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Jules ES, van Mantgem PJ, Iberle BG, Nesmith JCB, Rochefort RM. Whitebark Pine in the National Parks of the Pacific States: An Assessment of Population Vulnerability. NORTHWEST SCIENCE 2020. [DOI: 10.3955/046.094.0204] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Affiliation(s)
- Erik S. Jules
- Humboldt State University, 1 Harpst Street, Arcata, California 95521
| | - Phillip J. van Mantgem
- US Geological Survey, Western Ecological Research Center, 1655 Heindon Road, Arcata, California 95521
| | | | - Jonathan C. B. Nesmith
- National Park Service, Sierra Nevada Network, 47050 Generals Highway, Three Rivers, California, 93271
| | - Regina M. Rochefort
- North Cascades National Park Service Complex, 810 State Route 20, Sedro-Woolley, Washington 98284
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Ray C, Rochefort RM, Ransom JI, Nesmith JCB, Haultain SA, Schaming TD, Boetsch JR, Holmgren ML, Wilkerson RL, Siegel RB. Assessing trends and vulnerabilities in the mutualism between whitebark pine (Pinus albicaulis) and Clark's nutcracker (Nucifraga columbiana) in national parks of the Sierra-Cascade region. PLoS One 2020; 15:e0227161. [PMID: 33052936 PMCID: PMC7556478 DOI: 10.1371/journal.pone.0227161] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2019] [Accepted: 09/01/2020] [Indexed: 11/30/2022] Open
Abstract
Dispersal of whitebark pine (Pinus albicaulis Engelm.), a keystone species of many high-elevation ecosystems in western North America, depends on Clark’s nutcracker (Nucifraga columbiana Wilson), a seed-caching bird with an affinity for whitebark seeds. To the extent that this dependence is mutual, declines in whitebark seed production could cause declines in nutcracker abundance. Whitebark pine is in decline across much of its range due to interacting stressors, including the non-native pathogen white pine blister rust (Cronartium ribicola J. C. Fisch.). We used avian point-count data and tree surveys from four national park units to investigate whether trends in whitebark pine can explain trends in Clark’s nutcracker. Spatial trends were modeled using recent data from two parks, while temporal trends were modeled using longer time-series of nutcracker and whitebark data from two additional parks. To assess the potential dependence of nutcrackers on whitebark, we linked a model of nutcracker density (accounting for detection probability) with a model of whitebark trends, using a Bayesian framework to translate uncertainty in whitebark metrics to uncertainty in nutcracker density. In Mount Rainier National Park, temporal models showed dramatic declines in nutcracker density concurrent with significant increases in whitebark crown mortality and trees infected with white pine blister rust. However, nutcrackers did not trend with whitebark metrics in North Cascades National Park Service Complex. In spatial models of data from Yosemite National Park and Sequoia-Kings Canyon National Park, nutcracker density varied not only with local cover of whitebark but also with elevation and, in Sequoia-Kings Canyon, with cover of another species of white pine. Our results add support for the hypothesis that the mutualism between whitebark pine and Clark’s nutcracker is vulnerable to disruption by blister rust, and our approach integrates data across monitoring programs to explore trends in species interactions.
