Data from: Systematics and ecology of the Australasian genus Empodisma (Restionaceae) and description of a new species from peatlands in northern New Zealand

The genus Empodisma comprises two species that are ecologically important in wetland habitats. Empodisma gracillimum is restricted to south-western Australia, whereas Empodisma minus is found in Tasmania, eastern Australia and New Zealand. We sequenced three cpDNA genes for 15 individuals of Empodisma sampled from throughout the range of the species. The results support an Australian origin for Empodisma sometime during the late Oligocene to early Miocene with more recent dispersal, colonization and diversification in New Zealand. We recovered six genetically distinct maternal lineages: three Empodisma gracillimum haplotypes corresponding to the three accessions in our analysis, a wide-ranging Empodisma minus haplotype found in eastern Australia and Tasmania, an Empodisma minus haplotype found in New Zealand from Stewart Island to approximately 38° S latitude on the North Island, and a distinct haplotype restricted to the North Island of New Zealand north of 38° S latitude. The Eastern Australian and New Zealand haplotypes of Empodisma minus were supported by only one cpDNA gene, and we felt the relatively minor morphological differences and the small amount of genetic divergence did not warrant taxonomic recognition. However, we recommend that the northern New Zealand haplotype should be recognized as the new species Empodisma robustum and provide descriptions and a key to the species of Empodisma. Monophyly of Empodisma robustum is supported by all three cpDNA genes. Empodisma robustum can be distinguished from Empodisma gracillimum and Empodisma minus by its robust growth stature and distinct ecology. It is typically eliminated by fire and re-establishes by seed (seeder strategy), whereas Empodisma minus and Empodisma gracillimum regrow after fire (sprouter strategy).

Empodisma属包含两个在湿地生境中具有重要生态意义的物种。其中Empodisma gracillimum仅分布于澳大利亚西南部，而Empodisma minus则见于塔斯马尼亚、澳大利亚东部及新西兰。我们对覆盖该属所有分布范围的15份Empodisma样本进行了3个叶绿体DNA（cpDNA）基因的测序。研究结果表明，Empodisma属的起源地为澳大利亚，时间大致在渐新世晚期至中新世早期，后续在新西兰发生了更近的扩散、定殖与物种分化事件。我们共鉴定出6个遗传上独立的母系谱系：对应本研究中3个采集样本的3个Empodisma gracillimum单倍型；一种分布广泛的Empodisma minus单倍型，见于澳大利亚东部与塔斯马尼亚；一种Empodisma minus单倍型分布于新西兰，从斯图尔特岛直至北岛约南纬38°区域；以及一个仅分布于新西兰北岛南纬38°以北区域的独特单倍型。仅通过1个cpDNA基因的支持即可区分澳大利亚东部与新西兰的Empodisma minus单倍型，我们认为二者间相对细微的形态差异与有限的遗传分化，不足以支持其独立的分类学地位。不过，我们建议将新西兰北部的该单倍型认定为新物种Empodisma robustum，并在此提供该属所有物种的形态描述与分类检索表。基于3个cpDNA基因的分析均支持Empodisma robustum为单系群。Empodisma robustum可通过其粗壮的生长姿态与独特的生境偏好与另外两个物种区分：该物种通常会在火灾中完全死亡，并通过种子重新建立种群（实生更新策略）；而Empodisma minus与Empodisma gracillimum则可在火灾后通过萌蘖恢复种群（萌蘖更新策略）。