An awn typology for Australian native grasses (Poaceae)
Annette M. Cavanagh
A C , Robert C. Godfree B and John W. Morgan A
A Department of Ecology, Environment and Evolution, La Trobe University, Bundoora, Vic. 3086, Australia.
B CSIRO National Research Collections Australia, GPO Box 1700, Canberra, ACT 2601, Australia.
C Corresponding author. Email: a.m.cavanagh@outlook.com.au
Australian Journal of Botany 67(4) 309-334 https://doi.org/10.1071/BT18216
Submitted: 9 November 2018 Accepted: 16 May 2019 Published: 7 August 2019
Abstract
Australia has a large diversity of native grasses. The diaspores of many species possess awns that vary considerably in their number and shape. Some variations of awn shape have been found to be effective at diaspore dispersal. Although morphological descriptions of awns exist for most native grass species, the number of species that possess awns and the extent of awn variation is unknown. This makes it difficult to determine the evolutionary importance of awns and the potential function of the various morphologies. The aim of this study was to construct an awn typology based on morphological descriptions collated from published flora databases that will quantify the awn type diversity of all native grass species in Australia, and will inform awn type relationships and help to clarify the role of differing awn morphologies in diaspore dispersal. We found that 42.1% of 1000 Australian native grasses with a single awn type were determined to have a ‘significant’ awn. These could be classified into one of 20 awn types, the most common being (1) single, apical, geniculate (once-sharply bent) awns (93 species; 28 genera, especially Iseilema), (2) three, apically-attached, straight awns (59 species, mainly Aristida) and (3) single, apical, bigeniculate (twice-sharply bent) awns (46 species, mainly Austrostipa). Among Australian grasses, slightly (though significantly) more C3 species (49.2%) had awns than C4 species (39.9%), although the most common awn types in both contained sharply bent awns (bigeniculate and geniculate respectively). Our classification system will help to improve our understanding of the amount of awn morphological variation in Australian grasses and will enable further investigation into the important ecological role of awns in species fitness.
Additional keywords: diaspore, dispersal, hygroscopic, morphology.
References
Adams KM, Tainton NM (1990) The function of the hygroscopic awn of Themeda triandra. Journal of the Grassland Society of Southern Africa 7, 271–273.| The function of the hygroscopic awn of Themeda triandra.Crossref | GoogleScholarGoogle Scholar |
Chambers JC, MacMahon JA (1994) A day in the life of a seed: movement and fates of seeds and their implications for natural and managed systems. Annual Review of Ecology and Systematics 25, 263–292.
| A day in the life of a seed: movement and fates of seeds and their implications for natural and managed systems.Crossref | GoogleScholarGoogle Scholar |
Clayton WD, Vorontsova MS, Harman KT, Williamson H (2006) GrassBase: the Online World Grass Flora. Available at: http://www.kew.org/data/grasses-db.html (accessed 1 March 2018)
Elbaum R, Abraham Y (2014) Insights into the microstructure of hygroscopic movement in plant seed dispersal. Plant Science 223, 124–133.
| Insights into the microstructure of hygroscopic movement in plant seed dispersal.Crossref | GoogleScholarGoogle Scholar | 24767122PubMed |
Elbaum R, Zaltzman L, Burgert I, Fratzl P (2007) The role of wheat awns in the seed dispersal unit. Science 316, 884–886.
| The role of wheat awns in the seed dispersal unit.Crossref | GoogleScholarGoogle Scholar | 17495170PubMed |
Evangelista D, Hotton S, Dumais J (2011) The mechanics of explosive dispersal and self-burial in the seeds of the filaree, Erodium cicutarium (Geraniaceae). Journal of Experimental Biology 214, 521–529.
| The mechanics of explosive dispersal and self-burial in the seeds of the filaree, Erodium cicutarium (Geraniaceae).Crossref | GoogleScholarGoogle Scholar | 21270299PubMed |
Garnier LKM, Dajoz I (2001) Evolutionary significance of awn length variation in a clonal grass of fire-prone savannas. Ecology 82, 1720–1733.
| Evolutionary significance of awn length variation in a clonal grass of fire-prone savannas.Crossref | GoogleScholarGoogle Scholar |
Harper JL, Williams JT, Sagar GR (1965) The behaviour of seeds in soil: I. The heterogeneity of soil surfaces and its role in determining the establishment of plants from seed. Journal of Ecology 53, 273–286.
| The behaviour of seeds in soil: I. The heterogeneity of soil surfaces and its role in determining the establishment of plants from seed.Crossref | GoogleScholarGoogle Scholar |
Harper JL, Lovell PH, Moore KG (1970) The shapes and sizes of seeds. Annual Review of Ecology and Systematics 1, 327–356.
| The shapes and sizes of seeds.Crossref | GoogleScholarGoogle Scholar |
Hattersley PW (1983) The distribution of C3 and C4 grasses in Australia in relation to climate. Oecologia 57, 113–128.
| The distribution of C3 and C4 grasses in Australia in relation to climate.Crossref | GoogleScholarGoogle Scholar | 28310164PubMed |
Humphreys AM, Antonelli A, Pirie MD, Linder HP (2011) Ecology and evolution of the diaspore ‘burial syndrome’. Evolution 65, 1163–1180.
