Rediscovery of <i>Melanesobasis</i> Donnelly, 1984 (Odonata: Coenagrionidae) in Vanuatu reveals a pattern of vicariance in insular damselflies

Abstract The Vitiaz Arc provides a compelling opportunity to examine biogeographical patterns in the South Pacific. Previously, however, many groups lacked the appropriate taxon sampling to examine this system fully. Fieldwork aimed at improving our understanding of Vanuatu insect diversity and evolution resulted in the collection of two specimens of Melanesobasis bicellulare Donelly, 1984, a species previously known from a single specimen collected 40 years ago. Using a combination of morphological and molecular methods, we are able to associate the female, update distributional data, and record intraspecific variation, including the number of post-discoidal cells. We also use this genus, Melanesobasis Donnelly, 1984, found across Fiji and Vanuatu, to explore biogeographical patterns across the Vitiaz Arc. Our results provide additional evidence of the importance of the Vitiaz Arc in South Pacific damselfly biogeography and show a pattern of vicariance between the two island archipelagos.