In Maven 2, how do I know from which dependency comes a transitive dependency?

To add to @David Crow, here's a dependency:tree example from the Maven site:

mvn dependency:tree -Dincludes=velocity:velocity

might output

[INFO] [dependency:tree]
[INFO] org.apache.maven.plugins:maven-dependency-plugin:maven-plugin:2.0-alpha-5-SNAPSHOT
[INFO] \- org.apache.maven.doxia:doxia-site-renderer:jar:1.0-alpha-8:compile
[INFO]    \- org.codehaus.plexus:plexus-velocity:jar:1.1.3:compile
[INFO]       \- velocity:velocity:jar:1.4:compile

If you use eclipse and the m2eclipse plugin then there is a graphical version of dependency tree where you can filter by scope etc.

Using the Maven Dependency Plugin:

mvn dependency:tree