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Rutherford S, Rossetto M, Bragg JG, Wan JSH. Where to draw the boundaries? Using landscape genomics to disentangle the scribbly gum species complex. AMERICAN JOURNAL OF BOTANY 2023; 110:e16245. [PMID: 37747108 DOI: 10.1002/ajb2.16245] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/10/2023] [Revised: 09/18/2023] [Accepted: 09/18/2023] [Indexed: 09/26/2023]
Abstract
PREMISE Species delimitation is an integral part of evolution and ecology and is vital in conservation science. However, in some groups, species delimitation is difficult, especially where ancestral relationships inferred from morphological or genetic characters are discordant, possibly due to a complicated demographic history (e.g., recent divergences between lineages). Modern genetic techniques can take into account complex histories to distinguish species at a reasonable cost and are increasingly used in numerous applications. We focus on the scribbly gums, a group of up to five closely related and morphologically similar "species" within the eucalypts. METHODS Multiple populations of each recognized scribbly gum species were sampled over a wide region across climates, and genomewide scans were used to resolve species boundaries. RESULTS None of the taxa were completely divergent, and there were two genetically distinct entities: the inland distributed Eucalyptus rossii and a coastal conglomerate consisting of four species forming three discernible, but highly admixed groups. Divergence among taxa was likely driven by temporal vicariant processes resulting in partial separation across biogeographic barriers. High interspecific gene flow indicated separated taxa reconnected at different points in time, blurring species boundaries. CONCLUSIONS Our results highlight the need for genetic screening when dealing with closely related taxonomic entities, particularly those with modest morphological differences. We show that high-throughput sequencing can be effective at identifying species groupings and processes driving divergence, even in the most taxonomically complex groups, and be used as a standard practice for disentangling species complexes.
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Affiliation(s)
- Susan Rutherford
- Department of Environmental Science, College of Science, Mathematics and Technology, Wenzhou-Kean University, Wenzhou, Zhejiang Province, China
- Department of Environmental and Sustainability Sciences, The Dorothy and George Hennings College of Science, Mathematics and Technology, Kean University, Union, NJ, USA
- School of Environment and Safety Engineering, Jiangsu University, Zhenjiang, Jiangsu Province, China
- Research Centre for Ecosystem Resilience, Australian Institute of Botanic Science, Royal Botanic Garden Sydney, Mrs Macquaries Road, Sydney, New South Wales, Australia
- Zhejiang Bioinformatics International Science and Technology Cooperation Center, Wenzhou, Zhejiang Province, China
| | - Maurizio Rossetto
- Research Centre for Ecosystem Resilience, Australian Institute of Botanic Science, Royal Botanic Garden Sydney, Mrs Macquaries Road, Sydney, New South Wales, Australia
| | - Jason G Bragg
- Research Centre for Ecosystem Resilience, Australian Institute of Botanic Science, Royal Botanic Garden Sydney, Mrs Macquaries Road, Sydney, New South Wales, Australia
| | - Justin S H Wan
- School of Environment and Safety Engineering, Jiangsu University, Zhenjiang, Jiangsu Province, China
- Research Centre for Ecosystem Resilience, Australian Institute of Botanic Science, Royal Botanic Garden Sydney, Mrs Macquaries Road, Sydney, New South Wales, Australia
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Wilson TC, Rossetto M, Bain D, Yap JS, Wilson PD, Stimpson ML, Weston PH, Croft L. A turn in species conservation for hairpin banksias: demonstration of oversplitting leads to better management of diversity. AMERICAN JOURNAL OF BOTANY 2022; 109:1652-1671. [PMID: 36164832 PMCID: PMC9828017 DOI: 10.1002/ajb2.16074] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/07/2022] [Revised: 08/29/2022] [Accepted: 08/30/2022] [Indexed: 06/16/2023]
Abstract
PREMISE Understanding evolutionary history and classifying discrete units of organisms remain overwhelming tasks, and lags in this workload concomitantly impede an accurate documentation of biodiversity and conservation management. Rapid advances and improved accessibility of sensitive high-throughput sequencing tools are fortunately quickening the resolution of morphological complexes and thereby improving the estimation of species diversity. The recently described and critically endangered Banksia vincentia is morphologically similar to the hairpin banksia complex (B. spinulosa s.l.), a group of eastern Australian flowering shrubs whose continuum of morphological diversity has been responsible for taxonomic controversy and possibly questionable conservation initiatives. METHODS To assist conservation while testing the current taxonomy of this group, we used high-throughput sequencing to infer a population-scale evolutionary scenario for a sample set that is comprehensive in its representation of morphological diversity and a 2500-km distribution. RESULTS Banksia spinulosa s.l. represents two clades, each with an internal genetic structure shaped through historical separation by biogeographic barriers. This structure conflicts with the existing taxonomy for the group. Corroboration between phylogeny and population statistics aligns with the hypothesis that B. collina, B. neoanglica, and B. vincentia should not be classified as species. CONCLUSIONS The pattern here supports how morphological diversity can be indicative of a locally expressed suite of traits rather than relationship. Oversplitting in the hairpin banksias is atypical since genomic analyses often reveal that species diversity is underestimated. However, we show that erring on overestimation can yield negative consequences, such as the disproportionate prioritization of a geographically anomalous population.
