Integrative analyses reveal the evolution of the Old World Swallowtail in the Palearctic

Based on a dataset of 585 samples originating from across the Palearctic region and four genes (COI, CAD, Ca-ATPase, and 28S) for a subset of these samples, we studied the phylogenetic relationships within and between the Old World Swallowtail (Papilio machaon Linnaeus, 1758) and its closest relatives in the Palearctic region. We used Machine Learning (ML) to investigate the concordance of morphological characteristics with the molecular data. Our phylogenetic analyses showed that the Palearctic taxa everesti, archias and hippocrates formed strongly supported sister-group relationships with P. machaon. Within the Palearctic machaon a few distinct mitochondrial linages were observed, including one from the Himalayas and Central Asia, and another one that included all of the north African samples (taxa mauretanica, saharae and neosaharae) without any distinction. ML clustering was supportive of the haplotype and geographic analyses and a positive correlation was measured between average genetic phylogenetic and machine learnt specimen-image distances. Screening for Wolbachia revealed infection only in females of P. archias. We present a biogeographic scenario for the evolution of the P. machaon species group in the Palearctic region.