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Pfeilsticker TR, Jones RC, Steane DA, Vaillancourt RE, Potts BM. Molecular insights into the dynamics of species invasion by hybridisation in Tasmanian eucalypts. Mol Ecol 2023; 32:2913-2929. [PMID: 36807951 DOI: 10.1111/mec.16892] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2022] [Revised: 11/26/2022] [Accepted: 01/26/2023] [Indexed: 02/22/2023]
Abstract
In plants where seed dispersal is limited compared with pollen dispersal, hybridisation may enhance gene exchange and species dispersal. We provide genetic evidence of hybridisation contributing to the expansion of the rare Eucalyptus risdonii into the range of the widespread Eucalyptus amygdalina. These closely related tree species are morphologically distinct, and observations suggest that natural hybrids occur along their distribution boundaries and as isolated trees or in small patches within the range of E. amygdalina. Hybrid phenotypes occur outside the range of normal dispersal for E. risdonii seed, yet in some hybrid patches small individuals resembling E. risdonii occur and are hypothesised to be a result of backcrossing. Using 3362 genome-wide SNPs assessed from 97 individuals of E. risdonii and E. amygdalina and 171 hybrid trees, we show that (i) isolated hybrids match the genotypes expected of F1 /F2 hybrids, (ii) there is a continuum in the genetic composition among the isolated hybrid patches from patches dominated by F1 /F2 -like genotypes to those dominated by E. risdonii-backcross genotypes, and (iii) the E. risdonii-like phenotypes in the isolated hybrid patches are most-closely related to proximal larger hybrids. These results suggest that the E. risdonii phenotype has been resurrected in isolated hybrid patches established from pollen dispersal, providing the first steps in its invasion of suitable habitat by long-distance pollen dispersal and complete introgressive displacement of E. amygdalina. Such expansion accords with the population demographics, common garden performance data, and climate modelling which favours E. risdonii and highlights a role of interspecific hybridisation in climate change adaptation and species expansion.
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Affiliation(s)
- Thais R Pfeilsticker
- School of Natural Sciences and ARC Training Centre for Forest Value, University of Tasmania, Hobart, Tasmania, Australia
| | - Rebecca C Jones
- School of Natural Sciences and ARC Training Centre for Forest Value, University of Tasmania, Hobart, Tasmania, Australia
| | - Dorothy A Steane
- School of Natural Sciences and ARC Training Centre for Forest Value, University of Tasmania, Hobart, Tasmania, Australia
| | - René E Vaillancourt
- School of Natural Sciences and ARC Training Centre for Forest Value, University of Tasmania, Hobart, Tasmania, Australia
| | - Brad M Potts
- School of Natural Sciences and ARC Training Centre for Forest Value, University of Tasmania, Hobart, Tasmania, Australia
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Butcher CL, Rubin BY, Anderson SL, Lewis JD. Long-Distance Pollen Dispersal in Urban Green Roof and Ground-Level Habitats. Front Ecol Evol 2022. [DOI: 10.3389/fevo.2022.790464] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Long-distance pollen dispersal is critical for gene flow in plant populations, yet pollen dispersal patterns in urban habitats such as green roofs have not been extensively studied. Pollen dispersal patterns typically are assessed either by fitting non-linear models to the relationship between the degree of pollen dispersal and distance to the pollen source (i.e., curve fitting), or by fitting probability density functions (PDFs) to pollen dispersal probability histograms (i.e., PDF fitting). Studies using curve fitting typically report exponential decay patterns in pollen dispersal. However, PDF fitting typically produces more fat-tailed distributions, suggesting the exponential decay may not be the best fitting model. Because the two approaches may yield conflicting results, we used both approaches to examine pollen dispersal patterns in the wind-pollinated Amaranthus tuberculatus and the insect-pollinated Solanum lycopersicum at two green roof and two ground-level sites in the New York (NY, United States) metropolitan area. For the curve fitting analyses, the exponential decay and inverse power curves provided good fits to pollen dispersal patterns across both green roof and ground-level sites for both species. Similar patterns were observed with the PDF fitting analyses, where the exponential or inverse Gaussian were the top PDF at most sites for both species. While the curve fitting results are consistent with other studies, the results differ from most studies using PDF fitting, where long-distance pollen dispersal is more common than we observed. These results highlight the need for further research to compare curve and PDF fitting for predicting pollen dispersal patterns. And, critically, while long-distance pollen dispersal may be an important component of overall pollen dispersal for A. tuberculatus and S. lycopersicum in both urban green roof and ground-level sites, our results suggest it potentially may occur to a lesser extent compared with plants in less-urban areas.
