Geology-based and ecological processes of divergence between and within species of wingless darkling beetles

Aim: Discerning the relative role of geographical and ecological factors in promoting diversification is central to our understanding of the origin and maintenance of biodiversity. We explore the roles of geology and ecological tolerance in the diversification of a group of wingless beetles with low dispersal potential. Location: Western Mediterranean (Iberian Peninsula and North Africa). Taxon: Darkling beetles (Tenebrionidae: Misolampus). Methods: We sequenced nine gene fragments from the mitochondrial and nuclear genomes in all extant Misolampus species to reconstruct their phylogeny, evaluate species boundaries and potential contact zones and estimate divergence times. We modelled species distributions for different time periods to infer ecological preferences and assess the effects of climatic changes since the last interglacial. We used a time-stratified process-based biogeographical model to estimate ancestral areas of origin and the evolution of geographical ranges. Results: The palaeoclimatic model projections show contractions of favourable areas during the last interglacial period and mid-Holocene, and wide stretches of suitable areas during the last glacial maximum. Analyses of ancestral bioclimatic preferences reveal ecological adaptations in isolated lineages within three species. The phylogeny of Misolampus is strongly supported and unveils deep divergences within the six species. Two well-supported clades were recovered, one distributed in North Africa-Balearic Islands and another in the Iberian Peninsula. The divergence between the North African and Iberian clades occurred during the early Miocene. Biogeographical analyses infer an ancestral range including the Iberian, Betic and Rifean Plates, with subsequent splits followed by dispersal events. Main conclusions: Our results favour a dual role of vicariance and dispersal in driving the historical biogeography and diversification of Misolampus since the early Miocene. We also found evidence for incipient speciation events, underscoring the role of tectonic events and adaptation to local climatic conditions in the diversification of the group.Visit of PMP to the Institut des Sciences de l'Evolution de Montpellier (ISEM) was supported by the Ministerio de Ciencia, Innovación y Universidades, Spain (MICINN-FEDER) through contract BES-2016-077777. This study was supported by the Spanish government (MINECO/MIUC/AEI) and the European Fund for Regional Development (FEDER) under grants CGL2015-66571-P (collecting and Museum visits) and PID2019-110243GB-I00/AEI/10.13039/501100011033 (Ministerio de Ciencia, Innovación y Universidades, Spain) (molecular analyses) to MGP. Support of the publication fee was granted by the CSIC Open Access Publication Support Initiative through its Unit of Information Resources for Research (URICI)