Biogeographic history of <I>Pistacia</I> (Anacardiaceae), emphasizing the evolution of the Madrean-Tethyan and the eastern Asian-Tethyan disjunctions

Abstract

Pistacia L. exhibits a disjunct distribution in Mediterranean Eurasia and adjacent North Africa, eastern Asia, and North to Central America. The spatio-temporal diversification history of Pistacia was assessed to test hypotheses on the Madrean-Tethyan and the Eurasian Tethyan disjunctions through phylogenetic and biogeographic analyses. Maximum parsimony and Bayesian methods were employed to analyze sequences of multiple nuclear and plastid loci of Pistacia species. Bayesian dating analysis was conducted to estimate the divergence times of clades. The likelihood method LAGRANGE was used to infer ancestral areas. The New World species of Pistacia formed a clade sister to the Old World clade in all phylogenetic analyses. The eastern Asian Pistacia weinmannifolia–P. cucphuongensis clade was sister to a clade of the remaining Old World species, which were further resolved into three subclades. Pistacia was estimated to have originated at 37.60 mya (with 95% highest posterior density interval (HPD): 25.42–48.51 mya). A vicariance event in the early Miocene (19.79 mya with 95% HPD: 10.88–30.36 mya) was inferred to account for the intercontinental disjunction between the New World and the Old World species, which is consistent with the Madrean-Tethyan hypothesis. The two Old World eastern Asian-Tethyan disjunctions are best explained by one vicariance event in the early Miocene (15.87 mya with 95% HPD: 8.36–24.36 mya) and one dispersal event in late Miocene (5.89 mya with 95% HPD: 2.68–9.16 mya). The diversification of the Old World Pistacia species was significantly affected by extensive geological and climatic changes in the Qinghai-Tibetan plateau (QTP) and in the Mediterranean region.