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The Genetics and Ecology of Post-Fire Eucalyptus globulus Recruitment in an Isolated Stand in Central Portugal. FORESTS 2022. [DOI: 10.3390/f13050680] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Eucalyptus globulus Labill. is a widespread forest tree species, reported as naturalized across the introduced range, often showing abundant natural regeneration after wildfires. This paper studies a post-fire cohort of seedlings derived from a small, isolated E. globulus stand in central Portugal. The aim is to better understand the genetic dynamics and dispersal mechanisms of naturally established E. globulus populations in the introduced range. The seedling density at 55 m from adult trees was 12,000 ha−1, the farthest seedling being registered at 101 m. Post-fire expansion occurred in a southward direction, in accordance with predominant wind. Seedlings had significantly lower levels of genetic diversity (Ae = 5.8.; He = 0.8) than adult trees (Ae = 6.5; He = 0.8). Crossings were strongly unbalanced, with only eight trees contributing to the sampled seedlings, and one single tree contributing to 52% of these seedlings. Moreover, the co-ancestry amongst seedlings more than doubled (from θ = 0.03 to 0.076), and the population status number was around one third of the value registered for the adult population (from Ns = 16.2 to 6.6). Despite its isolation, external pollen was detected in the stand, and appears to have travelled at least 700 m, contributing to 22% of the offspring. Overall, the seedling cohort is much less diverse than the parent trees, with expected lower resilience and persistence to environmental stresses.
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Pfeilsticker TR, Jones RC, Steane DA, Harrison PA, Vaillancourt RE, Potts BM. Expansion of the rare Eucalyptus risdonii under climate change through hybridization with a closely related species despite hybrid inferiority. ANNALS OF BOTANY 2022; 129:1-14. [PMID: 34351372 PMCID: PMC8752398 DOI: 10.1093/aob/mcab103] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/27/2021] [Accepted: 08/04/2021] [Indexed: 05/31/2023]
Abstract
BACKGROUND AND AIMS Hybridization is increasingly recognized as an integral part of the dynamics of species range expansion and contraction. Thus, it is important to understand the reproductive barriers between co-occurring species. Extending previous studies that argued that the rare Eucalyptus risdonii was expanding into the range of the surrounding E. amygdalina by both seed and pollen dispersal, we here investigate the long-term fitness of both species and their hybrids and whether expansion is continuing. METHODS We assessed the survival of phenotypes representing a continuum between the two pure species in a natural hybrid swarm after 29 years, along with seedling recruitment. The performance of pure species as well as of artificial and natural hybrids was also assessed over 28 years in a common garden trial. KEY RESULTS In the hybrid zone, E. amygdalina adults showed greater mortality than E. risdonii, and the current seedling cohort is still dominated by E. risdonii phenotypes. Morphologically intermediate individuals appeared to be the least fit. Similar results were observed after growing artificial first-generation and natural hybrids alongside pure species families in a common garden trial. Here, the survival, reproduction, health and growth of the intermediate hybrids were significantly less than those of either pure species, consistent with hybrid inferiority, although this did not manifest until later reproductive ages. Among the variable progeny of natural intermediate hybrids, the most E. risdonii-like phenotypes were the most fit. CONCLUSIONS This study contributes to the increasing number of reports of hybrid inferiority in Eucalyptus, suggesting that post-zygotic barriers contribute to the maintenance of species integrity even between closely related species. However, with fitness rapidly recovered following backcrossing, it is argued that hybridization can still be an important evolutionary process, in the present case appearing to contribute to the range expansion of the rare E. risdonii in response to climate change.
