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Martin CA, Sheppard EC, Ali HAA, Illera JC, Suh A, Spurgin LG, Richardson DS. Genomic landscapes of divergence among island bird populations: Evidence of parallel adaptation but at different loci? Mol Ecol 2024; 33:e17365. [PMID: 38733214 DOI: 10.1111/mec.17365] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2023] [Accepted: 03/01/2024] [Indexed: 05/13/2024]
Abstract
When populations colonise new environments, they may be exposed to novel selection pressures but also suffer from extensive genetic drift due to founder effects, small population sizes and limited interpopulation gene flow. Genomic approaches enable us to study how these factors drive divergence, and disentangle neutral effects from differentiation at specific loci due to selection. Here, we investigate patterns of genetic diversity and divergence using whole-genome resequencing (>22× coverage) in Berthelot's pipit (Anthus berthelotii), a passerine endemic to the islands of three north Atlantic archipelagos. Strong environmental gradients, including in pathogen pressure, across populations in the species range, make it an excellent system in which to explore traits important in adaptation and/or incipient speciation. First, we quantify how genomic divergence accumulates across the speciation continuum, that is, among Berthelot's pipit populations, between sub species across archipelagos, and between Berthelot's pipit and its mainland ancestor, the tawny pipit (Anthus campestris). Across these colonisation timeframes (2.1 million-ca. 8000 years ago), we identify highly differentiated loci within genomic islands of divergence and conclude that the observed distributions align with expectations for non-neutral divergence. Characteristic signatures of selection are identified in loci associated with craniofacial/bone and eye development, metabolism and immune response between population comparisons. Interestingly, we find limited evidence for repeated divergence of the same loci across the colonisation range but do identify different loci putatively associated with the same biological traits in different populations, likely due to parallel adaptation. Incipient speciation across these island populations, in which founder effects and selective pressures are strong, may therefore be repeatedly associated with morphology, metabolism and immune defence.
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Affiliation(s)
- Claudia A Martin
- School of Biological Sciences, University of East Anglia, Norfolk, UK
- Terrestrial Ecology Unit, Biology Department, Ghent University, Ghent, Belgium
- School of Biological Sciences, The University of Edinburgh, Edinburgh, UK
| | | | - Hisham A A Ali
- Department of Biology, Edward Grey Institute of Field Ornithology, University of Oxford, Oxford, UK
| | - Juan Carlos Illera
- Biodiversity Research Institute (CSIC-Oviedo University-Principality of Asturias), University of Oviedo, Mieres, Asturias, Spain
| | - Alexander Suh
- School of Biological Sciences, University of East Anglia, Norfolk, UK
- Department of Organismal Biology - Systematic Biology, Evolutionary Biology Centre (EBC), Science for Life Laboratory, Uppsala University, Uppsala, Sweden
| | - Lewis G Spurgin
- School of Biological Sciences, University of East Anglia, Norfolk, UK
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Zhou W, Zhang N, Huang K, Lin H, Tu J, Zheng C, Que P, Chiang CY, Martinez J, Naerhulan H, Székely T, Zhang Z, Liu Y. Divergent Selection in Low Recombination Regions Shapes the Genomic Islands in Two Incipient Shorebird Species. Mol Biol Evol 2024; 41:msae006. [PMID: 38225175 PMCID: PMC10835341 DOI: 10.1093/molbev/msae006] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2023] [Revised: 01/02/2024] [Accepted: 01/08/2024] [Indexed: 01/17/2024] Open
Abstract
Speciation in the face of gene flow is usually associated with a heterogeneous genomic landscape of divergence in nascent species pairs. However, multiple factors, such as divergent selection and local recombination rate variation, can influence the formation of these genomic islands. Examination of the genomic landscapes of species pairs that are still in the early stages of speciation provides an insight into this conundrum. In this study, population genomic analyses were undertaken using a wide range of sampling and whole-genome resequencing data from 96 unrelated individuals of Kentish plover (Charadrius alexandrinus) and white-faced plover (Charadrius dealbatus). We suggest that the two species exhibit varying levels of population admixture along the Chinese coast and on the Taiwan Island. Genome-wide analyses for introgression indicate that ancient introgression had occurred in Taiwan population, and gene flow is still ongoing in mainland coastal populations. Furthermore, we identified a few genomic regions with significant levels of interspecific differentiation and local recombination suppression, which contain several genes potentially associated with disease resistance, coloration, and regulation of plumage molting and thus may be relevant to the phenotypic and ecological divergence of the two nascent species. Overall, our findings suggest that divergent selection in low recombination regions may be a main force in shaping the genomic islands in two incipient shorebird species.
