Not so ancient: Misclassification of alpine plants biases the dating of the evolution of alpine biota in the Himalaya-Tibet Orogen

Ding et al. (Science 2020) proposed that the extant lineages of the alpine flora of the Tibet Himalaya Hengduan region emerged by the early Oligocene. We argue that these results are based on misclassifying high montane taxa as alpine and that their data support alpine habitats only at about 7.5 mio years before present.

Sedimentary ancient DNA reveals a threat of warming-induced alpine habitat loss to Tibetan Plateau plant diversity

Studies along elevational gradients worldwide usually find the highest plant taxa richness in mid-elevation forest belts. Hence, an increase in upper elevation diversity is expected in the course of warming-related treeline rise. Here, we use a time-series approach to infer past taxa richness from sedimentary ancient DNA from the south-eastern Tibetan Plateau over the last ~18,000 years. We find the highest total plant taxa richness during the cool phase after glacier retreat when the area contained extensive and diverse alpine habitats (14–10 ka); followed by a decline when forests expanded during the warm early- to mid-Holocene (10–3.6 ka). Livestock grazing since 3.6 ka promoted plant taxa richness only weakly. Based on these inferred dependencies, our simulation yields a substantive decrease in plant taxa richness in response to warming-related alpine habitat loss over the next centuries. Accordingly, efforts of Tibetan biodiversity conservation should include conclusions from palaeoecological evidence.

Spatial and evolutionary predictability of phytochemical diversity

To cope with environmental challenges, plants produce a wide diversity of phytochemicals, which are also the source of numerous medicines. Despite decades of research in chemical ecology, we still lack an understanding of the organization of plant chemical diversity across species and ecosystems. To address this challenge, we hypothesized that molecular diversity is not only related to species diversity, but also constrained by trophic, climatic, and topographical factors. We screened the metabolome of 416 vascular plant species encompassing the entire alpine elevation range and four alpine bioclimatic regions in order to characterize their phytochemical diversity. We show that by coupling phylogenetic information, topographic, edaphic, and climatic variables, we predict phytochemical diversity, and its inherent composition, of plant communities throughout landscape. Spatial mapping of phytochemical diversity further revealed that plant assemblages found in low to midelevation habitats, with more alkaline soils, possessed greater phytochemical diversity, whereas alpine habitats possessed higher phytochemical endemism. Altogether, we present a general tool that can be used for predicting hotspots of phytochemical diversity in the landscape, independently of plant species taxonomic identity. Such an approach offers promising perspectives in both drug discovery programs and conservation efforts worldwide.

Phylogenetic delimitation of Apiospora and Arthrinium

In the present study six species of Arthrinium (including a new taxon, Ar. crenatum) are described and subjected to phylogenetic analysis. The analysis of ITS and 28S rDNA, as well as sequences of tef1 and tub2 exons suggests that Arthrinium s. str. and Apiospora represent independent lineages within Apiosporaceae. Morphologically, Arthrinium and Apiospora do not seem to have clear diagnostic features, although species of Arthrinium often produce variously shaped conidia (navicular, fusoid, curved, polygonal, rounded), while most species of Apiospora have rounded (face view) / lenticular (side view) conidia. Ecologically, most sequenced collections of Arthrinium were found on Cyperaceae or Juncaceae in temperate, cold or alpine habitats, while those of Apiospora were collected mainly on Poaceae (but also many other plant host families) in a wide range of habitats, including tropical and subtropical regions. A lectotype for Sphaeria apiospora (syn.: Ap. montagnei, type species of Apiospora) is selected among the original collections preserved at the PC fungarium, and the putative identity of this taxon, found on Poaceae in Mediterranean lowland habitats, is discussed. Fifty-five species of Arthrinium are combined to Apiospora, and a key to species of Arthrinium s. str. is provided.

Soil bacterial community diversity and composition vary more with elevation than seasons in alpine habitats of western Himalaya

Soil heterotrophic respiration-driven CO2 emissions, its impact on global warming and the mechanistic roles of soil bacterial communities in this process have been an area of active research. However, our knowledge regarding the effects of environmental changes on soil bacterial communities is limited. To this end, the climate-sensitive high-altitude alpine ecosystems offer ideal opportunities to investigate relationship between climate change and bacterial communities. While data from several high-altitude mountain regions suggest that local environment factors and geological patterns govern bacterial communities, no information is available from the Himalaya. Here we provide baseline information on seasonal soil bacterial community diversity and composition along a 3200-4000 m elevation gradient covering four alpine habitats (subalpine forest, alpine scrub, alpine meadow and moraine) in Gangotri National Park, western Himalaya. Bacterial metabarcoding data from 36 field-collected samples showed no elevation trend in the bacterial richness and a non-monotonous decrease in their diversity. Further, their community diversity and composition varied significantly among habitats along elevation but were stable seasonally within each habitat. The richness was primarily influenced by soil inorganic carbon (SOC) and total nitrogen (TN), whereas temperature, SOC and TN affected diversity and composition patterns. Given the importance of the Himalaya in the context of global carbon cycle this information will help in accurate modeling of climate adaptation scenarios of bacterial niches and their downstream impacts towards climate warming.