Alpine Botany最新文献

Climatic changes threaten the diverse and highly endemic páramo flora of the equatorial Andes with species loss and reduction of plant community diversity. Edward Whymper’s findings in his botanical exploration of the Ecuadorian Andes in 1880 offer an opportunity to examine the impact of climate changes on species distribution over time. To achieve these goals, we revised Whymper’s historical plant species collections, recorded elevational distribution of the same species along his 1880 sampling routes on two volcanoes, Chimborazo and Antisana, and applied to them ecological indicator values. Of the species recorded by Whymper, 24 on Antisana and 21 on Chimborazo, we resampled 21 and 14 of those species, respectively, in 2020. The highest record we found on Chimborazo was at 5385 m, seven meters above the zero-richness elevation predicted from Whymper’s distribution data, and at 4937 m on Antisana, 113 m below it. Mean upper range limits of species have shifted upward by 91.7 m on Chimborazo and by 27.1 m on Antisana, suggesting mean shift rates of 6.6 m and 1.9 m per decade, respectively. This rate of upslope migration ranks among the slowest reported worldwide. Humidity ecological indicator values suggest that species composition of páramo plant communities changed since 1880 in response not only to rising temperature, but also increasing dryness. Rather than a uniform upslope migration, the response of páramo plants to climate changes in the equatorial Andes has been species-specific, likely driven, among other factors, by coupled effects of increasing temperature and declining humidity.

The Sino-Himalaya region is located in the southeast margin of the Qinghai-Tibetan Plateau (QTP) with several Asian rivers in this area, namely the Yarlung Zangbo River (YZR), Salween, Mekong, and Jinshajiang River and their tributaries. All these rivers currently flow independently into the Indian Ocean, the South China Sea (Pacific Ocean) and the East China Sea (Pacific Ocean). In geologic history, however, these rivers flowed southward into the Paleo-Red River (PRR), forming a huge drainage system, which then flowed into the South China Sea. From the end of the Neogene to the beginning of the Quaternary, with further uplift of the QTP, the monsoon climate was formed and strengthened bringing abundant precipitation leading to river erosion, rapid undercutting and a series of river capture events resulting in modern drainage systems and the beheading of the huge PRR. The reorganization of the PRR led to changes in the spatial pattern of river systems, subsequently affecting the geographical distribution of plants in the river valley. This paper reviews the effects of drainage evolution on the genetic structure and geographical pattern of plants in this region, and summarizes the resulting four types of discontinuous distribution patterns observed, namely: (1) the discontinuous distribution pattern between the Three River Valleys (TRV) (Salween, Mekong, Jinshajiang and their tributaries) and the Red River Basin (RRB); (2) the discontinuity between the Yarlung Zangbo River and the TRV–RRB; (3) the discontinuity among the TRV, and (4) the discontinuity between the east and west ends of the QTP. The conclusions from this review, while providing botanical evidence supporting and confirming the drainage evolution in Sino-Himalaya China, are the following: (1) the reorganization of drainage systems made the original continuous distribution pattern discontinuous, forming unique genetic and biogeographical characteristics, promoting the genetic differentiation of species and the formation of new taxa; (2) river capture events link different river systems together, bringing together the genetic diversity of different river valley species, increasing the richness of genetic diversity and the exchange of genes among populations; (3) the reorganization of river systems impacts the evolutionary history of valley plants and shapes their modern distribution patterns.

Alpine plant radiations are common across all major mountain systems of the world, and have been regarded as the main explanation for the species diversity found within these areas. To study the mechanisms behind the origin of this diversity, it is necessary to determine phylogenetic relationships and species boundaries in radiating alpine groups. The genus Dendrosenecio (Asteraceae) is an iconic example of a tropical-alpine plant radiation in the East African high mountains. To this date, limited sampling of molecular markers has resulted in insufficient phylogenetic resolution and infrageneric classification, hindering a comprehensive understanding of the drivers of diversification. Here, we used Hyb-Seq and the Compositae1061 probe set to generate targeted nuclear and off-target plastid DNA data for 42 samples representing all currently accepted 11 species. We combined coalescent methods and paralogy analysis to infer phylogenetic relationships, estimate divergence times and evaluate species boundaries. Lineage differentiation in Dendrosenecio seems to have occurred between the Late Miocene and the Pleistocene, starting when the first high elevation habitats became available in East Africa. We retrieved four major clades corresponding to four geographically distant mountain groups, testifying the importance of allopatric speciation in the early diversification of the group. Cytonuclear discordance suggested the occurrence of historical hybridization following occasional long-distance dispersal between mountain groups. The species delimitation analysis favored 10 species, but only five were fully supported, suggesting that population-level studies addressing processes such as ecological speciation and hybridization after secondary contact are needed to determine the current diversity found in the genus.

