These problems are complicated by difficulties in classifying and detecting new whitefly biotypes and begomoviruses. However, two rootworm biotypes survive rotation. Some taxonomists consider it a group of related species, or possibly biotypes. It has been found in fish, and contains several biotypes. Instead unisexual Ambystoma should be considered distinct biotypes rather than species. Brucellosis is caused by different biotypes of "Brucella abortus" and "B. melitensis". It is also distinguished from classic biotypes by the production of hemolysins. Recent phlyogenetic analysis of field-collected basidiomes and cultures suggests that other biotypes may also exist.