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Affiliation(s)
- Wenjun Zhou
- State Key Laboratory of Biocontrol, School of Ecology, Sun Yat-sen University, Guangzhou, China
- Department of Zoology, University of Cambridge, Cambridge, UK
| | - Nan Zhang
- State Key Laboratory of Biocontrol, School of Ecology, Sun Yat-sen University, Guangzhou, China
| | - Kaichi Huang
- Department of Botany and Biodiversity Research Centre, University of British Columbia, Vancouver, Bc, Canada
| | - Hongzhou Lin
- State Key Laboratory of Biocontrol, School of Ecology, Sun Yat-sen University, Guangzhou, China
| | - Jie Tu
- State Key Laboratory of Biocontrol, School of Ecology, Sun Yat-sen University, Guangzhou, China
| | - Chenqing Zheng
- State Key Laboratory of Biocontrol, School of Ecology, Sun Yat-sen University, Guangzhou, China
| | - Pinjia Que
- Ministry of Education Key Laboratory for Biodiversity Sciences and Ecological Engineering, College of Life Sciences, Beijing Normal University, Beijing, China
- Sichuan Key Laboratory of Conservation Biology for Endangered Wildlife, Chengdu Research Base of Giant Panda Breeding, Sichuan Academy of Giant Panda, Chengdu, China
| | - Chung-Yu Chiang
- Department of Environmental Science, Tunghai University, Taichung, Taiwan, China
| | | | - Halimubieke Naerhulan
- Milner Centre for Evolution, Department of Biology and Biochemistry, University of Bath, Bath, UK
| | - Tamás Székely
- State Key Laboratory of Biocontrol, School of Ecology, Sun Yat-sen University, Guangzhou, China
- Ministry of Education Key Laboratory for Biodiversity Sciences and Ecological Engineering, College of Life Sciences, Beijing Normal University, Beijing, China
- Milner Centre for Evolution, Department of Biology and Biochemistry, University of Bath, Bath, UK
| | - Zhengwang Zhang
- Ministry of Education Key Laboratory for Biodiversity Sciences and Ecological Engineering, College of Life Sciences, Beijing Normal University, Beijing, China
| | - Yang Liu
- State Key Laboratory of Biocontrol, School of Ecology, Sun Yat-sen University, Guangzhou, China
- Milner Centre for Evolution, Department of Biology and Biochemistry, University of Bath, Bath, UK
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3
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Bock DG, Cai Z, Elphinstone C, González-Segovia E, Hirabayashi K, Huang K, Keais GL, Kim A, Owens GL, Rieseberg LH. Genomics of plant speciation. PLANT COMMUNICATIONS 2023; 4:100599. [PMID: 37050879 PMCID: PMC10504567 DOI: 10.1016/j.xplc.2023.100599] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/26/2023] [Revised: 03/21/2023] [Accepted: 04/06/2023] [Indexed: 06/19/2023]
Abstract
Studies of plants have been instrumental for revealing how new species originate. For several decades, botanical research has complemented and, in some cases, challenged concepts on speciation developed via the study of other organisms while also revealing additional ways in which species can form. Now, the ability to sequence genomes at an unprecedented pace and scale has allowed biologists to settle decades-long debates and tackle other emerging challenges in speciation research. Here, we review these recent genome-enabled developments in plant speciation. We discuss complications related to identification of reproductive isolation (RI) loci using analyses of the landscape of genomic divergence and highlight the important role that structural variants have in speciation, as increasingly revealed by new sequencing technologies. Further, we review how genomics has advanced what we know of some routes to new species formation, like hybridization or whole-genome duplication, while casting doubt on others, like population bottlenecks and genetic drift. While genomics can fast-track identification of genes and mutations that confer RI, we emphasize that follow-up molecular and field experiments remain critical. Nonetheless, genomics has clarified the outsized role of ancient variants rather than new mutations, particularly early during speciation. We conclude by highlighting promising avenues of future study. These include expanding what we know so far about the role of epigenetic and structural changes during speciation, broadening the scope and taxonomic breadth of plant speciation genomics studies, and synthesizing information from extensive genomic data that have already been generated by the plant speciation community.
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Affiliation(s)
- Dan G Bock
- Department of Botany and Biodiversity Research Centre, University of British Columbia, Vancouver, BC, Canada
| | - Zhe Cai
- Department of Botany and Biodiversity Research Centre, University of British Columbia, Vancouver, BC, Canada
| | - Cassandra Elphinstone
- Department of Botany and Biodiversity Research Centre, University of British Columbia, Vancouver, BC, Canada
| | - Eric González-Segovia
- Department of Botany and Biodiversity Research Centre, University of British Columbia, Vancouver, BC, Canada
| | | | - Kaichi Huang
- Department of Botany and Biodiversity Research Centre, University of British Columbia, Vancouver, BC, Canada
| | - Graeme L Keais
- Department of Botany and Biodiversity Research Centre, University of British Columbia, Vancouver, BC, Canada
| | - Amy Kim
- Department of Botany and Biodiversity Research Centre, University of British Columbia, Vancouver, BC, Canada
| | - Gregory L Owens
- Department of Biology, University of Victoria, Victoria, BC, Canada
| | - Loren H Rieseberg
- Department of Botany and Biodiversity Research Centre, University of British Columbia, Vancouver, BC, Canada.
