Sentence:  Churches can be strengthened through this process of <WSD>co-optation</WSD> so long as the environs of the church provide a sufficient pool of people who can fit the pattern of economic integration ; once the pool of recruits diminishes , the congregation is helpless - friendly contacts no longer keep it going . 
Meaning of the word marked with <WSD> tags:  the selection of a new member (usually by a vote of the existing membership)