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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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Magain N, Miadlikowska J, Goffinet B, Goward T, Pardo-De la Hoz C, Jüriado I, Simon A, Mercado-Díaz J, Barlow T, Moncada B, Lücking R, Spielmann A, Canez L, Wang L, Nelson P, Wheeler T, Lutzoni F, Sérusiaux E. High species richness in the lichen genus Peltigera ( Ascomycota, Lecanoromycetes): 34 species in the dolichorhizoid and scabrosoid clades of section Polydactylon, including 24 new to science. PERSOONIA 2023; 51:1-88. [PMID: 38665978 PMCID: PMC11041898 DOI: 10.3767/persoonia.2023.51.01] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/03/2021] [Accepted: 10/10/2022] [Indexed: 04/28/2024]
Abstract
Applying molecular methods to fungi establishing lichenized associations with green algae or cyanobacteria has repeatedly revealed the existence of numerous phylogenetic taxa overlooked by classical taxonomic approaches. Here, we report taxonomical conclusions based on multiple species delimitation and validation analyses performed on an eight-locus dataset that includes world-wide representatives of the dolichorhizoid and scabrosoid clades in section Polydactylon of the genus Peltigera. Following the recommendations resulting from a consensus species delimitation approach and additional species validation analysis (BPP) performed in this study, we present a total of 25 species in the dolichorhizoid clade and nine in the scabrosoid clade, including respectively 18 and six species that are new to science and formally described. Additionally, one combination and three varieties (including two new to science) are proposed in the dolichorhizoid clade. The following 24 new species are described: P. appalachiensis, P. asiatica, P. borealis, P. borinquensis, P. chabanenkoae, P. clathrata, P. elixii, P. esslingeri, P. flabellae, P. gallowayi, P. hawaiiensis, P. holtanhartwigii, P. itatiaiae, P. hokkaidoensis, P. kukwae, P. massonii, P. mikado, P. nigriventris, P. orientalis, P. rangiferina, P. sipmanii, P. stanleyensis, P. vitikainenii and P. willdenowii; the following new varieties are introduced: P. kukwae var. phyllidiata and P. truculenta var. austroscabrosa; and the following new combination is introduced: P. hymenina var. dissecta. Each species from the dolichorhizoid and scabrosoid clades is morphologically and chemically described, illustrated, and characterised with ITS sequences. Identification keys are provided for the main biogeographic regions where species from the two clades occur. Morphological and chemical characters that are commonly used for species identification in the genus Peltigera cannot be applied to unambiguously recognise most molecularly circumscribed species, due to high variation of thalli formed by individuals within a fungal species, including the presence of distinct morphs in some cases, or low interspecific variation in others. The four commonly recognised morphospecies: P. dolichorhiza, P. neopolydactyla, P. pulverulenta and P. scabrosa in the dolichorhizoid and scabrosoid clades represent species complexes spread across multiple and often phylogenetically distantly related lineages. Geographic origin of specimens is often helpful for species recognition; however, ITS sequences are frequently required for a reliable identification. Citation: Magain N, Miadlikowska J, Goffinet B, et al. 2023. High species richness in the lichen genus Peltigera (Ascomycota, Lecanoromycetes): 34 species in the dolichorhizoid and scabrosoid clades of section Polydactylon, including 24 new to science. Persoonia 51: 1-88. doi: 10.3767/persoonia.2023.51.01.
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Affiliation(s)
- N. Magain
- Evolution and Conservation Biology, InBioS Research Center, University of Liège, Sart Tilman B22, Quartier vallée 1, Chemin de la vallée 4, B-4000 Liège, Belgium
- Department of Biology, Duke University, Box 90338, Durham, North Carolina, 27708 USA
| | - J. Miadlikowska
- Department of Biology, Duke University, Box 90338, Durham, North Carolina, 27708 USA
| | - B. Goffinet
- Ecology and Evolutionary Biology, Unit 3043, University of Connecticut, 75 North Eagleville road, Storrs CT, 06269-3043 USA
| | - T. Goward
- Beaty Biodiversity Museum, University of British Columbia, Vancouver, British Columbia, V6T 1Z4, Canada
| | - C.J. Pardo-De la Hoz
- Department of Biology, Duke University, Box 90338, Durham, North Carolina, 27708 USA
| | - I. Jüriado
- Institute of Ecology and Earth Sciences, University of Tartu, J. Liivi 2, Tartu 50409, Estonia; Institute of Agricultural & Environmental Sciences, Estonian University of Life Sciences, Fr. R. Kreutzwaldi 5, Tartu 51006, Estonia
| | - A. Simon
- Evolution and Conservation Biology, InBioS Research Center, University of Liège, Sart Tilman B22, Quartier vallée 1, Chemin de la vallée 4, B-4000 Liège, Belgium
- Ecology and Evolutionary Biology, Unit 3043, University of Connecticut, 75 North Eagleville road, Storrs CT, 06269-3043 USA
| | - J.A. Mercado-Díaz
- Science & Education, The Field Museum, 1400 S. Lake Shore Drive, Chicago, Illinois, 60605 USA
| | - T. Barlow
- Department of Biology, Duke University, Box 90338, Durham, North Carolina, 27708 USA
| | - B. Moncada
- Licenciatura en Biología, Universidad Distrital Francisco José de Caldas, Cra. 4 No. 26B-54, Torre de Laboratorios, Herbario, Bogotá, Colombia; current address: Botanischer Garten, Freie Universität Berlin, Königin-Luise-Straße 6–8, 14195 Berlin, Germany
| | - R. Lücking
- Botanischer Garten, Freie Universität Berlin, Königin-Luise-Straße 6–8, 14195 Berlin, Germany
| | - A. Spielmann
- Laboratòrio de Botanica / Liquenologia, Instituto de Biociencias, Universidade Federal de Mato Grosso do Sul, Campo Grande – MS, Brazil
| | - L. Canez
- Laboratòrio de Botanica / Liquenologia, Instituto de Biociencias, Universidade Federal de Mato Grosso do Sul, Campo Grande – MS, Brazil
| | - L.S. Wang
- Key Laboratory for Plant Diversity and Biogeography of East Asia, Kunming Institute of Botany, CAS, Kunming 650201, China
| | - P. Nelson
- Natural and Behavioral Sciences Division, University of Maine – Fort Kent, Fort Kent, ME, USA
| | - T. Wheeler
- Division of Biological Sciences, University of Montana, Missoula, MT, USA
| | - F. Lutzoni
- Department of Biology, Duke University, Box 90338, Durham, North Carolina, 27708 USA
| | - E. Sérusiaux
- Evolution and Conservation Biology, InBioS Research Center, University of Liège, Sart Tilman B22, Quartier vallée 1, Chemin de la vallée 4, B-4000 Liège, Belgium
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Seeley MM, Stacy EA, Martin RE, Asner GP. Foliar functional and genetic variation in a keystone Hawaiian tree species estimated through spectroscopy. Oecologia 2023; 202:15-28. [PMID: 37171625 DOI: 10.1007/s00442-023-05374-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2022] [Accepted: 04/11/2023] [Indexed: 05/13/2023]
Abstract
Imaging spectroscopy has the potential to map closely related plant taxa at landscape scales. Although spectral investigations at the leaf and canopy levels have revealed relationships between phylogeny and reflectance, understanding how spectra differ across, and are inherited from, genotypes of a single species has received less attention. We used a common-garden population of four varieties of the keystone canopy tree, Metrosideros polymorpha, from Hawaii Island and four F1-hybrid genotypes derived from controlled crosses to determine if reflectance spectra discriminate sympatric, conspecific varieties of this species and their hybrids. With a single exception, pairwise comparisons of leaf reflectance patterns successfully distinguished varieties of M. polymorpha on Hawaii Island as well as populations of the same variety from different islands. Further, spectral variability within a single variety from Hawaii Island and the older island of Oahu was greater than that observed among the four varieties on Hawaii Island. F1 hybrids most frequently displayed leaf spectral patterns intermediate to those of their parent taxa. Spectral reflectance patterns distinguished each of two of the hybrid genotypes from one of their parent varieties, indicating that classifying hybrids may be possible, particularly if sample sizes are increased. This work quantifies a baseline in spectral variability for an endemic Hawaiian tree species and advances the use of imaging spectroscopy in biodiversity studies at the genetic level.