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Seeley MM, Martin RE, Giardina C, Luiz B, Francisco K, Cook Z, Hughes MA, Asner GP. Leaf spectroscopy of resistance to Ceratocystis wilt of 'Ōhi'a. PLoS One 2023; 18:e0287144. [PMID: 37352315 PMCID: PMC10289452 DOI: 10.1371/journal.pone.0287144] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2023] [Accepted: 05/31/2023] [Indexed: 06/25/2023] Open
Abstract
Plant pathogens are increasingly compromising forest health, with impacts to the ecological, economic, and cultural goods and services these global forests provide. One response to these threats is the identification of disease resistance in host trees, which with conventional methods can take years or even decades to achieve. Remote sensing methods have accelerated host resistance identification in agricultural crops and for a select few forest tree species, but applications are rare. Ceratocystis wilt of 'ōhi'a, caused by the fungal pathogen Ceratocystis lukuohia has been killing large numbers of the native Hawaiian tree, Metrosideros polymorpha or 'Ōhi'a, Hawaii's most common native tree and a biocultural keystone species. Here, we assessed whether resistance to C. lukuohia is detectable in leaf-level reflectance spectra (400-2500 nm) and used chemometric conversion equations to understand changes in leaf chemical traits of the plants as indicators of wilt symptom progression. We collected leaf reflectance data prior to artificially inoculating 2-3-year-old M. polymorpha clones with C. lukuohia. Plants were rated 3x a week for foliar wilt symptom development and leaf spectra data collected at 2 to 4-day intervals for 120 days following inoculation. We applied principal component analysis (PCA) to the pre-inoculation spectra, with plants grouped according to site of origin and subtaxon, and two-way analysis of variance to assess whether each principal component separated individuals based on their disease severity ratings. We identified seven leaf traits that changed in susceptible plants following inoculation (tannins, chlorophyll a+b, NSC, total C, leaf water, phenols, and cellulose) and leaf chemistries that differed between resistant and early-stage susceptible plants, most notably chlorophyll a+b and cellulose. Further, disease resistance was found to be detectable in the reflectance data, indicating that remote sensing work could expedite Ceratocystis wilt of 'ōhi'a resistance screenings.
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Affiliation(s)
- Megan M. Seeley
- Center for Global Discovery and Conservation Science, Arizona State University, Hilo, Hawaiʻi, United States of America
- School of Geographical Sciences and Urban Planning, Arizona State University, Tempe, Arizona, United States of America
| | - Roberta E. Martin
- Center for Global Discovery and Conservation Science, Arizona State University, Hilo, Hawaiʻi, United States of America
- School of Geographical Sciences and Urban Planning, Arizona State University, Tempe, Arizona, United States of America
| | - Christian Giardina
- Institute of Pacific Islands Forestry, Pacific Southwest Research Station, USDA Forest Service, Hilo, Hawaiʻi, United States of America
| | - Blaine Luiz
- Akaka Foundation for Tropical Forests, Hilo, Hawaiʻi, United States of America
| | - Kainana Francisco
- Institute of Pacific Islands Forestry, Pacific Southwest Research Station, USDA Forest Service, Hilo, Hawaiʻi, United States of America
| | - Zachary Cook
- Institute of Pacific Islands Forestry, Pacific Southwest Research Station, USDA Forest Service, Hilo, Hawaiʻi, United States of America
| | - Marc A. Hughes
- Institute of Pacific Islands Forestry, Pacific Southwest Research Station, USDA Forest Service, Hilo, Hawaiʻi, United States of America
| | - Gregory P. Asner
- Center for Global Discovery and Conservation Science, Arizona State University, Hilo, Hawaiʻi, United States of America
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Sun N, Yang L, Tian F, Zeng H, He Z, Zhao K, Wang C, Meng M, Feng C, Fang C, Lv W, Bo J, Tang Y, Gan X, Peng Z, Chen Y, He S. Sympatric or micro-allopatric speciation in a glacial lake? Genomic islands support neither. Natl Sci Rev 2022; 9:nwac291. [PMID: 36778108 PMCID: PMC9905650 DOI: 10.1093/nsr/nwac291] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2022] [Revised: 12/19/2022] [Accepted: 12/23/2022] [Indexed: 12/29/2022] Open
Abstract
Apparent cases of sympatric speciation may actually be due to micro-allopatric or micro-parapatric speciation. One way to distinguish between these models is to examine the existence and nature of genomic islands of divergence, wherein divergent DNA segments are interspersed with low-divergence segments. Such islands should be rare or absent under micro-allopatric speciation but common in cases of speciation with gene flow. Sympatric divergence of endemic fishes is known from isolated saline, crater, postglacial, and ancient lakes. Two morphologically distinct cyprinid fishes, Gymnocypris eckloni scoliostomus (GS) and G. eckloni eckloni (GE), in a small glacial lake on the Qinghai-Tibet Plateau, Lake Sunmcuo, match the biogeographic criteria of sympatric speciation. In this study, we examined genome-wide variation in 46 individuals from these two groups. The divergence time between the GS and GE lineages was estimated to be 20-60 Kya. We identified 54 large genomic islands (≥100 kb) of speciation, which accounted for 89.4% of the total length of all genomic islands. These islands harboured divergent genes related to olfactory receptors and olfaction signals that may play important roles in food selection and assortative mating in fishes. Although the genomic islands clearly indicated speciation with gene flow and rejected micro-allopatric speciation, they were too large to support the hypothesis of sympatric speciation. Theoretical and recent empirical studies suggested that continual gene flow in sympatry should give rise to many small genomic islands (as small as a few kilobases in size). Thus, the observed pattern is consistent with the extensive evidence on parapatric speciation, in which adjacent habitats facilitate divergent selection but also permit gene flow during speciation. We suggest that many, if not most, of the reported cases of sympatric speciation are likely to be micro-parapatric speciation.
