Publications by authors named "Yaowu Xing"

9 Publications

  • Page 1 of 1

Fossil-informed models reveal a Boreotropical origin and divergent evolutionary trajectories in the walnut family (Juglandaceae).

Syst Biol 2021 May 8. Epub 2021 May 8.

Department of Biology, University of Fribourg, 1700 Fribourg, Switzerland.

Temperate woody plants in the Northern Hemisphere have long been known to exhibit high species richness in East Asia and North America and significantly lower diversity in Europe, but the causes of this pattern remain debated. Here, we quantify the roles of dispersal, niche evolution, and extinction in shaping the geographic diversity of the temperate woody plant family Juglandaceae (walnuts and their relatives). Integrating evidence from molecular, morphological, fossil, and (paleo)environmental data, we find strong support for a Boreotropical origin of the family with contrasting evolutionary trajectories between the temperate subfamily Juglandoideae and the tropical subfamily Engelhardioideae. Juglandoideae rapidly evolved frost tolerance when the global climate shifted to ice-house conditions from the Oligocene, with diversification at high latitudes especially in Europe and Asia during the Miocene. Subsequent range contraction at high latitudes and high levels of extinction in Europe driven by global cooling led to the current regional disparity in species diversity. Engelhardioideae showed temperature conservatism while adapting to increased humidity, tracking tropical climates to low latitudes since the middle Eocene with comparatively little diversification, perhaps due to high competition in the tropical zone. The biogeographic history of Juglandaceae shows that the North Atlantic land bridge and Europe played more critical roles than previously thought in linking the floras of East Asia and North America, and showcases the complex interplay among climate change, niche evolution, dispersal, and extinction that shaped the modern disjunct pattern of species richness in temperate woody plants.
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http://dx.doi.org/10.1093/sysbio/syab030DOI Listing
May 2021

Fossil data support a pre-Cretaceous origin of flowering plants.

Nat Ecol Evol 2021 04 28;5(4):449-457. Epub 2021 Jan 28.

CAS Key Laboratory of Tropical Forest Ecology, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Mengla, China.

Flowering plants (angiosperms) are the most diverse of all land plants, becoming abundant in the Cretaceous and achieving dominance in the Cenozoic. However, the exact timing of their origin remains a controversial topic, with molecular clocks generally placing their origin much further back in time than the oldest unequivocal fossils. To resolve this discrepancy, we developed a Bayesian method to estimate the ages of angiosperm families on the basis of the fossil record (a newly compiled dataset of ~15,000 occurrences in 198 families) and their living diversity. Our results indicate that several families originated in the Jurassic, strongly rejecting a Cretaceous origin for the group. We report a marked increase in lineage accumulation from 125 to 72 million years ago, supporting Darwin's hypothesis of a rapid Cretaceous angiosperm diversification. Our results demonstrate that a pre-Cretaceous origin of angiosperms is supported not only by molecular clock approaches but also by analyses of the fossil record that explicitly correct for incomplete sampling.
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http://dx.doi.org/10.1038/s41559-020-01387-8DOI Listing
April 2021

Early Miocene flora of central Kazakhstan (Turgai Plateau) and its paleoenvironmental implications.

Plant Divers 2019 Jun 16;41(3):183-197. Epub 2019 Apr 16.

Xishuangbanna Tropical Botanical Garden of Chinese Academy of Sciences (CAS), Menglum, Mengla, Yunnan 666303, China.

The investigation of the fossil floras from the Turgai plateau (central Kazakhstan) contributes to a better understanding of the origin of the temperate Turgai type flora which spread to Kazakhstan and adjacent areas during the Oligocene-Miocene transition. In this paper, we present the results of a carpological and palynological study of the Kumyrtas flora collected from a flora-bearing horizon of the regional coal-bearing Zhilanchik suite, dated to the Aquitanian period. Pollen analysis identified 33 taxa, with are dominated by angiosperms (about 73%) and reflect zonal vegetation. The high percentages of (27%) and (7.5%) that were found in this flora allows comparisons with other Aquitanian floras of Kazakhstan. Based on descriptions of fossil fruits and seeds, we determined that 19 taxa were dominant; these taxa had meosphytic herbaceous components, suggesting mostly edaphic local conditions. The incongruence between the carpological and the pollen records suggests a significant taphonomical effect. Quantitative reconstruction of the palaeoclimate based on pollen records supports---and slightly extends---previous findings based on fossil leaf data, but contradicts findings deduced from the carpological record. Plant Functional Type (PFT) classification was used to characterize the vegetation patterns. Pollen records show that about 45% of diversity relates to the arboreal broadleaved deciduous components and ca. 35% to conifers. Fossil fruit and seed data indicate riverine vegetation with a high diversity of aquatic components and shrub stratum.
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http://dx.doi.org/10.1016/j.pld.2019.04.002DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6702428PMC
June 2019

Uplift-driven diversification in the Hengduan Mountains, a temperate biodiversity hotspot.