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Affiliation(s)
- M M Seeley
- Center for Global Discovery and Conservation Science, Arizona State University, Hilo, HI, 96720, USA.
- School of Geographical Sciences and Urban Planning, Arizona State University, Tempe, AZ, 85281, USA.
| | - E A Stacy
- School of Life Sciences, University of Nevada, Las Vegas, NV, 89154, USA
| | - R E Martin
- Center for Global Discovery and Conservation Science, Arizona State University, Hilo, HI, 96720, USA
- School of Geographical Sciences and Urban Planning, Arizona State University, Tempe, AZ, 85281, USA
| | - G P Asner
- Center for Global Discovery and Conservation Science, Arizona State University, Hilo, HI, 96720, USA
- School of Geographical Sciences and Urban Planning, Arizona State University, Tempe, AZ, 85281, USA
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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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5
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Sur GL, Zahn G, Stacy EA. Examination of host-taxon, environment, and distance effects on leaf fungal endophytes in the dominant woody genus, Metrosideros, on Oʻahu. FUNGAL ECOL 2021. [DOI: 10.1016/j.funeco.2021.101093] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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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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7
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Ottenlips MV, Mansfield DH, Buerki S, Feist MAE, Downie SR, Dodsworth S, Forest F, Plunkett GM, Smith JF. Resolving species boundaries in a recent radiation with the Angiosperms353 probe set: the Lomatium packardiae/L. anomalum clade of the L. triternatum (Apiaceae) complex. AMERICAN JOURNAL OF BOTANY 2021; 108:1217-1233. [PMID: 34105148 PMCID: PMC8362113 DOI: 10.1002/ajb2.1676] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/01/2020] [Accepted: 02/26/2021] [Indexed: 05/29/2023]
Abstract
PREMISE Speciation not associated with morphological shifts is challenging to detect unless molecular data are employed. Using Sanger-sequencing approaches, the Lomatium packardiae/L. anomalum subcomplex within the larger Lomatium triternatum complex could not be resolved. Therefore, we attempt to resolve these boundaries here. METHODS The Angiosperms353 probe set was employed to resolve the ambiguity within Lomatium triternatum species complex using 48 accessions assigned to L. packardiae, L. anomalum, or L. triternatum. In addition to exon data, 54 nuclear introns were extracted and were complete for all samples. Three approaches were used to estimate evolutionary relationships and define species boundaries: STACEY, a Bayesian coalescent-based species tree analysis that takes incomplete lineage sorting into account; ASTRAL-III, another coalescent-based species tree analysis; and a concatenated approach using MrBayes. Climatic factors, morphological characters, and soil variables were measured and analyzed to provide additional support for recovered groups. RESULTS The STACEY analysis recovered three major clades and seven subclades, all of which are geographically structured, and some correspond to previously named taxa. No other analysis had full agreement between recovered clades and other parameters. Climatic niche and leaflet width and length provide some predictive ability for the major clades. CONCLUSIONS The results suggest that these groups are in the process of incipient speciation and incomplete lineage sorting has been a major barrier to resolving boundaries within this lineage previously. These results are hypothesized through sequencing of multiple loci and analyzing data using coalescent-based processes.
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Affiliation(s)
| | | | - Sven Buerki
- Department of Biological SciencesBoise State UniversityBoiseID83725USA
| | | | - Stephen R. Downie
- Department of Plant BiologyUniversity of Illinois at Urbana‐ChampaignUrbanaIL61801USA
| | - Steven Dodsworth
- Royal Botanic Gardens, KewRichmondSurreyTW9 3AEUK
- School of Life SciencesUniversity of BedfordshireLutonLU1 3JUUK
| | - Félix Forest
- Royal Botanic Gardens, KewRichmondSurreyTW9 3AEUK
| | - Gregory M. Plunkett
- Cullman Program for Molecular SystematicsNew York Botanical Garden2900 Southern BoulevardBronxNY10458USA
| | - James F. Smith
- Department of Biological SciencesBoise State UniversityBoiseID83725USA
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Stacy EA, Sakishima T, Tharp H, Snow N. Isolation of Metrosideros ('Ohi'a) Taxa on O'ahu Increases with Elevation and Extreme Environments. J Hered 2021; 111:103-118. [PMID: 31844884 DOI: 10.1093/jhered/esz069] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2019] [Accepted: 11/08/2019] [Indexed: 01/04/2023] Open
Abstract
Species radiations should be facilitated by short generation times and limited dispersal among discontinuous populations. Hawaii's hyper-diverse, landscape-dominant tree, Metrosideros, is unique among the islands' radiations for its massive populations that occur continuously over space and time within islands, its exceptional capacity for gene flow by both pollen and seed, and its extended life span (ca. >650 years). Metrosideros shows the greatest phenotypic and microsatellite DNA diversity on O'ahu, where taxa occur in tight sympatry or parapatry in mesic and montane wet forest on 2 volcanoes. We document the nonrandom distributions of 12 taxa (including unnamed morphotypes) along elevation gradients, measure phenotypes of ~6-year-old common-garden plants of 8 taxa to verify heritability of phenotypes, and examine genotypes of 476 wild adults at 9 microsatellite loci to compare the strengths of isolation across taxa, volcanoes, and distance. All 8 taxa retained their diagnostic phenotypes in the common garden. Populations were isolated by taxon to a range of degrees (pairwise FST between taxa: 0.004-0.267), and there was no pattern of isolation by distance or by elevation; however, significant isolation between volcanoes was observed within monotypic species, suggesting limited gene flow between volcanoes. Among the infraspecific taxa of Metrosideros polymorpha, genetic diversity and isolation significantly decreased and increased, respectively, with elevation. Overall, 5 of the 6 most isolated taxa were associated with highest elevations or otherwise extreme environments. These findings suggest a principal role for selection in the origin and maintenance of the exceptional diversity that occurs within continuous Metrosideros stands on O'ahu.
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Affiliation(s)
- Elizabeth A Stacy
- Department of Biology, University of Hawai'i Hilo, Hilo, HI.,Tropical Conservation Biology and Environmental Science Graduate Program, University of Hawai'i Hilo, Hilo, HI
| | - Tomoko Sakishima
- Department of Biology, University of Hawai'i Hilo, Hilo, HI.,Tropical Conservation Biology and Environmental Science Graduate Program, University of Hawai'i Hilo, Hilo, HI
| | - Heaven Tharp
- Department of Biology, University of Hawai'i Hilo, Hilo, HI
| | - Neil Snow
- Department of Biology, Pittsburg State University, Pittsburg, KS
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Choi JY, Purugganan M, Stacy EA. Divergent Selection and Primary Gene Flow Shape Incipient Speciation of a Riparian Tree on Hawaii Island. Mol Biol Evol 2020; 37:695-710. [PMID: 31693149 PMCID: PMC7038655 DOI: 10.1093/molbev/msz259] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
A long-standing goal of evolutionary biology is to understand the mechanisms underlying the formation of species. Of particular interest is whether or not speciation can occur in the presence of gene flow and without a period of physical isolation. Here, we investigated this process within Hawaiian Metrosideros, a hypervariable and highly dispersible woody species complex that dominates the Hawaiian Islands in continuous stands. Specifically, we investigated the origin of Metrosideros polymorpha var. newellii (newellii), a riparian ecotype endemic to Hawaii Island that is purportedly derived from the archipelago-wide M. polymorpha var. glaberrima (glaberrima). Disruptive selection across a sharp forest-riparian ecotone contributes to the isolation of these varieties and is a likely driver of newellii's origin. We examined genome-wide variation of 42 trees from Hawaii Island and older islands. Results revealed a split between glaberrima and newellii within the past 0.3-1.2 My. Admixture was extensive between lineages within Hawaii Island and between islands, but introgression from populations on older islands (i.e., secondary gene flow) did not appear to contribute to the emergence of newellii. In contrast, recurrent gene flow (i.e., primary gene flow) between glaberrima and newellii contributed to the formation of genomic islands of elevated absolute and relative divergence. These regions were enriched for genes with regulatory functions as well as for signals of positive selection, especially in newellii, consistent with divergent selection underlying their formation. In sum, our results support riparian newellii as a rare case of incipient ecological speciation with primary gene flow in trees.
