Official websites use .gov
A
.gov website belongs to an official
government organization in the United States.
Secure .gov websites use HTTPS
A lock (
) or https:// means you've safely
connected to the .gov website. Share sensitive
information only on official, secure websites.
Simulated gene trees from a pair of populations that have contracted by a factor of 100. The populations exchange an average of one-half a gene every generation. Because the vertical axes are drawn to the same scale, the trees in the left two panels are so shallow that they are invisible.
