Science Daily is reporting that researchers from Washington University in St. Louis, Missouri are publishing the results of a study that uses molecular techniques to trace the heritage of, among other plant species, the invasive Saltcedar (Tamarix spp.). Apparently there are differences in populations that grow in different parts of the country, such that insects introduced for biological control will eat one type but not the other. It turns out that the most aggressive Saltcedar is actually a hybrid between two species that do not grow together in their native Asia. You can read more about the biocontrol program for Saltcedar by going here.