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Affiliation(s)
- Jae Young Choi
- Center for Genomics and Systems Biology, Department of Biology, New York University, New York, NY
| | - Michael Purugganan
- Center for Genomics and Systems Biology, Department of Biology, New York University, New York, NY.,Center for Genomics and Systems Biology, NYU Abu Dhabi Research Institute, New York University Abu Dhabi, Abu Dhabi, United Arab Emirates
| | - Elizabeth A Stacy
- School of Life Sciences, University of Nevada, Las Vegas, Las Vegas, NV
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Amada G, Kobayashi K, Izuno A, Mukai M, Ostertag R, Kitayama K, Onoda Y. Leaf trichomes in Metrosideros polymorpha can contribute to avoiding extra water stress by impeding gall formation. ANNALS OF BOTANY 2020; 125:533-542. [PMID: 31784739 PMCID: PMC7061171 DOI: 10.1093/aob/mcz196] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/01/2019] [Accepted: 11/28/2019] [Indexed: 05/30/2023]
Abstract
BACKGROUND AND AIMS Plants inhabiting arid environments tend to have leaf trichomes, but their adaptive significance remains unclear. Leaf trichomes are known to play a role in plant defence against herbivores, including gall makers. Because gall formation can increase water loss partly through increased surface area, we tested the novel hypothesis that leaf trichomes could contribute to avoiding extra water stress by impeding gall formation, which would have adaptive advantages in arid environments. METHODS We focused on Metrosideros polymorpha, an endemic tree species in the Hawaiian Islands, whose leaves often suffer from galls formed by specialist insects, Hawaiian psyllids (Pariaconus spp.). There is large variation in the amount of leaf trichomes (0-40 % of leaf mass) in M. polymorpha. Three gall types are found on the island of Hawaii: the largest is the 'cone' type, followed by 'flat' and 'pit' types. We conducted laboratory experiments to quantify the extent to which gall formation is associated with leaf water relations. We also conducted a field census of 1779 individuals from 48 populations across the entire range of habitats of M. polymorpha on the island of Hawaii to evaluate associations between gall formation (presence and abundance) and the amount of leaf trichomes. KEY RESULTS Our laboratory experiment showed that leaf minimum conductance was significantly higher in leaves with a greater number of cone- or flat-type galls but not pit-type galls. Our field census suggested that the amount of trichomes was negatively associated with probabilities of the presence of cone- or flat-type galls but not pit-type galls, irrespective of environmental factors. CONCLUSION Our results suggest that leaf trichomes in M. polymorpha can contribute to the avoidance of extra water stress through interactions with some gall-making species, and potentially increase the fitness of plants under arid conditions.
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Affiliation(s)
- Gaku Amada
- Graduate School of Agriculture, Kyoto University, Kitashirakawa Oiwake-cho, Sakyo-ku, Kyoto, Japan
| | - Keito Kobayashi
- Graduate School of Agriculture, Kyoto University, Kitashirakawa Oiwake-cho, Sakyo-ku, Kyoto, Japan
| | - Ayako Izuno
- Department of Forest Molecular Genetics and Biotechnology, Forestry and Forest Products Research Institute, 1 Matsunosato, Tsukuba, Ibaraki, Japan
| | - Mana Mukai
- Graduate School of Agriculture, Kyoto University, Kitashirakawa Oiwake-cho, Sakyo-ku, Kyoto, Japan
| | - Rebecca Ostertag
- Department of Biology, University of Hawai‘i at Hilo, 200 W. Kāwili St. Hilo, HI, USA
| | - Kanehiro Kitayama
- Graduate School of Agriculture, Kyoto University, Kitashirakawa Oiwake-cho, Sakyo-ku, Kyoto, Japan
| | - Yusuke Onoda
- Graduate School of Agriculture, Kyoto University, Kitashirakawa Oiwake-cho, Sakyo-ku, Kyoto, Japan
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11
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Gillespie RG, Bennett GM, De Meester L, Feder JL, Fleischer RC, Harmon LJ, Hendry AP, Knope ML, Mallet J, Martin C, Parent CE, Patton AH, Pfennig KS, Rubinoff D, Schluter D, Seehausen O, Shaw KL, Stacy E, Stervander M, Stroud JT, Wagner C, Wogan GOU. Comparing Adaptive Radiations Across Space, Time, and Taxa. J Hered 2020; 111:1-20. [PMID: 31958131 PMCID: PMC7931853 DOI: 10.1093/jhered/esz064] [Citation(s) in RCA: 95] [Impact Index Per Article: 23.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2019] [Accepted: 10/28/2019] [Indexed: 01/02/2023] Open
Abstract
Adaptive radiation plays a fundamental role in our understanding of the evolutionary process. However, the concept has provoked strong and differing opinions concerning its definition and nature among researchers studying a wide diversity of systems. Here, we take a broad view of what constitutes an adaptive radiation, and seek to find commonalities among disparate examples, ranging from plants to invertebrate and vertebrate animals, and remote islands to lakes and continents, to better understand processes shared across adaptive radiations. We surveyed many groups to evaluate factors considered important in a large variety of species radiations. In each of these studies, ecological opportunity of some form is identified as a prerequisite for adaptive radiation. However, evolvability, which can be enhanced by hybridization between distantly related species, may play a role in seeding entire radiations. Within radiations, the processes that lead to speciation depend largely on (1) whether the primary drivers of ecological shifts are (a) external to the membership of the radiation itself (mostly divergent or disruptive ecological selection) or (b) due to competition within the radiation membership (interactions among members) subsequent to reproductive isolation in similar environments, and (2) the extent and timing of admixture. These differences translate into different patterns of species accumulation and subsequent patterns of diversity across an adaptive radiation. Adaptive radiations occur in an extraordinary diversity of different ways, and continue to provide rich data for a better understanding of the diversification of life.