Proc Natl Acad Sci U S A 2017 04 3;114(17):E3444-E3451. Epub 2017 Apr 3.

Life Sciences Section, Integrative Research Center, The Field Museum, Chicago, IL 60605;

A common hypothesis for the rich biodiversity found in mountains is uplift-driven diversification-that orogeny creates conditions favoring rapid in situ speciation of resident lineages. We tested this hypothesis in the context of the Qinghai-Tibetan Plateau (QTP) and adjoining mountain ranges, using the phylogenetic and geographic histories of multiple groups of plants to infer the tempo (rate) and mode (colonization versus in situ diversification) of biotic assembly through time and across regions. We focused on the Hengduan Mountains region, which in comparison with the QTP and Himalayas was uplifted more recently (since the late Miocene) and is smaller in area and richer in species. Time-calibrated phylogenetic analyses show that about 8 million y ago the rate of in situ diversification increased in the Hengduan Mountains, significantly exceeding that in the geologically older QTP and Himalayas. By contrast, in the QTP and Himalayas during the same period the rate of in situ diversification remained relatively flat, with colonization dominating lineage accumulation. The Hengduan Mountains flora was thus assembled disproportionately by recent in situ diversification, temporally congruent with independent estimates of orogeny. This study shows quantitative evidence for uplift-driven diversification in this region, and more generally, tests the hypothesis by comparing the rate and mode of biotic assembly jointly across time and space. It thus complements the more prevalent method of examining endemic radiations individually and could be used as a template to augment such studies in other biodiversity hotspots.
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http://dx.doi.org/10.1073/pnas.1616063114DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5410793PMC
April 2017

On the complexity of triggering evolutionary radiations.

New Phytol 2015 Jul 17;207(2):313-326. Epub 2015 Feb 17.

Institute of Systematic Botany, University of Zurich, 107 Zollikerstrasse, Zurich, CH-8008, Switzerland.

Recent developments in phylogenetic methods have made it possible to reconstruct evolutionary radiations from extant taxa, but identifying the triggers of radiations is still problematic. Here, we propose a conceptual framework to explore the role of variables that may impact radiations. We classify the variables into extrinsic conditions vs intrinsic traits, whether they provide background conditions, trigger the radiation, or modulate the radiation. We used three clades representing angiosperm phylogenetic and structural diversity (Ericaceae, Fagales and Poales) as test groups. We located radiation events, selected variables potentially associated with diversification, and inferred the temporal sequences of evolution. We found 13 shifts in diversification regimes in the three clades. We classified the associated variables, and determined whether they originated before the relevant radiation (backgrounds), originated simultaneously with the radiations (triggers), or evolved later (modulators). By applying this conceptual framework, we establish that radiations require both extrinsic conditions and intrinsic traits, but that the sequence of these is not important. We also show that diversification drivers can be detected by being more variable within a radiation than conserved traits that only allow occupation of a new habitat. This framework facilitates exploration of the causative factors of evolutionary radiations.
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http://dx.doi.org/10.1111/nph.13331DOI Listing
July 2015

Do Mediterranean-type ecosystems have a common history?--insights from the Buckthorn family (Rhamnaceae).

Evolution 2015 Mar 27;69(3):756-71. Epub 2015 Feb 27.

Institute of Systematic Botany, University of Zurich, Zollikerstrasse 107, 8008, Zurich, Switzerland.

Mediterranean-type ecosystems (MTEs) are remarkable in their species richness and endemism, but the processes that have led to this diversity remain enigmatic. Here, we hypothesize that continent-dependent speciation and extinction rates have led to disparity in diversity between the five MTEs of the world: the Cape, California, Mediterranean Basin, Chile, and Western Australia. To test this hypothesis, we built a phylogenetic tree for 280 Rhamnaceae species, estimated divergence times using eight fossil calibrations, and used Bayesian methods and simulations to test for differences in diversification rates. Rhamnaceae lineages in MTEs generally show higher diversification rates than elsewhere, but speciation and extinction dynamics show a pattern of continent-dependence. We detected high speciation and extinction rates in California and significantly lower extinction rates in the Cape and Western Australia. The independent colonization of four of five MTEs may have occurred conterminously in the Oligocene/Early Miocene, but colonization of the Mediterranean Basin happened later, in the Late Miocene. This suggests that the in situ radiations of these clades were initiated before the onset of winter rainfall in these regions. These results indicate independent evolutionary histories of Rhamnaceae in MTEs, possibly related to the intensity of climate oscillations and the geological history of the regions.
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http://dx.doi.org/10.1111/evo.12605DOI Listing
March 2015

As old as the mountains: the radiations of the Ericaceae.

New Phytol 2015 Jul 19;207(2):355-367. Epub 2014 Dec 19.

Institute of Systematic Botany of the University of Zurich, Zollikerstrasse 107, 8008, Zurich, Switzerland.

