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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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2
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Hadi M, Stacy EA. An optimized RNA extraction method for diverse leaves of Hawaiian Metrosideros, a hypervariable tree species complex. APPLICATIONS IN PLANT SCIENCES 2023; 11:e11518. [PMID: 37342165 PMCID: PMC10278935 DOI: 10.1002/aps3.11518] [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] [Received: 09/02/2022] [Revised: 12/22/2022] [Accepted: 01/04/2023] [Indexed: 06/22/2023]
Abstract
Premise The isolation of RNA from trees is challenging due to the interference of polyphenols and polysaccharides with downstream processes. Furthermore, many RNA extraction protocols are time consuming and involve hazardous chemicals. To address these issues, we aimed to develop a safe protocol for high-quality RNA extraction from diverse Metrosideros taxa representing a broad range of leaf toughness, pubescence, and secondary metabolites. Methods and Results We tested popular RNA isolation kits and protocols that were effective on other recalcitrant trees, including a broad range of optimization and purification steps. We optimized a protocol involving two silica-membrane column-based kits that yielded high-quantity RNA with an RNA integrity number >7 and without DNA contamination. All RNA samples were used successfully in a follow-on RNA-Seq experiment. Conclusions We present an optimized high-throughput RNA extraction protocol that yielded high-quality and high-quantity RNA from three contrasting leaf phenotypes within a hyperdiverse woody species complex.
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Affiliation(s)
- Maryam Hadi
- School of Life SciencesUniversity of Nevada Las VegasLas VegasNevada89154USA
| | - Elizabeth A. Stacy
- School of Life SciencesUniversity of Nevada Las VegasLas VegasNevada89154USA
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3
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Weingarten E, Martin RE, Hughes RF, Vaughn NR, Shafron E, Asner GP. Early detection of a tree pathogen using airborne remote sensing. ECOLOGICAL APPLICATIONS : A PUBLICATION OF THE ECOLOGICAL SOCIETY OF AMERICA 2022; 32:e2519. [PMID: 34918400 DOI: 10.1002/eap.2519] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/20/2021] [Accepted: 08/25/2021] [Indexed: 06/14/2023]
Abstract
Native forests of Hawai'i Island are experiencing an ecological crisis in the form of Rapid 'Ōhi'a Death (ROD), a recently characterized disease caused by two fungal pathogens in the genus Ceratocystis. Since approximately 2010, this disease has caused extensive mortality of Hawai'i's keystone endemic tree, known as 'ōhi'a (Metrosideros polymorpha). Visible symptoms of ROD include rapid browning of canopy leaves, followed by death of the tree within weeks. This quick progression leading to tree mortality makes early detection critical to understanding where the disease will move at a timescale feasible for controlling the disease. We used repeat laser-guided imaging spectroscopy (LGIS) of forests on Hawai'i Island collected by the Global Airborne Observatory (GAO) in 2018 and 2019 to derive maps of foliar trait indices previously found to be important in distinguishing between ROD-infected and healthy 'ōhi'a canopies. Data from these maps were used to develop a prognostic indicator of tree stress prior to the visible onset of browning. We identified canopies that were green in 2018, but became brown in 2019 (defined as "to become brown"; TBB), and a corresponding set of canopies that remained green. The data mapped in 2018 showed separability of foliar trait indices between TBB and green 'ōhi'a, indicating early detection of canopy stress prior to the onset of ROD. Overall, a combination of linear and non-linear analyses revealed canopy water content (CWC), foliar tannins, leaf mass per area (LMA), phenols, cellulose, and non-structural carbohydrates (NSC) are primary drivers of the prognostic spectral capability which collectively result in strong consistent changes in leaf spectral reflectance in the near-infrared (700-1300 nm) and shortwave-infrared regions (1300-2500 nm). Results provide insight into the underlying foliar traits that are indicative of physiological responses of M. polymorpha trees infected with Ceratocycstis and suggest that imaging spectroscopy is an effective tool for identifying trees likely to succumb to ROD prior to the onset of visible symptoms.
