中国科学院昆明动物研究所机构知识库

黑刚毛鼠（Lophuromys aquilus）复合群现有11个物种，其中绝大多数物种在东部非洲强降雨森林区具有独特的分布格局，东非以具有丰富的物种多样性和特有性的非洲山地生物多样性热点区域（Afromontane Hot Spot）而闻名于世。在东非，黑刚毛鼠复合种群是一个多样性丰富但其分类不清啮齿动物类群。因此，本研究主要集中在黑刚毛鼠复合种的形态变异和生物地理，以此评估现有物种的有效性和颅骨变异。本研究利用游标卡尺共测量了696号完整的头骨标本，并利用相机拍摄头骨照片，这些标本分别代表11个现今确认的物种，且大多数标本来自模式产地，从地理隔离、性别、年龄角度，利用传统形态和几何形态分析方法重新评估了现今确认物种的有效性和头骨变化的模式。研究结果表明：多数头骨特征变异在该复合群的多个物种中存在重叠； 现有11个物种中，仅有3个物种能通过颅骨的形态变异完全分开，它们分别是梅鲁山的L. verhageni，乞力马扎罗山的L. aquilus和鲁文佐里的L. stanleyi。这种颅骨变异的特征表明其无固定模式的地理趋向，部分原因是物种的界限以及当地生物气候因子的限制。此外，头骨大小的回归曲线显示头骨有正态异速生长趋势，即物种生长、发育的正态生长趋势，说明其稳定的生境条件并缺乏波动不对称性。物种间同时也存在显著的性二型和年龄差异，且其协变量效应影响到种内和种间的差异。通过单变量比较和判别分析，探究遗传变异（通过2个核基因MC1R和IRBP以及2个线粒体基因CYTB和D-LOOP）和分布格局（海拔、坡向和植被）对外形特征（体重、头体长、后足长、耳长和尾与头体长的比例）的影响。结果表明，肯尼亚山的L. zena在外形变异上没有明显的规律。遗传分析显示该种的随机遗传变异较低，因此不能定义任何世系的限界。肯尼亚山样本内部的分化时间约在0.007到0.014 Mya，其与亚伯达的L. zena在0.0017到0.007 Mya，而与鲁文佐里山在0.021到0.037 Mya。另外，遗传结果进一步表明肯尼亚山和亚伯达的Lophuromys构成了单系群。与现有的分类体系相比，这两个物种在肯尼亚山和亚伯达山脉海拔上隔离开来。本研究还基于近年来在肯尼亚山沿海拔梯度采集的刚毛鼠（L. zena）标本及其海拔梯度分布、自然地理和遗传特征，以揭示其独特的地理分布和多样性。通过单变量比较和判别分析，探究了遗传变异（通过2个核基因MC1R和IRBP以及2个线粒体基因CYTB和D-LOOP）和分布格局（海拔、坡向和植被）对外形特征（体重、头体长、后足长、耳长和尾与头体长的比例）的影响。结果表明：肯尼亚山刚毛鼠（L. zena）在外形量度上缺乏可识别的变异；在遗传上，显示较低的随机遗传变异，而不能定义出任何世系的限界；肯尼亚山样本内部的分化时间约在0.007到0.014 Mya，其与阿布岱尔的L. zena分化时间在0.0017到0.007 Mya，而与鲁文佐里山在0.021到0.037 Mya。遗传分析结果支持肯尼亚山和阿布岱尔种群构成单系群，这与现今的分类观点不一 致，如：L. margarettae或 L. aquilus 分布于低海拔地区，而L. zena分布于高海拔地区。总之，本研究揭示仅采用形态学变量和地理隔离进行物种界定是具有一定的不确定性的，这不仅体现在黑刚毛鼠复合种中，在其它啮齿类或小型兽类中也可能如此。因此，在面对东非的物种多样性的问题上，应该整合形态学或改进的几何形态、遗传学等多种方法，这将会对生物多样性热点地区的保护起到积极作用。下一步的研究也将包括对这些物种特定环境因素的生态反映，如温度、季节性降水及性选择等。

Most species of the Lophuromys aquilus species complex have a unique pattern of distribution within the high-rainfall forests of Eastern Africa encompassing the Eastern Afromontane biodiversity hotspot which is world-renowned for its exceptional high species richness and endemism. In these regions, the L. aquilus group is the most abundant and yet taxonomically obscure group of rodents. This work focused on the morphological variation and biogeographic correlates of the Lophuromys aquilus species complex with the aim to evaluate the validity of the currently recognised species and the underlying patterns of craniometric variation and biogeography.In the second chapter, all the recognised species of the Lophuromys aquilus species complex were morphometrically characterized to reevaluate their validity and patterns of cranial morphological differences by geographical isolation, sex, and age. 696 skulls mostly from type localities representing 11 species were examined to establish whether the current taxonomic accounts were well supported by combined classical and geometric morphometric analyses. The results showed considerable but selective cranial variation among Lophuromys populations which discrepantly overlaps many supposed species of the complex. Of the 11 species assigned to the L. aquilus complex, only three can be outright discriminated while a fourth group clusters several populations across the sampled area. Mount Meru’s L. verhageni, Mount Kilimanjaro’s L. aquilus, and Rwenzori’s L. stanleyi are considerably discriminated from the cluster that broadly overlaps the remaining species/populations. The observed patterns of craniometric variation portray unpatterned geographical trends that are partly attributable to species boundaries and partly to local bioclimatic factors. Also, the regression of cranial shape on size showed a normal allometric trend which pointed to a normal trend of growth and development of specimens, implying stable habitat conditions and absence of fluctuating asymmetry. There were statistically significant sexual dimorphism and age class differences whose covariant effects did influence between-group and within-group distinctions.The third chapter focuses on the elevational distribution, physical and genetic characterisation of Mount Kenya’s Lophuromys with the aim to shed light on its unique distribution and abundance. Univariate comparisons and discriminant function analysis were used to examine how external body features (weight, head-body, hind feet, ear, and tail % of head-body) clustered by genetic (nuclear (MC1R, IRBP) and mitochondrial (CYTB, D-LOOP) genes) variation and distribution patterns (elevation, aspect, and vegetation). The results showed the Mount Kenya’s Lophuromys lacking any detectable patterns in the variation of external measurements. The two pairs of mitochondrial and nuclear genes revealed low random genetic variations which could not define any lineage boundary. The evolutionary divergence within Mt Kenya samples was 0.007 – 0.014 Million years ago (Mya) while between Mt Kenya and Aberdares’ L. zena was 0.007 – 0.0017 Mya and between Mt Kenya and Mt Rwenzori’s L. aquilus was 0.021 – 0.037. The results support the monophyly of the Mount Kenya and the Aberdare Ranges Lophuromys and contrast the current taxonomic works which document either L. margarettae or L. aquilus occurring at lower elevations and L. zena at the higher elevations.Overall, the study’s findings highlight the indeterminacy of exclusive reliance on morphological variability and geographical isolation for not only delimiting the Lophuromys aquilus species but as might be pertinent to other rodents/small mammals. In essence, there is need to embrace more holistic systematic approaches that integrate morphological and genetic gaps and refined techniques such as geometric morphometrics for more resolved differences analyses to accurately account for East Africa’s true biodiversity and enhance the effectiveness of conservational initiatives towards safeguarding biodiversity hotspots. Future studies could examine the responses of these rodents to specific habitat variables such as changing temperature and precipitation regimes and sexual selection targeting candidate speciation genes.