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Affiliation(s)
- Chris Ray
- The Institute for Bird Populations, Petaluma, California, United States of America
- * E-mail:
| | - Regina M. Rochefort
- North Cascades National Park Service Complex, Sedro-Woolley, Washington, United States of America
| | - Jason I. Ransom
- North Cascades National Park Service Complex, Sedro-Woolley, Washington, United States of America
| | - Jonathan C. B. Nesmith
- National Park Service, Sierra Nevada Network, Three Rivers, California, United States of America
| | - Sylvia A. Haultain
- National Park Service, Sierra Nevada Network, Three Rivers, California, United States of America
| | - Taza D. Schaming
- Northern Rockies Conservation Cooperative, Jackson, Wyoming, United States of America
| | - John R. Boetsch
- National Park Service, North Coast and Cascades Network, Port Angeles, Washington, United States of America
| | - Mandy L. Holmgren
- The Institute for Bird Populations, Petaluma, California, United States of America
| | - Robert L. Wilkerson
- The Institute for Bird Populations, Petaluma, California, United States of America
| | - Rodney B. Siegel
- The Institute for Bird Populations, Petaluma, California, United States of America
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Dudney JC, Nesmith JCB, Cahill MC, Cribbs JE, Duriscoe DM, Das AJ, Stephenson NL, Battles JJ. Compounding effects of white pine blister rust, mountain pine beetle, and fire threaten four white pine species. Ecosphere 2020. [DOI: 10.1002/ecs2.3263] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Affiliation(s)
- Joan C. Dudney
- Department of Environmental Science Policy and Management University of California at Berkeley Berkeley California 94720 USA
| | - Jonathan C. B. Nesmith
- Sierra Nevada Network Inventory & Monitoring Program National Park Service Three Rivers California 93271 USA
| | | | - Jennifer E. Cribbs
- Sierra Nevada Network Inventory & Monitoring Program National Park Service Three Rivers California 93271 USA
| | | | - Adrian J. Das
- Western Ecological Research Center U.S. Geological Survey Three Rivers California 93271 USA
| | - Nathan L. Stephenson
- Western Ecological Research Center U.S. Geological Survey Three Rivers California 93271 USA
| | - John J. Battles
- Department of Environmental Science Policy and Management University of California at Berkeley Berkeley California 94720 USA
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Climatic Correlates of White Pine Blister Rust Infection in Whitebark Pine in the Greater Yellowstone Ecosystem. FORESTS 2019. [DOI: 10.3390/f10080666] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Whitebark pine, a foundation species at tree line in the Western U.S. and Canada, has declined due to native mountain pine beetle epidemics, wildfire, and white pine blister rust. These declines are concerning for the multitude of ecosystem and human benefits provided by this species. An understanding of the climatic correlates associated with spread is needed to successfully manage impacts from forest pathogens. Since 2000 mountain pine beetles have killed 75% of the mature cone-bearing trees in the Greater Yellowstone Ecosystem, and 40.9% of monitored trees have been infected with white pine blister rust. We identified models of white pine blister rust infection which indicated that an August and September interaction between relative humidity and temperature are better predictors of white pine blister rust infection in whitebark pine than location and site characteristics in the Greater Yellowstone Ecosystem. The climate conditions conducive to white pine blister rust occur throughout the ecosystem, but larger trees in relatively warm and humid conditions were more likely to be infected between 2000 and 2018. We mapped the infection probability over the past two decades to identify coarse-scale patterns of climate conditions associated with white pine blister rust infection in whitebark pine.
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Effects of Disturbance on Tree Community Dynamics in Whitebark Pine (Pinus albicaulis Engelm.) Ecosystems. FORESTS 2018. [DOI: 10.3390/f9090566] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Whitebark pine (Pinus albicaulis Engelm.), an ecologically important tree species in high-elevation ecosystems of western North America, is threatened by white pine blister rust (Cronartium ribicola Fischer) and increased pressure from mountain pine beetle (Dendroctonus ponderosae Hopkins) due to climate warming. In addition, there is concern that fire suppression may be leading to successional replacement of whitebark by late-seral trees. Despite widespread knowledge that the tree is in decline, there is limited understanding of its successional dynamics, particularly in forests disturbed by white pine blister rust and mountain pine beetle. Our objective was to examine how disturbances have affected forest composition, structure, and seedling regeneration over a 22-year period (1990–2012) at 19 sites in the Cascade Mountains of Washington State (USA). Over that time, 13 sites (68%) were infected by white pine blister rust, 11 (58%) were disturbed by mountain pine beetle, and 5 (26%) experienced wildfire. Tree community composition changed significantly during the study period, primarily due to significant mortality of mature (≥20-cm diameter at breast height) whitebark pine. Despite loss of mature whitebark trees, we found little evidence of successional replacement by other tree species. Whitebark seedling density was unrelated to basal area of mature whitebark pine, but positively correlated with the presence of herb and shrub cover. Our results demonstrate the value of long-term repeated measurements for elucidating successional dynamics.