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Affiliation(s)
- Trevor C. Wilson
- Plant Discovery and Evolution, Australian Institute of Botanical ScienceRoyal Botanic Gardens and Domain TrustSydneyAustralia
- Research Centre for Ecosystem Resilience, Australian Institute of Botanical ScienceThe Royal Botanic Garden SydneyAustralia
| | - Maurizio Rossetto
- Research Centre for Ecosystem Resilience, Australian Institute of Botanical ScienceThe Royal Botanic Garden SydneyAustralia
| | - David Bain
- Ecosystems and Threatened Species, Biodiversity Conservation and ScienceNSW Department of Planning and EnvironmentWollongongAustralia
| | - Jia‐Yee S. Yap
- Research Centre for Ecosystem Resilience, Australian Institute of Botanical ScienceThe Royal Botanic Garden SydneyAustralia
| | - Peter D. Wilson
- Research Centre for Ecosystem Resilience, Australian Institute of Botanical ScienceThe Royal Botanic Garden SydneyAustralia
| | - Margaret L. Stimpson
- Botany, School of Environmental and Rural ScienceUniversity of New EnglandArmidaleNSW2351Australia
| | - Peter H. Weston
- Plant Discovery and Evolution, Australian Institute of Botanical ScienceRoyal Botanic Gardens and Domain TrustSydneyAustralia
| | - Larry Croft
- Centre of Integrative Ecology, School of Life and Environmental SciencesDeakin UniversityGeelong3125VictoriaAustralia
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Rutherford S, Wilson TC, Yap JYS, Lee E, Errington G, Rossetto M. Evolutionary processes in an undescribed eucalypt: implications for the translocation of a critically endangered species. ANNALS OF BOTANY 2022; 130:491-508. [PMID: 35802354 PMCID: PMC9510949 DOI: 10.1093/aob/mcac091] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/11/2022] [Accepted: 07/07/2022] [Indexed: 06/15/2023]
Abstract
BACKGROUND AND AIMS Knowledge of the evolutionary processes responsible for the distribution of threatened and highly localized species is important for their conservation. Population genomics can provide insights into evolutionary processes to inform management practices, including the translocation of threatened plant species. In this study, we focus on a critically endangered eucalypt, Eucalyptus sp. Cattai, which is restricted to a 40-km2 area of Sydney, Australia, and is threatened by increased urbanization. Eucalyptus sp. Cattai has yet to be formally described in part due to its suspected hybrid origin. Here, we examined evolutionary processes and species boundaries in E. sp. Cattai to determine whether translocation was warranted. METHODS We used genome-wide scans to investigate the evolutionary relationships of E. sp. Cattai with related species, and to assess levels of genetic health and admixture. Morphological trait and genomic data were obtained from seedlings of E. sp. Cattai propagated in a common garden to assess their genetic provenance and hybrid status. KEY RESULTS All analyses revealed that E. sp. Cattai was strongly supported as a distinct species. Genetic diversity varied across populations, and clonality was unexpectedly high. Interspecific hybridization was detected, and was more prevalent in seedlings compared to in situ adult plants, indicating that post-zygotic barriers may restrict the establishment of hybrids. CONCLUSIONS Multiple evolutionary processes (e.g. hybridization and clonality) can operate within one rare and restricted species. Insights regarding evolutionary processes from our study were used to assist with the translocation of genetically 'pure' and healthy ex situ seedlings to nearby suitable habitat. Our findings demonstrate that it is vital to provide an understanding of evolutionary relationships and processes with an examination of population genomics in the design and implementation of an effective translocation strategy.
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Affiliation(s)
| | - Trevor C Wilson
- Research Centre for Ecosystem Resilience, Australian Institute of Botanic Science, Royal Botanic Garden Sydney, Sydney, Australia
| | - Jia-Yee Samantha Yap
- Research Centre for Ecosystem Resilience, Australian Institute of Botanic Science, Royal Botanic Garden Sydney, Sydney, Australia
| | - Enhua Lee
- Biodiversity and Conservation Division, New South Wales Department of Planning and Environment, Sydney, Australia
| | - Graeme Errington
- Australian PlantBank, Australian Institute of Botanical Science, Australian Botanic Garden, Mount Annan, New South Wales, Australia
| | - Maurizio Rossetto
- Research Centre for Ecosystem Resilience, Australian Institute of Botanic Science, Royal Botanic Garden Sydney, Sydney, Australia
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Yap JYS, Rossetto M, Das S, Wilson PD, Beaumont LJ, Henry RJ. Tracking habitat or testing its suitability? Similar distributional patterns can hide very different histories of persistence versus nonequilibrium dynamics. Evolution 2022; 76:1209-1228. [PMID: 35304742 DOI: 10.1111/evo.14460] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2021] [Revised: 12/20/2021] [Accepted: 12/29/2021] [Indexed: 01/21/2023]
Abstract
The expansions and contractions of a species' range in response to temporal changes in selective filters leave genetic signatures that can inform a more accurate reconstruction of their evolutionary history across the landscape. After a long period of continental decline, Australian rainforests settled into localized patterns of contraction or expansion during the climatic fluctuations of the Quaternary. The environmental impacts of recurring glacial and interglacial periods also intensified the arrival of new lineages from the Sunda shelf, and it can be expected that immigrant versus locally persistent taxa responded to environmental challenges in quantifiably different manner. To investigate how such differences impact on species' distribution, we contrast landscape genomic patterns and changes in habitat availability between a species with a long continental history on Doryphora sassafras and a Sunda-derived species (Toona ciliata), across a distributional overlap. Extensive landscape-level homogeneity across chloroplast and nuclear genomes for the Sunda-derived T. ciliata, characterize the genetic signature of a very recent invasion and a rapid southern "exploratory" expansion that had not been previously recorded in the Australian flora (i.e., of Gondwanan origin or Sahul-derived). In contrast, D. sassafras is consistent with other Sahul-derived species characterized by strong geographical divergence and regional differentiation. Interestingly, our findings suggest that admixture between genetically divergent populations during expansion events might be a contributing factor to the successful colonization of novel habitats. Overall, this study identifies some of the mechanisms regulating the rearrangements in species distributions and assemblage composition that follow major environmental shifts, and reminds us how a species' current range might not necessarily define species' habitat preference, with the consequence that estimates of past or future range might not always be reliable.
