Hymenoptera of Galápagos: diversity and distribution of one of the most species-rich insect orders in the archipelago

Despite the importance of the Galápagos archipelago as a key site for the study of biodiversity and evolution, significant components of its invertebrate biodiversity, particularly Hymenoptera, remain insufficiently documented. Occurrence records of Hymenoptera from 1959–2025 were combined from structured surveys of non-formicid Hymenoptera, long-term ant sampling, museum collections, literature, and online sources to assess the richness, distribution, and species composition of hymenopterans across the archipelago. Based on 21,364 records, 524 species/morphospecies, including 137 species, one subspecies, and 386 morphospecies are documented. These records include 20 newly recorded species and 134 newly recorded genera for Galápagos, representing 11 previously unrecorded families. These records substantially increase previous estimates, with the greatest additions observed in Chalcidoidea and Ichneumonoidea. Species accumulation curves and incidence-based richness estimators (Bootstrap = 595.47, Jackknife 1 = 673.38, Chao2 = 658.26) indicate that additional species/morphospecies may remain undocumented. Species/morphospecies richness was positively associated with island area after accounting for sampling effort. Species composition showed partial similarity among some islands and overlap among the littoral, dry, and transition zones; the humid zone contained the highest proportion of unique species/morphospecies. A considerable proportion of the named species were classified as introduced. Overall, this study establishes an updated baseline for future Hymenoptera research in Galápagos and provides a framework for evaluating biogeographic patterns in oceanic island systems.