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Whitebark Pine in the Northern Cascades: Tracking the Effects of Blister Rust on Population Health in North Cascades National Park Service Complex and Mount Rainier National Park. FORESTS 2018. [DOI: 10.3390/f9050244] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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7
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Pinus albicaulis Engelm. (Whitebark Pine) in Mixed-Species Stands throughout Its US Range: Broad-Scale Indicators of Extent and Recent Decline. FORESTS 2018. [DOI: 10.3390/f9030131] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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8
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Historic Frequency and Severity of Fire in Whitebark Pine Forests of the Cascade Mountain Range, USA. FORESTS 2018. [DOI: 10.3390/f9020078] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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Bullington LS, Lekberg Y, Sniezko R, Larkin B. The influence of genetics, defensive chemistry and the fungal microbiome on disease outcome in whitebark pine trees. MOLECULAR PLANT PATHOLOGY 2018; 19:1847-1858. [PMID: 29388309 PMCID: PMC6638087 DOI: 10.1111/mpp.12663] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/11/2017] [Revised: 01/02/2018] [Accepted: 01/26/2018] [Indexed: 05/23/2023]
Abstract
The invasive fungal pathogen Cronartium ribicola infects and kills whitebark pine (Pinus albicaulis) throughout western North America. Whitebark pine has been proposed for listing under the Endangered Species Act in the USA, and the loss of this species is predicted to have severe impacts on ecosystem composition and function in high-elevation forests. Numerous fungal endophytes live inside whitebark pine tissues and may influence the severity of C. ribicola infection, either directly by inhibition of pathogen growth or indirectly by the induction of chemical defensive pathways in the tree. Terpenes, a form of chemical defence in pine trees, can also influence disease. In this study, we characterized fungal endophyte communities in whitebark pine seedlings before and after experimental inoculation with C. ribicola, monitored disease progression and compared fungal community composition in susceptible vs. resistant seedlings in a common garden. We analysed the terpene composition of these same seedlings. Seed family identity or maternal genetics influenced both terpenes and endophyte communities. Terpene and endophyte composition correlated with disease severity, and terpene concentrations differed in resistant vs. susceptible seedlings. These results suggest that the resistance to C. ribicola observed in natural whitebark pine populations is caused by the combined effects of genetics, endophytes and terpenes within needle tissue, in which initial interactions between microbes and hosts take place. Tree genotype, terpene and microbiome combinations associated with healthy trees could help to predict or reduce disease severity and improve outcomes of future tree breeding programmes.
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Affiliation(s)
- Lorinda S. Bullington
- MPG RanchFlorenceMT 59833USA
- Interdisciplinary Sciences, University of MontanaMissoulaMT 59801USA
| | - Ylva Lekberg
- MPG RanchFlorenceMT 59833USA
- College of Forestry and ConservationUniversity of MontanaMissoulaMT 59801USA
| | - Richard Sniezko
- USDA Forest Service, Dorena Genetic Resource CenterCottage GroveOR 97424USA
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10
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Shanahan E, Irvine KM, Thoma D, Wilmoth S, Ray A, Legg K, Shovic H. Whitebark pine mortality related to white pine blister rust, mountain pine beetle outbreak, and water availability. Ecosphere 2016. [DOI: 10.1002/ecs2.1610] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Affiliation(s)
- Erin Shanahan
- Greater Yellowstone Inventory and Monitoring Network National Park Service Bozeman Montana 59715 USA
| | - Kathryn M. Irvine
- U.S. Geological Survey Northern Rocky Mountain Science Center Bozeman Montana 59715 USA
| | - David Thoma
- Greater Yellowstone Inventory and Monitoring Network National Park Service Bozeman Montana 59715 USA
| | - Siri Wilmoth
- U.S. Geological Survey Northern Rocky Mountain Science Center Bozeman Montana 59715 USA
| | - Andrew Ray
- Greater Yellowstone Inventory and Monitoring Network National Park Service Bozeman Montana 59715 USA
| | - Kristin Legg
- Greater Yellowstone Inventory and Monitoring Network National Park Service Bozeman Montana 59715 USA
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11
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Keane RE, Holsinger LM, Mahalovich MF, Tomback DF. Evaluating future success of whitebark pine ecosystem restoration under climate change using simulation modeling. Restor Ecol 2016. [DOI: 10.1111/rec.12419] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Robert E. Keane
- Missoula Fire Sciences Laboratory; U.S. Forest Service, Rocky Mountain Research Station; 5775 Hwy 10 West Missoula MT 59808 U.S.A
| | - Lisa M. Holsinger
- Missoula Fire Sciences Laboratory; U.S. Forest Service, Rocky Mountain Research Station; 5775 Hwy 10 West Missoula MT 59808 U.S.A
| | - Mary F. Mahalovich
- U.S. Forest Service, Northern, Rocky Mountain, Southwestern, and Intermountain Regions, Forestry Sciences Laboratory; Moscow ID 83844 U.S.A
