Evolution and biogeography of the widespread dragonfly genus Orthetrum ( Odonata: Anisoptera: Libellulidae ): Massive dispersal in the tertiary

Abstract

With 67 species, Orthetrum Newman is the most speciose genus within the family Libellulidae Leach (Odonata: Anisoptera), distributed across the Afrotropical, Palearctic, Indo‐Malayan, Malagasy, Oceania, Wallacea and Australasian regions. Despite its wide distribution, serving as a top predator in freshwater ecosystems, the evolutionary history of Orthetrum has remained unresolved, with prior studies limited to morphology and sparse genetic sampling (<33% of species). We present here the most comprehensive phylogenetic study of Orthetrum to date, sampling 50 of 67 species (~75%) using Anchored Hybrid Enrichment (AHE). Our analyses, integrating concatenated maximum likelihood and coalescent‐based approaches, provide a robust, strongly supported phylogeny that confirms the monophyly of Orthetrum and reveals four distinct clades. Two clades comprise mostly Afrotropical species, whereas the remaining clades are from the Palearctic, Indo‐Malayan, Oceania, Wallacea and Australasian regions. Divergence time estimates indicate that Orthetrum originated ~32 million years ago, with major diversification occurring from ~28 Ma onward, well after major continental fragmentation events. Ancestral range reconstruction under the best supported Dispersal–Extinction–Cladogenesis (DEC) framework does not support a single‐region origin; instead, early lineages are inferred to have occupied a broadly connected Afro–Eurasian system. Subsequent diversification is characterized by stepwise dispersal across adjacent regions, including repeated expansions into the Indo‐Malayan and Palearctic regions, followed by colonization of Australasia, Wallacea and Oceania. The Afrotropical region emerges as a major centre of lineage persistence and diversification, with subsequent range expansion in some lineages during the early Miocene (~23 Ma), whereas Madagascar reflects at least five independent colonization events from Africa resulting in endemic species.