Dorothy Steane

Climate adaptation and ecological restoration in eucalypts

Publisher: CSIRO Publishing

Date: 2016

DOI: 10.1071/RS16004

Abstract: Eucalypts are the cornerstone of ecological restoration efforts across the highly modified agricultural landscapes of southern Australia. ‘Local provenancing’ is the established strategy for sourcing germplasm for ecological restoration plantings, yet this approach gives little consideration to the persistence of these plantings under future climates. This paper provides a synopsis of recent and ongoing research that the authors are undertaking on climate adaptation in eucalypts, combining new genomic approaches with ecophysiological evidence from provenance trials. These studies explore how adaptive ersity is distributed within and among populations, whether populations are buffered against change through capacity for phenotypic plasticity, and how this informs provenancing strategies. Results to date suggest that eucalypts have some capacity to respond to future environmental instability through adaptive phenotypic plasticity or selection of putatively adaptive alleles. Despite this, growing evidence suggests that eucalypts will still be vulnerable to change. Provenancing strategies that exploit adaptations found in non-local provenances could thus confer greater climate-resilience in ecological restoration plantings, although they will also need to account for potential interactions between climate adaptations and other factors (e.g. cryptic evolutionary variation, non-climate-related adaptations, herbivory and elevated CO2).

Managing Australia’s eucalypt gene pools: assessing the risk of exotic gene flow

Publisher: CSIRO Publishing

Date: 2016

DOI: 10.1071/RS16003

Abstract: Most eucalypts are endemic to Australia but they have been introduced into more than 100 countries and there are now over 20 million hectares of eucalypt plantations globally. These plantations are grown mainly for pulpwood but there is expanding interest in their use as a renewable source of solid wood products and energy. In Australia, the eucalypt plantation estate is nearing one million hectares, located mainly in temperate regions and dominated by Eucalyptus globulus and E. nitens (subgenus Symphyomyrtus), which are grown mainly outside their natural ranges. While eucalypt species from different major subgenera do not hybridise, hybrids within subgenera are often reported, including hybrids with plantation species. Concerns were raised in the late 1990s that pollen-mediated gene flow from locally exotic plantation eucalypts may affect the integrity of adjacent native eucalypt gene pools. As Australia is the centre-of-origin of most eucalypt species used in plantations around the world, exotic gene flow is one of the many issues that require management for industry sustainability and certification purposes. We here summarise over a decade of research aimed at providing the framework and biological data to help assess and manage the risk of gene flow from these plantations into native gene pools in Australia.

Origins, Diversity and Naturalization of Eucalyptus globulus (Myrtaceae) in California

Publisher: MDPI AG

Date: 23-08-2021

DOI: 10.3390/F12081129

Abstract: Eucalyptus globulus is native to southeastern Australia, including the island of Tasmania, but is one of the most widely grown hardwood forestry species in the world and is naturalized on several continents. We studied its naturalization in California, where the species has been planted for over 150 years. We s led 70 E. globulus trees from 53 locations spanning the entire range of the species in California to quantify the genetic variation present and test whether particular genotypes or native origin affect variation in naturalization among locations. Diversity and native affinities were determined based on six nuclear microsatellite markers and sequences from a highly variable chloroplast DNA region (JLA+). The likely native origin was determined by DNA-based comparison with a range-wide native stand collection. Most of California’s E. globulus originated from eastern Tasmania. Genetic ersity in California is greatly reduced compared with that of the native Australian population, with a single chloroplast haplotype occurring in 66% of the Californian s les. Throughout California, the degree of E. globulus naturalization varies widely but was not associated with genotype or native origin of the trees, arguing that factors such as local climate and disturbance are more important than pre-introduction evolutionary history.

Evidence for adaptation and acclimation in a widespread eucalypt of semi-arid Australia

Publisher: Oxford University Press (OUP)

Date: 30-03-2017

DOI: 10.1093/BIOLINNEAN/BLW051

Microsatellite analysis of population structure in Eucalyptus globulus

Publisher: Canadian Science Publishing

Date: 09-2017

DOI: 10.1139/GEN-2016-0218

Abstract: Eucalyptus globulus subsp. globulus Labill. (Tasmanian Blue Gum), native to southeast Australia, is a benchmark species for the pulp and paper industry. We genotyped 397 trees from 16 populations of E. globulus representing the native ersity in Australia using 24 microsatellite loci. Eight genetically distinct groups were detected, consistent with genetic groupings detected in previous quantitative and molecular studies. A s le of 29 Portuguese in iduals was added to help clarify the origin of the Portuguese landrace. The results suggest a southern and eastern Tasmania origin for the Portuguese landrace. This genetic framework will enable researchers to investigate the provenance of in iduals of unknown pedigree and assess the levels of representation of E. globulus natural variation in the Portuguese landrace.

