As event-based social networks (EBSNs) such as Meetup.com and Facebook Events gain popularity in managing local events like farmers' markets and social gatherings, they create two-sided cultural niches where event organizers and participants benefit from the platform while influencing each other. Among various factors, niche overlap, an ecological feature, has been studied as a key factor that shapes the success of online communities. While such ecological factors may also shape the success of EBSN-based local groups, the context of EBSNs raises unique challenges in understanding the roles of cultural niches due to the informal nature of these local groups and their geographical embeddedness. In this paper, we examine the effects of Meetup groups' topic overlap and geospatial correlation on the activity levels of both organizers and participants, using one-year Meetup data for 500 cities in the United States. We find that (1) a group's topic overlap with other groups on EBSNs is associated with its activity levels, and (2) local groups' geospatial correlation may moderate the effects of topic overlap for EBSN users, but inconsistently. The results provide a baseline understanding of EBSN-based groups from an ecological perspective.
* Myeong Lee is the corresponding author.