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Affiliation(s)
- Erin Weingarten
- Center for Global Discovery and Conservation Science, Arizona State University, Tempe, Arizona, USA
- School of Geographical Sciences and Urban Planning, Arizona State University, Tempe, Arizona, USA
| | - Roberta E Martin
- Center for Global Discovery and Conservation Science, Arizona State University, Tempe, Arizona, USA
- School of Geographical Sciences and Urban Planning, Arizona State University, Tempe, Arizona, USA
| | | | - Nicholas R Vaughn
- Center for Global Discovery and Conservation Science, Arizona State University, Tempe, Arizona, USA
| | - Ethan Shafron
- Center for Global Discovery and Conservation Science, Arizona State University, Tempe, Arizona, USA
| | - Gregory P Asner
- Center for Global Discovery and Conservation Science, Arizona State University, Tempe, Arizona, 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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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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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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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: 105] [Impact Index Per Article: 26.3] [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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Affiliation(s)
- Deborah A. Roach
- Department of Biology University of Virginia Charlottesville VA USA
| | - Erin F. Smith
- Department of Biology University of Virginia Charlottesville VA USA
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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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12
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Johnson MA, Clark JR, Wagner WL, McDade LA. A molecular phylogeny of the Pacific clade of Cyrtandra (Gesneriaceae) reveals a Fijian origin, recent diversification, and the importance of founder events. Mol Phylogenet Evol 2017; 116:30-48. [DOI: 10.1016/j.ympev.2017.07.004] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2016] [Revised: 05/01/2017] [Accepted: 07/07/2017] [Indexed: 12/14/2022]
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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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14
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Porter CK, Benkman CW. Assessing the Potential Contributions of Reduced Immigrant Viability and Fecundity to Reproductive Isolation. Am Nat 2017; 189:580-591. [DOI: 10.1086/691191] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
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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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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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17
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Price MR, O'Rorke R, Amend AS, Hadfield MG. Diet selection at three spatial scales: Implications for conservation of an endangered Hawaiian tree snail. Biotropica 2016. [DOI: 10.1111/btp.12339] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Melissa R. Price
- Pacific Biosciences Research Center; University of Hawai‘i; Mānoa HI U.S.A
- Department of Natural Resources and Environmental Management; University of Hawai‘i; Mānoa HI U.S.A
- Sherman Hall; University of Hawai‘i; 1910 East West Rd. Honolulu HI 96822 U.S.A
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18
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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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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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Incipient radiation within the dominant Hawaiian tree Metrosideros polymorpha. Heredity (Edinb) 2014; 113:334-42. [PMID: 24824285 DOI: 10.1038/hdy.2014.47] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2013] [Revised: 03/23/2014] [Accepted: 04/01/2014] [Indexed: 01/19/2023] Open
Abstract
Although trees comprise a primary component of terrestrial species richness, the drivers and temporal scale of divergence in trees remain poorly understood. We examined the landscape-dominant tree, Metrosideros polymorpha, for variation at nine microsatellite loci across 23 populations on young Hawai'i Island, sampling each of the island's five varieties throughout its full geographic range. For four varieties, principal coordinate analysis revealed strong clustering of populations by variety across the 10 430 km(2) island, indicating partitioning of the species into multiple evolutionarily significant units. The single island-endemic form, riparian var. newellii, showed especially strong differentiation from other varieties despite occurring in sympatry with other varieties and likely evolved from a bog form on the oldest volcano, Kohala, within the past 500 000 years. Along with comparable riparian forms on other Pacific Islands, var. newellii appears to represent parallel incipient ecological speciation within Metrosideros. Greater genetic distance among the more common varieties on the oldest volcano and an inverse relationship between allelic diversity and substrate age appear consistent with colonization of Hawai'i Island by older, partially diverged varieties followed by increased hybridization among varieties on younger volcanoes. This study demonstrates that broad population-level sampling is required to uncover patterns of diversification within a ubiquitous and long-lived tree species. Hawaiian Metrosideros appears to be a case of incipient radiation in trees and thus should be useful for studies of divergence and the evolution of reproductive isolating barriers at the early stages of speciation.
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