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Affiliation(s)
- T R Pfeilsticker
- School of Natural Sciences and ARC Training Centre for Forest Value, University of Tasmania, Hobart, Australia
| | - R C Jones
- School of Natural Sciences and ARC Training Centre for Forest Value, University of Tasmania, Hobart, Australia
| | - D A Steane
- School of Natural Sciences and ARC Training Centre for Forest Value, University of Tasmania, Hobart, Australia
| | - P A Harrison
- School of Natural Sciences and ARC Training Centre for Forest Value, University of Tasmania, Hobart, Australia
| | - R E Vaillancourt
- School of Natural Sciences and ARC Training Centre for Forest Value, University of Tasmania, Hobart, Australia
| | - B M Potts
- School of Natural Sciences and ARC Training Centre for Forest Value, University of Tasmania, Hobart, Australia
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Butcher CL, Rubin BY, Anderson SL, Lewis JD. Pollen dispersal patterns differ among sites for a wind-pollinated species and an insect-pollinated species. AMERICAN JOURNAL OF BOTANY 2020; 107:1504-1517. [PMID: 33108685 DOI: 10.1002/ajb2.1554] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/10/2020] [Accepted: 07/23/2020] [Indexed: 06/11/2023]
Abstract
PREMISE Pollen dispersal, the main component of overall plant gene flow, generally decreases with increasing distance from the pollen source, but the pattern of this relationship may differ among sites. Although site-based differences in pollen dispersal may lead to over- or underestimation of gene flow, no studies have investigated pollen dispersal patterns among differing urban site types, despite the incongruent range of habitats in urban areas. METHODS We used paternity assignment to assess pollen dispersal patterns in a wind-pollinated species (waterhemp; Amaranthus tuberculatus) and in an insect-pollinated species (tomato; Solanum lycopersicum) in experimental arrays at four disparate sites (two roof-level sites, two ground-level sites) in the New York (New York, USA) metropolitan area. RESULTS The number of seeds or fruits, a proxy for the number of flowers pollinated, decreased with increasing distance from the pollen donors at all sites for both species. However, the mean number of Amaranthus tuberculatusseeds produced at a given distance differed two-fold among sites, while the slope of the relationship between Solanum lycopersicumfruit production and distance differed by a factor of four among sites. CONCLUSIONS Pollen dispersal patterns may differ substantially among sites, both in the amount of pollen dispersed at a given distance and in the proportional decrease in pollen dispersal with increasing distance, and these effects may act independently. Accordingly, the capacity of plant species to adapt to climate change and other selection pressures may be different from predictions based on pollen dispersal patterns at a single location.
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Affiliation(s)
- Chelsea L Butcher
- Louis Calder Center - Biological Field Station, Fordham University, 31 Whippoorwill Road, Armonk, New York, 10504, USA
- Center for Urban Ecology, Fordham University, 441 East Fordham Road, Bronx, New York, 10458, USA
- Department of Biological Sciences, Fordham University, 441 East Fordham Road, Bronx, New York, 10458, USA
- Department of Mathematics and Natural Sciences, Northwood University, 4000 Whiting Drive, Midland, Michigan, 48640, USA
| | - Berish Y Rubin
- Department of Biological Sciences, Fordham University, 441 East Fordham Road, Bronx, New York, 10458, USA
| | - Sylvia L Anderson
- Department of Biological Sciences, Fordham University, 441 East Fordham Road, Bronx, New York, 10458, USA
| | - James D Lewis
- Louis Calder Center - Biological Field Station, Fordham University, 31 Whippoorwill Road, Armonk, New York, 10504, USA
- Center for Urban Ecology, Fordham University, 441 East Fordham Road, Bronx, New York, 10458, USA
- Department of Biological Sciences, Fordham University, 441 East Fordham Road, Bronx, New York, 10458, USA
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Bezemer N, Hopper SD, Krauss SL, Phillips RD, Roberts DG. Primary pollinator exclusion has divergent consequences for pollen dispersal and mating in different populations of a bird‐pollinated tree. Mol Ecol 2019; 28:4883-4898. [DOI: 10.1111/mec.15264] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2019] [Revised: 09/23/2019] [Accepted: 09/30/2019] [Indexed: 01/09/2023]
Affiliation(s)
- Nicole Bezemer
- Centre of Excellence in Natural Resource Management School of Agriculture and Environment The University of Western Australia Albany WA Australia
- Department of Biodiversity Conservation and Attractions Kings Park Science West Perth WA Australia
| | - Stephen D. Hopper
- Centre of Excellence in Natural Resource Management School of Agriculture and Environment The University of Western Australia Albany WA Australia
| | - Siegy L. Krauss
- Department of Biodiversity Conservation and Attractions Kings Park Science West Perth WA Australia
- Biological Sciences The University of Western Australia Crawley WA Australia
| | - Ryan D. Phillips
- Department of Biodiversity Conservation and Attractions Kings Park Science West Perth WA Australia
