群落历史动态是研究生物多样性形成和维持的关键，然而目前大部分研究都仅局限于探究单个或少数物种的种群历史动态。尽管这类研究结果能启发群落可能的历史动态，然而群落物种众多，物种性状差别较大，在群落中的分布情况也存在较大差异，因此零散的单物种种群历史动态必然无法完整的揭示群落的历史动态。本研究选取了东北针阔混交林内广泛分布的30个物种，以群落为单位进行取样，使用3个叶绿体通用引物，通过分析物种和群落水平的遗传多样性和遗传分化格局，推测东北针阔混交林植物群落与群落内物种末次冰期以来的历史动态，分析物种性状对群落内不同物种种群历史动态的可能影响。

研究发现，无论是在被子植物还是裸子植物中，叶绿体psbA-trnH片段的遗传多样性均最高，相比于trnD-trnE和trnL-trnF片段，psbA-trnH片段能够提供更加丰富的遗传多样性信息。在采样物种中，76.67%的物种具有遗传多态性，其中多数物种无显著的纬度梯度格局，也无显著的谱系地理格局。在群落水平上，我们也未发现遗传多样性的纬度梯度分布格局。我们推测，尽管部分物种可能在冰期时南退，但是东北部分地区保留了较为完整的针阔混交林群落。

在长白山地区，HC群落和LHS群落由较多具有私有单倍型的物种组成，相应物种占比为45.45%和 42.11%，同时这两个群落也表现出了较高的遗传分化水平，说明这两个区域保存针阔混交林群落的完整性可能更高。在小龙门地区存在分布的物种中，72.73%的多态物种在小龙门地区具有私有单倍型。除了刺五加和山葡萄在东北地区具有共享单倍型外，其余物种均表现出与东北地区截然不同的单倍型多样性格局，极有可能形成了独立于东北的谱系。小兴安岭北部的SS区域具有较高的群落遗传多样性和分化水平，群落内物种遗传多样性差异较大，其中少数物种（比如刺五加和裂叶榆）在SS群落具有较高的遗传多样性，可能能在该区域找到避难所。小兴安岭南部的LS群落以及邻近长白山余脉的RH群落具有较低的遗传多样性和分化水平。群落内物种遗传多样性普遍较低，几乎无私有单倍型，导致群落内物种遗传多样性的差异较小，说明群落是近期扩张形成的。此外，我们还对被子植物的不同种子传播方式（动物传播和风媒传播）和花粉传播方式（风媒传播和虫媒传播）在物种遗传多样性π、私有单倍型丰富度Rp和遗传分化参数Nst之间的差异进行了比较。然而，仅发现了风媒传粉的物种的遗传多样性显著高于虫媒传粉的物种的遗传多样性，其余数值之间均不具有显著差异。

本研究通过群落水平的谱系格局分析、比较，初步揭示了东北针阔混交林群落的遗传多样性分布规律和群落历史动态。我们推测末次冰期时，长白山南部地区可能存在较为完整的针阔混交林群落，小兴安岭胜山地区也有零星物种存在，华北地区暖温带落叶阔叶林的谱系多独立于东北，所以华北地区对东北针阔混交林群落的冰期后重建的贡献可能比较有限。然而本研究群落数、每个群落物种数、以及每个物种的基因取样数都非常有限，未来需要提高这三个水平的取样数，以期得到更多群落历史动态的细节。

Historical community dynamics are key to the study of the formation and maintenance of biodiversity, however most current researches are limited to explore the populational historical dynamics about single or a few species. Although the results of such studies can shed light on the possible historical dynamics of communities, the large number of species in a community, the wide variation in species traits and their distribution within the community make it inevitable that fragmented historical dynamics of single species populations will not provide a complete picture of the historical dynamics of the community. In this study, 30 species widely distributed within the coniferous and broadleaf mixed forest in Northeast China（CBMFNC）were sampled on a community basis. Three universal chloroplast primers were used to analyse genetic diversity and genetic differentiation patterns at the species and community levels. We try to infer the historical dynamics of plant communities and species within CBMFNC since the last glacial period, and to analyse the possible influence of species traits on the historical dynamics of different species populations within communities.

We found that the genetic diversity of the chloroplast psbA-trnH fragment was highest in both angiosperms and gymnosperms. psbA-trnH fragment provided richer genetic diversity information than the trnD-trnE and trnL-trnF fragments. 76.67% were genetically polymorphic among the 30 species. Most species had no significant latitudinal gradient pattern, as well as no significant phylogeographic pattern. At the community level, we also did not find a latitudinal gradient distribution pattern of genetic diversity. We speculated that although some species may have retreated southward during the glacial period, a relatively complete CBMFNC community remained in some parts of northeast China.

In the Changbai Mountain, the HC and LHS communities consist of more species with private haplotypes, with 45.45% and 42.11% of the corresponding species. The two communities also show high levels of genetic differentiation, suggesting a high integrity of the CBMFNC communities in these two regions. 72.73% of  the polymorphic species had private haplotypes in the Xiaolongmen Region. Except Eleutherococcus senticosus and Vitis amurensis, most species shown distinct haplotype diversity patterns from the Northeast China. It is highly likely that they have formed a separate lineage from the Northeast China. One community in the northern Xiaoxing’an Range ("SS”) has a high level of community genetic diversity and genetic differentiation. Few species (e.g. Eleutherococcus senticosus and Ulmus laciniata) with high genetic diversity may contribute to the specific pattern in SS. It suggests that these species may found refugia in the region. The LS communities in the southern Xiaoxing’an Range and the RH communities in the North of Changbai Mountain have low genetic diversity and differentiation. The genetic diversity of species within the communities is generally low, and almost species have no private haplotypes, resulting in low variation in the genetic diversity of species within the communities, which suggests that the communities were formed by recent expansion.

We compared the level of genetic diversity π, private haplotype richness Rp and genetic differentiation  Nst between species dispersal traits. We only found significantly high genetic diversity for wind-pollinated species than insect-pollinated species.

In this study, we used community-level phylogeographic pattern analysis and comparison to initially reveal the distribution pattern of genetic diversity and community history dynamics of CBMFNC. We hypothesize that a more complete mixed conifer community may have existed in the southern Changbai Mountains at the time of the last ice age. Some scattered species present in the “SS” area of the Xiaoxing’an Range. The lineage of warm-temperate deciduous broad-leaved forests in North China is mostly independent of that of Northeast China, so the contribution of North China to the post-ice age reconstruction of mixed conifer communities in Northeast China may be relatively limited. However, the number of communities, the number of species per community, and the number of genes sampled per species are all very limited in this study. There is a need to increase the number of samples taken at these three levels in the future, with a view to obtaining more details of the historical community dynamics.