Across the Gobi Desert: impact of landscape features on the biogeography and phylogeographically-structured release calls of the Mongolian Toad, Strauchbufo raddei in East Asia

Abstract

Landscape structures drive biogeographic patterns and population connectivity of animals distributed across diverse biotopes. Here, we provide a fresh insight on the impact of five landscape types in East Asia on the phylogeography and acoustic variability of the widespread Mongolian Toad, Strauchbufo raddei. For the first time, we reconstructed the biogeography of S. raddei over the species’ entire range throughout East Asia (N = 293; assembled up to 2,613 bp of concatenated CR-COI-12S rRNA-16S rRNA) using fossil-based molecular dating and genetic connectivity assessments. In addition, we addressed past population dynamics in relation to landscape types, and geographic variations in release calls for the clades occurring in the steppes of northern Mongolia and the Amur River basin (N = 147). Our results recovered two separate ancestors of S. raddei in East Asia, supporting a basal split between the northeastern and southern lineages in the Middle Miocene, c. 9.48–13.77 Mya. Ancestral range estimates suggested a Late Miocene radiation within the northeastern lineage, likely due to aridity-induced vicariance and dispersal from the central Asian steppes, c. 7.89 (5.25–11.50) Mya. The southern lineage emerged subsequently from glacial refugia, c. 6.84 (3.48–2.63) Mya, expanding northward and crossing the Gobi Desert and current-day Mongolia, c. 2.60 (1.15–3.72) Mya. At the exception of the pre-Tibetan Plateau clade, our reconstruction of migration trajectories highlighted the presence of effective gene flow across other landscapes, notably among the central and northeastern Chinese clades in the habitats defined as steppe, river basin and canyon. Significant variation in release calls between the clades in northern Mongolia and the Amur River Basin reflected the isolation between the two clades, and supported the presence of a northern refugium and post-glacial expansion of the southern lineage into northwestern Mongolia. In contrast with prior studies, our finding indicates that release calls can reflect phylogeographic patterns. © 2022, The Author(s), under exclusive licence to Springer Nature Switzerland AG.