Hymenachne amplexicaulis, also known as West Indian marsh grass in the US, Olive hymenachne in Australia, and hereafter referred to as hymenachne, is New World species[1] in the genusHymenachne. Hymenachne is from the Greek hymen meaning "membrane" and achne meaning "chaff, glume, scale" and amplexicaulis is from Latin, literally "embracing the stem" or "stem-clasping.[2][3] This freshwater species is native to the tropical and subtropical regions of the West Indies, Northern South America, and Central America.[4]
Hymenachne is a perennial grass that primarily reproduces via stolons.[4] This robust species is commonly found growing 1–2.5m tall.[4] The stems are hairless and float prostrate across the top of the water, then grow upright from these bases to support leaves.[4] The flat, triangular leaves (10–45cm long, up to 3cm wide) have a prominent clasping bases, or auricles.[4] The auricles help to distinguish it from other invasive wetland grasses and the native H. acutigluma in Australia.[5] Hymenachne has been shown to increase the stem length between nodes to keep leaves above water during periods of flooding.[6] Its stem is packed with airy tissue called aerenchyma to help the stems float and to aid in flood tolerability.[5]
Hymenachne flowers in the early fall and seeds in late fall.[7] The flower is a panicle[8] that can grow to half a meter.[5] Researchers at the University of Florida have seen multiple panicles per plant originating from branching at a single node.[9] Hymenachne can produce thousands of seeds with up to 98% germination right off the panicle.[10][11][12]
Habitat
Hymenachne prefers constantly inundated soil and is known to survive comfortably in about a meter of water for 20 years.[5][13] This species was shown to survive poorly in Australia where flooding exceeded 1.2 m.[14][12] In its native range in Venezuela, and in invaded areas of Florida, hymenachne was documented to survive in >1.2m of water for nearly a year.[15][16] Hymenachne has also been found in water greater than 4m deep persisting in floating mats, likely dislodged after a storm event. Conversely, hymenachne is not recorded to survive sites that entirely desiccate.[17]
Hymenachne is known to colonize and form dense monocultures in floodplains, roadside ditches, and lake margins in invaded and native areas.[14][18][19][4] It is often found colonizing areas with little shading and competition from other species.[5] Although limited information is available on soil preferences of hymenachne, it has been found in deep, poorly drained muck soils in Florida.[20] It is not found in waters with a significant salt concentration.[21][5]
Invasion
There have been three introductions of hymenachne into Australia, one in Florida, and one in Louisiana.[22][23][5] Australia now lists hymenachne as one of the top twenty worst weeds.[24] Hymenachne invasions have been shown to decrease species richness, increase invasive fish populations, and overall cause fundamental changes in floral and faunal composition in Australia.[13] Hymenachne was introduced in Australia as forage for cattle, and likely for the same reason in Florida.[5] The species was used in ponded pastures, or artificial ponds created to hold water for use in the dry season.[5] High reproducibility from stem fragments aids in the dispersal and invasion of this species.[10] The first herbarium record of hymenachne in Florida is from 1957.[23][25] The second specimen is not recorded until 1977.[25] The cause for this gap is unknown; however, today it is recorded in 28 counties across the state.[26][27]
↑ Diaz, R., Overholt, W.A., Cuda, J.P., Pratt, P.D. and Fox, A. (2009). Host specificity of Ishnodemus variegates, an herbivore of West Indian marsh grass (Hymenachne amplexicaulis). BioControl 54, 307-21.
↑ Campbell, S.D., Carter, E.A. and Setter, M.J. (2009). Germination of Hymenachne amplexicaulis and H. acutigluma under contrasting light, temperature and nitrate regimes. Plant Protection Quarterly 24, 10-14.
1 2 Sellers, B.A., Diaz, R., Overholt, W.A., Langeland, K.A. and Gray, C.J. (2008). Control of West Indian marsh grass with glyphosate and imazapyr. Journal of Aquatic Plant Management 46, 189-92.
↑ Tropical Weeds Research Centre. 2006. Hymenachne (Hymenachne amplexicaulis) control and management in Queensland. http://www.nrm.qld.gov.au/ tropical_weeds/projects/hymenachnecontrol.html. Accessed February 17, 2019.
1 2 Lyons, J. (1991). Developing ponded pastures at ‘Wambiana’. Ponded pastures in North Queensland, eds P. Anning and J. Kernot. North Queensland Beef Production Series. Department of Primary Industries, Queensland Government.
1 2 Gonzalez-Jimenez, E. and Escobar, A. (1977). Flood adaptation and productivity of savanna grasses. Proceedings of Plant Protection Quarterly Vol.00(0) 0000 15 the 13th International Grassland Congress Sec. Pap. Sections 3-4-5, Leipzig.
↑ Tejos, M.R. (1980). Production of water straw grass (Hymenachne amplexicaulis (Rudge) Nees) during a savanna period. Congreso Venezolano de Zootecnia, Guanare (Venezuela), p. 54.
↑ Kalmbacher, R., Mullahey, J. and Hill, J. (1998). Limpgrass and hymenachne grown on flatwoods range pond margins. Journal of Range Management 51, 282-7.
↑ Medina, E. and Motta, N. (1990). Metabolism and distribution of grasses in tropical flooded savannas in Venezuela. Journal of Tropical Ecology 6, 77-89.
↑ Costa, M. (2005). Estimate of net primary productivity of aquatic vegetation of the Amazon floodplain using Radarsat and JERS-1. International Journal of Remote Sensing 26, 4527-36.
↑ Enriquez-Quiroz, J.F., Quero-Carrillo, A.R., Hernandez-Garay, A. and Garcia-Moya, E. (2006). Azuche, Hymenachne amplexicaulis (Rudge) Nees, forage genetic resources for floodplains in tropical Mexico. Genetic Resources and Crop Evolution 53, 1405-12.
↑ Hill, K.U. (1996). Hymenachne amplexicaulis:A review of the literature andsummary of the work in Florida. URL: http://www.naples.net/~kuh/hymen.htm (accessed 17 Feb 2019).
↑ Meerman, J.C., Howe, A., Choco, S., Ack, A., Choc, E., Kok, S. and Muke, A. (2006). Rapid ecological assessment of aguacalient wildlife sanctuary. Aguacaliente REA. Data stored in BERDS: URL: http://www.biodiversity.bz (accessed 17 Feb 2019).
↑ Urbatsch LE; Saichuk JK, 2014. Hymenachne amplexicaulis new for Louisiana. Phytoneuron, 50:1-4.
↑ Williams, Jann A.; West, Carol J. (2000). "Environmental weeds in Australia and New Zealand: issues and approaches to management". Austral Ecology. 25 (5): 425–444. doi:10.1046/j.1442-9993.2000.01081.x. ISSN1442-9993.
↑ Wunderlin, Richard P. (2011). Guide to the vascular plants of Florida. Hansen, Bruce F. (3rded.). Gainesville, FL: University Press of Florida. ISBN9780813035437. OCLC700199921.
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