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Affiliation(s)
| | | | | | | | | | | | - Cheng Wang
- State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan 430072, China,University of Chinese Academy of Sciences, Beijing 100049, China
| | - Minghui Meng
- State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan 430072, China
| | - Chenguang Feng
- State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan 430072, China,School of Ecology and Environment, Northwestern Polytechnical University, Xi’an 710129, China
| | - Chengchi Fang
- State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan 430072, China
| | - Wenqi Lv
- State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan 430072, China,University of Chinese Academy of Sciences, Beijing 100049, China
| | - Jing Bo
- Institute of Deep-Sea Science and Engineering, Chinese Academy of Sciences, Sanya 572000, China,University of Chinese Academy of Sciences, Beijing 100049, China
| | - Yongtao Tang
- Key Laboratory of Adaptation and Evolution of Plateau Biota, Northwest Institute of Plateau Biology, Chinese Academy of Sciences, Xining 810008, China
| | - Xiaoni Gan
- State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan 430072, China
| | - Zuogang Peng
- Key Laboratory of Freshwater Fish Reproduction and Development (Ministry of Education), Southwest University School of Life Sciences, Chongqing 400700, China
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6
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Doyle JJ. Cell types as species: Exploring a metaphor. FRONTIERS IN PLANT SCIENCE 2022; 13:868565. [PMID: 36072310 PMCID: PMC9444152 DOI: 10.3389/fpls.2022.868565] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/02/2022] [Accepted: 07/29/2022] [Indexed: 06/05/2023]
Abstract
The concept of "cell type," though fundamental to cell biology, is controversial. Cells have historically been classified into types based on morphology, physiology, or location. More recently, single cell transcriptomic studies have revealed fine-scale differences among cells with similar gross phenotypes. Transcriptomic snapshots of cells at various stages of differentiation, and of cells under different physiological conditions, have shown that in many cases variation is more continuous than discrete, raising questions about the relationship between cell type and cell state. Some researchers have rejected the notion of fixed types altogether. Throughout the history of discussions on cell type, cell biologists have compared the problem of defining cell type with the interminable and often contentious debate over the definition of arguably the most important concept in systematics and evolutionary biology, "species." In the last decades, systematics, like cell biology, has been transformed by the increasing availability of molecular data, and the fine-grained resolution of genetic relationships have generated new ideas about how that variation should be classified. There are numerous parallels between the two fields that make exploration of the "cell types as species" metaphor timely. These parallels begin with philosophy, with discussion of both cell types and species as being either individuals, groups, or something in between (e.g., homeostatic property clusters). In each field there are various different types of lineages that form trees or networks that can (and in some cases do) provide criteria for grouping. Developing and refining models for evolutionary divergence of species and for cell type differentiation are parallel goals of the two fields. The goal of this essay is to highlight such parallels with the hope of inspiring biologists in both fields to look for new solutions to similar problems outside of their own field.
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Liang S, Zhang X, Wei R. Ecological adaptation shaped the genetic structure of homoploid ferns against strong dispersal capacity. Mol Ecol 2022; 31:2679-2697. [DOI: 10.1111/mec.16420] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2021] [Revised: 02/26/2022] [Accepted: 02/28/2022] [Indexed: 11/26/2022]
Affiliation(s)
- Si‐Qi Liang
- State Key Laboratory of Systematic and Evolutionary Botany Institute of Botany The Chinese Academy of Sciences Beijing 100093 China
- University of Chinese Academy of Sciences College of Life Sciences Beijing 100049 China
| | - Xian‐Chun Zhang
- State Key Laboratory of Systematic and Evolutionary Botany Institute of Botany The Chinese Academy of Sciences Beijing 100093 China
| | - Ran Wei
- State Key Laboratory of Systematic and Evolutionary Botany Institute of Botany The Chinese Academy of Sciences Beijing 100093 China
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Liu Y, Yu W, Wu B, Li J. Patterns of genomic divergence in sympatric and allopatric speciation of three Mihoutao ( Actinidia) species. HORTICULTURE RESEARCH 2022; 9:uhac054. [PMID: 35591930 PMCID: PMC9113235 DOI: 10.1093/hr/uhac054] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/01/2021] [Accepted: 02/19/2022] [Indexed: 06/15/2023]
Abstract
Isolation by geographic distance is involved in the formation of potential genomic islands and the divergence of genomes, which often result in speciation. The mechanisms of sympatric and allopatric speciation associated with geographic distance remain a topic of interest to evolutionary biologists. Here, we examined genomic divergence in three Actinidia species from large-scale sympatric and allopatric regions. Genome sequence data revealed that hexaploid Actinidia deliciosa originated from Actinidia chinensis and supported the speciation-with-gene-flow model in sympatric regions. The common ancestor of Actinidia setosa and A. deliciosa migrated from the mainland to the Taiwan Island ~2.91 Mya and formed A. setosa ~0.92 Mya, and the speciation of A. setosa is consistent with the divergence-after-speciation model with selective sweeps. Geographic isolation resulted in population contraction and accelerated the process of lineage sorting and speciation due to natural selection. Genomic islands contained genes associated with organ development, local adaptation, and stress resistance, indicating selective sweeps on a specific set of traits. Our results highlight the patterns of genomic divergence in sympatric and allopatric speciation, with the mediation of geographic isolation in the formation of genomic islands during Actinidia speciation.
