Beyond dyads: an ecosystem approach to third-sector legitimacy in public services

Third-sector organizations (TSOs) play an increasing role in public service provision, yet their legitimacy remains underexplored beyond dyadic and organization-centric accounts. This paper develops an ecosystem-based explanation by integrating legitimacy theory with the Public Service Ecosystem (PSE) framework. Drawing on a qualitative multi-case study of four TSOs delivering children’s services in Scotland, the findings show that legitimacy emerges through interdependencies among actors and institutions across macro, meso, and micro levels. Three mechanisms are identified: institutional translation, leadership coordination, and temporal reconfiguration. The study conceptualizes legitimacy as an emergent, cross-level process and a central dynamic shaping coordination and participation within PSEs.