Worth J R P, Holland B R, Beeton N J, Schönfeld B, Rossetto M, Vaillancourt R E, Jordan G J
Forestry and Forest Products Research Institute, Matsunosato 1, Tsukuba, Ibaraki 305-8687, Japan.
School of Physical Sciences, University of Tasmania, Private Bag 37, Hobart, Tasmania 7001, Australia.
Ann Bot. 2017 Oct 17;120(4):539-549. doi: 10.1093/aob/mcx086.
Investigating species distributions across geographic barriers is a commonly utilized method in biogeography to help understand the functional traits that allow plants to disperse successfully. Here the biogeographic pattern analysis approach is extended by using chloroplast DNA whole-genome 'mining' to examine the functional traits that have impacted the dispersal of widespread temperate forest species across an intermittent seaway, the 200 km wide Bass Strait of south-eastern Australia.
Multiple, co-distributed species of both dry and wet forests were sampled from five regions on either side of the Strait to obtain insights into past dispersal of these biomes via seed. Using a next-generation sequencing-based pool-seq method, the sharing of single nucleotide polymorphisms (SNPs) was estimated between all five regions in the chloroplast genome.
A total of 3335 SNPs were detected in 20 species. SNP sharing patterns between regions provided evidence for significant seed-mediated gene flow across the study area, including across Bass Strait. A higher proportion of shared SNPs in dry forest species, especially those dispersed by birds, compared with wet forest species suggests that dry forest species have undergone greater seed-mediated gene flow across the study region during past climatic oscillations and sea level changes associated with the interglacial/glacial cycles.
This finding is consistent with a greater propensity for long-distance dispersal for species of open habitats and proxy evidence that expansive areas of dry vegetation occurred during times of exposure of Bass Strait during glacials. Overall, this study provides novel genetic evidence that habitat type and its interaction with dispersal traits are major influences on dispersal of plants.
研究地理屏障两侧的物种分布是生物地理学中常用的方法，有助于了解使植物成功扩散的功能性状。在此，通过使用叶绿体DNA全基因组“挖掘”来扩展生物地理模式分析方法，以研究影响广泛分布的温带森林物种跨越一条间歇性海峡（澳大利亚东南部宽200公里的巴斯海峡）扩散的功能性状。
从海峡两侧的五个区域采集了干湿森林中多种共分布的物种样本，以深入了解这些生物群落过去通过种子进行的扩散情况。使用基于新一代测序的混合测序方法，估计叶绿体基因组中所有五个区域之间单核苷酸多态性（SNP）的共享情况。
在20个物种中总共检测到3335个SNP。区域间的SNP共享模式为整个研究区域，包括跨越巴斯海峡的种子介导的显著基因流提供了证据。与湿林物种相比，干林物种中共享SNP的比例更高，尤其是那些由鸟类传播的物种，这表明在过去与间冰期/冰期循环相关的气候振荡和海平面变化期间，干林物种在整个研究区域经历了更大的种子介导的基因流。
这一发现与开阔栖息地物种具有更大的远距离扩散倾向一致，也有替代性证据表明在冰川期巴斯海峡暴露期间出现了大面积的干燥植被。总体而言，本研究提供了新的遗传证据，表明栖息地类型及其与扩散性状的相互作用是影响植物扩散的主要因素。
