Data from: Crossing the uncrossable: novel trans-valley biogeographic patterns revealed in the genetic history of low dispersal mygalomorph spiders (Antrodiaetidae, Antrodiaetus) from California

Antrodiaetus riversi is a dispersal-limited, habitat specialized mygalomorph spider species endemic to mesic woodlands of northern and central California. Here we build upon prior phylogeographic research using a much larger geographic sample and include additional nuclear genes, providing more detailed biogeographic insights throughout the range of this complex. Of particular interest is the uncovering of unexpected and replicated trans-valley biogeographic patterns, where in two separate genetic clades western haplotypes in the California south Coast Ranges are phylogenetically closely-related to eastern haplotypes from central and northern Sierran foothills. In both instances, these trans-valley phylogenetic patterns are strongly supported by multiple genes. These western and eastern populations are currently separated by the Central Valley, a well-recognized modern-day and historical biogeographic barrier in California. For one clade the directionality is clearly northeast to southwest, and all available evidence is consistent with a jump dispersal event estimated at 1.2-1.3 million years ago. During this time period, paleogeographic data indicate that northern Sierran rivers emptied to the ocean in the south Coast Ranges, rather than at the San Francisco Bay. For the other trans-valley clade genetic evidence is less conclusive regarding the mechanism and directionality of biogeographic exchange, although the estimated timeframe is similar (approximately 1.8 Ma). Despite the large number of biogeographic studies previously conducted in central California, to the best of our knowledge no prior studies have discussed or revealed a northern Sierran to south Coast Range biogeographic connection. This uniqueness may reflect the low-dispersal biology of mygalomorph spiders, where “post-event” gene exchange rarely erases historical biogeographic signal.

里氏林栖蛛（Antrodiaetus riversi）是一种扩散能力受限、生境特化的猛蛛（mygalomorph）物种，仅分布于美国加利福尼亚州北部与中部的湿润林地带。本研究依托此前的谱系地理学研究，采用了规模更大的地理采样方案，并新增了核基因（nuclear gene）标记，从而为该物种复合群的整个分布范围提供了更为详尽的生物地理学解析。尤为值得关注的是，本研究发现了既出乎意料又具有重复性的跨谷生物地理学模式：在两个独立的遗传支系（clade）中，加利福尼亚南海岸山脉的西部单倍型（haplotype），与内华达山脉中部及北部山麓的东部单倍型在系统发育（phylogenetic）关系上高度近缘。上述两类跨谷系统发育模式均得到了多个基因位点的强力支持。目前，这些西部与东部种群被中央谷地分隔开来——该谷地是加利福尼亚州公认的现代与历史生物地理屏障。其中一个支系的扩散方向明确为东北至西南，所有现有证据均支持一起发生于120万至130万年前的跳跃扩散（jump dispersal）事件。在该地质时期，古地理（paleogeographic）数据显示，内华达山脉北部的河流是向南海岸山脉注入海洋，而非如今的旧金山湾。另一跨谷支系的生物地理交流（gene exchange）机制与方向的遗传证据则相对不足，但其估算的发生时间相近（约1.8 Ma，百万年）。尽管此前在加利福尼亚中部开展过大量生物地理学研究，但据我们所知，尚无任何研究提及或揭示过内华达山脉北部与南海岸山脉之间的生物地理联系。这一独特性或反映了猛蛛的低扩散生物学特性——事件发生后的基因交流极少会抹去历史生物地理学信号。