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Affiliation(s)
- Jia-Yee Samantha Yap
- Research Centre for Ecosystem Resilience, Australian Institute of Botanical Science, The Royal Botanic Garden, Sydney, New South Wales, Australia.,Queensland Alliance of Agriculture and Food Innovation, University of Queensland, Brisbane, Queensland, Australia
| | - Maurizio Rossetto
- Research Centre for Ecosystem Resilience, Australian Institute of Botanical Science, The Royal Botanic Garden, Sydney, New South Wales, Australia.,Queensland Alliance of Agriculture and Food Innovation, University of Queensland, Brisbane, Queensland, Australia
| | - Sourav Das
- Department of Biological Sciences, Macquarie University, Brisbane, New South Wales, Australia.,Department of Forestry and Environmental Science, Shahjalal University of Science and Technology, Sylhet, Bangladesh
| | - Peter D Wilson
- Research Centre for Ecosystem Resilience, Australian Institute of Botanical Science, The Royal Botanic Garden, Sydney, New South Wales, Australia.,Department of Biological Sciences, Macquarie University, Brisbane, New South Wales, Australia
| | - Linda J Beaumont
- Department of Biological Sciences, Macquarie University, Brisbane, New South Wales, Australia
| | - Robert J Henry
- Queensland Alliance of Agriculture and Food Innovation, University of Queensland, Brisbane, Queensland, Australia
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Wang Z, Pierce NE. Fine-scale genome-wide signature of Pleistocene glaciation in Thitarodes moths (Lepidoptera: Hepialidae), host of Ophiocordyceps fungus in the Hengduan Mountains. Mol Ecol 2022; 32:2695-2714. [PMID: 35377501 DOI: 10.1111/mec.16457] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2021] [Revised: 02/12/2022] [Accepted: 03/21/2022] [Indexed: 11/28/2022]
Abstract
The Hengduan Mountains region is a biodiversity hotspot known for its topologically complex, deep valleys and high mountains. While landscape and glacial refugia have been evoked to explain patterns of inter-species divergence, the accumulation of intra-species (i.e. population level) genetic divergence across the mountain-valley landscape in this region has received less attention. We used genome-wide restriction site-associated DNA sequencing (RADseq) to reveal signatures of Pleistocene glaciation in populations of Thitarodes shambalaensis (Lepidoptera: Hepialidae), the host moth of parasitic Ophiocordyceps sinensis (Hypocreales: Ophiocordycipitaceae) or "caterpillar fungus" endemic to the glacier of eastern Mt. Gongga. We used moraine history along the glacier valleys to model the distribution and environmental barriers to gene flow across populations of T. shambalaensis. We found that moth populations separated by less than 10 km exhibited valley-based population genetic clustering and isolation-by-distance (IBD), while gene flow among populations was best explained by models using information about their distributions at the local last glacial maximum (LGML , 58 kya), not their contemporary distribution. Maximum likelihood lineage history among populations, and among subpopulations as little as 500 meters apart, recapitulated glaciation history across the landscape. We also found signals of isolated population expansion following the retreat of LGML glaciers. These results reveal the fine-scale, long-term historical influence of landscape and glaciation on the genetic structuring of populations of an endangered and economically important insect species. Similar mechanisms, given enough time and continued isolation, could explain the contribution of glacier refugia to the generation of species diversity among the Hengduan Mountains.
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Affiliation(s)
- Zhengyang Wang
- Museum of Comparative Zoology and Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA, 02138, USA
| | - Naomi E Pierce
- Museum of Comparative Zoology and Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA, 02138, USA
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Dai ZC, Zhu B, Wan JSH, Rutherford S. Editorial: Global Changes and Plant Invasions. Front Ecol Evol 2022. [DOI: 10.3389/fevo.2022.845816] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
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