BACKGROUND Climatic variation and geologic change both play significant roles in shaping species distributions, thus affecting their evolutionary history. In Sahara-Sahel, climatic oscillations shifted the desert extent during the Pliocene-Pleistocene interval, triggering the diversification of several species. Here, we investigated how these biogeographical and ecological events have shaped patterns of genetic diversity and divergence in African Jerboas, desert specialist rodents. We focused on two sister and cryptic species, Jaculus jaculus and J. hirtipes, where we (1) evaluated their genetic differentiation, (2) reconstructed their evolutionary and demographic history; (3) tested the level of gene flow between them, and (4) assessed their ecological niche divergence. RESULTS The analyses based on 231 individuals sampled throughout North Africa, 8 sequence fragments (one mitochondrial and seven single copy nuclear DNA, including two candidate genes for fur coloration: MC1R and Agouti), 6 microsatellite markers and ecological modelling revealed: (1) two distinct genetic lineages with overlapping distributions, in agreement with their classification as different species, J. jaculus and J. hirtipes, with (2) low levels of gene flow and strong species divergence, (3) high haplotypic diversity without evident geographic structure within species, and (4) a low level of large-scale ecological divergence between the two taxa, suggesting species micro-habitat specialization. CONCLUSIONS Overall, our results suggest a speciation event that occurred during the Pliocene-Pleistocene transition. The contemporary distribution of genetic variation suggests ongoing population expansions. Despite the largely overlapping distributions at a macrogeographic scale, our genetic results suggest that the two species remain reproductively isolated, as only negligible levels of gene flow were observed. The overlapping ecological preferences at a macro-geographic scale and the ecological divergence at the micro-habitat scale suggest that local adaptation may have played a crucial role in the speciation process of these species.

中文翻译：

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北非跳鼠的两种神秘物种的进化史。

背景气候变化和地质变化在塑造物种分布方面都发挥着重要作用，从而影响其进化历史。在撒哈拉-萨赫勒地区，上新世-更新世期间的气候波动改变了沙漠的范围，引发了几个物种的多样化。在这里，我们研究了这些生物地理和生态事件如何塑造非洲跳鼠（沙漠专家啮齿动物）的遗传多样性和分化模式。我们重点研究了两个姐妹和神秘物种，Jaculus jaculus 和 J. hirtipes，我们（1）评估了它们的遗传分化，（2）重建了它们的进化和人口统计历史；（3）测试它们之间的基因流水平，（4）评估它们的生态位差异。结果 基于北非各地采样的 231 个人、8 个序列片段（1 个线粒体和 7 个单拷贝核 DNA，包括两个毛皮着色候选基因：MC1R 和 Agouti）、6 个微卫星标记和生态模型进行的分析显示：（1）两个具有重叠分布的不同遗传谱系，与它们作为不同物种（J. jaculus 和 J. hirtipes）的分类一致，具有（2）低水平的基因流和强烈的物种分化，（3）高单倍型多样性，物种内没有明显的地理结构，（4）两个类群之间的大规模生态分歧程度较低，表明物种微栖息地的专业化。结论 总的来说，我们的结果表明在上新世-更新世过渡期间发生了物种形成事件。遗传变异的当代分布表明人口正在持续扩张。尽管在宏观地理尺度上分布很大程度上重叠，但我们的遗传结果表明，这两个物种仍然是生殖隔离的，因为只观察到了可以忽略不计的基因流水平。宏观地理尺度上生态偏好的重叠和微生境尺度上的生态分化表明，局部适应可能在这些物种的物种形成过程中发挥了至关重要的作用。