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Affiliation(s)
- Rosemary G Gillespie
- University of California, Berkeley, Essig Museum of Entomology & Department of Environmental Science, Policy, and Management, Berkeley, CA
| | - Gordon M Bennett
- University of California Merced, Life and Environmental Sciences Unit, Merced, CA
| | - Luc De Meester
- University of Leuven, Laboratory of Aquatic Ecology, Evolution and Conservation, Leuven, Belguim
| | - Jeffrey L Feder
- University of Notre Dame, Dept. of Biological Sciences, Notre Dame, IN
| | - Robert C Fleischer
- Center for Conservation Genomics, Smithsonian Conservation Biology Institute, National Zoological Park, Washington, DC
| | - Luke J Harmon
- University of Idaho, Dept. of Biological Sciences, Moscow, ID
| | | | | | | | - Christopher Martin
- University of California Berkeley, Integrative Biology and Museum of Vertebrate Zoology, Berkeley, CA
| | | | - Austin H Patton
- Washington State University, School of Biological Sciences, Pullman, WA
| | - Karin S Pfennig
- University of North Carolina at Chapel Hill, Department of Biology, Chapel Hill, NC
| | - Daniel Rubinoff
- University of Hawaiʻi at Manoa, Department of Plant and Environmental Protection Sciences, Honolulu, HI
| | | | - Ole Seehausen
- Institute of Ecology & Evolution, University of Bern, Bern, BE, Switzerland
- Center for Ecology, Evolution & Biogeochemistry, Eawag, Kastanienbaum, LU, Switzerland
| | - Kerry L Shaw
- Cornell University, Neurobiology and Behavior, Tower Road,, Ithaca, NY
| | - Elizabeth Stacy
- University of Nevada Las Vegas, School of Life Sciences, Las Vegas, NV
| | - Martin Stervander
- University of Oregon, Institute of Ecology and Evolution, Eugene, OR
| | - James T Stroud
- Washington University in Saint Louis, Biology, Saint Louis, MO
| | | | - Guinevere O U Wogan
- University of California Berkeley, Environmental Science Policy, and Management, Berkeley, CA
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12
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Updated Genome Assembly and Annotation for Metrosideros polymorpha, an Emerging Model Tree Species of Ecological Divergence. G3-GENES GENOMES GENETICS 2019; 9:3513-3520. [PMID: 31540972 PMCID: PMC6829130 DOI: 10.1534/g3.119.400643] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Accurate feature annotation as well as assembly contiguity are important requisites of a modern genome assembly. They allow large-scale comparison of genomes across and within species and identification of polymorphisms, leading evolutionary and functional studies. We report an updated genome resource for Metrosideros polymorpha, the most dominant tree species in the Hawaiian native forests and a unique example of rapid and remarkable ecological diversification of woody species. Ninety-one percent of the bases in the sequence assembly (304 Mb) were organized into 11 pseudo-molecules, which would represent the chromosome structure of the species assuming the synteny to a close relative Eucalyptus. Our complementary approach using manual annotation and automated pipelines identified 11.30% of the assembly to be transposable elements, in contrast to 4.1% in previous automated annotation. By increasing transcript and protein sequence data, we predicted 27,620 gene models with high concordance from the supplied evidence. We believe that this assembly, improved for contiguity, and annotation will be valuable for future evolutionary studies of M. polymorpha and closely related species, facilitating the isolation of specific genes and the investigation of genome-wide polymorphisms associated with ecological divergence.
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13
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MARTIN CHRISTOPHERH, RICHARDS EMILIEJ. The paradox behind the pattern of rapid adaptive radiation: how can the speciation process sustain itself through an early burst? ANNUAL REVIEW OF ECOLOGY, EVOLUTION, AND SYSTEMATICS 2019; 50:569-593. [PMID: 36237480 PMCID: PMC9555815 DOI: 10.1146/annurev-ecolsys-110617-062443] [Citation(s) in RCA: 41] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/27/2023]
Abstract
Rapid adaptive radiation poses a distinct question apart from speciation and adaptation: what happens after one speciation event? That is, how are some lineages able to continue speciating through a rapid burst? This question connects global macroevolutionary patterns to microevolutionary processes. Here we review major features of rapid radiations in nature and their mismatch with theoretical models and what is currently known about speciation mechanisms. Rapid radiations occur on three major diversification axes - species richness, phenotypic disparity, and ecological diversity - with exceptional outliers on each axis. The paradox is that the hallmark early stage of adaptive radiation, a rapid burst of speciation and niche diversification, is contradicted by most existing speciation models which instead predict continuously decelerating speciation rates and niche subdivision through time. Furthermore, while speciation mechanisms such as magic traits, phenotype matching, and physical linkage of co-adapted alleles promote speciation, it is often not discussed how these mechanisms could promote multiple speciation events in rapid succession. Additional mechanisms beyond ecological opportunity are needed to understand how rapid radiations occur. We review the evidence for five emerging theories: 1) the 'transporter' hypothesis: introgression and the ancient origins of adaptive alleles, 2) the 'signal complexity' hypothesis: the dimensionality of sexual traits, 3) the connectivity of fitness landscapes, 4) 'diversity begets diversity', and 5) flexible stem/'plasticity first'. We propose new questions and predictions to guide future work on the mechanisms underlying the rare origins of rapid radiation.
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Affiliation(s)
- CHRISTOPHER H. MARTIN
- Department of Biology, University of North Carolina at Chapel Hill, NC, USA
- Integrative Biology and Museum of Vertebrate Zoology, University of California, Berkeley, CA, USA
| | - EMILIE J. RICHARDS
- Department of Biology, University of North Carolina at Chapel Hill, NC, USA
- Integrative Biology and Museum of Vertebrate Zoology, University of California, Berkeley, CA, USA
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14
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Ekar JM, Price DK, Johnson MA, Stacy EA. Varieties of the highly dispersible and hypervariable tree, Metrosideros polymorpha, differ in response to mechanical stress and light across a sharp ecotone. AMERICAN JOURNAL OF BOTANY 2019; 106:1106-1115. [PMID: 31330066 DOI: 10.1002/ajb2.1331] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/23/2018] [Accepted: 05/28/2019] [Indexed: 05/26/2023]
Abstract
PREMISE The drivers of isolation between sympatric populations of long-lived and highly dispersible conspecific plants are not well understood. In the Hawaiian Islands, the landscape-dominant tree, Metrosideros polymorpha, displays extraordinary phenotypic differences among sympatric varieties despite high dispersibility of its pollen and seeds, thereby presenting a unique opportunity to investigate how disruptive selection alone can maintain incipient forms. Stenophyllous M. polymorpha var. newellii is a recently evolved tree endemic to the waterways of eastern Hawai'i Island that shows striking neutral genetic differentiation from its ancestor, wet-forest M. polymorpha var. glaberrima, despite sympatry of these forms. We looked for evidence for, and drivers of, differential local adaptation of these varieties across the range of M. polymorpha var. newellii. METHODS For paired populations of these varieties, we compared seedling performance under contrasting light conditions and a strong water current characteristic of the riparian zone. We also conducted a reciprocal transplant experiment and contrasted adult leaf anatomy. RESULTS Results suggest that the riparian zone is harsh and that selection involving the mechanical stress of rushing water, and secondarily, light, led to significant reciprocal immigrant inviability in adjacent forest and riparian environments. The strongest adaptive divergence between varieties was seen in leaves and seedlings from the site with the sharpest ecotone, coincident with the strongest genetic isolation of M. polymorpha var. newellii observed previously. CONCLUSIONS These findings suggest that disruptive selection across a sharp ecotone contributes to the maintenance of an incipient riparian ecotype from within a continuous population of a long-lived and highly dispersible tree species.