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Affiliation(s)
| | - Wenhao Yu
- State Key Laboratory of Environmental Criteria and Risk Assessment,
Chinese Research Academy of Environmental Sciences, 8 Dayangfang, Beijing 100012, China
| | - Baofeng Wu
- State Key Laboratory of Environmental Criteria and Risk Assessment,
Chinese Research Academy of Environmental Sciences, 8 Dayangfang, Beijing 100012, China
| | - Junsheng Li
- State Key Laboratory of Environmental Criteria and Risk Assessment,
Chinese Research Academy of Environmental Sciences, 8 Dayangfang, Beijing 100012, China
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Izuno A, Onoda Y, Amada G, Kobayashi K, Mukai M, Isagi Y, Shimizu KK. Demography and selection analysis of the incipient adaptive radiation of a Hawaiian woody species. PLoS Genet 2022; 18:e1009987. [PMID: 35061669 PMCID: PMC8782371 DOI: 10.1371/journal.pgen.1009987] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2021] [Accepted: 12/09/2021] [Indexed: 11/18/2022] Open
Abstract
Ecological divergence in a species provides a valuable opportunity to study the early stages of speciation. We focused on Metrosideros polymorpha, a unique example of the incipient radiation of woody species, to examine how an ecological divergence continues in the face of gene flow. We analyzed the whole genomes of 70 plants collected throughout the island of Hawaii, which is the youngest island with the highest altitude in the archipelago and encompasses a wide range of environments. The continuous M. polymorpha forest stands on the island of Hawaii were differentiated into three genetic clusters, each of which grows in a distinctive environment and includes substantial genetic and phenotypic diversity. The three genetic clusters showed signatures of selection in genomic regions encompassing genes relevant to environmental adaptations, including genes associated with light utilization, oxidative stress, and leaf senescence, which are likely associated with the ecological differentiation of the species. Our demographic modeling suggested that the glaberrima cluster in wet environments maintained a relatively large population size and two clusters split: polymorpha in the subalpine zone and incana in dry and hot conditions. This ecological divergence possibly began before the species colonized the island of Hawaii. Interestingly, the three clusters recovered genetic connectivity coincidentally with a recent population bottleneck, in line with the weak reproductive isolation observed in the species. This study highlights that the degree of genetic differentiation between ecologically-diverged populations can vary depending on the strength of natural selection in the very early phases of speciation. Knowledge about how genetic barriers are formed between populations in distinct environments is valuable to understand the processes of speciation and conserve biodiversity. Metrosideros polymorpha, an endemic woody species in the Hawaiian Islands, is a good system to study developing genetic barriers in a species, because it colonized the diverse environments and diversified the morphology for a relatively short period of time. We analyzed the genomes of 70 M. polymorpha plants from a broad range of environments on the island of Hawaii to infer the current and past genetic barriers among them. Currently, M. polymorpha plants growing in different environments have substantially different genomes, especially at the genomic regions with genes putatively controlling physiology to fit in distinct environment. However, in its history, they had hybridized with one another, possibly because plants formerly growing in different environments came into close contact due to the climate changes. It is suggested that genetic barriers can easily strengthen or weaken depending on environments splitting the ecology of a species before reproductive isolation becomes complete.
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Affiliation(s)
- Ayako Izuno
- Department of Forest Molecular Genetics and Biotechnology, Forestry and Forest Products Research Institute, Tsukuba, Japan
- Department of Evolutionary Biology and Environmental Studies, University of Zurich, Zurich, Switzerland
- * E-mail:
| | - Yusuke Onoda
- Graduate School of Agriculture, Kyoto University, Kyoto, Japan
| | - Gaku Amada
- Graduate School of Agriculture, Kyoto University, Kyoto, Japan
| | - Keito Kobayashi
- Graduate School of Agriculture, Kyoto University, Kyoto, Japan
| | - Mana Mukai
- Graduate School of Agriculture, Kyoto University, Kyoto, Japan
| | - Yuji Isagi
- Graduate School of Agriculture, Kyoto University, Kyoto, Japan
| | - Kentaro K. Shimizu
- Department of Evolutionary Biology and Environmental Studies, University of Zurich, Zurich, Switzerland
- Kihara Institute for Biological Research, Yokohama City University, Yokohama, Japan
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Muniz AC, Pimenta RJG, Cruz MV, Rodrigues JG, Buzatti RSDO, Heuertz M, Lemos‐Filho JP, Lovato MB. Hybrid zone of a tree in a Cerrado/Atlantic Forest ecotone as a hotspot of genetic diversity and conservation. Ecol Evol 2022; 12:e8540. [PMID: 35127043 PMCID: PMC8803295 DOI: 10.1002/ece3.8540] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2021] [Accepted: 12/17/2021] [Indexed: 01/10/2023] Open
Abstract
The Cerrado, the largest Neotropical savanna, and the Brazilian Atlantic Forest form large ecotonal areas where savanna and forest habitats occupy adjacent patches with closely related species occurring side by side, providing opportunities for hybridization. Here, we investigated the evolutionary divergence between the savanna and forest ecotypes of the widely distributed tree Plathymenia reticulata (n = 233 individuals). Genetic structure analysis of P. reticulata was congruent with the recognition of two ecotypes, whose divergence captured the largest proportion of genetic variance in the data (F CT = 0.222 and F ST = 0.307). The ecotonal areas between the Cerrado and the Atlantic Forest constitute a hybrid zone in which a diversity of hybrid classes was observed, most of them corresponding to second-generation hybrids (F2) or backcrosses. Gene flow occurred mainly toward the forest ecotype. The genetic structure was congruent with isolation by environment, and environmental correlates of divergence were identified. The observed pattern of high genetic divergence between ecotypes may reflect an incipient speciation process in P. reticulata. The low genetic diversity of the P. reticulata forest ecotype indicate that it is threatened in areas with high habitat loss on Atlantic Forest. In addition, the high divergence from the savanna ecotype suggests it should be treated as a different unit of management. The high genetic diversity found in the ecotonal hybrid zone supports the view of ecotones as important areas for the origin and conservation of biodiversity in the Neotropics.
