This leads to a clonal expansion of malignant B lymphocytes. This recombinational process that produces clonal antibody paratope diversity is called V(D)J or VJ recombination. Activation leads to clonal expansion and affinity maturation. Layering is the technique most used for propagation of clonal apple rootstocks. Most of these undergo negative selection by clonal deletion. The results of these clonal studies led to the notion of lineage bias. Researchers do epidemiological and phylogenetical studies by comparing STs of different clonal complexes. The most common cause of clonal thrombocythemia is a myeloproliferative neoplasm. Extensive sampling within colonies confirms that many colonies harbor a homogeneous (clonal) "Symbiodinium" population. This interaction leads to a role in clonal expansion of T cells. Some, but not all, milkweeds also reproduced by clonal (or vegetative) reproduction. Some plants produce adventitious shoots and may form a clonal colony. Myriad receptors are produced through a process known as clonal selection. The most extreme form involves the production of clonal offspring. The basis for clonal aging was clarified by transplantation experiments of Aufderheide in 1986.