- Department of Ecology, Environment and Evolution La Trobe University Melbourne Vic. Australia
| | - David G. Roberts
- Centre of Excellence in Natural Resource Management School of Agriculture and Environment The University of Western Australia Albany WA Australia
- Department of Biodiversity Conservation and Attractions Kings Park Science West Perth WA Australia
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Schlaepfer DR, Braschler B, Rusterholz HP, Baur B. Genetic effects of anthropogenic habitat fragmentation on remnant animal and plant populations: a meta-analysis. Ecosphere 2018. [DOI: 10.1002/ecs2.2488] [Citation(s) in RCA: 72] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Affiliation(s)
- Daniel R. Schlaepfer
- School of Forestry and Environmental Studies; Yale University; New Haven Connecticut 06511 USA
| | - Brigitte Braschler
- Section of Conservation Biology; Department of Environmental Sciences; University of Basel; CH-4056 Basel Switzerland
| | - Hans-Peter Rusterholz
- Section of Conservation Biology; Department of Environmental Sciences; University of Basel; CH-4056 Basel Switzerland
| | - Bruno Baur
- Section of Conservation Biology; Department of Environmental Sciences; University of Basel; CH-4056 Basel Switzerland
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Sampson J, Tapper S, Coates D, Hankinson M, Mcarthur S, Byrne M. Persistence with episodic range expansion from the early Pleistocene: the distribution of genetic variation in the forest tree Corymbia calophylla (Myrtaceae) in south-western Australia. Biol J Linn Soc Lond 2018. [DOI: 10.1093/biolinnean/blx168] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
Affiliation(s)
- Jane Sampson
- Science and Conservation Division, Department of Biodiversity, Conservation and Attractions, Bentley Delivery Centre, WA, Australia
| | - Sarah Tapper
- Science and Conservation Division, Department of Biodiversity, Conservation and Attractions, Bentley Delivery Centre, WA, Australia
| | - David Coates
- Science and Conservation Division, Department of Biodiversity, Conservation and Attractions, Bentley Delivery Centre, WA, Australia
| | - Maggie Hankinson
- Science and Conservation Division, Department of Biodiversity, Conservation and Attractions, Bentley Delivery Centre, WA, Australia
| | - Shelley Mcarthur
- Science and Conservation Division, Department of Biodiversity, Conservation and Attractions, Bentley Delivery Centre, WA, Australia
| | - Margaret Byrne
- Science and Conservation Division, Department of Biodiversity, Conservation and Attractions, Bentley Delivery Centre, WA, Australia
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Larcombe MJ, Costa E Silva J, Tilyard P, Gore P, Potts BM. On the persistence of reproductive barriers in Eucalyptus: the bridging of mechanical barriers to zygote formation by F1 hybrids is counteracted by intrinsic post-zygotic incompatibilities. ANNALS OF BOTANY 2016; 118:431-44. [PMID: 27401540 PMCID: PMC4998977 DOI: 10.1093/aob/mcw115] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/24/2016] [Accepted: 05/04/2016] [Indexed: 05/04/2023]
Abstract
BACKGROUND AND AIMS Many previous studies conclude that pre-zygotic barriers such as mechanical isolation account for most reproductive isolation between pairs of taxa. However, the inheritance and persistence of barriers such as these after the first generation of hybridization is rarely quantified, even though it is a vital consideration in understanding gene flow potential. There is an asymmetrical pre-zygotic mechanical barrier to hybridization between Eucalyptus nitens and Eucalyptus globulus, which completely prevents small-flowered E. nitens pollen from mating with large E. globulus flowers, while the reverse cross is possible. We aimed to determine the relative importance of pre- and post-zygotic barriers in preventing gene flow following secondary contact between E. nitens and E. globulus, including the inheritance of barriers in advanced-generation hybrids. METHODS Experimental crossing was used to produce outcrossed E. nitens, E. globulus and their F1, F2, BCg and BCn hybrids. The strength and inheritance of a suite of pre- and post-zygotic barriers were assessed, including 20-year survival, growth and reproductive capacity. KEY RESULTS The mechanical barrier to hybridization was lost or greatly reduced in the F1 hybrid. In contrast, intrinsic post-zygotic barriers were strong and persistent. Line-cross analysis indicated that the outbreeding depression in the hybrids was best explained by epistatic loss. CONCLUSIONS The removal of strong mechanical barriers between E. nitens and E. globulus allows F1 hybrids to act as a bridge for bi-directional gene flow between these species. However, strong and persistent post-zygotic barriers exist, meaning that wherever F1 hybridization does occur, intrinsic post-zygotic barriers will be responsible for most reproductive isolation in this system. This potential transient nature of mechanical barriers to zygote formation due to additive inheritance in hybrids appears under-appreciated, and highlights the often important role that intrinsic post-mating barriers play in maintaining species boundaries at zones of secondary contact.