Mountains are reservoirs for a tremendous biodiversity which was fostered by a suite of factors acting in concert throughout evolutionary times. These factors can be climatic, geological, or biotic, but the way they combine through time to generate diversity remains unknown. Here, we investigate these factors as correlates of diversification of three closely related sections of Gentiana in the European Alpine System. Based upon phylogenetic approaches coupled with divergence dating and ancestral state reconstructions, we attempted to identify the role of bedrock preferences, chromosome numbers coupled with relative genome sizes estimates, as well as morphological features through time. We also investigated extant climatic preferences using a heavily curated set of occurrence records individually selected for superior precision, and quantified rates of climatic niche evolution in each section. We found that a number of phylogenetic incongruences derail the identification of correlates of diversification, yet a number of patterns persist regardless of the topology considered. All the studied correlates are likely to have contributed to the diversification of Gentiana in Europe, however, their respective importance varied through time and across clades. Chromosomal variation and divergence of climatic preferences appear to correlate with diversification throughout the evolution of European Gentiana (Oligocene to present), whereas shifts in bedrock preferences appear to have been more defining during recent diversification (Pliocene). Overall, a complex interaction among climatic, geological and biotic attributes appear to have supported the diversification of Gentiana across the mountains of Europe, which based upon phylogenetic as well as other evidence, was probably also bolstered by hybridization.

Mountains are rugged structures in the landscape that are difficult to delineate. Given that they host an overproportional fraction of biodiversity of high ecological and conservational value, conventions on what is mountainous and what not are in need. This short communication aims at explaining the differences among various popular mountain definitions. Defining mountainous terrain is key for global assessments of plant species richness in mountains and their likely responses to climatic change, as well as for assessing the human population density in and around mountainous terrain.

Alpine habitats are characterized by a high rate of range restricted species compared to those of lower elevations. This is also the case for the Irano-Anatolian global biodiversity hotspot in South-West Asia, which is a mountainous area harbouring a high amount of endemic species. Using two quantitative approaches, Endemicity Analysis and Network-Clustering, we want to identify areas of concordant species distribution patterns in the alpine zone of this region as well as to test the hypothesis that, given the high proportion of endemics among alpine species, delimitation of these areas is determined mainly by endemic alpine species, i.e., areas of concordant species distribution patterns are congruent with areas of endemism. Endemicity Analysis identified six areas of concordant species distribution patterns irrespective of dataset (total alpine species versus endemic alpine species), whereas the Network-Clustering approach identified five and four Bioregions from total alpine species and endemic alpine species, respectively. Most of these areas have been previously identified using the endemic flora of different elevational zones. The identified units using both methods and both datasets are strongly congruent, proposing that they reveal meaningful distribution patterns. Bioregionalization in the Irano-Anatolian biodiversity hotspot appears to be strongly influenced by the endemic alpine species, a pattern likely to hold in alpine regions outside the Irano-Anatolian hotspot.

Phylogeographic studies of alpine plants have evolved considerably in the last two decades from ad hoc interpretations of genetic data to statistical model-based approaches. In this review we outline the developments in alpine plant phylogeography focusing on the recent approach of integrative distributional, demographic and coalescent (iDDC) modeling. By integrating distributional data with spatially explicit demographic modeling and subsequent coalescent simulations, the history of alpine species can be inferred and long-standing hypotheses, such as species-specific responses to climate change or survival on nunataks during the last glacial maximum, can be efficiently tested as exemplified by available case studies. We also discuss future prospects and improvements of iDDC.

