Impact of geoclimatic events on the diversification of newly defined Megelenophorini (Coleoptera: Tenebrionidae) in South America

Abstract

The uplift of Andes caused fundamental geomorphological and climatic changes in South America and had a strong impact on the continent’s biodiversity, especially in arid regions west of the Cordillera such as the Atacama Desert. With the fading of the main uplift phase of the Central Andes, global climate change since then affected the region fundamentally. This complex geoclimatic history provides a suitable scenario to study how organisms diversify and to investigate the effects of major forcing factors such as climate or tectonics on biological evolution. We used desert beetles of the tribe Elenophorini (Coleoptera: Tenebrionidae) to obtain insights into driving forces that were responsible for diversification under such extreme and unstable conditions in arid environments. Elenophorini comprises only three genera: Leptoderis from southern Europe, together with Psammetichus and Megelenophorus from South America, suggesting an ancient origin of this tribe. The monotypic Megelenophorus, one of the largest tenebrionid beetles in South America, is restricted to a region east of the Andes in northwestern and central Argentina. The thirteen described species of Psammetichus are distributed west of the Andes in the deserts of Peru and Chile. We performed a phylogenetic analysis including all known species of Elenophorini and subsequently reconstructed the biogeographical history of the South American members. The results suggest that Elenophorini is not a monophyletic group. We therefore propose to raise the subtribe Megelenophorina established for Psammetichus and Megelenophorus to its own tribe: Megelenophorini. The diversification of Megelenophorini started around 4.9 Ma. This separation of the common ancestor of Psammetichus and Megelenophorus could be related to the global climate cooling in the early Pliocene, which first affected the high altitude habitats in the Andean mountains, already above 3000 m.a.s.l. in the study area at that time. The subsequent emergence of five species groups in Psammetichus can be related to hyperarid periods in the Atacama Desert between 4 and 2 Ma. Speciation within these groups was accelerated during the Mid-Pleistocene Transition (<1 Ma), possibly due to high amplitude climate fluctuations.