Evolutionary response of cold‐adapted chasmophytic plants to Quaternary climatic oscillations in the Mountains of Central Asia (a world hotspot of biodiversity)

Abstract

AimPast climatic oscillations are the main driving force of evolutionary changes in alpine species. Species' response to paleoclimatic oscillations is crucial in forecasting their future response in face of climate warming. The aim of this research is to explore the effect of climatic fluctuations on the evolutionary history, demography, and distribution of high‐mountain bellflowers (Campanula lehmanniana complex), the flagship and taxonomically problematic members of chasmophytic vegetation within an underexplored biodiversity hotspot, the Mountains of Central Asia.LocationCentral Asia (Tian Shan, Alai and Zeravshan‐Hissar Mountains).MethodsWe used molecular data (ITS, cpDNA, DArTseq‐based SNPs) of 262 individuals (70 for the phylogeny reconstruction, and 247 from 31 localities for population studies). We analysed the data using phylogenetic and molecular clock reconstructions, coalescent simulations, and ecological niche modelling.ResultsTertiary isolation between the Tian‐Shanian and Pamir‐Alaian populations led to the differentiation of the two main lineages (~5–6 Mya) corresponding to C. eugeniae and C. lehmanniana, whereas further Quaternary isolation into subregions led to intraspecific genetic differentiation, which starts almost simultaneously for both species (~2.7–1.5 Mya). The relatively small genetic admixture among populations indicates rare historic events of connectivity. In response to Holocene warming, the analysed species experienced a substantial decline in effective population size. Currently, the distribution of both taxa is highly influenced by precipitation in the coldest and driest quarters.Main ConclusionsOur results highlight a general principle that glacial–interglacial cycles and contemporary island‐like habitats distribution, shape the genomic variation of high‐mountain species. The similar declining demographic trend of examined taxa may suggest the overall response to ongoing climate warming. The results underline also the urgent need for conservation action in alpine regions to preserve their biodiversity.

Hybrids as mirrors of the past: genomic footprints reveal spatio-temporal dynamics and extinction risk of alpine extremophytes in the mountains of Central Asia

“…In particular, special attention should be paid to the potentially negative effects of interspecific gene flow that could threaten the integrity or even existence of the involved parental lineages ( Vallejo-Marin and Hiscock, 2016 ; Nobis et al., 2019 ). The extensive regional framework devoted to evolutionary processes would contribute to the development of effective management strategies and the selection of key conservation priorities across High Mountain Asia in view of the continuing global warming ( Yu et al., 2019 ; Nobis et al., 2023 ).…”

Insight into the phylogeny and responses of species from the genus Sergia (Campanulaceae) to the climate changes predicted for the Mountains of Central Asia (a world biodiversity hotspot)

“…In our studies, samples of C. alberti are grouped together with S. sewerzowii in both cpDNA and DArT analyses. These two mentioned above taxa split probably in the late Pliocene-early Pleistocene similarly as the other species of rocky-related endemic plants of this region, i.e., C. lehmanniana and C. eugeniae [ 7 ], and can be also regarded altitudinal vicariants within the Tian Shan Mts. Based on the morphology of the flowers, the corolla of S. sewerzowii , that is deeply divided into 5 longer than wide lobes, fused in the lower part (Fig.…”

“…The three species are also phylogenetically closely related to Cylindrocarpa sewerzowii (Regel) Regel, occurring mainly in southern Kazakhstan [ 34 , 35 , 43 ]. Having in mind that S. regelii has an inconsistent position within the Sergia-Asyneuma clade, it can not be excluded that during Pleistocene glaciations the range of these two Sergia species and C. alberti could be much broader, and similarly as in the case of other cold-adapted alpine species [ 6 , 7 ], gene flow events between these taxa may have occurred in the past. Since all of the above-mentioned species (except C. alberti ) were grouped by Xu & Hong [ 35 ] within one common clade, they suggest merging them (together with selected species from such genera as Asyneuma , Campanula or Phyteuma L., etc.)…”

“…Finally, the species will remain only in small high-mountain refugia, and thus become critically threatened with extinction in the near future. The described consequences, with severe range contractions as a response to recent climate change, are already being observed [ 52 , 53 ] and/or predicted for many alpine species [ 54 – 56 ], including chasmophytic plant species from the Mountains of Central Asia, such as Stipa zeravshanica [ 6 ] and C. lehmanniana [ 7 ].…”

“…The most rapid species response to climate changes is observed in alpine regions in the form of altitudinal range shifts [ 4 ]. Along with increasing temperature, cold-adapted mountain species are forced to move to cooler areas, which in this case means to the north or higher elevations, depending on their dispersal capacities and the availability of suitable habitats [ 5 – 7 ]. In extreme cases, upslope movement results in species extinction because they reach the highest elevations and have no place to escape [ 8 ].…”