Effect of selected environmental factors on the seed germination of the invasive species Polygala myrtifolia (Polygalaceae) in Australia
Natalie Roberts A , Katrina Moloney A , Kristin Monie A and Singarayer Florentine![https://orcid.org/0000-0002-5734-3421](/media/client/orcid_16x16.png)
A The Future Regions Research Centre, Institute of Innovation, Science and Sustainability, Federation University Australia, Mount Helen, PO Box 663, Ballarat, Vic. 3350, Australia.
B School of Science, RMIT University, Melbourne, Vic. 3001, Australia.
Australian Journal of Botany 71(6) 286-295 https://doi.org/10.1071/BT22094
Submitted: 22 August 2022 Accepted: 27 April 2023 Published: 26 May 2023
© 2023 The Author(s) (or their employer(s)). Published by CSIRO Publishing. This is an open access article distributed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License (CC BY-NC-ND)
Abstract
Context: Polygala myrtifolia L. has become a significant environmental weed in Australia, where it has invaded coastal ecosystems in temperate regions and there is a high risk of extensive further spread. Knowledge of seed-germination behaviour is essential to understand the potential future impact of this species.
Aims: We investigated the effects of selected environmental factors and dormancy on P. myrtifolia seed germination and emergence to improve management strategies.
Methods: Seeds were exposed to light, temperature, pH, salinity, osmotic potential and burial depth treatments to assess germination responses, dormancy and viability.
Key results: Non-dormant seeds readily germinated to high percentages (93.0–95.0%) under specific day–night temperatures of 25°C–15°C regardless of light conditions and across all soil pH (75.0–100.0%). Salinities were tolerated up to 100 mM NaCl (70.0% germination) before sharply declining. Germination reduced from 98.3% to 40.0% at osmotic potentials of −0.4 MPa and −0.6 MPa respectively. Emergence was greatest on the soil surface (48.33%) and absent from depths of 8 cm.
Conclusions: Germination was high during autumn, winter and spring conditions and across soils of any pH. The species is unlikely to invade areas of high salinity; however, it is moderately tolerant of low soil moisture during germination.
Implications: There is high risk of P. myrtifolia further invading sensitive ecosystems because of its high germination success. Preventing seed dispersal and ensuring seedlings are controlled on emergence are critical to reducing its impact. We recommend that the cultivation and sale of this species should be prohibited across Australia to prevent further spread.
Keywords: burial depth, coastal, dune ecosystem, salinity, seed germination, soil moisture, temperature, weeds.
References
Adair RJ, Neser S, Stajsic V (2011) Phytophagous organisms associated with the woody shrub Polygala myrtifolia (Polygalaceae) and their potential for classical biological control in Australia. Plant Protection Quarterly 26, 72–80.Adair RJ, Shackleton A, Stajsic V, Gajaweera R (2012) The biology of Australian Weeds 61. Polygala myrtifolia L. Plant Protection Quarterly 27, 119–130.
Agriculture Victoria (2020a) Impact assessment – myrtle-leaf milkwort (Polygala myrtifolia) in Victoria. (Agriculture Victoria: Vic., Australia). Available at http://vro.agriculture.vic.gov.au/dpi/vro/vrosite.nsf/pages/impact_myrtle_leaf_milkwort
Agriculture Victoria (2020b) Salt-spray tolerant plants – coastal region. (Agriculture Victoria: Vic., Australia). Available at https://vro.agriculture.vic.gov.au/dpi/vro/vrosite.nsf/pages/sip_coastal_salt_spray
Atlas of Living Australia (2021) Polygala myrtifolia L. Available at https://spatial.ala.org.au/?q=lsid:https:%2F%2Fid.biodiversity.org.au%2Fnode%2Fapni%2F2 895392
Baskin JM, Baskin CC (2004) A classification system for seed dormancy. Seed Science Research 14, 1–16.
| A classification system for seed dormancy.Crossref | GoogleScholarGoogle Scholar |
Bond WJ, Honig M, Maze KE (1999) Seed size and seedling emergence: an allometric relationship and some ecological implications. Oecologia 120, 132–136.
