Dataset Information

Phylogeographic patterns of the desert poplar in Northwest China shaped by both geology and climatic oscillations.

ABSTRACT: BACKGROUND:The effects of historical geology and climatic events on the evolution of plants around the Qinghai-Tibetan Plateau region have been at the center of debate for years. To identify the influence of the uplift of the Tianshan Mountains and/or climatic oscillations on the evolution of plants in arid northwest China, we investigated the phylogeography of the Euphrates poplar (Populus euphratica) using chloroplast DNA (cpDNA) sequences and nuclear microsatellites, and estimated its historical distribution using Ecological Niche Modeling (ENM). RESULTS:We found that the Euphrates poplar differed from another desert poplar, P. pruinosa, in both nuclear and chloroplast DNA. The low clonal diversity in both populations reflected the low regeneration rate by seed/seedlings in many locations. Both cpDNA and nuclear markers demonstrated a clear divergence between the Euphrates poplar populations from northern and southern Xinjiang regions. The divergence time was estimated to be early Pleistocene based on cpDNA, and late Pleistocene using an Approximate Bayesian Computation analysis based on microsatellites. Estimated gene flow was low between these two regions, and the limited gene flow occurred mainly via dispersal from eastern regions. ENM analysis supported a wider distribution of the Euphrates poplar at 3 Ma, but a more constricted distribution during both the glacial period and the interglacial period. CONCLUSIONS:These results indicate that the deformation of the Tianshan Mountains has impeded gene flow of the Euphrates poplar populations from northern and southern Xinjiang, and the distribution constriction due to climatic oscillations further accelerated the divergence of populations from these regions. To protect the desert poplars, more effort is needed to encourage seed germination and seedling establishment, and to conserve endemic gene resources in the northern Xinjiang region.

SUBMITTER: Zeng YF

PROVIDER: S-EPMC5970483 | biostudies-literature | 2018 May

REPOSITORIES: biostudies-literature

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Phylogeographic patterns of the desert poplar in Northwest China shaped by both geology and climatic oscillations.

Zeng Yan-Fei YF Zhang Jian-Guo JG Abuduhamiti Bawerjan B Wang Wen-Ting WT Jia Zhi-Qing ZQ

BMC evolutionary biology 20180525 1

<h4>Background</h4>The effects of historical geology and climatic events on the evolution of plants around the Qinghai-Tibetan Plateau region have been at the center of debate for years. To identify the influence of the uplift of the Tianshan Mountains and/or climatic oscillations on the evolution of plants in arid northwest China, we investigated the phylogeography of the Euphrates poplar (Populus euphratica) using chloroplast DNA (cpDNA) sequences and nuclear microsatellites, and estimated its ...[more]

PMID: 29801429

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Project description:Background and aimsThe Mediterranean-type forest of central Chile is considered a 'biodiversity hotspot' and a relic of a wider ancient distribution produced by past climatic oscillations. Nothofagus macrocarpa, commonly known as 'roble de Santiago', is a threatened palaeoendemic of this forest, poorly represented in the protected area system. This tree has been repeatedly misidentified as the sister species N. obliqua, which has affected its recognition and protection. Only a few populations of N. macrocarpa remain within a matrix of intensive land use that has been affected by recent forest fires. We tested the hypothesis that current populations of N. macrocarpa are a relic state of a previously widespread range, with the aim of contributing to its identification, its biogeographical history and the design of conservation measures using genetic information.MethodsWe analysed remnant N. macrocarpa forests using nuclear (nDNA) and chloroplast DNA (cpDNA) sequences, conducted phylogenetic and phylogeographical analyses to reconstruct its biogeographical history, and assessed microsatellites [simple sequence repeats (SSRs)] to determine contemporary patters of diversity within and among all remnant populations. We also examined the degree of past, current and potential future isolation of N. macrocarpa populations using ecological niche models (ENMs).Key resultsThe species N. macrocarpa was confirmed by nDNA sequences, as previously suggested by chromosomal analysis. Small isolated populations of N. macrocarpa exhibited moderate to high genetic diversity according to SSRs. cpDNA analysis revealed a marked past latitudinal geographical structure, whereas analysis of SSRs did not find such current structure. ENM analyses revealed local expansion-contraction of the N. macrocarpa range during warmer periods, particularly in the northern and central ranges where basal-most cpDNA haplotypes were detected, and recent expansion to the south of the distribution.ConclusionsGenetic patterns confirm that N. macrocarpa is a distinct species and suggest a marked latitudinal relic structure in at least two evolutionarily significant units, despite contemporary among-population gene flow. This information must be considered when choosing individuals (seeds and/or propagules) for restoration purposes, to avoid the admixture of divergent genetic stocks.

