Investigations on mycorrhizal associates and nutritional resources of mycoheterotrophic orchids in Taiwan

大约1%的兰花物种是无叶绿素的，在整个生命周期中依赖于菌根伙伴的碳和矿物质营养供应。这些无绿叶兰花被称为真菌异养植物。在温带和北方森林中，真菌异养兰花与外生菌根真菌的狭窄分支相关联，并通过地下菌根网络从邻近树木获得光合产物。与这些研究结果相反，在热带和亚热带森林中，一些真菌异养兰花已被报道与腐生性非丝核菌真菌相关联，并通过其木材或凋落物腐烂的能力获得营养。尽管如此，也有报道外生菌根相关的真菌异养兰花的亚热带森林。因此，亚热带和热带森林的共生真菌异养兰花与木材或凋落物腐烂真菌和外生菌根真菌可能。与温带地区（例如整个欧洲有两种真菌异养兰花）相比，热带和亚热带亚洲的真菌异养兰花种类繁多（超过120种）。在台湾，其中。记录了400种本地兰科植物，16属50余种完全MH兰科植物。台湾大部分真菌异养兰花的真菌伙伴及营养模式仍不清楚。本项目将利用分子生物学方法、多元素稳定同位素自然丰度法和示踪剂技术，对6个属的真菌异养兰科植物进行研究，并实现以下目标：（1）鉴定20多种真菌异养兰科植物的真菌伴生菌。(2)我们将使用宏基因组分析比较这些兰花的菌根真菌多样性（OTU）。(3)为了揭示其营养资源，我们将分析不同森林类型和山地海拔带中与不同真菌类群共生的真菌异养兰科植物的碳、氮、氢和氧稳定同位素天然丰度，并将这些同位素丰度与共生的完全自养植物进行比较。通过本项目，我们期望获得以下结果：（1）本研究将鉴定目标兰花之菌根伴生菌，并了解台湾原生真菌异养兰花之菌根多样性、特异性及分布型态。(2)我们将追踪营养资源和营养流的目标兰花物种与不同的菌根合作伙伴和发生在不同的栖息地从高/低海拔和不同的森林类型。

About 1 % of all orchid species is achlorophyllous and depends on mycorrhizal partners for carbon and mineral nutrient supplies throughout their entire life cycle. These achlorophyllous orchids are known as mycoheterotrophic plants. In temperate and boreal forests, mycoheterotrophic orchids associate with narrow clades of ectomycorrhizal fungi and obtain photosynthates from neighbouring trees through underground mycorrhizal networks. In contrast to these findings, in tropical and subtropical forests a couple of mycoheterotrophic orchids have been reported to associate with saprotrophic non-rhizoctonia fungi and obtain nutrients through their ability of wood- or litter-decay. Nonetheless, also ectomycorrhizal-associated mycoheterotrophic orchids have been reported for subtropical forests. Thus, for subtropical and tropical forests a co-occurrence of mycoheterotrophic orchids associated with wood or litter-decay fungi and with ectomycorrhizal fungi is likely. As compared to the temperate region (e.g. two mycoheterotrophic orchid species in entire Europe), a great diversity of mycoheterotrophic orchids (more than 120 species) occurs in tropical and subtropical Asia. In Taiwan, among the ca. 400 native orchids, more than 50 fully MH orchids of 16 genera were recorded. The fungal partners and nutritional modes of most mycoheterotrophic orchids in Taiwan are still unknown. In this joint call project of MOST-DFG we will use molecular methods together with a multi-element stable isotope natural abundance approach and tracer applications to investigate a wide range of mycoheterotrophic orchid species from six genera and to address the following objectives:(1) We are going to identify the fungal associates of more than 20 mycoheterotrophic orchid species.(2) We are going to compare the fungal diversity (OTUs) in mycorrhiza of these orchids using metagenomic analysis.(3) To reveal their nutritional resources, we are going to analyze carbon, nitrogen, hydrogen and oxygen stable isotope natural abundances of mycoheterotrophic orchids associated with different fungal groups in various forest types and mountain elevation zones and compare these isotope abundances to co-occurring fully autotrophic plants.From this project we expect to obtain the following results:(1) We will identify the mycorrhizal associates of the target orchid species studied in this project and understand the mycorrhizal diversity, specificity and distribution patterns of native mycoheterotrophic orchids in Taiwan.(2) We will trace the nutritional resources and nutrient flows of the target orchid species associated with different mycorrhizal partners and occurring in various habitats from high/low elevation and different forest types.