| | - Diana F. Tomback
- Department of Integrative Biology; University of Colorado Denver; Denver CO 80202 U.S.A
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Complex Challenges of Maintaining Whitebark Pine in Greater Yellowstone under Climate Change: A Call for Innovative Research, Management, and Policy Approaches. FORESTS 2016. [DOI: 10.3390/f7030054] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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13
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Larson ER, Van De Gevel SL, Grissino-Mayer HD. Variability in fire regimes of high-elevation whitebark pine communities, western Montana, USA. ECOSCIENCE 2015. [DOI: 10.2980/16-3-3240] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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Mock KE, Bentz BJ, O'neill EM, Chong JP, Orwin J, Pfrender ME. Landscape-scale genetic variation in a forest outbreak species, the mountain pine beetle (Dendroctonus ponderosae). Mol Ecol 2006; 16:553-68. [PMID: 17257113 DOI: 10.1111/j.1365-294x.2006.03158.x] [Citation(s) in RCA: 87] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The mountain pine beetle Dendroctonus ponderosae is a native species currently experiencing large-scale outbreaks in western North American pine forests. We sought to describe the pattern of genetic variation across the range of this species, to determine whether there were detectable genetic differences between D. ponderosae occupying different host trees in common localities, and to determine whether there was molecular evidence for a past demographic expansion. Using a combination of amplified fragment length polymorphism (AFLP) and mitochondrial sequencing analyses, we found evidence of genetic structuring among populations that followed a broad isolation-by-distance pattern. Our results suggest that the geographical pattern of gene flow follows the core distribution of the principal D. ponderosae host species, around rather than across the Great Basin and Mojave Deserts. Patterns of haplotype diversity and divergence were consistent with a range-wide population expansion. This signal was particularly pronounced in the northern part of the species' range, where outbreak activity is currently increasing. Using AFLP markers, we were unable to detect significant differences among groups of insects sampled from different host trees in common locations. Incidentally, we found that a large proportion of the polymorphic AFLP markers were gender-specific, occurring only in males. While we did not include these markers in our analyses, this finding warrants further investigation.
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Affiliation(s)
- K E Mock
- Department of Wildland Resources, Utah State University, Logan, Utah 84322-5230, USA.
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Cognato AI, Gillette NE, Bolaños RC, Sperling FAH. Mitochondrial phylogeny of pine cone beetles (Scolytinae, Conophthorus) and their affiliation with geographic area and host. Mol Phylogenet Evol 2005; 36:494-508. [PMID: 16039147 DOI: 10.1016/j.ympev.2005.04.019] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2004] [Revised: 03/25/2005] [Accepted: 04/25/2005] [Indexed: 11/28/2022]
Abstract
Pine cone beetles (Conophthorus spp.) feed and kill immature cones of Pinus species, thereby reducing seed production and seriously impairing reforestation of forest ecosystems. Population variation of Conophthorus reproductive behavior has hampered the development of semiochemical control of these pests. This difficulty is compounded by a lack of taxonomic knowledge and species diagnostic characters. Researchers and managers rely, in part, on host associations and geographic locality for species identifications and these have arguable taxonomic utility. However, host use and/or geographic separation may influence Conophthorus lineage diversification. To improve Conophthorus taxonomy and understand the association of host and geography with lineage diversification, a phylogeny of 43 individuals, including all valid species and a robust sample of C. ponderosae from different hosts, is reconstructed using 785 nucleotides of the 3'-end of the mitochondrial cytochrome oxidase I gene. Thirty trees were recovered in a parsimony analysis and the strict consensus was well resolved and supported by branch support measures. Conophthorus was monophyletic but mitochondrial polyphyly was uncovered for several species. The data also suggested an underestimation of species diversity. Phylogenetically related Conophthorus lineages were significantly associated with geographic proximity but not with host, as indicated by comparisons of character optimized geographic distributions and host associations against randomized distributions of these attributes on the parsimony tree. These results suggest that geographic separation better explains the mode of Conophthorus lineage diversification than does host specialization. Based on these results, researchers and managers of Conophthorus should consider populations as potentially different evolutionary entities until species boundaries are delineated via a robust phylogenetic revision of Conophthorus.
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Affiliation(s)
- Anthony I Cognato
- Department of Entomology, Texas A&M University, College Station, TX 77845, USA.