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Affiliation(s)
- Matthew J Larcombe
- Department of Botany, University of Otago, PO Box 56, Dunedin 9011, New Zealand
| | - João Costa E Silva
- Centro de Estudos Florestais, Instituto Superior de Agronomia, Universidade de Lisboa, Tapada da Ajuda, 1349-017 Lisboa, Portugal
| | - Paul Tilyard
- School of Biological Sciences, and ARC Centre for Forest Value, 10 University of Tasmania, Private Bag 55, Hobart, Tasmania 7001, Australia
| | - Peter Gore
- seedEnergy Pty Ltd, 2 Derwent Avenue, Margate, Tasmania 7054, Australia
| | - Brad M Potts
- School of Biological Sciences, and ARC Centre for Forest Value, 10 University of Tasmania, Private Bag 55, Hobart, Tasmania 7001, Australia
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Larcombe MJ, Holland B, Steane DA, Jones RC, Nicolle D, Vaillancourt RE, Potts BM. Patterns of Reproductive Isolation inEucalyptus—A Phylogenetic Perspective. Mol Biol Evol 2015; 32:1833-46. [DOI: 10.1093/molbev/msv063] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
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Thrall PH, Oakeshott JG, Fitt G, Southerton S, Burdon JJ, Sheppard A, Russell RJ, Zalucki M, Heino M, Ford Denison R. Evolution in agriculture: the application of evolutionary approaches to the management of biotic interactions in agro-ecosystems. Evol Appl 2015; 4:200-15. [PMID: 25567968 PMCID: PMC3352559 DOI: 10.1111/j.1752-4571.2010.00179.x] [Citation(s) in RCA: 102] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2010] [Accepted: 11/30/2010] [Indexed: 01/04/2023] Open
Abstract
Anthropogenic impacts increasingly drive ecological and evolutionary processes at many spatio-temporal scales, demanding greater capacity to predict and manage their consequences. This is particularly true for agro-ecosystems, which not only comprise a significant proportion of land use, but which also involve conflicting imperatives to expand or intensify production while simultaneously reducing environmental impacts. These imperatives reinforce the likelihood of further major changes in agriculture over the next 30–40 years. Key transformations include genetic technologies as well as changes in land use. The use of evolutionary principles is not new in agriculture (e.g. crop breeding, domestication of animals, management of selection for pest resistance), but given land-use trends and other transformative processes in production landscapes, ecological and evolutionary research in agro-ecosystems must consider such issues in a broader systems context. Here, we focus on biotic interactions involving pests and pathogens as exemplars of situations where integration of agronomic, ecological and evolutionary perspectives has practical value. Although their presence in agro-ecosystems may be new, many traits involved in these associations evolved in natural settings. We advocate the use of predictive frameworks based on evolutionary models as pre-emptive management tools and identify some specific research opportunities to facilitate this. We conclude with a brief discussion of multidisciplinary approaches in applied evolutionary problems.
