Complex sentence: The reigning national champions are the North Dakota State University Bison, which also won the championship in 2011,2012, and in 2013, the first team to win three consecutive titles since Appalachian State accomplished this feat in 2005--2007.
Split into simpler sentences: The reigning national champions are the North Dakota State University Bison, which also won the championship in 2011,2012 and in 2013. The first team to win three consecutive titles since Appalachian State accomplished this feat in 2005--2007.