High density, genome-wide markers and intra-specific replication yield an unprecedented phylogenetic reconstruction of a globally significant, speciose lineage of Eucalyptus

Publisher: Elsevier BV

Date: 12-2016

DOI: 10.1016/J.YMPEV.2016.08.009

Abstract: We used genome-wide markers and an unprecedented scale of s ling to construct a phylogeny for a globally significant Eucalyptus lineage that has been impacted by hybridisation, recent radiation and morphological convergence. Our approach, using 3109 DArT markers distributed throughout the genome and 540 s les covering 185 terminal taxa in sections Maidenaria, Exsertaria, Latoangulatae and related smaller sections, with multiple geographically widespread s les per terminal taxon, produced a phylogeny that largely matched the morphological treatment of sections, though sections Exsertaria and Latoangulatae were polyphyletic. At lower levels there were numerous inconsistencies between the morphological treatment and the molecular phylogeny, and taxa within the three main sections were generally not monophyletic at the series (at least 62% polyphyly) or species (at least 52% polyphyly) level. Some of the discrepancies appear to be the result of morphological convergence or misclassifications, and we propose some taxonomic reassessments to address this. However, many inconsistencies appear to be the products of incomplete speciation and/or hybridisation. Our analysis represents a significant advance on previous phylogenies of these important eucalypt sections (which have mainly used single s les to represent each species), thus providing a robust phylogenetic framework for evolutionary and ecological studies.

Genome-wide scans detect adaptation to aridity in a widespread forest tree species

Publisher: Wiley

Date: 05-2014

DOI: 10.1111/MEC.12751

Abstract: Patterns of adaptive variation within plant species are best studied through common garden experiments, but these are costly and time-consuming, especially for trees that have long generation times. We explored whether genome-wide scanning technology combined with outlier marker detection could be used to detect adaptation to climate and provide an alternative to common garden experiments. As a case study, we s led nine provenances of the widespread forest tree species, Eucalyptus tricarpa, across an aridity gradient in southeastern Australia. Using a Bayesian analysis, we identified a suite of 94 putatively adaptive (outlying) sequence-tagged markers across the genome. Population-level allele frequencies of these outlier markers were strongly correlated with temperature and moisture availability at the site of origin, and with population differences in functional traits measured in two common gardens. Using the output from a canonical analysis of principal coordinates, we devised a metric that provides a holistic measure of genomic adaptation to aridity that could be used to guide assisted migration or genetic augmentation.

Bioclimatic transect networks: Powerful observatories of ecological change

Publisher: Wiley

Date: 19-05-2017

DOI: 10.1002/ECE3.2995

Molecular insights into the dynamics of species invasion by hybridisation in Tasmanian eucalypts

Publisher: Wiley

Date: 27-02-2023

DOI: 10.1111/MEC.16892

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 in iduals resembling E. risdonii occur and are hypothesised to be a result of backcrossing. Using 3362 genome‐wide SNPs assessed from 97 in iduals of E. risdonii and E. amygdalina and 171 hybrid trees, we show that (i) isolated hybrids match the genotypes expected of F 1 /F 2 hybrids, (ii) there is a continuum in the genetic composition among the isolated hybrid patches from patches dominated by F 1 /F 2 ‐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.

Genomic divergence in sympatry indicates strong reproductive barriers and cryptic species within Eucalyptus salubris

Publisher: Wiley

Date: 29-03-2021

DOI: 10.1002/ECE3.7403

Abstract: Genetic studies are increasingly detecting cryptic taxa that likely represent a significant component of global bio ersity. However, cryptic taxa are often criticized because they are typically detected serendipitously and may not receive the follow‐up study required to verify their geographic or evolutionary limits. Here, we follow‐up a study of Eucalyptus salubris that unexpectedly detected two ergent lineages but was not s led sufficiently to make clear interpretations. We undertook comprehensive s ling for an independent genomic analysis (3,605 SNPs) to investigate whether the two purported lineages remain discrete genetic entities or if they intergrade throughout the species’ range. We also assessed morphological and ecological traits, and sequenced chloroplast DNA. SNP results showed strong genome‐wide ergence ( F ST = 0.252) between two discrete lineages: one dominated the north and one the southern regions of the species’ range. Within lineages, gene flow was high, with low differentiation (mean F ST = 0.056) spanning hundreds of kilometers. In the central region, the lineages were interspersed but maintained their genomic distinctiveness: an indirect demonstration of reproductive isolation. Populations of the southern lineage exhibited significantly lower specific leaf area and occurred on soils with lower phosphorus relative to the northern lineage. Finally, two major chloroplast haplotypes were associated with each lineage but were shared between lineages in the central distribution. Together, these results suggest that these lineages have non‐contemporary origins and that ecotypic adaptive processes strengthened their ergence more recently. We conclude that these lineages warrant taxonomic recognition as separate species and provide fascinating insight into eucalypt speciation.

Expansion of the rare Eucalyptus risdonii under climate change through hybridization with a closely related species despite hybrid inferiority

Publisher: Oxford University Press (OUP)

Date: 05-08-2021

DOI: 10.1093/AOB/MCAB103

Abstract: 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. 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. 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 in iduals 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. 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.

University Of Oxford

Location: United Kingdom of Great Britain and Northern Ireland

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University Of Tasmania

Location: Australia

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Discovery Projects - Grant ID: DP190102053

Start Date: 01-2019

End Date: 12-2024

Amount: $475,000.00

Funder: Australian Research Council