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Affiliation(s)
| | | | - Gary Fitt
- CSIRO Ecosystem Sciences Indooroopilly, Qld, Australia
| | | | | | | | | | - Myron Zalucki
- The University of Queensland, School of Integrative Biology Qld, Australia
| | - Mikko Heino
- Department of Biology, University of Bergen Bergen, Norway
| | - R Ford Denison
- University of Minnesota, Ecology, Evolution, and Behavior St. Paul, MN, USA
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Lee DJ, Brawner JT, Pegg GS. Screening Eucalyptus cloeziana and E. argophloia Populations for Resistance to Puccinia psidii. PLANT DISEASE 2015; 99:71-79. [PMID: 30699734 DOI: 10.1094/pdis-04-14-0353-re] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Disease screening to determine the threat Puccinia psidii poses to plantation and native eucalypts in Australia was undertaken in half-sib families of two contrasting eucalypt species, Eucalyptus cloeziana and E. argophloia. Artificial inoculation with a single-lesion isolate of P. psidii was used to screen these species for resistance to the biotype of P. psidii established in Australia. The objective was to characterize resistance to P. psidii within these two distinct species: E. argophloia, a vulnerable species with a narrow distribution, and E. cloeziana, a species with a broad and extensive distribution in Queensland. Results for E. cloeziana indicate that inland provenances are more resistant to P. psidii infection than provenances from coastal regions. Heritability estimates for the two assessment systems used (resistance on a 1-to-5 ordinal scale verses resistance on a 0-to-1 binomial scale) were low to high (0.24 to 0.63) for E. argophloia and moderate to high (0.4 to 0.91) for E. cloeziana, indicating a significant level of additive genetic variance for rust resistance within the populations. This study demonstrates the potential to select resistant families within the tested populations and indicates that P. psidii could detrimentally affect these species in native forests, nurseries, and plantations.
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Affiliation(s)
- D J Lee
- Forest Industries Research Centre, University of the Sunshine Coast, Maroochydore DC Qld 4558 Australia, and Forestry & Biosciences, Agri-Science Queensland, Department of Agriculture, Fisheries and Forestry, Brisbane Qld 4001 Australia
| | - J T Brawner
- Forest Industries Research Centre, University of the Sunshine Coast and CSIRO Plant Industries, St. Lucia Qld 4067 Australia
| | - G S Pegg
- Forest Industries Research Centre, University of the Sunshine Coast and Forestry & Biosciences, Agri-Science Queensland, Department of Agriculture, Fisheries and Forestry
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Ramírez-Valiente JA, Robledo-Arnuncio JJ. Adaptive consequences of human-mediated introgression for indigenous tree species: the case of a relict Pinus pinaster population. TREE PHYSIOLOGY 2014; 34:1376-1387. [PMID: 25466514 DOI: 10.1093/treephys/tpu097] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Human-induced gene movement via afforestation and restoration programs is a widespread phenomenon throughout the world. However, its effects on the genetic composition of native populations have received relatively little attention, particularly in forest trees. Here, we examine to what extent gene flow from allochthonous plantations of Pinus pinaster Aiton impacts offspring performance in a neighboring relict natural population and discuss the potential consequences for the long-term genetic composition of the latter. Specifically, we conducted a greenhouse experiment involving two contrasting watering treatments to test for differences in a set of functional traits and mortality rates between P. pinaster progenies from three different parental origins: (i) local native parents, (ii) exotic parents and (iii) intercrosses between local mothers and exotic fathers (intraspecific hybrids). Our results showed differences among crosses in cumulative mortality over time: seedlings of exotic parents exhibited the lowest mortality rates and seedlings of local origin the highest, while intraspecific hybrids exhibited an intermediate response. Linear regressions showed that seedlings with higher water-use efficiency (WUE, δ(13)C) were more likely to survive under drought stress, consistent with previous findings suggesting that WUE has an important role under dry conditions in this species. However, differences in mortality among crosses were only partially explained by WUE. Other non-measured traits and factors such as inbreeding depression in the relict population are more likely to explain the lower performance of native progenies. Overall, our results indicated that intraspecific hybrids and exotic individuals are more likely to survive under stressful conditions than local native individuals, at least during the first year of development. Since summer drought is the most important demographic and selective filter affecting tree establishment in Mediterranean ecosystems, a potential early selective advantage of exotic and hybrid genotypes would enhance initial steps of introgression of non-native genes into the study relict population of P. pinaster.