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Affiliation(s)
- Jill M Ekar
- The Microbial and Plant Genomics Institute, University of Minnesota-Twin Cities, 1500 Gortner Avenue, Saint Paul, Minnesota, 55108, USA
- Tropical Conservation Biology and Environmental Science Graduate Program, University of Hawai'i at Hilo, 200 West Kawili Street, Hilo, Hawai'i, 96720, USA
| | - Donald K Price
- Tropical Conservation Biology and Environmental Science Graduate Program, University of Hawai'i at Hilo, 200 West Kawili Street, Hilo, Hawai'i, 96720, USA
- School of Life Sciences, University of Nevada Las Vegas, 4505 South Maryland Parkway, Las Vegas, Nevada, 89154, USA
| | - Melissa A Johnson
- USDA-Agricultural Research Service, Daniel K. Inouye U.S. Pacific Basin Agricultural Research Center, Hilo, Hawai'i, 96720, USA
| | - Elizabeth A Stacy
- Tropical Conservation Biology and Environmental Science Graduate Program, University of Hawai'i at Hilo, 200 West Kawili Street, Hilo, Hawai'i, 96720, USA
- School of Life Sciences, University of Nevada Las Vegas, 4505 South Maryland Parkway, Las Vegas, Nevada, 89154, USA
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15
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Menezes T, Romeiras MM, de Sequeira MM, Moura M. Phylogenetic relationships and phylogeography of relevant lineages within the complex Campanulaceae family in Macaronesia. Ecol Evol 2017; 8:88-108. [PMID: 29321854 PMCID: PMC5756848 DOI: 10.1002/ece3.3640] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2017] [Revised: 09/30/2017] [Accepted: 10/30/2017] [Indexed: 12/18/2022] Open
Abstract
Macaronesia has long been recognized as a natural model for studying evolutionary processes in plant diversification. Several studies have attempted to focus on single lineages, and few have covered the diversification of a family across all the archipelagos. We used a comprehensive sample to clarify the phylogenetic relationships and the biogeographic history of the Macaronesian Campanulaceae. Hypotheses related to the colonization of these archipelagos will be used to examine the diversification patterns of different lineages. We sequenced the ITS region and six cpDNA markers (atpB, matK, petD, rbcL, trnL-F, and psbA-trnH) from 10 Campanulaceae species, including seven endemic species in Macaronesia. The phylogeny of these taxa was reconstructed using maximum parsimony, maximum likelihood, and Bayesian inference. To study the relationships within each lineage, haplotype networks were calculated using NeighborNet and TCS algorithms. Moreover, data were combined with fossil information to construct time-calibrated trees for the Macaronesian Campanulaceae species. The phylogenetic analyses are largely congruent with current taxon circumscriptions, and all the endemic genera formed monophyletic clades, namely Azorina in Azores; Musschia in Madeira; and Campanula in Cape Verde. The Azorina clade and the Cape Verde endemic Campanula may share a common ancestor in North Africa, and the divergence was dated ca. 12.3 million years ago (Mya). The divergence of the Musschia clade began in the Pliocene ca. 3.4 Mya. Moreover, several examples of intraspecific variation were revealed among the native species with a clear geographic structured patterns, suggesting that cryptic diversity might exist within the native Macaronesian Campanulaceae when compared to the close mainland taxa (e.g., Campanula erinus, Trachelium caeruleum), but additional studies are needed to support the molecular data. This study highlights the power of combining data (e.g., phylogeny and divergence times, with species distribution data) for testing diversification hypotheses within the unique Macaronesian flora, providing useful information for future conservation efforts.
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Affiliation(s)
- Tiago Menezes
- CIBIO Research Centre in Biodiversity and Genetic Resources InBIO Associate Laboratory Faculdade de Ciências e Tecnologia Universidade dos Açores Ponta Delgada Azores Portugal
| | - Maria M Romeiras
- Linking Landscape, Environment, Agriculture and Food (LEAF) Instituto Superior de Agronomia Universidade de Lisboa Lisbon Portugal.,Centre for Ecology, Evolution and Environmental Changes (cE3c) Faculdade de Ciências Universidade de Lisboa Lisbon Portugal
| | - Miguel M de Sequeira
- Madeira Botanical Group Faculdade de Ciências da Vida Universidade de Madeira Alto da PenteadaFunchal Madeira Portugal
| | - Mónica Moura
- CIBIO Research Centre in Biodiversity and Genetic Resources InBIO Associate Laboratory Faculdade de Ciências e Tecnologia Universidade dos Açores Ponta Delgada Azores Portugal
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16
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Mueller LO, Breza LC, Genung MA, Giardina CP, Stone NE, Sidak‐Loftis LC, Busch JD, Wagner DM, Bailey JK, Schweitzer JA. Ecosystem consequences of plant genetic divergence with colonization of new habitat. Ecosphere 2017. [DOI: 10.1002/ecs2.1743] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Affiliation(s)
- Liam O. Mueller
- Department of Ecology and Evolutionary Biology University of Tennessee Knoxville Tennessee 37996 USA
| | - Lauren C. Breza
- Department of Ecology and Evolutionary Biology University of Tennessee Knoxville Tennessee 37996 USA
| | - Mark A. Genung
- Department of Ecology, Evolution and Natural Resources Rutgers University New Brunswick New Jersey 08901 USA
| | - Christian P. Giardina
- Institute for Pacific Islands Forestry Pacific Southwest Research Station USDA Forest Service Hilo Hawai`i 96720 USA
| | - Nathan E. Stone
- Center for Microbial Genetics and Genomics Northern Arizona University Flagstaff Arizona 86001 USA
| | - Lindsay C. Sidak‐Loftis
- Center for Microbial Genetics and Genomics Northern Arizona University Flagstaff Arizona 86001 USA
| | - Joseph D. Busch
- Center for Microbial Genetics and Genomics Northern Arizona University Flagstaff Arizona 86001 USA
| | - David M. Wagner
- Center for Microbial Genetics and Genomics Northern Arizona University Flagstaff Arizona 86001 USA
| | - Joseph K. Bailey
- Department of Ecology and Evolutionary Biology University of Tennessee Knoxville Tennessee 37996 USA
| | - Jennifer A. Schweitzer
- Department of Ecology and Evolutionary Biology University of Tennessee Knoxville Tennessee 37996 USA
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17
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Amada G, Onoda Y, Ichie T, Kitayama K. Influence of leaf trichomes on boundary layer conductance and gas-exchange characteristics inMetrosideros polymorpha(Myrtaceae). Biotropica 2017. [DOI: 10.1111/btp.12433] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Affiliation(s)
- Gaku Amada
- Graduate School of Agriculture; Kyoto University; Kitashirakawa Oiwake-Cho Sakyo-Ku Kyoto 606-8502 Japan
| | - Yusuke Onoda
- Graduate School of Agriculture; Kyoto University; Kitashirakawa Oiwake-Cho Sakyo-Ku Kyoto 606-8502 Japan
| | - Tomoaki Ichie
- Faculty of Agriculture; Kochi University; B200, Monobe Nankoku 783-8502 Japan
| | - Kanehiro Kitayama
- Graduate School of Agriculture; Kyoto University; Kitashirakawa Oiwake-Cho Sakyo-Ku Kyoto 606-8502 Japan
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18
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Stacy EA, Paritosh B, Johnson MA, Price DK. Incipient ecological speciation between successional varieties of a dominant tree involves intrinsic postzygotic isolating barriers. Ecol Evol 2017; 7:2501-2512. [PMID: 28428842 PMCID: PMC5395442 DOI: 10.1002/ece3.2867] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2016] [Revised: 02/06/2017] [Accepted: 02/06/2017] [Indexed: 01/18/2023] Open
Abstract
Whereas disruptive selection imposed by heterogeneous environments can lead to the evolution of extrinsic isolating barriers between diverging populations, the evolution of intrinsic postzygotic barriers through divergent selection is less certain. Long-lived species such as trees may be especially slow to evolve intrinsic isolating barriers. We examined postpollination reproductive isolating barriers below the species boundary, in an ephemeral hybrid zone between two successional varieties of the landscape-dominant Hawaiian tree, Metrosideros polymorpha, on volcanically active Hawai'i Island. These archipelago-wide sympatric varieties show the weakest neutral genetic divergence of any taxon pair on Hawai'i Island but significant morphological and ecological differentiation consistent with adaptation to new and old lava flows. Cross-fertility between varieties was high and included heterosis of F1 hybrids at the seed germination stage, consistent with a substantial genetic load apparent within varieties through low self-fertility and a lack of self-pollen discrimination. However, a partial, but significant, barrier was observed in the form of reduced female and male fertility of hybrids, especially backcross hybrids, consistent with the accumulation of genetic incompatibilities between varieties. These results suggest that partial intrinsic postzygotic barriers can arise through disruptive selection acting on large, hybridizing populations of a long-lived species.