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Affiliation(s)
- André Carneiro Muniz
- Departamento de Genética, Ecologia e EvoluçãoUniversidade Federal de Minas GeraisBelo HorizonteBrazil
| | | | - Mariana Vargas Cruz
- Departamento de Genética, Ecologia e EvoluçãoUniversidade Federal de Minas GeraisBelo HorizonteBrazil
| | | | | | | | - José P. Lemos‐Filho
- Departamento de BotânicaUniversidade Federal de Minas GeraisBelo HorizonteBrazil
| | - Maria Bernadete Lovato
- Departamento de Genética, Ecologia e EvoluçãoUniversidade Federal de Minas GeraisBelo HorizonteBrazil
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11
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Larson DA, Vargas OM, Vicentini A, Dick CW. Admixture may be extensive among hyperdominant Amazon rainforest tree species. THE NEW PHYTOLOGIST 2021; 232:2520-2534. [PMID: 34389989 PMCID: PMC9292926 DOI: 10.1111/nph.17675] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/23/2021] [Accepted: 08/04/2021] [Indexed: 05/25/2023]
Abstract
Admixture is a mechanism by which species of long-lived plants may acquire novel alleles. However, the potential role of admixture in the origin and maintenance of tropical plant diversity is unclear. We ask whether admixture occurs in an ecologically important clade of Eschweilera (Parvifolia clade, Lecythidaceae), which includes some of the most widespread and abundant tree species in Amazonian forests. Using target capture sequencing, we conducted a detailed phylogenomic investigation of 33 species in the Parvifolia clade and investigated specific hypotheses of admixture within a robust phylogenetic framework. We found strong evidence of admixture among three ecologically dominant species, E. coriacea, E. wachenheimii and E. parviflora, but a lack of evidence for admixture among other lineages. Accepted species were largely distinguishable from one another, as was geographic structure within species. We show that hybridization may play a role in the evolution of the most widespread and ecologically variable Amazonian tree species. While admixture occurs among some species of Eschweilera, it has not led to widespread erosion of most species' genetic or morphological identities. Therefore, current morphological based species circumscriptions appear to provide a useful characterization of the clade's lineage diversity.
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Affiliation(s)
- Drew A. Larson
- Department of Ecology & Evolutionary BiologyUniversity of MichiganAnn ArborMI48109USA
| | - Oscar M. Vargas
- Department of Biological SciencesHumboldt State UniversityArcataCA95521USA
| | - Alberto Vicentini
- Instituto Nacional de Pesquisas da Amazônia (INPA)ManausAMCEP 69067‐375Brazil
| | - Christopher W. Dick
- Department of Ecology & Evolutionary BiologyUniversity of MichiganAnn ArborMI48109USA
- Smithsonian Tropical Research InstitutePanama CityRepublic of Panama
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12
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Choi JY, Dai X, Alam O, Peng JZ, Rughani P, Hickey S, Harrington E, Juul S, Ayroles JF, Purugganan MD, Stacy EA. Ancestral polymorphisms shape the adaptive radiation of Metrosideros across the Hawaiian Islands. Proc Natl Acad Sci U S A 2021; 118:e2023801118. [PMID: 34497122 PMCID: PMC8449318 DOI: 10.1073/pnas.2023801118] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/17/2021] [Indexed: 01/05/2023] Open
Abstract
Some of the most spectacular adaptive radiations begin with founder populations on remote islands. How genetically limited founder populations give rise to the striking phenotypic and ecological diversity characteristic of adaptive radiations is a paradox of evolutionary biology. We conducted an evolutionary genomics analysis of genus Metrosideros, a landscape-dominant, incipient adaptive radiation of woody plants that spans a striking range of phenotypes and environments across the Hawaiian Islands. Using nanopore-sequencing, we created a chromosome-level genome assembly for Metrosideros polymorpha var. incana and analyzed whole-genome sequences of 131 individuals from 11 taxa sampled across the islands. Demographic modeling and population genomics analyses suggested that Hawaiian Metrosideros originated from a single colonization event and subsequently spread across the archipelago following the formation of new islands. The evolutionary history of Hawaiian Metrosideros shows evidence of extensive reticulation associated with significant sharing of ancestral variation between taxa and secondarily with admixture. Taking advantage of the highly contiguous genome assembly, we investigated the genomic architecture underlying the adaptive radiation and discovered that divergent selection drove the formation of differentiation outliers in paired taxa representing early stages of speciation/divergence. Analysis of the evolutionary origins of the outlier single nucleotide polymorphisms (SNPs) showed enrichment for ancestral variations under divergent selection. Our findings suggest that Hawaiian Metrosideros possesses an unexpectedly rich pool of ancestral genetic variation, and the reassortment of these variations has fueled the island adaptive radiation.