Project description:BACKGROUND: Populus euphratica Oliv and P. pruinosa Schrenk (Salicaceae) both grow in dry desert areas with high summer temperatures. However, P. euphratica is distributed in dry deserts with deep underground water whereas P. pruinosa occurs in deserts in which there is underground water close to the surface. We therefore hypothesized that these two sister species may have evolved divergent regulatory and metabolic pathways during their interaction with different salt habitats and other stresses. To test this hypothesis, we compared transcriptomes from callus exposed to 24 h of salt stress and control callus samples from both species and identified differentially expressed genes (DEGs) and alternative splicing (AS) events that had occurred under salt stress. RESULTS: A total of 36,144 transcripts were identified and 1430 genes were found to be differentially expressed in at least one species in response to salt stress. Of these DEGs, 884 and 860 were identified in P. euphratica and P. pruinosa, respectively, while 314 DEGs were common to both species. On the basis of parametric analysis of gene set enrichment, GO enrichment in P. euphratica was found to be significantly different from that in P. pruinosa. Numerous genes involved in hormone biosynthesis, transporters and transcription factors showed clear differences between the two species in response to salt stress. We also identified 26,560 AS events which were mapped to 8380 poplar genomic loci from four libraries. GO enrichments for genes undergoing AS events in P. euphratica differed significantly from those in P. pruinosa. CONCLUSIONS: A number of salt-responsive genes in both P. euphratica and P. pruinosa were identified and candidate genes with potential roles in the salinity adaptation were proposed. Transcriptome comparisons of two sister desert poplar species under salt stress suggest that these two species may have developed different genetic pathways in order to adapt to different desert salt habitats. The DEGs that were found to be common to both species under salt stress may be especially important for future genetic improvement of cultivated poplars or other crops through transgenic approaches in order to increase tolerance of saline soil conditions.

Project description:Desert mound springs of the Great Artesian Basin in central Australia maintain an endemic fauna that have historically been considered ubiquitous throughout all of the springs. Recent studies, however, have shown that several endemic invertebrate species are genetically highly structured and contain previously unrecognised species, suggesting that individuals may be geographically 'stranded in desert islands'. Here we further tested the generality of this hypothesis by conducting genetic analyses of the obligate aquatic phreatoicid isopod Phreatomerus latipes. Phylogenetic and phylogeographic relationships amongst P. latipes individuals were examined using a multilocus approach comprising allozymes and mtDNA sequence data. From the Lake Eyre region in South Australia we collected data for 476 individuals from 69 springs for the mtDNA gene COI; in addition, allozyme electrophoresis was conducted on 331 individuals from 19 sites for 25 putative loci. Phylogenetic and population genetic analyses showed three major clades in both allozyme and mtDNA data, with a further nine mtDNA sub-clades, largely supported by the allozymes. Generally, each of these sub-clades was concordant with a traditional geographic grouping known as spring complexes. We observed a coalescent time between ?2-15 million years ago for haplotypes within each of the nine mtDNA sub-clades, whilst an older total time to coalescence (>15 mya) was observed for the three major clades. Overall we observed that multiple layers of phylogeographic history are exemplified by Phreatomerus, suggesting that major climate events and their impact on the landscape have shaped the observed high levels of diversity and endemism. Our results show that this genus reflects a diverse fauna that existed during the early Miocene and appears to have been regionally restricted. Subsequent aridification events have led to substantial contraction of the original habitat, possibly over repeated Pleistocene ice age cycles, with P. latipes populations becoming restricted in the distribution to desert springs.

Dataset Information

Phylogeographic patterns of the desert poplar in Northwest China shaped by both geology and climatic oscillations.

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Phylogeographic patterns of the desert poplar in Northwest China shaped by both geology and climatic oscillations.

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