栽培山嵛菜与三个野生种的核型比较

研究了山嵛菜属(Eutrema)广泛栽培的山嵛菜和3个野生种的核型。栽培山嵛菜(E．wasabi Maxim)的体细胞染色体数目和核型为2n=4x=28=7m 17sm 4st,3个野生种分别是三角叶山嵛菜(E．dettoideum(Hook．f．et Thoms)O．E．Sehulz)核型为2n=2x=14=10m 4sm;密序山嵛菜(E．heterophylla(W．W．Smith)Hara)核型为2n=2x=14=6m(2SAT) 8sm;云南山嵛菜(E．yunnanense Franch．)核型为：2n=4x=28=12m(2SAT) 16sm。对它们的核型进行了比较分析,其结果为杂交培育新品种提供细胞遗传学资料。     

Demographic expansion and genetic load of the halophyte model plant Eutrema salsugineum

The halophyte model plant Eutrema salsugineum (Brassicaceae) disjunctly occurs in temperate to subarctic Asia and North America. This vast, yet extremely discontinuous distribution constitutes an ideal system to examine long‐distance dispersal and the ensuing accumulation of deleterious mutations as expected in expanding populations of selfing plants. In this study, we resequenced individuals from 23 populations across the range of E. salsugineum. Our population genomic data indicate that E. salsugineum migrated “out of the Altai region” at least three times to colonize northern China, northeast Russia and western China. It then expanded its distribution into North America independently from northeast Russia and northern China, respectively. The species colonized northern China around 33.7 thousand years ago (kya) and underwent a considerable expansion in range size approximately 7–8 kya. The western China lineage is likely a hybrid derivative of the northern China and Altai lineages, originating approximately 25–30 kya. Deleterious alleles accumulated in a stepwise manner from (a) Altai to northern China and North America and (b) Altai to northeast Russia and North America. In summary, E. salsugineum dispersed from Asia to North America and deleterious mutations accumulated in a stepwise manner during the expansion of the species’ distribution.     

Genomic insight into “sky island” species diversification in a mountainous biodiversity hotspot

“Sky island” species diversification contributes greatly to mountainous biodiversity. However, the underlying genomic divergence and the inferred drivers remain largely unknown. In this study, we examined the diversification history of five diploid species with three exclusively endemic to the sky islands (mountains) of the Himalaya–Hengduan Mountains biodiversity hotspot. All of them together comprise a clade of the genus Eutrema (Brassicaceae). We resequenced genomes of multiple individuals of the found populations for each species. We recovered the inconsistent phylogenetic relationships between plastome and nuclear‐genome trees for one species. Based on nuclear population genomic data, we detected high genetic divergence between five species with limited gene flow. Four species seemed to diverge mainly through geographical isolation, whereas one arose through hybrid origin. The origins of the sampled five species were dated to within the late Miocene when mountains were uplifted and climates oscillated. All species decreased their population sizes since the inferred origin of each species initially, but only two of them expanded after the Last Glacial Maximum. Together, these findings suggest that geographic isolation plays an important role in driving the sky island species diversification of the sampled species in addition to the occasional gene flow that might have led to the hybrid origin of some sky island species, similar to the species diversification of sea islands.     

Phylogenomics and rapid diversification of the genus Eutrema on the Qinghai–Tibet Plateau and adjacent regions

Both geographic isolation and polyploidization are assumed to play an important role in driving species diversification. However, this is rarely illustrated through phylogenomic analyses. The genus Eutrema (Brassicaceae), which also includes the salt-resistant species, are distributed mainly in Asia with extensive species diversification in the Qinghai–Tibet Plateau (QTP) and adjacent regions. In this study, we revealed almost fully resolved backbone relationships of the genus with genome re-sequencing data for genomes of 168 individuals from 28 species. Phylogenetic analyses of both plastomes and single-copy nuclear genes from the whole genome recovered six well-supported clades with almost consistent relationships. The first two clades are mainly distributed in central China and central Asia, while the other four in the QTP and adjacent regions. All of them diversified within 12 million years. Within each clade, we recovered numerous conflicts in the interspecific relationships between nuclear and plastome phylogenies, likely suggesting hybridization and incomplete lineage sorting during species diversification. Our estimation of genome size and comparison of the number of the single-copy nuclear genes demonstrated frequent occurrences of polyploids in the genus. Except for an establishment of the backbone phylogeny, our phylogenomic analyses suggest that in addition to strong geographic isolation, polyploidization may have played an important role in species diversification of this genus.     

安徽白马寨、清凉峰和六股尖的新地理分布植物

近年来我们从事了安徽省植物的调查、研究与植物标本的采集工作,1983年4—11月间,本文作者沈显生、张小平、刘登义三人曾分别到皖鄂边境的本省金寨县白马寨(海拔1729米)、皖浙边境的本省歙县清凉峰(海拔1787米)、皖赣边境的本省休宁县六股尖(海拔1630米),广泛收集资料和采集大量植物标本,并进行整理与鉴定。现将确认为是安徽省地理分布新记录的属共5个(Actaea L., Eutrema R. Br., Aegopodi-