Although it is unknown how long Donatism persisted, some Christian historians believe that the schism and its ensuing unrest in the Christian community facilitated the seventh-century Muslim conquest of the region. Donatism is associated with a number of other groups, including:    In Mauretania and Numidia, the splinter groups were so numerous that the Donatists could not name them all. The Donatists followed a succession of bishops:   For several centuries during the High Middle Ages and the Reformation, accusations of Donatism were leveled against church-reform movements which criticized clerical immorality on theological grounds. The early reformers John Wycliffe and Jan Hus were accused of Donatism by their theological opponents. Wycliffe taught that the moral corruption of priests invalidated their offices and sacraments, a belief characterizing Donatism. Hus similarly argued that a prelate's moral character determined his ecclesiastical authority, a position his contemporaries compared to Donatism and condemned as heresy at the Council of Constance. During the Reformation, Catholic Counter-Reformers such as Johann Eck accused the magisterial Reformers of Donatism (although the latter had partially distanced themselves from Wycliffe's theology to avoid such a charge). Magisterial Reformers like Ulrich Zwingli labeled radical Reformers, such as the Anabaptists, as Donatists; Catholics were portrayed in Reformation rhetoric as Pelagian, another early Christian heresy. In Eastern Orthodoxy, the Bezpopovtsy (priestless) strain of Old Believers believed that because the Russian bishops acquiesced to Patriarch Nikon's reforms they (and the other patriarchs) forfeited any claim to apostolic succession. Accusations of Donatism remain common in contemporary intra-Christian polemics. Conservative Lutherans are sometimes called Donatists by their liberal brethren, referring to their doctrine of church fellowship and their position that churches which deny that Jesus’ body and blood are eaten during the Eucharist do not celebrate a valid Lord's Supper. In the Catholic Church, the Society of Saint Pius X has been accused of Donatist beliefs.