Featured Research

from universities, journals, and other organizations

Evolution: New understandings of how populations change over time

Date:
October 19, 2012
Source:
Veterinärmedizinische Universität Wien
Summary:
Since 1859, when Darwin’s classic work “On the Origin of Species” was published, we have known that populations change over the course of time.  The ability to adapt to changing surroundings is the basis for evolution and is crucial for animals and plants to come to terms with new environmental conditions, for example as a consequence of climate change.  Despite the obvious importance of the process, however, we still do not understand the underlying mechanisms.  It is clear that organisms change their DNA in response to selection pressures.  But how? 

Fruit flies are bred in special containers.
Credit: Vetmeduni Vienna/Kapun

Since 1859, when Darwin's classic work "On the Origin of Species" was published, we have known that populations change over the course of time. The ability to adapt to changing surroundings is the basis for evolution and is crucial for animals and plants to come to terms with new environmental conditions, for example as a consequence of climate change. Despite the obvious importance of the process, however, we still do not understand the underlying mechanisms. It is clear that organisms change their DNA in response to selection pressures. But how?

Important clues come from the work of Pablo Orozco-terWengel in the group of Christian Schlötterer at the University of Veterinary Medicine, Vienna. The results are published in the current issue of the journal Molecular Ecology.

In the long run, all organisms must adapt to survive as their surroundings do not remain constant for ever. The major difficulty with understanding adaption relates to the length of time required for experiments: evolution is by its very nature a gradual process. Fortunately, however, recent breakthroughs in experimental evolution using model organisms are providing important insights into the process. The nature of the underlying genetic changes has generally remained elusive but recent work at the Institute of Population Genetics of the University of Veterinary Medicine, Vienna is helping to show us how evolution may operate.

To discover what happens when an organism -- in this case the fruit fly, Drosophila melanogaster -- is confronted with new conditions for a prolonged period of time, terWengel and colleagues Martin Kapun and Viola Nolte subjected flies to an unfamiliar temperature regime, in which 12-hour days at 28oC alternated with 12-hour nights at 18oC. Throughout the experiment, the scientists monitored the changes to the flies' DNA by sequencing pools of female flies taken after certain numbers of generations. The complicated study was made possible by developments in sequencing technology that enable the rapid sequencing of entire genomes and by new and sophisticated software algorithms that permit the frequency of gene variants (alleles or polymorphisms) to be directly compared across different populations.

At the start of the experiment, the fly genomes contained sufficient polymorphisms to enable natural selection to act on the population. The researchers were able to confirm that the genetic changes over time were not random but presumably driven by a selective force: the X chromosome proved to be more stable than chromosome III, for example, despite its far smaller population size (each pair of flies carries a total of four copies of chromosome III but only a single X chromosome). They also showed that genetic changes were widespread and rapid: within a mere 15 generations, the frequencies of variants at nearly 5000 positions in the genome had altered significantly more than expected.

Surprisingly, however, not all changes took place at the same rate. The scientists found that while the frequencies of variants of some genes continued to rise throughout the entire course of the study (37 generations), the proportions of alleles of other genes rose rapidly at the start of the experiment but reached a plateau after about 15 generations. The reasons for this levelling out are still unclear but may relate to the fluctuating temperatures employed in the work, which could result in different selective advantages being conferred by several different alleles of a particular gene.

As Schlötterer puts it, "we expected the flies to respond genetically to the changes in their environment. But we did not expect the genetic adaptations to group so neatly into two classes, with so little overlap between them. It will be intriguing to try to find out whether the two categories of gene affect distinct groups of traits."


Story Source:

The above story is based on materials provided by Veterinärmedizinische Universität Wien. Note: Materials may be edited for content and length.


Journal Reference:

  1. Pablo Orozco-terWengel, Martin Kapun, Viola Nolte, Robert Kofler, Thomas Flatt, Christian Schlötterer. Adaptation ofDrosophilato a novel laboratory environment reveals temporally heterogeneous trajectories of selected alleles. Molecular Ecology, 2012; 21 (20): 4931 DOI: 10.1111/j.1365-294X.2012.05673.x

Cite This Page:

Veterinärmedizinische Universität Wien. "Evolution: New understandings of how populations change over time." ScienceDaily. ScienceDaily, 19 October 2012. <www.sciencedaily.com/releases/2012/10/121019071417.htm>.
Veterinärmedizinische Universität Wien. (2012, October 19). Evolution: New understandings of how populations change over time. ScienceDaily. Retrieved July 28, 2014 from www.sciencedaily.com/releases/2012/10/121019071417.htm
Veterinärmedizinische Universität Wien. "Evolution: New understandings of how populations change over time." ScienceDaily. www.sciencedaily.com/releases/2012/10/121019071417.htm (accessed July 28, 2014).

Share This




More Fossils & Ruins News

Monday, July 28, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Did ISIS Destroy Jonah's Tomb?

Did ISIS Destroy Jonah's Tomb?

Newsy (July 25, 2014) — Unverified footage posted to YouTube purportedly shows ISIS militants destroying a shrine widely believed to be the tomb of the prophet Jonah. Video provided by Newsy
Powered by NewsLook.com
Richard III's Car Park Burial Site Opens to Public

Richard III's Car Park Burial Site Opens to Public

AFP (July 25, 2014) — Visitors will be able to look down from a glass walkway on the grave of King Richard III when a new centre opens in the English cathedral city of Leicester, where the infamous hunchback was found under a car park in 2012. Duration: 00:35 Video provided by AFP
Powered by NewsLook.com
Mobile App Gives Tour of Battle of Atlanta Sites

Mobile App Gives Tour of Battle of Atlanta Sites

AP (July 25, 2014) — Emory University's Center for Digital Scholarship has launched a self-guided mobile tour app to coincide with the 150th anniversary of the Civil War's Battle of Atlanta. (July 25) Video provided by AP
Powered by NewsLook.com
Tyrannosaur Pack-Hunting Theory Aided By New Footprints

Tyrannosaur Pack-Hunting Theory Aided By New Footprints

Newsy (July 24, 2014) — A new study claims a set of prehistoric T-Rex footprints supports the theory that the giant predators hunted in packs instead of alone. Video provided by Newsy
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
 
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:  

Breaking News:
from the past week

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:  

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile iPhone Android Web
Follow Facebook Twitter Google+
Subscribe RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins