The diversification of neotenic beetle lineages has not been studied, despite the potential for defining biodiversity hotspots and elucidating the history of regional faunas. Additionally, neotenics may provide insight into the process of speciation in small populations with extremely low dispersal ability and a limited range. Here, we used two rDNA and three mtDNA markers to investigate the phylogeny of Scarelus, a neotenic lineage endemic to Southeast Asian rainforests. Most genetic differentiation was associated with Palaeogene geographical divisions, which remain distinct despite temporary connections. Dispersal events were rare, with only two inferred for Scarelus: from Borneo to the Philippines 28.3 million years ago (Ma) and from Sumatra to Java 13.9 Ma. We suggest that speciation resulted from allopatric range fragmentation, and Scarelus diversified readily when conditions were favourable; in this case, at different times in the eastern (19.3-39.1 Ma) and western (3.5-13.9 Ma) parts of Sundaland. The observed strong phenotypic similarity was preserved under speciation through complete allopatry. Neotenic Lycidae have survived for a long time in very stable habitats, and extremely low dispersal activity has not limited their persistence; however, the long-term diversification rate of neotenics is low and diversification is nonexistent under stable conditions. The modern ranges of neotenic lineages are indicative of ancient rainforest refugia and may be used in biodiversity conservation management. Most neotenics are at risk of extinction because of their small ranges and a low dispersal potential.

Department of Zoology Faculty of Science Palacky University Tr Svobody 26 771 46 Olomouc Czech Republic

References provided by Crossref.org

Analysis of the Holarctic Dictyoptera aurora Complex (Coleoptera, Lycidae) Reveals Hidden Diversity and Geographic Structure in Müllerian Mimicry Ring

Dominican amber net-winged beetles suggest stable paleoenvironment as a driver for conserved morphology in a paedomorphic lineage

Hide-and-Seek with Tiny Neotenic Beetles in One of the Hottest Biodiversity Hotspots: Towards an Understanding of the Real Diversity of Jurasaidae (Coleoptera: Elateroidea) in the Brazilian Atlantic Forest

Conspicuousness, phylogenetic structure, and origins of Müllerian mimicry in 4000 lycid beetles from all zoogeographic regions

Interactions in multi-pattern Müllerian communities support origins of new patterns, false structures, imperfect resemblance and mimetic sexual dimorphism

Hidden diversity in the Brazilian Atlantic rainforest: the discovery of Jurasaidae, a new beetle family (Coleoptera, Elateroidea) with neotenic females

The Malacca Strait separates distinct faunas of poorly-flying Cautires net-winged beetles

Molecular Phylogeny, Diversity and Zoogeography of Net-Winged Beetles (Coleoptera: Lycidae)

Slowly dispersing neotenic beetles can speciate on a penny coin and generate space-limited diversity in the tropical mountains

The discovery of Iberobaeniidae (Coleoptera: Elateroidea): a new family of beetles from Spain, with immatures detected by environmental DNA sequencing

The taxonomy and diversity of Platerodrilus (Coleoptera, Lycidae) inferred from molecular data and morphology of adults and larvae

Molecular phylogeny reveals high diversity, geographic structure and limited ranges in neotenic net-winged beetles platerodrilus (coleoptera: lycidae)

Phylogeography of Poorly Dispersing Net-Winged Beetles: A Role of Drifting India in the Origin of Afrotropical and Oriental Fauna