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Affiliation(s)
- Elizabeth A. Stacy
- Department of BiologyUniversity of Hawai'i HiloHiloHIUSA
- Tropical Conservation Biology and Environmental Science Graduate ProgramUniversity of Hawai'i HiloHiloHIUSA
- Present address: School of Life SciencesUniversity of Nevada, Las Vegas4505 S Maryland PkwyLas VegasNV89154USA
| | - Bhama Paritosh
- Department of BiologyUniversity of Hawai'i HiloHiloHIUSA
| | - Melissa A. Johnson
- Tropical Conservation Biology and Environmental Science Graduate ProgramUniversity of Hawai'i HiloHiloHIUSA
- Present address: Department of BotanyClaremont Graduate University, Rancho Santa Ana Botanic Garden1500 N. College Ave.ClaremontCA91711USA
| | - Donald K. Price
- Department of BiologyUniversity of Hawai'i HiloHiloHIUSA
- Tropical Conservation Biology and Environmental Science Graduate ProgramUniversity of Hawai'i HiloHiloHIUSA
- Present address: School of Life SciencesUniversity of Nevada, Las Vegas4505 S Maryland PkwyLas VegasNV89154USA
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19
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Izuno A, Kitayama K, Onoda Y, Tsujii Y, Hatakeyama M, Nagano AJ, Honjo MN, Shimizu-Inatsugi R, Kudoh H, Shimizu KK, Isagi Y. The population genomic signature of environmental association and gene flow in an ecologically divergent tree species Metrosideros polymorpha
(Myrtaceae). Mol Ecol 2017; 26:1515-1532. [DOI: 10.1111/mec.14016] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2015] [Revised: 12/13/2016] [Accepted: 12/28/2016] [Indexed: 12/23/2022]
Affiliation(s)
- Ayako Izuno
- Graduate School of Agriculture; Kyoto University; Kitashirakawa Oiwake-cho, Sakyo-ku Kyoto 606-8502 Japan
- Department of Evolutionary Biology and Environmental Studies; University of Zurich; Winterthurerstrasse 190 8057 Zurich Switzerland
| | - Kanehiro Kitayama
- Graduate School of Agriculture; Kyoto University; Kitashirakawa Oiwake-cho, Sakyo-ku Kyoto 606-8502 Japan
| | - Yusuke Onoda
- Graduate School of Agriculture; Kyoto University; Kitashirakawa Oiwake-cho, Sakyo-ku Kyoto 606-8502 Japan
| | - Yuki Tsujii
- Graduate School of Agriculture; Kyoto University; Kitashirakawa Oiwake-cho, Sakyo-ku Kyoto 606-8502 Japan
| | - Masaomi Hatakeyama
- Department of Evolutionary Biology and Environmental Studies; University of Zurich; Winterthurerstrasse 190 8057 Zurich Switzerland
- Functional Genomics Center Zurich; Winterthurerstrasse 190 8057 Zurich Switzerland
| | - Atsushi J. Nagano
- Faculty of Agriculture; Ryukoku University; 1-5 Yokatani, Seta Ohe-cho Otsu Shiga 520-2194 Japan
- PRESTO, Japan Science and Technology Agency; 4-1-8 Honcho Kawaguchi, Saitama 332-0012 Japan
- Center for Ecological Research; Kyoto University; 2-509-3 Hirano Otsu Shiga 520-2113 Japan
| | - Mie N. Honjo
- Center for Ecological Research; Kyoto University; 2-509-3 Hirano Otsu Shiga 520-2113 Japan
| | - Rie Shimizu-Inatsugi
- Department of Evolutionary Biology and Environmental Studies; University of Zurich; Winterthurerstrasse 190 8057 Zurich Switzerland
| | - Hiroshi Kudoh
- Center for Ecological Research; Kyoto University; 2-509-3 Hirano Otsu Shiga 520-2113 Japan
| | - Kentaro K. Shimizu
- Department of Evolutionary Biology and Environmental Studies; University of Zurich; Winterthurerstrasse 190 8057 Zurich Switzerland
- Center for Ecological Research; Kyoto University; 2-509-3 Hirano Otsu Shiga 520-2113 Japan
- Kihara Institute for Biological Research; Yokohama City University; 641-12 Maioka, Totsuka-ward Yokohama Kanagawa 244-0813 Japan
| | - Yuji Isagi
- Graduate School of Agriculture; Kyoto University; Kitashirakawa Oiwake-cho, Sakyo-ku Kyoto 606-8502 Japan
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20
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Percy DM. Making the most of your host: the Metrosideros-feeding psyllids (Hemiptera, Psylloidea) of the Hawaiian Islands. Zookeys 2017:1-163. [PMID: 28325970 PMCID: PMC5345378 DOI: 10.3897/zookeys.649.10213] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2016] [Accepted: 01/05/2017] [Indexed: 12/31/2022] Open
Abstract
The Hawaiian psyllids (Psylloidea, Triozidae) feeding on Metrosideros (Myrtaceae) constitute a remarkable radiation of more than 35 species. This monophyletic group has diversified on a single, highly polymorphic host plant species, Metrosiderospolymorpha. Eleven Metrosideros-feeding species included in the Insects of Hawaii by Zimmerman are redescribed, and an additional 25 new species are described. Contrary to previous classifications that placed the Metrosideros-feeders in two genera, Trioza Foerster, 1848 and Kuwayama Crawford, 1911, all 36 named species are placed in Pariaconus Enderlein, 1926; and the relationship of this genus to other Pacific taxa within the family Triozidae, and other Austro-Pacific taxa feeding on host plants in Myrtaceae is clarified. The processes of diversification in Pariaconus include shifts in galling habit, geographic isolation within and between islands, and preferences for different morphotypes of the host plant. Four species groups are recognized: the bicoloratus and minutus groups are free-living or form pit galls, and together with the kamua group (composing all of the Kauai species) form a basal assemblage; the more derived closed gall species in the ohialoha group are found on all major islands except Kauai. The diversification of Pariaconus has likely occurred over several million years. Within island diversification is exemplified in the kamua group, and within species variation in the ohialoha group, but species discovery rates suggest this radiation remains undersampled. Mitochondrial DNA barcodes are provided for 28 of the 36 species. Genetic divergence, intraspecific genetic structure, and parallel evolution of different galling biologies and morphological traits are discussed within a phylogenetic framework. Outgroup analysis for the genus Pariaconus and ancestral character state reconstruction suggest pit-galling may be the ancestral state, and the closest outgroups are Palaearctic-Australasian taxa rather than other Pacific Metrosideros-feeders.
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Affiliation(s)
- Diana M Percy
- Department of Life Sciences, Natural History Museum, Cromwell Road, London, UK, and University of British Columbia, Faculty of Science, University Boulevard, Vancouver, BC, Canada
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21
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Stacy EA, Johansen JB, Sakishima T, Price DK. Genetic analysis of an ephemeral intraspecific hybrid zone in the hypervariable tree, Metrosideros polymorpha, on Hawai'i Island. Heredity (Edinb) 2016; 117:173-83. [PMID: 27301333 PMCID: PMC4981685 DOI: 10.1038/hdy.2016.40] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2015] [Revised: 03/16/2016] [Accepted: 05/08/2016] [Indexed: 02/03/2023] Open
Abstract
Intraspecific hybrid zones involving long-lived woody species are rare and can provide insights into the genetic basis of early-diverging traits in speciation. Within the landscape-dominant Hawaiian tree, Metrosideros polymorpha, are morphologically distinct successional varieties, incana and glaberrima, that dominate new and old lava flows, respectively, below 1200 me on volcanically active Hawai'i Island, with var. glaberrima also extending to higher elevations and bogs. Here, we use morphological measurements on 86 adult trees to document the presence of an incana-glaberrima hybrid zone on the 1855 Mauna Loa lava flow on east Hawai'i Island and parent-offspring analysis of 1311 greenhouse seedlings from 71 crosses involving 72 adults to estimate heritabilities and genetic correlations among vegetative traits. Both the variation in adult leaf pubescence at the site and the consistency between adult and offspring phenotypes suggest the presence of two hybrid classes, F1s and var. incana backcrosses, as would be expected on a relatively young lava flow. Nine nuclear microsatellite loci failed to distinguish parental and hybrid genotypes. All four leaf traits examined showed an additive genetic basis with moderate to strong heritabilities, and genetic correlations were stronger for the more range-restricted var. incana. The differences between varieties in trait values, heritabilities and genetic correlations, coupled with high genetic variation within but low genetic variation between varieties, are consistent with a multi-million-year history of alternating periods of disruptive selection in contrasting environments and admixture in ephemeral hybrid zones. Finally, the contrasting genetic architectures suggest different evolutionary trajectories of leaf traits in these forms.
