TY - STD TI - Proceedings of the National Academy of Sciences USA, [http://www.pnas.org] UR - http://www.pnas.org ID - ref1 ER - TY - STD TI - Scott L. Nuismer, [http://www.sci.uidaho.edu/biosci/faculty/nuismer.html] UR - http://www.sci.uidaho.edu/biosci/faculty/nuismer.html ID - ref2 ER - TY - STD TI - Sarah P. Otto, [http://www.zoology.ubc.ca/~otto/] UR - http://www.zoology.ubc.ca/~otto/ ID - ref3 ER - TY - STD TI - Loren H. Reiseberg, [http://www.bio.indiana.edu/facultyresearch/faculty/Rieseberg.html] UR - http://www.bio.indiana.edu/facultyresearch/faculty/Rieseberg.html ID - ref4 ER - TY - STD TI - Clifford W. Zeyl, [http://www.wfu.edu/%7Ezeylcw/] UR - http://www.wfu.edu/%7Ezeylcw/ ID - ref5 ER -