The main, continuous mountain range of the European Alpine System (i.e., the Alps) hosts a diversified pool of species whose evolution has long been investigated. The legacy of past climate changes on the distribution of high-elevation plants as well as taxa differentially adapted to the mosaic of edaphic conditions (i.e., surmised ecotypes on calcareous, siliceous, serpentine bedrocks) and the origin of new species are here discussed based on available evidence from endemic taxa across the Alps. The integration of main spatial and ecological patterns within and among species supports speciation driven by spatial isolation in main glacial refugia where plant populations survived during cold phases and hindered by intense gene flow along main expansion pathways during warm phases. Despite patterns of genetic differentiation matching environmental heterogeneity, processes underlying the dynamics of distribution ranges likely promoted recurrent homogenization of incipient divergence and generally hindered the completion of speciation (except for cases of hybrid speciation). Even intense selective pressures on toxic bedrocks such as serpentine seemingly fail to support the completion of speciation. Accordingly, typical scenarios of ecological speciation whereby local adaptation to environmental heterogeneity initiates and supports long-term reduction of gene flow may rarely be at the origin of stable species in the Alps. Although consistent with neutral processes whereby spatial isolation driven by past climate changes promoted reproductive isolation and yielded limited diversification, mechanisms at the origin of new species across heterogeneous landscapes of the Alps remain insufficiently known. Necessary advances to reliably understand the evolution of biodiversity in the Alps and identify possible museums or cradles of variation in face of climate changes are discussed.

Seed germination and seedling recruitment are key processes in the life cycle of plants. They enable populations to grow, migrate, or persist. Both processes are under environmental control and influenced by site conditions and plant–plant interactions. Here, we present the results of a seed-sowing experiment performed along an elevation gradient (2000–2900 m a.s.l.) in the European eastern Alps. We monitored the germination of seeds and seedling recruitment for 2 years. Three effects were investigated: effects of sites and home sites (seed origin), effects of gaps, and plant–plant interactions. Seeds of eight species originating from two home sites were transplanted to four sites (home site and ± in elevation). Seed sowing was performed in experimentally created gaps. These gap types (‘gap + roots’, ‘neighbor + roots’, and ‘no-comp’) provided different plant–plant interactions and competition intensities. We observed decreasing germination with increasing elevation, independent of the species home sites. Competition-released gaps favored recruitment, pointing out the important role of belowground competition and soil components in recruitment. In gaps with one neighboring species, neutral plant–plant interactions occurred (with one exception). However, considering the relative vegetation cover of each experimental site, high vegetation cover resulted in positive effects on recruitment at higher sites and neutral effects at lower sites. All tested species showed intraspecific variability when responding to the experimental conditions. We discuss our findings considering novel site and climatic conditions.

The monumental work of Olov Hedberg provided deep insights into the spectacular and fragmented tropical alpine flora of the African sky islands. Here we review recent molecular and niche modelling studies and re-examine Hedberg’s hypotheses and conclusions. Colonisation started when mountain uplift established the harsh diurnal climate with nightly frosts, accelerated throughout the last 5 Myr (Plio-Pleistocene), and resulted in a flora rich in local endemics. Recruitment was dominated by long-distance dispersals (LDDs) from seasonally cold, remote areas, mainly in Eurasia. Colonisation was only rarely followed by substantial diversification. Instead, most of the larger genera and even species colonised the afroalpine habitat multiple times independently. Conspicuous parallel evolution occurred among mountains, e.g., of gigantism in Lobelia and Dendrosenecio and dwarf shrubs in Alchemilla. Although the alpine habitat was ~ 8 times larger and the treeline was ~ 1000 m lower than today during the Last Glacial Maximum, genetic data suggest that the flora was shaped by strong intermountain isolation interrupted by rare LDDs rather than ecological connectivity. The new evidence points to a much younger and more dynamic island scenario than envisioned by Hedberg: the afroalpine flora is unsaturated and fragile, it was repeatedly disrupted by the Pleistocene climate oscillations, and it harbours taxonomic and genetic diversity that is unique but severely depauperated by frequent bottlenecks and cycles of colonisation, extinction, and recolonisation. The level of intrapopulation genetic variation is alarmingly low, and many afroalpine species may be vulnerable to extinction because of climate warming and increasing human impact.