Recent mtDNA haplotype diversification in Adesmia cancellata(Coleoptera, Tenebrionidae) across the peninsular desert of Qatar

The darkling beetle Adesmia cancellata Solier, 1835 (Coleoptera: Tenebrionidae) with a wide distribution throughout the Arabian Desert, is considered a dominant arthropod in the Qatari desert. To gain insight into the processes that have favored the success of the species in such an extreme environment, we have reconstructed its demographic and evolutionary history through phylogenetic and phylogeographic approaches. We performed a preliminary phylogenetic analysis including samples from the four subgenera within Adesmia. The analysis recovered two main clades that included species inhabiting the Arabian Desert and the Maghreb/North Africa region, reflecting a parallel evolutionary history of the two clades along a West–East axis. In one of these clades, Adesmia cancellata from Qatar and Adesmia maroccana from Morocco clustered together with the Onymacris samples from Namib, rendering Adesmia paraphyletic. Phylogeographic patterns were inferred through the analysis of mitochondrial genetic diversity in 33 populations distributed across Qatar. We framed the evolutionary history of the species during the Quaternary glaciations. Our results revealed strong mitochondrial homogeneity and an absence of geographical structure in the studied area. Habitat fragmentation and microhabitat preferences do not seem to be relevant factors in patterning the population genetic structure or in disrupting the cohesiveness of the species throughout the peninsula. A well-differentiated haplotype, however, was found in three individuals from Al Otouriyah. This rare haplotype could correspond to a retained ancestral polymorphism, suggesting that a large population of A. cancellata persisted in the area during the Plesitocene with recurrently expansions and colonizations following the marine transgression/regression cycles. Alternatively, the polymorphism could be representing remnants of past introductions. The lack of geographic structure of mtDNA across Qatar, the relatively low diversity and a recent temporal estimate of haplotype MRCAs, could be indicating then that the species colonized the Qatar peninsula recently, probably during the late Pleistocene. The successive erosion of the genetic diversity by cyclical population bottlenecks caused by the marine transgression/regressions cycles related to glacial/interglacial periods could account for the low levels of differentiation observed. In any case, the species has experienced a demographic growth since 30,000–25,000 yrs ago, probably coupled to the increase of aridity conditions in the area. A. cancellata can be considered a good example of the importance of past aridity episodes for population growth and diversification within the group, which has led darkling beetles to become one of the most impressive evolutionary radiations in desert biotas worldwide.Peer reviewe