Across the Gobi Desert: impact of landscape features on the phylogeography and release calls of the Mongolian Toad Strauchbufo raddei in East Asia

Landscape structures drive biogeographic patterns and population connectivity of animals distributed across diverse biotopes. Here, we provide new fresh insights on the genetic structurephylogeography of the widespread Mongolian Toad, Strauchbufo raddei on diverse landscapes of East Asia. We then refine its phylogeographyreconstructed the biogeography of S. raddei throughout Eastnortheast Asia (n N = 299; assembled up to 2,613 bp of concatenated CR-COI-16S-12S fragments) using fossil-based molecular dating and genetic connectivity assessments. In addition, we refined our analyses and address phylogenetic andpast population dynamics and geographic variations in release calls for the clades occurring in the steppes of northern Mongolia and the Amur River basin (n N = 147). Our results support recovereda dual origintwo separate ancestors of S. raddei across East Asia, and estimated asupported a basal split Mid-Miocene split between the northeastern and southern cladeslineages in Middle Miocene (c. 9.48 – 13.77 Mya). Ancestral range estimates suggest a the earliest radiation of thewithin northeastern lineage, likely followed by dispersal andattributes to the aridity-induced vicariance and dispersal from the central Asian steppes (Late Miocene; c. 7.89 [5.25-11.50] Mya). The southern lineage emerged subsequently from glacial refugium, c. 6.84 [3.48-2.63] Mya, expanding northward from the to thewestern margin of the Hentiyn Mountains, crossing of, and most likely across the Gobi Desert and Mongolia, c. 2.60 (1.15-3.72) Mya. Despite effective genetic barrier found in pre-Tibetan Plateau clade, The the trajectory of migrationhaplotype network however highlighted the presence of effective gene flow cross-landscapes, notably among central and northeastern Chinese clades occupied the habitats defined as steppe, river basin and canyon. Significant variation in release calls between the two mainnorthern Mongolia and Amur River Basin lineages clades reflected the a geographic isolation, and the supporting the northern refugia and post-glacial expansion of southern lineage into northwestern Mongolia, . likely linking the variations in release with the evolutionaryInterestingly, our finding indicates release calls can reflect to historical factor linked to phylogeography history of the clade.

景观格局调控着分布于多样生境中的动物的生物地理模式与种群连通性。本研究针对广泛分布于东亚多样景观中的蒙古蟾蜍（Strauchbufo raddei），为其遗传结构与系统地理学（phylogeography）提供了全新的研究见解。随后，我们优化了该物种的系统地理学分析流程，并基于化石校准的分子定年与遗传连通性评估，重构了东亚及东北亚区域蒙古蟾蜍的生物地理演化历史；本次研究共纳入299份样本，拼接得到总长2613 bp的控制区（CR）、细胞色素c氧化酶亚基I（COI）、16S核糖体RNA（16S rRNA）及12S核糖体RNA（12S rRNA）联合基因片段。此外，针对分布于蒙古北部草原与黑龙江流域的支系（样本量n=147），我们优化了分析方案，探讨了其系统发育关系、历史种群动态以及释放鸣叫的地理变异特征。研究结果显示，东亚地区的蒙古蟾蜍存在双重起源，即由两个独立的祖先支系演化而来；同时推断，东北支系与南方支系的基部分化事件发生于中新世中期（约9.48–13.77 百万年前）。祖先分布区重建结果表明，东北支系是该物种最早发生辐射演化的支系；晚中新世时期（约7.89 [5.25–11.50] 百万年前），中亚草原的干旱化引发了隔离事件，驱动了种群的扩散与分化。南方支系随后于约6.84 [3.48–2.63] 百万年前从冰期避难所中分化而来，并从杭爱山脉西缘向北扩散，期间大概率跨越了戈壁沙漠与蒙古全境，扩散事件发生于约2.60（1.15–3.72）百万年前。尽管在青藏高原隆升前的支系中发现了有效的遗传屏障，但种群迁移轨迹与单倍型网络（haplotype network）分析结果均显示，跨景观的有效基因流广泛存在，尤其在占据草原、河流盆地与峡谷生境的中国中部及东北支系之间。蒙古北部与黑龙江流域的两个主要支系之间的释放鸣叫存在显著差异，这反映了二者的地理隔离，同时也支持了北方避难所的存在以及南方支系在冰期后向蒙古西北部的扩张事件。值得注意的是，本研究结果表明，释放鸣叫的差异可反映该支系系统地理演化历史相关的历史进程。