Data_Sheet_1_Altitudinal Patterns in Adaptive Evolution of Genome Size and Inter-Genome Hybridization Between Three Elymus Species From the Qinghai–Tibetan Plateau.ZIP

Genome size variation and hybridization occur frequently within or between plant species under diverse environmental conditions, which enrich species diversification and drive the evolutionary process. Elymus L. is the largest genus in Triticeae with five recognized basic genomes (St, H, P, W, and Y). However, the data on population cytogenetics of Elymus species are sparse, especially whether genome hybridization and chromosomal structure can be affected by altitude are still unknown. In order to explore the relationship between genome sizes, we studied interspecific hybridization and altitude of Elymus species at population genetic and cytological levels. Twenty-seven populations at nine different altitudes (2,800–4,300 m) of three Elymus species, namely, hexaploid E. nutans (StHY, 2n = 6x = 42), tetraploid E. burchan-buddae (StY, 2n = 4x = 28), and E. sibiricus (StH, 2n = 4x = 28), were sampled from the Qinghai–Tibetan Plateau (QTP) to estimate whether intraspecific variation could affect the genomic relationships by genomic in situ hybridization (GISH), and quantify the genome size of Elymus among different altitude ecological groups by flow cytometry. The genome size of E. nutans, E. burchan-buddae, and E. sibiricus varied from 12.38 to 22.33, 8.81 to 18.93, and 11.46 to 20.96 pg/2C with the averages of 19.59, 12.39, and 16.85 pg/2C, respectively. The curve regression analysis revealed a strong correlation between altitude and nuclear DNA content in three Elymus species. In addition, the chromosomes of the St and Y genomes demonstrated higher polymorphism than that of the H genome. Larger genome size variations occurred in the mid-altitude populations (3,900–4,300 m) compared with other-altitude populations, suggesting a notable altitudinal pattern in genome size variation, which shaped genome evolution by altitude. This result supports our former hypothesis that genetic richness center at medium altitude is useful and valuable for species adaptation to highland environmental conditions, germplasm utilization, and conservation.

基因组大小变异与杂交现象在不同环境条件下的植物物种内部或物种间频繁发生，这一过程可丰富物种多样性并推动演化进程。披碱草属（Elymus L.）是小麦族（Triticeae）中最大的属，已知包含5个基本基因组：St、H、P、W和Y。然而，目前关于披碱草属物种的群体细胞遗传学数据仍较为匮乏，尤其是基因组杂交与染色体结构是否会受海拔高度影响这一问题，尚未得到明确解答。为探究基因组大小与种间杂交、海拔之间的关联，本研究从群体遗传与细胞生物学层面，针对披碱草属物种展开相关研究。本研究从青藏高原（Qinghai–Tibetan Plateau, QTP）采集了3种披碱草属植物的27个种群，涵盖9个海拔梯度（2800~4300 m），分别为六倍体垂穗披碱草（E. nutans，StHY，2n=6x=42）、四倍体布尔干-布达披碱草（E. burchan-buddae，StY，2n=4x=28）以及西伯利亚披碱草（E. sibiricus，StH，2n=4x=28）。通过基因组原位杂交（genomic in situ hybridization, GISH）技术，本研究旨在评估种内变异是否会影响基因组关联；同时利用流式细胞术，量化不同海拔生态类群中披碱草属的基因组大小。垂穗披碱草、布尔干-布达披碱草与西伯利亚披碱草的基因组大小分别为12.38~22.33 pg/2C、8.81~18.93 pg/2C与11.46~20.96 pg/2C，平均基因组大小依次为19.59、12.39和16.85 pg/2C。曲线回归分析结果显示，3种披碱草属植物的海拔与核DNA含量之间存在显著相关性。此外，St基因组与Y基因组的染色体多态性高于H基因组。相较于其他海拔类群的种群，中海拔种群（3900~4300 m）的基因组大小变异幅度更大，表明基因组大小变异存在显著的海拔分布模式，且海拔可塑造基因组演化进程。本研究结果验证了我们此前提出的假说：中海拔区域的遗传多样性中心对于物种适应高原环境、种质资源利用与保护均具有重要价值。