First insights into the origin of Iranian cave beetle diversity with description of two new species of the genus Duvalius (Carabidae)

Subterranean environments of Iran are severely understudied. Here, we advance the knowledge of Iranian cave biodiversity by following three goals: (i) to investigate Iranian caves for troglobiotic beetles; (ii) to understand the phylogenetic relationships and estimate the timing of Iranian cave colonization by Duvalius Delarouzee, 1859; and (iii) to comment on the current knowledge of the Iranian troglobiotic fauna to facilitate future research. Through field efforts and morphological examination, we describe two new Duvalius species from caves of Zagros Mts., Iran: the troglobiotic Duvalius nezelensis sp. nov. and the non-troglobiotic Duvalius achaemenius sp. nov. For phylogenetic analyses, we provide original sequences of two mitochondrial (COI, 16S) and two nuclear (18S, 28S) genes for three Duvalius species from the Zagros Mts., and combine them with published molecular datasets using other Duvalius species with relevant outgroup genera. Using Bayesian inference and maximum likelihood, we reconstruct a species-level phylogeny of Duvalius and closely related genera, then use BEAST to explore divergence times of major lineages. Our phylogenies recover a well-supported Zagros clade, with its split from other congeners estimated at 9.7 Ma. Within the Zagros clade, the split of D. nezelensis and its sister group is estimated at 7.8 Ma, while the split of D. achaemenius and D. kileri is estimated to a recent 0.78 Ma. We provide some resolution in understanding the species richness of cave beetles in Iran and the timing of their subterranean colonization. However, our phylogenies confirm taxonomic problems as several genera are nested deep within the Duvalius tree.

Automated summary

This study advances the knowledge of Iranian cave biodiversity by describing two new Duvalius species from caves in the Zagros Mountains, investigating their phylogenetic relationships, and estimating the timing of their colonization. Phylogenetic analyses reveal a well-supported Zagros clade, with the split from other congeners estimated at 9.7 Ma, providing insights into the species richness of cave beetles in Iran and the timing of their subterranean colonization. However, taxonomic problems persist as several genera are nested deep within the Duvalius tree.