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Affiliation(s)
- E A Stacy
- Department of Biology, University of Hawai‘i Hilo, Hilo, HI, USA
- Tropical Conservation Biology and Environmental Science Graduate Program, University of Hawai‘i Hilo, Hilo, HI, USA
| | - J B Johansen
- Tropical Conservation Biology and Environmental Science Graduate Program, University of Hawai‘i Hilo, Hilo, HI, USA
| | - T Sakishima
- Tropical Conservation Biology and Environmental Science Graduate Program, University of Hawai‘i Hilo, Hilo, HI, USA
| | - D K Price
- Department of Biology, University of Hawai‘i Hilo, Hilo, HI, USA
- Tropical Conservation Biology and Environmental Science Graduate Program, University of Hawai‘i Hilo, Hilo, HI, USA
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Izuno A, Hatakeyama M, Nishiyama T, Tamaki I, Shimizu-Inatsugi R, Sasaki R, Shimizu KK, Isagi Y. Genome sequencing of Metrosideros polymorpha (Myrtaceae), a dominant species in various habitats in the Hawaiian Islands with remarkable phenotypic variations. JOURNAL OF PLANT RESEARCH 2016; 129:727-736. [PMID: 27052216 DOI: 10.1007/s10265-016-0822-3] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/12/2016] [Accepted: 02/15/2016] [Indexed: 06/05/2023]
Abstract
Whole genome sequences, which can be provided even for non-model organisms owing to high-throughput sequencers, are valuable in enhancing the understanding of adaptive evolution. Metrosideros polymorpha, a tree species endemic to the Hawaiian Islands, occupies a wide range of ecological habitats and shows remarkable polymorphism in phenotypes among/within populations. The biological functions of genetic variations observed within this species could provide significant insights into the adaptive radiation found in a single species. Here de novo assembled genome sequences of M. polymorpha are presented to reveal basic genomic parameters about this species and to develop our knowledge of ecological divergences. The assembly yielded 304-Mbp genome sequences, half of which were covered by 19 scaffolds with >5 Mbp, and contained 30 K protein-coding genes. Demographic history inferred from the genome-wide heterozygosity indicated that this species experienced a dramatic rise and fall in the effective population size, possibly owing to past geographic or climatic changes in the Hawaiian Islands. This M. polymorpha genome assembly represents a high-quality genome resource useful for future functional analyses of both intra- and interspecies genetic variations or comparative genomics.
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Affiliation(s)
- Ayako Izuno
- Graduate School of Agriculture, Kyoto University, Kitashirakawa Oiwake-cho, Sakyo-ku, Kyoto, 606-8502, Japan.
| | - Masaomi Hatakeyama
- Department of Evolutionary Biology and Environmental Studies, University of Zurich, Winterthurerstrasse 190, 8057, Zurich, Switzerland
- Functional Genomics Center Zurich, Winterthurerstrasse 190, 8057, Zurich, Switzerland
| | - Tomoaki Nishiyama
- Advanced Science Research Center, Kanazawa University, 13-1 Takara-machi, Kanazawa, 920-0934, Japan
| | - Ichiro Tamaki
- Gifu Academy of Forest Science and Culture, 88 Sodai, Mino, Gifu, 501-3714, Japan
| | - Rie Shimizu-Inatsugi
- Department of Evolutionary Biology and Environmental Studies, University of Zurich, Winterthurerstrasse 190, 8057, Zurich, Switzerland
| | - Ryuta Sasaki
- Organization of Frontier Science and Innovation, Kanazawa University, Kakuma-machi, Kanazawa, 920-1192, Japan
| | - Kentaro K Shimizu
- Department of Evolutionary Biology and Environmental Studies, University of Zurich, Winterthurerstrasse 190, 8057, Zurich, Switzerland
| | - Yuji Isagi
- Graduate School of Agriculture, Kyoto University, Kitashirakawa Oiwake-cho, Sakyo-ku, Kyoto, 606-8502, Japan
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Bailey S, Percy DM, Hefer CA, Cronk QCB. The transcriptional landscape of insect galls: psyllid (Hemiptera) gall formation in Hawaiian Metrosideros polymorpha (Myrtaceae). BMC Genomics 2015; 16:943. [PMID: 26572921 PMCID: PMC4647832 DOI: 10.1186/s12864-015-2109-9] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2015] [Accepted: 10/19/2015] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Recent studies show that galling Hymenoptera and Diptera are able to synthesize the plant hormone indole-3-acetic acid (auxin) from tryptophan and that plant response to insect-produced auxin is implicated in gall formation. We examined the leaf transcriptome of galled and ungalled leaves of individuals of the Hawaiian endemic plant Metrosideros polymorpha (Myrtaceae) subject to infestation by psyllid (Hemiptera) gall-makers in the genus Trioza (Triozidae). RESULTS Transcript libraries were sequenced using Illumina technology and the reads assembled de novo into contigs. Functional identification of contigs followed a two-step procedure, first identifying contigs by comparison to the completely sequenced genome of the related Eucalyptus, followed by identifying the equivalent Arabidopsis gene using a pre-computed mapping between Eucalyptus and Arabidopsis genes. This allowed us to use the rich functional annotation of the Arabidopsis genome to assess the transcriptional landscape of galling in Metrosideros. Comparing galled and ungalled leaves, we find a highly significant enrichment of expressed genes with a gene ontology (GO) annotation to auxin response in the former. One gene consistently expressed in all galled trees examined but not detected in any libraries from ungalled leaves was the Metrosideros version of SMALL AUXIN UPREGULATED (SAUR) 67 which appears to be a marker for leaf-galling in Metrosideros. CONCLUSIONS We conclude that an auxin response is involved in galling by Metrosideros psyllids. The possibility should therefore be considered that psyllids (like other insects examined) are able to synthesize auxin.
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Affiliation(s)
- Sebastian Bailey
- School of Biological and Chemical Sciences, Queen Mary University of London, London, E1 4NS, UK
| | - Diana M Percy
- Department of Life Sciences, Natural History Museum, London, SW7 5BD, UK.