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Affiliation(s)
- Jae Young Choi
- Center for Genomics and Systems Biology, Department of Biology, New York University, New York, NY 10003;
| | - Xiaoguang Dai
- Oxford Nanopore Technologies Inc., New York, NY 10013
| | - Ornob Alam
- Center for Genomics and Systems Biology, Department of Biology, New York University, New York, NY 10003
| | - Julie Z Peng
- Department of Ecology and Evolutionary Biology, Princeton University, Princeton, NJ 08544
| | | | - Scott Hickey
- Oxford Nanopore Technologies Inc., San Francisco, CA 94501
| | | | - Sissel Juul
- Oxford Nanopore Technologies Inc., New York, NY 10013
| | - Julien F Ayroles
- Department of Ecology and Evolutionary Biology, Princeton University, Princeton, NJ 08544
| | - Michael D Purugganan
- Center for Genomics and Systems Biology, Department of Biology, New York University, New York, NY 10003
| | - Elizabeth A Stacy
- School of Life Sciences, University of Nevada, Las Vegas, Las Vegas, NV 89119;
- College of Agriculture, Forestry, and Natural Resource Management, University of Hawaii Hilo, Hilo, HI 96720
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13
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Rautsaw RM, Schramer TD, Acuña R, Arick LN, DiMeo M, Mercier KP, Schrum M, Mason AJ, Margres MJ, Strickland JL, Parkinson CL. Genomic Adaptations to Salinity Resist Gene Flow in the Evolution of Floridian Watersnakes. Mol Biol Evol 2021; 38:745-760. [PMID: 33035326 PMCID: PMC7947766 DOI: 10.1093/molbev/msaa266] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
The migration-selection balance often governs the evolution of lineages, and speciation with gene flow is now considered common across the tree of life. Ecological speciation is a process that can facilitate divergence despite gene flow due to strong selective pressures caused by ecological differences; however, the exact traits under selection are often unknown. The transition from freshwater to saltwater habitats provides strong selection targeting traits with osmoregulatory function. Several lineages of North American watersnakes (Nerodia spp.) are known to occur in saltwater habitat and represent a useful system for studying speciation by providing an opportunity to investigate gene flow and evaluate how species boundaries are maintained or degraded. We use double digest restriction-site associated DNA sequencing to characterize the migration-selection balance and test for evidence of ecological divergence within the Nerodia fasciata-clarkii complex in Florida. We find evidence of high intraspecific gene flow with a pattern of isolation-by-distance underlying subspecific lineages. However, we identify genetic structure indicative of reduced gene flow between inland and coastal lineages suggesting divergence due to isolation-by-environment. This pattern is consistent with observed environmental differences where the amount of admixture decreases with increased salinity. Furthermore, we identify significantly enriched terms related to osmoregulatory function among a set of candidate loci, including several genes that have been previously implicated in adaptation to salinity stress. Collectively, our results demonstrate that ecological differences, likely driven by salinity, cause strong divergent selection which promotes divergence in the N. fasciata-clarkii complex despite significant gene flow.
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Affiliation(s)
- Rhett M Rautsaw
- Department of Biological Sciences, Clemson University, Clemson, SC.,Department of Biology, University of Central Florida, Orlando, FL
| | | | - Rachel Acuña
- Department of Biology, University of Central Florida, Orlando, FL
| | - Lindsay N Arick
- Department of Biology, University of Central Florida, Orlando, FL
| | - Mark DiMeo
- Department of Biological Sciences, Clemson University, Clemson, SC.,Department of Biology, University of Central Florida, Orlando, FL
| | - Kathryn P Mercier
- Department of Biological Sciences, Clemson University, Clemson, SC.,Department of Biology, University of Central Florida, Orlando, FL.,Department of Biology, City College of New York, New York, NY.,PhD Program in Biology, The Graduate Center of the City University of New York, New York, NY
| | - Michael Schrum
- Department of Biology, University of Central Florida, Orlando, FL
| | - Andrew J Mason
- Department of Biological Sciences, Clemson University, Clemson, SC.,Department of Biology, University of Central Florida, Orlando, FL
| | - Mark J Margres
- Department of Biological Sciences, Clemson University, Clemson, SC.,Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA.,Department of Integrative Biology, University of South Florida, Tampa, FL
| | - Jason L Strickland
- Department of Biological Sciences, Clemson University, Clemson, SC.,Department of Biology, University of Central Florida, Orlando, FL.,Department of Biology, University of South Alabama, Mobile, AL
| | - Christopher L Parkinson
- Department of Biological Sciences, Clemson University, Clemson, SC.,Department of Biology, University of Central Florida, Orlando, FL.,Department of Forestry and Environmental Conservation, Clemson University, Clemson, SC
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14
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O'Connell KA, Prates I, Scheinberg LA, Mulder KP, Bell RC. Speciation and secondary contact in a fossorial island endemic, the São Tomé caecilian. Mol Ecol 2021; 30:2859-2871. [PMID: 33969550 DOI: 10.1111/mec.15928] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2020] [Revised: 04/07/2021] [Accepted: 04/14/2021] [Indexed: 02/06/2023]
Abstract
A period of isolation in allopatry typically precedes local adaptation and subsequent divergence among lineages. Alternatively, locally adapted phenotypes may arise and persist in the face of gene flow, resulting in strong correlations between ecologically-relevant phenotypic variation and corresponding environmental gradients. Quantifying genetic, ecological, and phenotypic divergence in such lineages can provide insights into the abiotic and biotic mechanisms that structure populations and drive the accumulation of phenotypic and taxonomic diversity. Low-vagility organisms whose distributions span ephemeral geographic barriers present the ideal evolutionary context within which to address these questions. Here, we combine genetic (mtDNA and genome-wide SNPs) and phenotypic data to investigate the divergence history of caecilians (Amphibia: Gymnophiona) endemic to the oceanic island of São Tomé in the Gulf of Guinea archipelago. Consistent with a previous mtDNA study, we find two phenotypically and genetically distinct lineages that occur along a north-to-south axis with extensive admixture in the centre of the island. Demographic modelling supports divergence in allopatry (~300 kya) followed by secondary contact (~95 kya). Consequently, in contrast to a morphological study that interpreted latitudinal phenotypic variation in these caecilians as a cline within a single widespread species, our analyses suggest a history of allopatric lineage divergence and subsequent hybridization that may have blurred species boundaries. We propose that late Pleistocene volcanic activity favoured allopatric divergence between these lineages with local adaptation to climate maintaining a stable hybrid zone in the centre of São Tomé Island. Our study joins a growing number of systems demonstrating lineage divergence on volcanic islands with stark environmental transitions across small geographic distances.
