Abstract
Multiple team membership (MTM) configurations have received considerable scholarly attention since O'Leary, Mortensen, and Woolley's (2011) foundational work. However, research has predominantly focused on the quantity of external memberships, with limited examination of team-level MTM variety—the aggregated diversity of knowledge and experiences team members acquire through their external team involvements. Team-level MTM variety presents theoretical tension: it can enhance information processing capabilities while simultaneously increasing coordination costs. To reconcile these competing perspectives, we examine intra-team subgroup configurations (i.e., faultlines) as moderators and incorporate a temporal perspective for investigating newcomer proportions. Using monthly longitudinal data from 201 mutual fund management teams spanning 918 fund managers and 11,531 observations (January 2000- December 2017), we find that MTM knowledge variety has a positive relationship with team performance, above and beyond MTM number. This positive relationship is weakened when demographic faultlines are strong but amplified when informational faultlines are strong. Additionally, newcomer proportion moderates the MTM variety-performance relationship temporally: the relationship becomes positive between the fourth to sixth months and subsequently diminishes, suggesting that integration processes require time to translate MTM variety into performance benefits.