Bayesian Total-Evidence Dating Reshapes the Age and Historical Biogeography of Parnassiinae

Although incomplete, the fossil record offers direct evidence for the existence of a lineage, providing insights into its age and geographic location. Reconstructing time-calibrated phylogenies, including both extant and fossil taxa as lineages (total-evidence dating) under the fossilized birth-death process, can provide new information about the phylogenetic position of fossil specimens, the time at which they diverged from closely related species, and can impact inferences of clades’ historical biogeography. Here, we focus on the origin and radiation of Apollo butterflies (Papilionidae: Parnassiinae), whose origin has been estimated in the late Eocene in Central Asia. The two fossil taxa recovered in the subfamily Parnassiinae, dated to the late Oligocene (†Thaites ruminiana Scudder) and late Miocene (†Doritites bosniaskii Rebel) in the Western Palearctic, thus challenge the Central Asian origin. We performed a Bayesian total-evidence dating approach to explore the impact of dating analyses and past fossil distributions on the estimation of the evolutionary history of the group. We obtained a more credible dating and historical biogeography for the group, placing its origin in the late Paleocene (ca. 57 Ma) in the Western Palearctic + Western Asia and Caucasus regions, followed by dispersals to Central Asia and the Himalayas. This study also highlights the importance of investigating fossil position in addition to clock partitioning and models for molecular dating. Furthermore, we confirm that a few fossils are sufficient to cast doubt on the origin and biogeographic history of a group, especially when those fossils were dispersed outside of the current center of diversity.