| Seed size and seedling emergence: an allometric relationship and some ecological implications.Crossref | GoogleScholarGoogle Scholar |
Bradshaw CJA, Hoskins AJ, Haubrock PJ, Cuthbert RN, Diagne C, Leroy B, Andrews L, Page B, Cassey P, Sheppard AW, Courchamp F (2021) Detailed assessment of the reported economic costs of invasive species in Australia. NeoBiota 67, 511–550.
| Detailed assessment of the reported economic costs of invasive species in Australia.Crossref | GoogleScholarGoogle Scholar |
Bureau of Meteorology (2022) Climate statistics for Australian locations: summary statistics Queenscliff. (Australian Government). Available at http://www.bom.gov.au/climate/averages/tables/cw_087054.shtml
Carr GW, Yugovic JV, Robinson KE (1992) ‘Environmental weed invasions in Victoria: conservation and management implications.’ (Department of Conservation and Environment and Ecological Horticulture: Vic., Australia)
Carter RJ, Cooke DA, Chapman G, Sheridan P (1990) South African milkworts, Polygala spp., in southern Australia. In ‘Proceedings of the 9th Australian weeds conference’. pp. 116–120. (Weed Society of South Australia: Adelaide, Australia)
Chachalis D, Reddy KN (2000) Factors affecting Campsis radicans seed germination and seedling emergence. Weed Science 48, 212–216.
| Factors affecting Campsis radicans seed germination and seedling emergence.Crossref | GoogleScholarGoogle Scholar |
Dalziell EL, Lewandrowski W, Commander LE, Elliott CP, Erickson TE, Tudor EP, Turner SR, Merritt DJ (2022) Seed traits inform the germination niche for biodiverse ecological restoration. Seed Science and Technology 50, 103–124.
| Seed traits inform the germination niche for biodiverse ecological restoration.Crossref | GoogleScholarGoogle Scholar |
Department of Primary Industries and Regions (2021) Controlling weeds – Polygala myrtifolia. (Government of South Australia). Available at https://pir.sa.gov.au/biosecurity/weeds/controlling-weeds/polygala
Eyre Peninsula Natural Resources Management Board (2018) ‘Pest species regional management plan: Polygala myrtifolia myrtle-leaf milkwort.’ (Government of South Australia)
Fenner M, Thompson K (2009) ‘The ecology of seeds.’ (Cambridge University Press: New York, USA). https://doi.org/10.1017/cbo9780511614101
Florentine S, Weller S, King A, Florentine A, Dowling K, Westbrooke M, Chauhan BS (2018) Seed germination response of a noxious agricultural weed Echium plantagineum to temperature, light, pH, drought stress, salinity, heat and smoke. Crop & Pasture Science 69, 326–333.
| Seed germination response of a noxious agricultural weed Echium plantagineum to temperature, light, pH, drought stress, salinity, heat and smoke.Crossref | GoogleScholarGoogle Scholar |
Flowers TJ, Colmer TD (2008) Salinity tolerance in halophytes. New Phytologist 179, 945–963.
| Salinity tolerance in halophytes.Crossref | GoogleScholarGoogle Scholar |
Forest F, Chase MW, Persson C, Crane PR, Hawkins JA (2007) The role of biotic and abiotic factors in evolution of ant dispersal in the milkwort family (Polygalaceae). Evolution 61, 1675–1694.
| The role of biotic and abiotic factors in evolution of ant dispersal in the milkwort family (Polygalaceae).Crossref | GoogleScholarGoogle Scholar |
GBIF.org (2021) GBIF occurrence download (Polygala myrtifolia). Available at https://doi.org/10.15468/dl.j7jwqm
Government of South Australia (2021) Declare plant policy: Polygala myrtifolia. Available at https://pir.sa.gov.au/__data/assets/pdf_file/0012/223212/polygala_policy.pdf
Hoffmann BD, Broadhurst LM (2016) The economic cost of managing invasive species in Australia. NeoBiota 31, 1–18.
| The economic cost of managing invasive species in Australia.Crossref | GoogleScholarGoogle Scholar |
Hoyle JA, McElroy JS, Guertal EA (2013) Soil texture and planting depth affect large crabgrass (Digitaria sanguinalis), Virginia buttonweed (Diodia virginiana), and Cock’s-comb Kyllinga (Kyllinga squamulata) emergence. HortScience 48, 633–636.