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Affiliation(s)
- José Alberto Ramírez-Valiente
- Department of Forest Ecology and Genetics, INIA-CIFOR, Carretera de La Coruña km 7.5, E-28040 Madrid, Spain Present address: Department of Ecology, Evolution and Behavior, University of Minnesota, 1987 Upper Buford Circle, Saint Paul, MN 55108, USA
| | - Juan José Robledo-Arnuncio
- Department of Forest Ecology and Genetics, INIA-CIFOR, Carretera de La Coruña km 7.5, E-28040 Madrid, Spain
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Laikre L, Schwartz MK, Waples RS, Ryman N. Compromising genetic diversity in the wild: unmonitored large-scale release of plants and animals. Trends Ecol Evol 2010; 25:520-9. [DOI: 10.1016/j.tree.2010.06.013] [Citation(s) in RCA: 372] [Impact Index Per Article: 26.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2009] [Revised: 06/21/2010] [Accepted: 06/22/2010] [Indexed: 11/24/2022]
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Mimura M, Barbour RC, Potts BM, Vaillancourt RE, Watanabe KN. Comparison of contemporary mating patterns in continuous and fragmented Eucalyptus globulus native forests. Mol Ecol 2009; 18:4180-92. [PMID: 19769693 DOI: 10.1111/j.1365-294x.2009.04350.x] [Citation(s) in RCA: 70] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
While habitat fragmentation is a central issue in forest conservation studies in the face of broad-scale anthropogenic changes to the environment, its effects on contemporary mating patterns remain controversial. This is partly because of the inherent variation in mating patterns which may exist within species and the fact that few studies have replication at the landscape level. To study the effect of forest fragmentation on contemporary mating patterns, including effective pollen dispersal, we compared four native populations of the Australian forest tree, Eucalyptus globulus. We used six microsatellite markers to genotype 1289 open-pollinated offspring from paired fragmented and continuous populations on the island of Tasmania and in Victoria on mainland Australia. The mating patterns in the two continuous populations were similar, despite large differences in population density. In contrast, the two fragmented populations were variable and idiosyncratic in their mating patterns, particularly in their pollen dispersal kernels. The continuous populations showed relatively high outcrossing rates (86-89%) and low correlated paternity (0.03-0.06) compared with the fragmented populations (65-79% and 0.12-0.20 respectively). A greater proportion of trees contributed to reproduction in the fragmented (de/d>or= 0.5) compared with the continuous populations (de/d = 0.03-0.04). Despite significant inbreeding in the offspring of the fragmented populations, there was little evidence of loss of genetic diversity. It is argued that enhanced medium- and long-distance dispersal in fragmented landscapes may act to partly buffer the remnant populations from the negative effects of inbreeding and drift.
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Affiliation(s)
- Makiko Mimura
- Graduate School of Life and Environmental Sciences, University of Tsukuba, Tenoudai 1-1-1,Tsukuba, Japan.
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Sampson JF, Byrne M. Outcrossing between an agroforestry plantation and remnant native populations of Eucalyptus loxophleba. Mol Ecol 2008; 17:2769-81. [PMID: 18444981 DOI: 10.1111/j.1365-294x.2008.03779.x] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Gene dispersal among populations of a species is an important force influencing their genetic structure. Dispersal may also occur between taxa that would normally be isolated when nonendemic, domesticated or transgenic species are planted within the natural range of interfertile taxa. Such a mosaic of populations is typical of many agricultural landscapes, and investigations are needed to assess the risks of genetic contamination of the endemic populations but a combination of approaches may be necessary because of the limitations of research in this landscape. This study used microsatellite markers and a range of analyses (mating system, paternity exclusion, Bayesian assignment) to examine gene dispersal between remnants of the endemic Eucalyptus loxophleba ssp. supralaevis and a plantation of a nonendemic subspecies. Our results indicate that remnant populations are connected by significant dispersal to pollen sources up to 1.94 km away including the plantation. The combined analyses showed that the pollen pool and outcrossing rates of individuals within remnants varied significantly probably because of asynchronous flowering and that the likelihood of paternity was not correlated with spatial proximity. More than half of all progeny had male parents from outside their stand with the largest proportions estimated to come from the plantation by exclusion (42.4%) or Bayesian analyses (18.8-76%). Fragmentation may not be associated with decreased gene dispersal between populations of tree species, natural or planted, so that the distances required to buffer endemic trees in fragmented rural landscapes are likely to be large.
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Affiliation(s)
- Jane F Sampson
- Science Division, Department of Environment and Conservation, Locked Bag 104, Bentley Delivery Centre, Bentley, WA 6983, Australia.
