Rolshausen Gregor, Dal Grande Francesco, Otte Jürgen, Schmitt Imke
Senckenberg Biodiversity and Climate Research Centre (SBiK-F), Frankfurt am Main, Germany.
Center for Wildlife Genetics, Senckenberg Research Institute, Gelnhausen, Germany.
Mol Ecol. 2023 Dec;32(23):6619-6630. doi: 10.1111/mec.16471. Epub 2022 Apr 22.
Holobionts are dynamic ecosystems that may respond to abiotic drivers with compositional changes. Uncovering elevational diversity patterns within these microecosystems can further our understanding of community-environment interactions. Here, we assess how the major components of lichen holobionts-fungal hosts, green algal symbionts, and the bacterial community-collectively respond to an elevational gradient. We analyse populations of two lichen symbioses, Umbilicaria pustulata and U. hispanica, along an elevational gradient spanning 2100 altitudinal metres and covering three major biomes. Our study shows (i) discontinuous genomic variation in fungal hosts with one abrupt genomic differentiation within each of the two host species, (ii) altitudinally structured bacterial communities with pronounced turnover within and between hosts, and (iii) altitude-specific presence of algal symbionts. Alpha diversity of bacterial communities decreased with increasing elevation. A marked turnover in holobiont diversity occurred across two altitudinal belts: at 11°C-13°C average annual temperature (here: 800-1200 m a.s.l.), and at 7°C-9°C average annual temperature (here: 1500-1800 m a.s.l.). The two observed zones mark a clustering of distribution limits and community shifts. The three ensuing altitudinal classes, that is, the most frequent combinations of species in holobionts, approximately correspond to the Mediterranean, cool-temperate, and alpine climate zones. We conclude that multitrophic microecosystems, such as lichen holobionts, respond with concerted compositional changes to climatic factors that also structure communities of macroorganisms, for example, vascular plants.
共生功能体是动态的生态系统，可能会通过组成变化对非生物驱动因素做出反应。揭示这些微观生态系统中的海拔多样性模式有助于我们进一步理解群落与环境的相互作用。在这里，我们评估地衣共生功能体的主要组成部分——真菌宿主、绿藻共生体和细菌群落——如何共同响应海拔梯度。我们分析了两种地衣共生关系，即脓疱脐衣和西班牙脐衣，沿着跨越2100米海拔高度并覆盖三个主要生物群落的海拔梯度的种群。我们的研究表明：（i）真菌宿主中存在不连续的基因组变异，两种宿主物种各自内部都有一个突然的基因组分化；（ii）细菌群落具有海拔结构，宿主内部和宿主之间有明显的更替；（iii）藻类共生体存在海拔特异性。细菌群落的α多样性随着海拔升高而降低。共生功能体多样性在两个海拔带发生了显著变化：年平均温度为11°C - 13°C（此处：海拔800 - 1200米），以及年平均温度为7°C - 9°C（此处：海拔1500 - 1800米）。观察到的这两个区域标志着分布界限的聚类和群落转移。随后的三个海拔类别，即共生功能体中最常见的物种组合，大致对应地中海、凉爽温带和高山气候带。我们得出结论，多营养微观生态系统，如地衣共生功能体，会通过协调的组成变化对气候因素做出反应，而这些气候因素也构建了大型生物群落，如维管植物群落。