| Soil texture and planting depth affect large crabgrass (Digitaria sanguinalis), Virginia buttonweed (Diodia virginiana), and Cock’s-comb Kyllinga (Kyllinga squamulata) emergence.Crossref | GoogleScholarGoogle Scholar |
Inkson T (2015) ‘Garden escapees & other weeds of bushlands & reserves: a responsible gardening guide for the Mid North Coast of New South Wales.’ 3rd edn. (Great Lakes Council)
Kaushik P, Pati PK, Khan ML, Khare PK (2022) Plant functional traits best explain invasive species’ performance within a dynamic ecosystem – a review. Trees, Forests and People 8, 100260
| Plant functional traits best explain invasive species’ performance within a dynamic ecosystem – a review.Crossref | GoogleScholarGoogle Scholar |
Michel BE (1983) Evaluation of the water potentials of solutions of polyethylene glycol 8000 both in the absence and presence of other solutes. Plant Physiology 72, 66–70.
| Evaluation of the water potentials of solutions of polyethylene glycol 8000 both in the absence and presence of other solutes.Crossref | GoogleScholarGoogle Scholar |
Moles AT, Westoby M (2004) Seedling survival and seed size: a synthesis of the literature. Journal of Ecology 92, 372–383.
| Seedling survival and seed size: a synthesis of the literature.Crossref | GoogleScholarGoogle Scholar |
Moxham C (2003) Action statement bellarine yellow gum. Department of Sustainability and the Environment, Victorian State Government, Melbourne, Vic., Australia.
Müller FL, Raitt LM, Cyster LF, Cupido CF, Samuels MI, Chimphango SBM, Boatwright JS (2019) The effects of temperature, water availability and seed burial depth on seed germination and seedling establishment of Calobota sericea (Fabaceae). South African Journal of Botany 121, 224–229.
| The effects of temperature, water availability and seed burial depth on seed germination and seedling establishment of Calobota sericea (Fabaceae).Crossref | GoogleScholarGoogle Scholar |
Nešić M, Obratov-Petković D, Skočajić D, Bjedov I, Čule N (2022) Factors affecting seed germination of the invasive species Symphyotrichum lanceolatum and their implication for invasion success. Plants (Basel) 11, 969
| Factors affecting seed germination of the invasive species Symphyotrichum lanceolatum and their implication for invasion success.Crossref | GoogleScholarGoogle Scholar |
Newton R, Hay FR, Probert RJ (2009) Protocol for comparative seed longevity testing. (Millennial Seed Bank Project, Kew: London, UK) p. 2. Available at www.kew.org/msbp. [Accessed 10 January 2020]
Pausas JG, Lamont BB (2022) Fire-released seed dormancy – a global synthesis. Biological Reviews 97, 1612–1639.
| Fire-released seed dormancy – a global synthesis.Crossref | GoogleScholarGoogle Scholar |
Rees D (2002) Sorrento mapsheet – soil pit sites: CLRA07. (Agriculture Victoria: Vic., Australia). Available at https://vro.agriculture.vic.gov.au/dpi/vro/coranregn.nsf/pages/soil_landform_soil_pits_clra7
Rees D, Crawford D, Robinson N, Reynard K, Boyle G (2002) CLRA44. Sorrento map sheet – soil pit sites. (Agriculture Victoria: Vic., Australia). Available at http://vro.agriculture.vic.gov.au/dpi/vro/coranregn.nsf/pages/soil_landform_soil_pits_clra44
Welgama A, Florentine S, Marchante H, Javaid MM, Turville C (2019) The germination success of Acacia longifolia subsp. longifolia (Fabaceae): a comparison between its native and exotic ranges. Australian Journal of Botany 67, 414–424.
| The germination success of Acacia longifolia subsp. longifolia (Fabaceae): a comparison between its native and exotic ranges.Crossref | GoogleScholarGoogle Scholar |
White M, Cheal D, Carr GW, Adair R, Blood K, Muir A, Meagher D (2022) Advisory list of environmental weeds in Victoria 2022. Arthur Rylah Institute for Environmental Research. Department of Environment, Land, Water and Planning, Melbourne, Vic., Australia.