Mountains are often more species-rich than lowlands. This could be the result of migration from lowlands to mountains, of a greater survival rate in mountains, or of a higher diversification rate in mountains. We investigated this question in the globally distributed family Ericaceae, which includes c. 4426 species ranging from sea level to > 5000 m. We predict that the interaction of low specific leaf area (SLA) and montane habitats is correlated with increased diversification rates. A molecular phylogeny of Ericaceae based on rbcL and matK sequence data was built and dated with 18 fossil calibrations and divergence time estimates. We identified radiations using bamm and correlates of diversification rate changes using binary-state speciation and extinction (BiSSE) and multiple-state speciation and extinction (MuSSE) analyses. Analyses revealed six largely montane radiations. Lineages in mountains diversified faster than nonmountain lineages (higher speciation rate, but no difference in extinction rate), and lineages with low SLA diversified faster than high-SLA lineages. Further, habitat and trait had a positive interactive effect on diversification. Our results suggest that the species richness in mountains is the result of increased speciation rather than reduced extinction or increased immigration. Increased speciation in Ericaceae was facilitated by low SLA.
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http://dx.doi.org/10.1111/nph.13234DOI Listing
July 2015

Fossils and a large molecular phylogeny show that the evolution of species richness, generic diversity, and turnover rates are disconnected.

Evolution 2014 Oct 13;68(10):2821-32. Epub 2014 Aug 13.

Institut für Systematische Botanik, Universität Zürich, Zollikerstrasse107, 8008, Zürich, Switzerland.

The magnitude and extent of global change during the Cenozoic is remarkable, yet the impacts of these global changes on the biodiversity and evolutionary dynamics of species diversification remain poorly understood. To investigate this question, we combine paleontological and neontological data for the angiosperm order Fagales, an ecologically important clade of about 1370 species of trees with an exceptional fossil record. We show differences in patterns of accumulation of generic diversity, species richness, and turnover rates for Fagales. Generic diversity evolved rapidly since the Late Cretaceous and peaked during the Eocene or Oligocene. Turnover rates were high during periods of extreme global climate change, but relatively low when the climate remained stable. Species richness accumulated gradually throughout the Cenozoic, possibly at an accelerated pace after the Middle Miocene. Species diversification occurred in new environments: Quercoids radiating in Oligocene subtropical seasonally arid habitats, Casuarinaceae in Australian pyrophytic biomes, and Betula in Late Neogene holarctic habitats. These radiations were counterbalanced by regional extinctions in Late Neogene mesic warm-temperate forests. Thus, the overall diversification at species level is linked to regional radiations of clades with appropriate ecologies exploiting newly available habitats.
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http://dx.doi.org/10.1111/evo.12489DOI Listing
October 2014

Phylogeographic analysis reveals significant spatial genetic structure of Incarvillea sinensis as a product of mountain building.

BMC Plant Biol 2012 Apr 30;12:58. Epub 2012 Apr 30.

Kunming Institute of Botany, Chinese Academy of Sciences, Kunming, Yunnan, China.

Background: Incarvillea sinensis is widely distributed from Southwest China to Northeast China and in the Russian Far East. The distribution of this species was thought to be influenced by the uplift of the Qinghai-Tibet Plateau and Quaternary glaciation. To reveal the imprints of geological events on the spatial genetic structure of Incarvillea sinensis, we examined two cpDNA segments ( trnH- psbA and trnS- trnfM) in 705 individuals from 47 localities.

Results: A total of 16 haplotypes was identified, and significant genetic differentiation was revealed (GST =0.843, NST = 0.975, P < 0.05). The survey detected two highly divergent cpDNA lineages connected by a deep gap with allopatric distributions: the southern lineage with higher genetic diversity and differentiation in the eastern Qinghai-Tibet Plateau, and the northern lineage in the region outside the Qinghai-Tibet Plateau. The divergence between these two lineages was estimated at 4.4 MYA. A correlation between the genetic and the geographic distances indicates that genetic drift was more influential than gene flow in the northern clade with lower diversity and divergence. However, a scenario of regional equilibrium between gene flow and drift was shown for the southern clade. The feature of spatial distribution of the genetic diversity of the southern lineage possibly indicated that allopatric fragmentation was dominant in the collections from the eastern Qinghai-Tibet Plateau.

Conclusions: The results revealed that the uplift of the Qinghai-Tibet Plateau likely resulted in the significant divergence between the lineage in the eastern Qinghai-Tibet Plateau and the other one outside this area. The diverse niches in the eastern Qinghai-Tibet Plateau created a wide spectrum of habitats to accumulate and accommodate new mutations. The features of genetic diversity of populations outside the eastern Qinghai-Tibet Plateau seemed to reveal the imprints of extinction during the Glacial and the interglacial and postglacial recolonization. Our study is a typical case of the significance of the uplift of the Qinghai-Tibet Plateau and the Quaternary Glacial in spatial genetic structure of eastern Asian plants, and sheds new light on the evolution of biodiversity in the Qinghai-Tibet Plateau at the intraspecies level.
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http://dx.doi.org/10.1186/1471-2229-12-58DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3447706PMC
April 2012