Laboratorio de Biología Evolutiva, Departamento de Ecología, Facultad de Ciencias Biológicas, Pontificia Universidad Católica de Chile, Santiago, Chile.
Grupo de Biodiversidad y Cambio Global (GBCG), Departamento de Ciencias Básicas, Universidad del Bío-Bío, Chillán, Chile.
BMC Ecol Evol. 2024 Jan 6;24(1):5. doi: 10.1186/s12862-023-02196-w.
The diversity and population genetic structure of many species have been shaped by historical and contemporary climatic changes. For the species of the South American Altiplano, the historical climatic changes are mainly related to the wet events of great magnitude and regional influence that occurred during the Pleistocene climatic oscillations (PCOs). In contrast, contemporary climate changes are associated with events of lesser magnitude and local influence related to intensifications of the South American Summer Monsoon (SASM). Although multiple studies have analyzed the effect of PCOs on the genetic patterns of highland aquatic species, little is known about the impact of contemporary climate changes in recent evolutionary history. Therefore, in this study, we investigated the change in population structure and connectivity using nuclear and mitochondrial markers throughout the distribution range of Heleobia ascotanensis, a freshwater Cochliopidae endemic to the Ascotán Saltpan. In addition, using geometric morphometric analyses, we evaluated the concomitance of genetic divergence and morphological differentiation.
The mitochondrial sequence analysis results revealed the presence of highly divergent co-distributed and geographically nested haplotypes. This pattern reflects an extension in the distribution of groups that previously would have differentiated allopatrically. These changes in distribution would have covered the entire saltpan and would be associated with the large-scale wet events of the PCOs. On the other hand, the microsatellite results defined five spatially isolated populations, separated primarily by geographic barriers. Contemporary gene flow analyses suggest that post-PCO, climatic events that would have connected all populations did not occur. The morphometric analyses results indicate that there is significant morphological differentiation in the populations that are more isolated and that present the greatest genetic divergence.
The contemporary population structure and morphological variation of H. ascotanensis mainly reflect the post-PCO climatic influence. Although both markers exhibit high genetic structuring, the microsatellite and morphology results show the preponderant influence of fragmentation in recent evolutionary history. The contemporary genetic pattern shows that in species that have limited dispersal capabilities, genetic discontinuities can appear rapidly, erasing signs of historical connectivity.
许多物种的多样性和种群遗传结构都受到历史和当代气候变化的影响。对于南美高原的物种来说，历史气候变化主要与更新世气候震荡（PCO）期间发生的大规模、区域性影响的湿润事件有关。相比之下，当代气候变化与规模较小、与南美夏季风增强有关的局部影响的事件有关。尽管多项研究分析了 PCO 对高地水生物种遗传模式的影响，但对于当代气候变化在近期进化历史中的影响知之甚少。因此，在这项研究中，我们通过核和线粒体标记在整个淡水 Cochliopidae 特有种 Ascotán 盐沼的分布范围内研究了种群结构和连通性的变化。此外，我们使用几何形态测量分析评估了遗传分化和形态分化的伴随性。
线粒体序列分析结果显示存在高度分化的共分布和地理嵌套单倍型。这种模式反映了分布范围的扩展，之前这些分布范围是由地理隔离分化的。这种分布的变化将覆盖整个盐沼，并与 PCO 的大规模湿润事件有关。另一方面，微卫星结果定义了五个空间隔离的种群，主要由地理屏障隔开。当代基因流分析表明，PCO 之后，没有发生连接所有种群的气候事件。形态测量分析结果表明，在更隔离且具有最大遗传分化的种群中存在显著的形态分化。
H. ascotanensis 的当代种群结构和形态变异主要反映了 PCO 后的气候影响。尽管两种标记都表现出高度的遗传结构，但微卫星和形态结果表明，在最近的进化历史中，碎裂的影响占主导地位。当代遗传模式表明，在扩散能力有限的物种中，遗传不连续性可能会迅速出现，抹去历史连通性的迹象。