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Affiliation(s)
- Kyle A O'Connell
- Department of Vertebrate Zoology, National Museum of Natural History, Smithsonian Institution, Washington, DC, USA.,Global Genome Initiative, National Museum of Natural History, Smithsonian Institution, Washington, DC, USA.,Department of Biological Sciences, George Washington University, Washington, DC, USA
| | - Ivan Prates
- Department of Vertebrate Zoology, National Museum of Natural History, Smithsonian Institution, Washington, DC, USA.,Department of Ecology and Evolutionary Biology and Museum of Zoology, University of Michigan, Ann Arbor, MI, USA
| | - Lauren A Scheinberg
- Department of Herpetology, California Academy of Sciences, San Francisco, CA, USA
| | - Kevin P Mulder
- Department of Vertebrate Zoology, National Museum of Natural History, Smithsonian Institution, Washington, DC, USA.,CIBIO/InBIO, Centro de Investigação em Biodiversidade e Recursos Genéticos, Universidade do Porto, Vairão, Portugal.,Center for Conservation Genomics, Smithsonian Conservation Biology Institute, National Zoological Park, Washington, DC, USA
| | - Rayna C Bell
- Department of Vertebrate Zoology, National Museum of Natural History, Smithsonian Institution, Washington, DC, USA.,Department of Herpetology, California Academy of Sciences, San Francisco, CA, USA
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15
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Chen Y, Zhao L, Teng H, Shi C, Liu Q, Zhang J, Zhang Y. Population genomics reveal rapid genetic differentiation in a recently invasive population of Rattus norvegicus. Front Zool 2021; 18:6. [PMID: 33499890 PMCID: PMC7836188 DOI: 10.1186/s12983-021-00387-z] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2020] [Accepted: 01/17/2021] [Indexed: 12/19/2022] Open
Abstract
Background Invasive species bring a serious effect on local biodiversity, ecosystems, and even human health and safety. Although the genetic signatures of historical range expansions have been explored in an array of species, the genetic consequences of contemporary range expansions have received little attention, especially in mammal species. In this study, we used whole-genome sequencing to explore the rapid genetic change and introduction history of a newly invasive brown rat (Rattus norvegicus) population which invaded Xinjiang Province, China in the late 1970s. Results Bayesian clustering analysis, principal components analysis, and phylogenetic analysis all showed clear genetic differentiation between newly introduced and native rat populations. Reduced genetic diversity and high linkage disequilibrium suggested a severe population bottleneck in this colonization event. Results of TreeMix analyses revealed that the introduced rats were derived from an adjacent population in geographic region (Northwest China). Demographic analysis indicated that a severe bottleneck occurred in XJ population after the split off from the source population, and the divergence of XJ population might have started before the invasion of XJ. Moreover, we detected 42 protein-coding genes with allele frequency shifts throughout the genome for XJ rats and they were mainly associated with lipid metabolism and immunity, which could be seen as a prelude to future selection analyses in the novel environment of XJ. Conclusions This study presents the first genomic evidence on genetic differentiation which developed rapidly, and deepens the understanding of invasion history and evolutionary processes of this newly introduced rat population. This would add to our understanding of how invasive species become established and aid strategies aimed at the management of this notorious pest that have spread around the world with humans. Supplementary Information The online version contains supplementary material available at 10.1186/s12983-021-00387-z.
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Affiliation(s)
- Yi Chen
- The State Key Laboratory of Integrated Management of Pest Insects and Rodents, Institute of Zoology, Chinese Academy of Sciences, Beijing, China.,CAS Center for Excellence in Biotic Interactions, University of Chinese Academy of Sciences, Beijing, China
| | - Lei Zhao
- The State Key Laboratory of Integrated Management of Pest Insects and Rodents, Institute of Zoology, Chinese Academy of Sciences, Beijing, China.,CAS Center for Excellence in Biotic Interactions, University of Chinese Academy of Sciences, Beijing, China
| | - Huajing Teng
- Beijing Institutes of Life Science, Chinese Academy of Sciences, Beijing, China
| | - Chengmin Shi
- CAS Key Laboratory of Genomic and Precision Medicine, Beijing Institute of Genomics, Chinese Academy of Sciences, Beijing, China
| | - Quansheng Liu
- Guangdong Key Laboratory of Animal Conservation and Resource Utilization, Guangdong Public Laboratory of Wild Animal Conservation and Utilization, Institute of Zoology, Guangdong Academy of Sciences, Guangzhou, China
| | - Jianxu Zhang
- The State Key Laboratory of Integrated Management of Pest Insects and Rodents, Institute of Zoology, Chinese Academy of Sciences, Beijing, China. .,CAS Center for Excellence in Biotic Interactions, University of Chinese Academy of Sciences, Beijing, China.
| | - Yaohua Zhang
- The State Key Laboratory of Integrated Management of Pest Insects and Rodents, Institute of Zoology, Chinese Academy of Sciences, Beijing, China. .,CAS Center for Excellence in Biotic Interactions, University of Chinese Academy of Sciences, Beijing, China.
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