction. However, quantum dots are not only used as "dyes", they are also used in solar cells or as semiconductor devices, right up to computational building blocks, the qubits, of a quantum supercomputer.

Now, a team led by Dr. Annika Bande at HZB has extended the understanding of the interaction between several quantum dots with an atomistic view in a theoretical publication. 

Annika Bande heads the "Theory of Electron Dynamics and Spectroscopy" group at HZB and is particularly interested in the origins of quantum physical phenomena. Although quantum dots are extremely tiny nanocrystals, they consist of thousands of atoms with, in turn, multiples of electrons. Even with supercomputers, the electronic structure of such a semiconductor crystal could hardly be calculated, emphasizes the theoretical chemist, who recently completed her habilitation at Freie Universität. "But we are developing methods that describe the problem approximately," Bande explains. "In this case, we worked with scaled-down quantum dot versions of only about a hundred atoms, which nonetheless feature the characteristic properties of real nanocrystals."

With this approach, after a year and a half of development and in collaboration with Prof. Jean Christophe Tremblay from the CNRS-Université de Lorraine in Metz, we succeeded in simulating the interaction of two quantum dots, each made of hundreds of atoms, which exchange energy with each other. Specifically, we have investigated how these two quantum dots can absorb, exchange and permanently store the energy controlled by light. A first light pulse is used for excitation, while the second light pulse induces storage.

In total, we investigated three different pairs of quantum dots to capture the effect of size and geometry. We calculated the electronic structure with the highest precision and simulated the electronic motion in real-time at femtosecond resolution (10-15 s).

The results are also very useful for experimental research and development in many fields of application, for example for the development of qubits or to support photocatalysis, to produce green hydrogen gas by sunlight. "We are constantly working on extending our models towards even more realistic descriptions of quantum dots," says Bande, "e.g. to capture the influence of temperature and environment."