Melitians and Manichaeans
Aside from the monasteries that joined Pachomius' federation of cenobitic monasteries, there were also other cenobitic Christian groups who decided not to join him. The Melitians and the Manichaeans are examples of these cenobitic groups.
Even before Pachomius had started on his path toward monastic communities, the Melitians as a group were already recruiting members. The Melitians were a heretical Christian sect founded by Meletius of Lycopolis They actually had "heard of Pachomius' monastic aspirations and tried to recruit him" to join their community.
As for Manichaeans, members of a religion founded by a man named Mani, some scholars believe they were the "pioneers of communal asceticism in Egypt," and not Pachomius and the Pachomians as has become the common thought. Mani, himself, was actually influenced to begin cenobitic monasticism from other groups, including Buddhists and Jewish-Christian Elkasites who were practising this tradition already.
The overall idea of cenobitic monasticism cannot be traced to a single source, however, as many have tried to do in calling Pachomius the "founder" of the tradition, but rather is thanks to the ideas and work of numerous groups, including the aforementioned Melitians, Manichaeans, Elkasites, Buddhists and, of course, the Pachomians.
Read more about this topic: Cenobitic Monasticism