| | - Charles A Hefer
- Agricultural Research Council, Private Bag X05, Onderstepoort, Pretoria, 0110, South Africa
| | - Quentin C B Cronk
- School of Biological and Chemical Sciences, Queen Mary University of London, London, E1 4NS, UK
- Department of Botany, University of British Columbia, 3529-6270 University Blvd., Vancouver, BC, Canada, V6T 1Z4
- Jodrell Laboratory, Royal Botanic Gardens, Kew, Richmond, Surrey, TW9 3AB, UK
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Harter DEV, Thiv M, Weig A, Jentsch A, Beierkuhnlein C. Spatial and ecological population genetic structures within two island-endemic Aeonium species of different niche width. Ecol Evol 2015; 5:4327-44. [PMID: 26664682 PMCID: PMC4667834 DOI: 10.1002/ece3.1682] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2015] [Revised: 07/13/2015] [Accepted: 07/22/2015] [Indexed: 01/21/2023] Open
Abstract
The Crassulacean genus Aeonium is a well-known example for plant species radiation on oceanic archipelagos. However, while allopatric speciation among islands is documented for this genus, the role of intra-island speciation due to population divergence by topographical isolation or ecological heterogeneity has not yet been addressed. The aim of this study was to investigate intraspecific genetic structures and to identify spatial and ecological drivers of genetic population differentiation on the island scale. We analyzed inter simple sequence repeat variation within two island-endemic Aeonium species of La Palma: one widespread generalist that covers a large variety of different habitat types (Ae. davidbramwellii) and one narrow ecological specialist (Ae. nobile), in order to assess evolutionary potentials on this island. Gene pool differentiation and genetic diversity patterns were associated with major landscape structures in both species, with phylogeographic implications. However, overall levels of genetic differentiation were low. For the generalist species, outlier loci detection and loci-environment correlation approaches indicated moderate signatures of divergent selection pressures linked to temperature and precipitation variables, while the specialist species missed such patterns. Our data point to incipient differentiation among populations, emphasizing that ecological heterogeneity and topographical structuring within the small scales of an island can foster evolutionary processes. Very likely, such processes have contributed to the radiation of Aeonium on the Canary Islands. There is also support for different evolutionary mechanisms between generalist and specialist species.
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Affiliation(s)
| | - Mike Thiv
- State Museum of Natural History StuttgartStuttgartGermany
| | - Alfons Weig
- DNA Analytics and EcoinformaticsBayCEERUniversity of BayreuthBayreuthGermany
| | - Anke Jentsch
- Disturbance EcologyBayCEERUniversity of BayreuthBayreuthGermany
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A quantitative analysis of phenotypic variations of Metrosideros polymorpha within and across populations along environmental gradients on Mauna Loa, Hawaii. Oecologia 2015; 180:1049-59. [DOI: 10.1007/s00442-015-3416-1] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2015] [Accepted: 07/25/2015] [Indexed: 10/23/2022]
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Kueffer C, Drake DR, Fernández-Palacios JM. Island biology: looking towards the future. Biol Lett 2014; 10:20140719. [PMID: 25339655 PMCID: PMC4272214 DOI: 10.1098/rsbl.2014.0719] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2014] [Accepted: 09/29/2014] [Indexed: 11/12/2022] Open
Abstract
Oceanic islands are renowned for the profound scientific insights that their fascinating biotas have provided to biologists during the past two centuries. Research presented at Island Biology 2014-an international conference, held in Honolulu, Hawaii (7-11 July 2014), which attracted 253 presenters and 430 participants from at least 35 countries(1)-demonstrated that islands are reclaiming a leading role in ecology and evolution, especially for synthetic studies at the intersections of macroecology, evolution, community ecology and applied ecology. New dynamics in island biology are stimulated by four major developments. We are experiencing the emergence of a truly global and comprehensive island research community incorporating previously neglected islands and taxa. Macroecology and big-data analyses yield a wealth of global-scale synthetic studies and detailed multi-island comparisons, while other modern research approaches such as genomics, phylogenetic and functional ecology, and palaeoecology, are also dispersing to islands. And, increasingly tight collaborations between basic research and conservation management make islands places where new conservation solutions for the twenty-first century are being tested. Islands are home to a disproportionate share of the world's rare (and extinct) species, and there is an urgent need to develop increasingly collaborative and innovative research to address their conservation requirements.
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Affiliation(s)
- Christoph Kueffer
- Institute of Integrative Biology, ETH Zurich, Universitätsstrasse 16, 8092 Zurich, Switzerland
| | - Donald R Drake
- Department of Botany, University of Hawaii, Honolulu, HI 96822, USA
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27
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Pillon Y, Johansen J, Sakishima T, Chamala S, Barbazuk WB, Stacy EA. Primers for low-copy nuclear genes in Metrosideros and cross-amplification in Myrtaceae. APPLICATIONS IN PLANT SCIENCES 2014; 2:apps1400049. [PMID: 25309837 PMCID: PMC4189496 DOI: 10.3732/apps.1400049] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/06/2014] [Accepted: 08/13/2014] [Indexed: 05/29/2023]
Abstract
PREMISE OF THE STUDY Primers were developed to amplify low-copy nuclear genes in Hawaiian Metrosideros (Myrtaceae). • METHODS AND RESULTS Data from a pooled 454 Titanium run of the partial transcriptomes of four Metrosideros taxa were used to identify the loci of interest. Ten exon-primed intron-crossing (EPIC) markers were amplified and sequenced directly with success in Metrosideros, as well as in a representative selection of Myrtaceae, including Syzygium, Psidium, and Melaleuca for most of the markers. The loci amplified ranged between 500 and 1100 bp, and up to 117 polymorphic sites were observed within an individual gene alignment. Two introns contained microsatellites in some of the species. • CONCLUSIONS These novel primer pairs should be useful for phylogenetic analysis and population genetics of a broad range of Myrtaceae, particularly the diverse fleshy-fruited tribes Syzygieae and Myrteae.
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Affiliation(s)
- Yohan Pillon
- Tropical Conservation Biology and Environmental Science Program, University of Hawai‘i at Hilo, 200 West Kawili Street, Hilo, Hawai‘i 96720 USA
| | - Jennifer Johansen
- Tropical Conservation Biology and Environmental Science Program, University of Hawai‘i at Hilo, 200 West Kawili Street, Hilo, Hawai‘i 96720 USA
| | - Tomoko Sakishima
- Tropical Conservation Biology and Environmental Science Program, University of Hawai‘i at Hilo, 200 West Kawili Street, Hilo, Hawai‘i 96720 USA
| | - Srikar Chamala
- Department of Biology, University of Florida, Gainesville, Florida 32611 USA
- Genetics Institute, University of Florida, Gainesville, Florida 32610 USA
| | - W. Brad Barbazuk
- Department of Biology, University of Florida, Gainesville, Florida 32611 USA
- Genetics Institute, University of Florida, Gainesville, Florida 32610 USA
| | - Elizabeth A. Stacy
- Tropical Conservation Biology and Environmental Science Program, University of Hawai‘i at Hilo, 200 West Kawili Street, Hilo, Hawai‘i 96720 USA
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Morrison KR, Stacy EA. Intraspecific divergence and evolution of a life-history trade-off along a successional gradient in Hawaii's Metrosideros polymorpha. J Evol Biol 2014; 27:1192-204. [PMID: 24848688 DOI: 10.1111/jeb.12393] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2013] [Revised: 03/21/2014] [Accepted: 03/31/2014] [Indexed: 01/16/2023]
Abstract
The importance of environmental gradients in the diversification of long-lived tree species is poorly understood. Two morphologically distinct varieties of the endemic Hawaiian tree, 'ōhi'a lehua (Metrosideros polymorpha), are the canopy dominants at alternate extremes of a successional gradient formed by the recurring disturbance of lava flows on east Hawai'i Island. The maintenance of these varieties despite hybridization may be due to disruptive selection at either end of the successional gradient. To test this hypothesis, seeds from three, replicate monotypic stands of each variety on east Hawai'i Island were germinated and the resulting seedlings grown under four combinations of light and nitrogen levels in a greenhouse, and at early- and late-successional field sites. Growth and survivorship measures revealed differential fitness of these varieties in high- and low-light environments in the greenhouse with corresponding differential fitness in early- and late-successional field sites. Unique light-by-nitrogen interaction effects on growth were observed in each variety, and only the late-successional variety appeared to be nitrogen limited. These two varieties exhibit the classic plant life-history trade-off between fast growth in high light and high survivorship in shade, but notably within a single tree species. These findings strongly implicate a role for Hawaii's striking environmental heterogeneity in the emergence of at least two endemic forms of this woody genus.
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Affiliation(s)
- K R Morrison
- Department of Tropical Conservation Biology & Environmental Science, University of Hawai'i Hilo, Hilo, HI, USA
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