| Ecology and evolution of the diaspore ‘burial syndrome’.Crossref | GoogleScholarGoogle Scholar | 21062276PubMed |
Johnson EE, Baruch Z (2014) Awn length variation and its effect on dispersal unit burial of Trachypogon spicatus (Poaceae). Revista de Biología Tropical 62, 321–326.
| Awn length variation and its effect on dispersal unit burial of Trachypogon spicatus (Poaceae).Crossref | GoogleScholarGoogle Scholar | 24912361PubMed |
Liu HL, Zhang DY, Duan SM, Wang XY, Song MF (2014) The relationship between diaspore characteristics with phylogeny, life history traits, and their ecological adaptation of 150 species from the cold desert of northwest China. The Scientific World Journal 2014, 510343
Magwa RA, Zhao H, Yao W, Xie W, Yang L, Xing Y, Bai X (2016) Genomewide association analysis for awn length linked to the seed shattering gene qSH1 in rice. Journal of Genetics 95, 639–646.
| Genomewide association analysis for awn length linked to the seed shattering gene qSH1 in rice.Crossref | GoogleScholarGoogle Scholar | 27659335PubMed |
Mallett K (2005) ‘Flora of Australia. Vol. 44B: Poaceae 3.’ (ABRS/CSIRO: Melbourne, Vic.)
Mallett K, Orchard AE (2002) ‘Flora of Australia. Vol. 43: Poaceae 1 – Introduction and atlas.’ (ABRS/CSIRO: Melbourne, Vic.)
Murbach L (1900) Note on the mechanics of the seed-burying awns of Stipa avenacea. Botanical Gazette 30, 113–117.
| Note on the mechanics of the seed-burying awns of Stipa avenacea.Crossref | GoogleScholarGoogle Scholar |
Peart MH (1979) Experiments on the biological significance of the morphology of seed-dispersal units in grasses. Journal of Ecology 67, 843–863.
| Experiments on the biological significance of the morphology of seed-dispersal units in grasses.Crossref | GoogleScholarGoogle Scholar |
Peart MH (1981) Further experiments on the biological significance of the morphology of seed-dispersal units in grasses. Journal of Ecology 69, 425–436.
| Further experiments on the biological significance of the morphology of seed-dispersal units in grasses.Crossref | GoogleScholarGoogle Scholar |
Peart MH (1984) The effects of morphology, orientation and position of grass diaspores on seedling survival. Journal of Ecology 72, 437–453.
| The effects of morphology, orientation and position of grass diaspores on seedling survival.Crossref | GoogleScholarGoogle Scholar |
Peart MH, Clifford HT (1987) The influence of diaspore morphology and soil-surface properties on the distribution of grasses. Journal of Ecology 75, 569–576.
| The influence of diaspore morphology and soil-surface properties on the distribution of grasses.Crossref | GoogleScholarGoogle Scholar |
PlantNET (2004) New South Wales Flora Online. The NSW Plant Information Network System, Royal Botanic Gardens and Domain Trust, Sydney. Available at: http://plantnet.rbgsyd.nsw.gov.au (accessed 1 March 2018)
R Core Team (2017) ‘R: A language and environment for statistical computing.’ (R Foundation for Statistical Computing, Vienna) Available at: https://www.R-project.org/ (accessed 29 June 2019)
Simon BK, Alfonso Y (2011) AusGrass2: Grasses of Australia. Available at: http://ausgrass2.myspecies.info/ (accessed 1 March 2018)
Sindel BM, Davidson SJ, Kilby MJ, Groves RH (1993) Germination and establishment of Themeda triandra (kangaroo grass) as affected by soil and seed characteristics. Australian Journal of Botany 41, 105–117.
| Germination and establishment of Themeda triandra (kangaroo grass) as affected by soil and seed characteristics.Crossref | GoogleScholarGoogle Scholar |
Soreng RJ, Peterson PM, Romaschenko K, Davidse G, Zuloaga FO, Judziewicz EJ, Filgueiras TS, Davis JI, Morrone O (2015) A worldwide phylogenetic classification of the Poaceae (Gramineae). Journal of Systematics and Evolution 53, 117–137.
| A worldwide phylogenetic classification of the Poaceae (Gramineae).Crossref | GoogleScholarGoogle Scholar |
Stamp NE (1984) Self-burial behaviour of Erodium cicutarium seeds. Journal of Ecology 72, 611–620.
| Self-burial behaviour of Erodium cicutarium seeds.Crossref | GoogleScholarGoogle Scholar |
VicFlora (2016) ‘Flora of Victoria.’ (Royal Botanic Gardens Victoria: Melbourne, Vic.) Available at: http://vicflora.rbg.vic.gov.au (accessed 1 March 2018)
Wang D, Jiao J, Lei D, Wang N, Du H, Jia Y (2013) Effects of seed morphology on seed removal and plant distribution in the Chinese hill-gully Loess Plateau region. Catena 104, 144–152.
| Effects of seed morphology on seed removal and plant distribution in the Chinese hill-gully Loess Plateau region.Crossref | GoogleScholarGoogle Scholar |
Wilson A (2009) ‘Flora of Australia. Vol. 44A: Poaceae 2.’ (ABRS/CSIRO: Melbourne, Vic.)