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Hamelin RC, Allaire M, Bergeron MJ, Nicole MC, Lecours N. Molecular epidemiology of white pine blister rust: recombination and spatial distribution. PHYTOPATHOLOGY 2005; 95:793-799. [PMID: 18943012 DOI: 10.1094/phyto-95-0793] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
ABSTRACT Multilocus haplotypes (MLHs) were derived for the spermogonial (monokaryotic haploid) stage of Cronartium ribicola, the causal agent of white pine blister rust. Six random amplified polymorphic DNA loci and three single-strand conformational polymorphism markers were analyzed for 246 rust samples collected from two heavily infected white pine plantations. All cankers sampled were spatially located within the plantations. The hypothesis that spores are not locally disseminated was supported by the absence of any spatial clustering in the distribution of the MLHs. A large number of MLHs was found at both sites and the haplotypic diversity was close to the maximum (one) in both populations. All measures of recombination were not different from expectations under a scenario of sexual recombination. Genetic differentiation between the two sites was very low (theta = 0.023), yet it was significantly different from zero (P < 0.01). This analysis is in agreement with a scenario of extensive sexual recombination followed by some long-distance dispersal.
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Hamelin RC, Dusabenyagasani M, Et-Touil K. Fine-level genetic structure of white pine blister rust populations. PHYTOPATHOLOGY 1998; 88:1187-1191. [PMID: 18944852 DOI: 10.1094/phyto.1998.88.11.1187] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
ABSTRACT The fine-level genetic structure of the white pine blister rust agent, Cronartium ribicola, was investigated by sampling multiple monokaryotic spermogonia directly on cankers in four eastern Canadian white pine (Pinus strobus) plantations and assessing genetic variability, using random amplified polymorphic DNA (RAPD) markers. Ninety-eight percent of the cankers surveyed contained a single DNA haplotype, suggesting spermogonia within cankers are the result of clonal reproduction. A single canker contained two haplotypes that were divided between the upper and lower parts of the canker, suggesting it represented two confluent cankers. In contrast, genotypic diversity was high among cankers. Thirty-seven haplotypes were found among forty-three cankers sampled, and an analysis of molecular variance indicated that 93% (P < 0.001) of the total genetic diversity was attributable to sampling of different cankers, strongly suggesting that multiple infections do not take place in the white pine blister rust pathosystem, i.e., a canker is the result of infection by a single genotype. This result is in contrast with the high level of genetic diversity previously reported among dikaryotic aecidia within cankers and is consistent with the hypothesis that variability in the aecidial stage is the result of outcrossing between resident spermogonia and alien spermatia. The genetic structure of the spermogonial stage, which is the vegetative extension of infection by basidiospores and, therefore, the indirect result of meiosis, was consistent with random mating; the observed genotypic diversity was not significantly different (P > 0.05) from the genotypic diversity expected under the assumption of panmixis. The results indicate that monokaryotic cankers can be genotyped by sampling a single unopened spermogonia per canker.
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Hamelin RC, Beaulieu J, Plourde A. Genetic diversity in populations of Cronartium ribicola in plantations and natural stands of Pinus strobus. TAG. THEORETICAL AND APPLIED GENETICS. THEORETISCHE UND ANGEWANDTE GENETIK 1995; 91:1214-1221. [PMID: 24170049 DOI: 10.1007/bf00220932] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/05/1995] [Accepted: 05/25/1995] [Indexed: 06/02/2023]
Abstract
Genetic diversity was studied in 22 populations of the white pine blister rust fungus Cronartium ribicola from natural stands and plantations of eastern white pine, Pinus strobus. Pseudo-allelic frequencies were estimated at each of 7 putative RAPD loci by scoring for presence or absence of amplified fragments in dikaryotic aecidiospores. Analysis of genetic distance between all pairs of populations did not reveal any trend with regard to geographic origin or type of white pine stand. In addition, when hierarchical population structure was analysed, total genetic diversity (H s =0.214) was mostly attributable to diversity within populations (H s =0.199; AMOVA φ st =0.121, P<0.01). Genetic diversity of populations relative to region of origin (east, centre, and west) or type of stand (natural stands vs plantations) was not significantly different from zero (P>0.10) Nevertheless, a significant proportion of genetic differentiation was found between populations within region or stand type (F st =0.114; φ sc =0.132, P<0.001). This result indicates that some population structure exists but that it appears to be independent of region of origin or type of stand. At least for 2 populations from white pine plantations, it appears possible that a recent introduction of a limited number of propagules was responsible for low levels of genetic diversity. We interpret these results as meaning that either long-distance dispersal is taking place between populations more than 1000 km apart or that these populations share a common recent ancestor. In addition, we suggest that C. ribicola may still be expanding its distribution by colonizing new plantations.
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Affiliation(s)
- R C Hamelin
- Natural Resources Canada, Canadian Forest Service, Quebec Region, 1055 du PEPS, PO Box 3800, G1V 4C7, Sainte-Foy, Quebec, Canada
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