Unravelling Amegilla (Glossamegilla) diversity across the Wallace Line: new species, wing morphometrics, and biogeographic boundaries (Hymenoptera, Apidae)

The Indo-Australian Archipelago is a large and biologically complex region that straddles the famous transitionary border between the Indo-Malayan and Australasian biogeographic realms called the Wallace Line. This archipelago contains much of the diversity of Amegilla (Glossamegilla) Brooks, 1988 that was previously revised during the 20^th century by the Dutch entomologist Maurits Lieftinck, but no modern works on the subject have been made. We present a new revision of the subgenus Glossamegilla in the Indo-Australian Archipelago using wing morphometrics to validate existing species concepts, as well as more complete type revision and examination of undetermined material. These efforts result in the new synonymy of <i>A. bouwmani</i> (Lieftinck, 1944), <b>syn. nov.</b> with <i>A. amymone</i> (Bingham, 1896) and unveiled five novelties, namely <i>A. floresiana</i> Carion & Wood, <b>sp. nov.</b> (Indonesia: Flores), <i>A. suzanneae</i> Carion & Wood, <b>sp. nov.</b> (Malaysia: Sabah), <i>A. celineae</i> Carion, <b>sp. nov.</b> (Indonesia: East Kalimantan), and the unknown males of <i>A. gigas</i> (Friese, 1922) and <i>A. vigilans</i> (Smith, 1860). In total, 20 species are currently known in the Indo-Australian Archipelago. Wing morphometrics were found to strongly support most of the existing species concepts. No individual <i>Glossamegilla</i> species were found to occur on both sides of the Wallace Line, and the subgenus as a whole is not known to the east of the Lydddeker Line. Overall, wing morphometrics can help to determine <i>Glossamegilla</i> species in the Indo-Australian Archipelago but need to be coupled with other characters such as additional morphological features or biogeography. Future research involving new collections of specimens are needed to thoroughly understand the evolutionary history and biogeography of the subgenus in the Indo-Australian Archipelago.