Seorsus aequatorius (Myrtaceae), a Borneon endemic, rediscovered after 129 years: Conservation implications

Seorsus aequatorius (Myrtaceae), endemic to Borneo, was first described from a single herbarium specimen collected by H. Hallier on Mount Kelam in 1893–1894. However, a minor error in the published collection number of the type specimen for S. aequatorius requires correction. In 2019, during an expedition on Mount Kelam, Dr. Muhammad Mansur and his colleagues rediscovered S. aequatorius (locally known as ‘pohon embun’). This research aimed to correct information on the collection number of the type specimen, conduct a conservation assessment, and propose conservation strategies. The study involved examining herbarium specimens. The conservation status of the species was evaluated using IUCN guidelines. We outline the rediscovery of S. aequatorius after 129 years. The correct type specimen identified as “H. Hallier 2308”. Seorsus aequatorius is preliminarily categorized as Endangered on the IUCN Red List of Threatened Species. Short-term conservation strategies include ex-situ conservation of S. aequatorius at the Kuningan Botanical Garden in West Java. This is suitable because the species’ habitat, growing on rocks at around 800 m above sea level, matches the theme and elevation of the botanical garden, dedicated to rocky area plants at 490–870 m above sea level. Meanwhile, in-situ conservation strategies for S. aequatorius include conducting population studies, performing habitat rehabilitation or restoration, protecting both habitats and species through legal regulations, and reintroducing seedlings from ex-situ conservation. Designating S. aequatorius as Mount Kelam’s mascot could also raise public awareness.