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Byrne M, Elliott CP, Yates CJ, Coates DJ. Maintenance of high pollen dispersal in Eucalyptus wandoo, a dominant tree of the fragmented agricultural region in Western Australia. CONSERV GENET 2007. [DOI: 10.1007/s10592-007-9311-5] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Foster SA, McKinnon GE, Steane DA, Potts BM, Vaillancourt RE. Parallel evolution of dwarf ecotypes in the forest tree Eucalyptus globulus. THE NEW PHYTOLOGIST 2007; 175:370-380. [PMID: 17587385 DOI: 10.1111/j.1469-8137.2007.02077.x] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/16/2023]
Abstract
Three small populations of a dwarf ecotype of the forest tree Eucalyptus globulus are found on exposed granite headlands in south-eastern Australia. These populations are separated by at least 100 km. Here, we used 12 nuclear microsatellites and a chloroplast DNA marker to investigate the genetic affinities of the dwarf populations to one another and to their nearest populations of tall E. globulus. Cape Tourville was studied in greater detail to assess the processes enabling the maintenance of distinct ecotypes in close geographical proximity. The three dwarf populations were not related to one another and were more closely related to adjacent tall trees than to one another. At Cape Tourville the dwarf and tall ecotypes were significantly differentiated in microsatellites and in chloroplast DNA. The dwarf and tall populations differed in flowering time and no evidence of pollen dispersal from the more extensive tall to the dwarf population was found. The three dwarf populations have evolved in parallel from the local tall ecotypes. This study shows that small marginal populations of eucalypts are capable of developing reproductive isolation from nearby larger populations through differences in flowering time and/or minor spatial separation, making parapatric speciation possible.
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Affiliation(s)
- Susan A Foster
- School of Plant Science and Cooperative Research Centre for Forestry, University of Tasmania, Private Bag 55, Hobart, Tasmania 7001, Australia
| | - Gay E McKinnon
- School of Plant Science and Cooperative Research Centre for Forestry, University of Tasmania, Private Bag 55, Hobart, Tasmania 7001, Australia
| | - Dorothy A Steane
- School of Plant Science and Cooperative Research Centre for Forestry, University of Tasmania, Private Bag 55, Hobart, Tasmania 7001, Australia
| | - Brad M Potts
- School of Plant Science and Cooperative Research Centre for Forestry, University of Tasmania, Private Bag 55, Hobart, Tasmania 7001, Australia
| | - René E Vaillancourt
- School of Plant Science and Cooperative Research Centre for Forestry, University of Tasmania, Private Bag 55, Hobart, Tasmania 7001, Australia
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Jones TH, Vaillancourt RE, Potts BM. Detection and visualization of spatial genetic structure in continuous Eucalyptus globulus forest. Mol Ecol 2006; 16:697-707. [PMID: 17284205 DOI: 10.1111/j.1365-294x.2006.03180.x] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Visualizing the pattern of variation using microsatellites within a Eucalyptus globulus forest on the island of Tasmania provided surprising insights into the complex nature of the fine-scale spatial genetic structure that resides in these forests. We used spatial autocorrelation and principal coordinate analysis to compare fine-scale genetic structure between juvenile and mature cohorts in a study area, 140 m in diameter, located within a typical, continuous E. globulus forest. In total, 115 juvenile and 168 mature individuals were genotyped with eight highly polymorphic microsatellite loci. There was no significant difference in the level of genetic diversity between cohorts. However, there were differences in the spatial distribution of the genetic variation. Autocorrelation analysis provided clear evidence for significant spatial genetic structure in the mature cohort and significant, but weaker, structure in the juvenile cohort. The spatial interpolation of principal coordinate axes, derived from ordination of the genetic distance matrix between individuals, revealed a spatially coherent family group which was evident in both cohorts. Direct comparison of the genetic structure within each cohort allowed visualization of a shift in the spatial distribution of genetic variation within the population of approximately 10 m. As the shift coincided with the direction of prevailing winds, it is hypothesized that this phenomenon is due to downwind dispersal of seeds and is indicative of the important role of prevailing winds in forcing eastward gene flow in these high-latitude forests.
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Affiliation(s)
- Tim H Jones
- School of Plant Science and Cooperative Research Centre for Forestry, University of Tasmania, Private Bag 55, Hobart, Australia.
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