The dilemma of Guinea grass (Megathyrsus maximus): a valued pasture grass and a highly invasive species

Rhodes, Aaron C.; Plowes, Robert M.; Goolsby, John A.; Gaskin, John F.; Musyoka, Boaz; Calatayud, Paul‐André; Cristofaro, Massimo; Grahmann, Eric D.; Martins, Dino J.; Gilbert, Lawrence E.

doi:10.1007/s10530-021-02607-3

Cited by 23 publications

(31 citation statements)

References 96 publications

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“…The invasive success of trade‐off species where the same characteristics that favour their intentional planting (i.e. vigorous growth, ability to persist and establish in a range of conditions) contribute to their invasive success has been recognized (Overholt & Franck, 2017; Rhodes et al, 2021; Scasta et al, 2015; Williams & Baruch, 2000). Our results identified that seed characteristics associated with increased propagule pressure is most important in determining levels of invasion in native communities.…”

Section: Discussionmentioning

confidence: 99%

Understanding patterns and pathways of exotic perennial grass invasion in South‐eastern Australian grassy communities

Rayment

French

Bedward

2022

Diversity and Distributions

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Aim Exotic perennial grasses (EPGs) are significant invaders of native grassy communities. We sought to determine how the profile of invading perennial grasses varies among different climatic regions and different grassy communities, to understand at which scale management is best undertaken. We investigated whether invader occurrence was related to specific plant traits. Location New South Wales, Australia. Method Field surveys of EPGs at 139 sites from nine grassy communities across four regions were assessed for variation in invasion profiles amongst regions and communities. We used a ranking of invasion risk based on plant characteristics to identify grasses likely to be more invasive and tested whether this ranking predicted the level of invasion in the survey. Results Using multivariate analysis, we found that all communities were significantly invaded. These assemblages were distinct regionally, and for most plant communities. Five widespread invaders were established in all regions and communities. Invasion by pasture grasses (termed trade‐off species) was the most significant threat, coupled with capacity to develop long‐term seed banks and use allelopathy. Species with higher risk rankings were recorded in more sites, although a few grasses had much greater occurrences than their ranking predicted. Conclusions Grassy communities across all regions were invaded by a suite of EPGs, some that have not been considered as problematic previously. Higher levels of invasion were associated with higher ranked species based on plant traits, indicating that our risk assessment is valuable as a management prioritization tool. Findings support community level management, although some species are important widespread invaders and could be managed at larger scales. Differences in species assemblages compared to nearby agricultural areas confirm different invasion pathways, with significant invasion from pasture grasses. Aided by the risk assessment tool, we propose that EPG management in native communities considers the climatic, community (including surrounding) and species level for prioritization.

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Section: Discussionmentioning

confidence: 99%

Understanding patterns and pathways of exotic perennial grass invasion in South‐eastern Australian grassy communities

Rayment

French

Bedward

2022

Diversity and Distributions

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“…Jacobs] is a large-statured tropical grass that has been planted around the world for use as livestock forage (Burton et al 1973). Native to intertropical and southeast Africa, it is now considered an invasive species in parts of Asia, North and South America, Australia, and many tropical islands (CABI 2021) due to its ability to shade and outcompete other species (Rhodes et al 2021). In subtropical southern Texas, it is implicated in the long-term declines of ground-dwelling granivorous birds such as quail and the facilitation of cattle fever tick [Rhipicephalus microplus (Canestrini)] invasion (Esteve-Gassent et al 2014;Mercadier et al 2009;Vacek et al 2021).…”

Section: Introductionmentioning

confidence: 99%

“…Hybrids of these species are found in East Africa (Savidan and Pernès 1982), and perhaps elsewhere, and have made taxonomic identification difficult (Clayton and Renvoize 1982). Megathyrsus maximus has been assigned multiple scientific names over the years (see Rhodes et al 2021), and the taxonomic confusion has been compounded by introductions from multiple African sources and approximately 35 cultivars listed in the Tropical Forages website (Cook et al 2005). Both tall and short forms of M. maximus exist, with 28 and 7 cultivars listed for each, respectively.…”

Section: Introductionmentioning

confidence: 99%

“…The tall form is generally 50% larger in plant height and leaf size and occurs in wetter and shadier conditions than the short form. The size differences may be due to hybridization between genotypes or differences in ploidy level (Rhodes et al 2021). In the southern United States and the neotropics, the short form of the species (abbreviated as SMm in this study) is considered invasive, while the tall form (TMm) is utilized as a forage grass, mostly in the neotropics (Rhodes et al 2021;Soti et al 2020).…”

Section: Introductionmentioning

confidence: 99%

“…The size differences may be due to hybridization between genotypes or differences in ploidy level (Rhodes et al 2021). In the southern United States and the neotropics, the short form of the species (abbreviated as SMm in this study) is considered invasive, while the tall form (TMm) is utilized as a forage grass, mostly in the neotropics (Rhodes et al 2021;Soti et al 2020). The short form is considered invasive in Texas, USA, because it may better tolerate drought and can form dense stands in open pastures and disturbed areas, suppressing or displacing local plants on fertile soils in pastures (Rhodes et al 2021).…”

Section: Introductionmentioning

confidence: 99%

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Identifying the geographic origins of invasiveMegathyrsus maximusin the United States using molecular data

Gaskin

Goolsby

Bon³

et al. 2022

Invasive plant sci. manag.

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Guineagrass is non-native in the neotropics, with a tall form that is commonly used as a forage grass and a smaller statured form that is considered invasive in south Texas, USA. Biological control researchers are challenged to find an agent that will attack the short form, but not the desirable tall form in other parts of the Neotropics. We conducted molecular analyses on 155 Guineagrass samples from its native range in Africa and compared them to USA short form samples to help determine the geographic origins of its invasion. We found eight distinct genotypes in 34 short form samples from Texas and Florida, USA. Highest genetic similarity of invasive samples was with plants from South Africa, while highest matches for the desirable tall form were from Kenya, Uganda, Ivory Coast and Zambia. Ongoing biological control agent exploration and research has found agents from Kenya that are associated with a Guineagrass genotype not well-matched to the invasive short form, thus leading to a lack of rearing success. Two eriophyoid mite agents from the genetic match locality in South Africa have been evaluated but are not sufficiently host-specific, as they develop on both the short and tall forms. Additional exploration is needed at the genetic match populations in South Africa to discover and evaluate potential biological control agents for the invasive form of Guineagrass. Management Implications: The results of this genetic analysis identify native range origins of invasive Guineagrass in south Texas, allowing for potential to find highly host-specific biological control agents that will attack the invasive short form of Guineagrass and not attack the desirable tall form that is a valuable forage in the neoptropics.

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Adding insult to injury: Light competition and allelochemical weapons interact to facilitate grass invasion

et al. 2023

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Biological invasions are a leading ecological issue of the 21st century because of their worldwide contributions to biodiversity loss and degradation of ecosystem services. Answering general questions about the mechanisms facilitating the spread of successful invasives is key to understanding how to manage them moving forward. The success of introduced primary producers has often been attributed to superior competitive ability or to their release from natural enemies that constrained them in their native range. In contrast, nonnative primary producers can successfully invade and establish in new areas by releasing allelochemical compounds into the environment that are toxic to the native flora. The interactive effects of allelopathy and competition remain underexplored. Here, we evaluated the mechanism of invasion by Guinea grass, a globally distributed tallgrass from tropical and subtropical Africa with known allelopathic effects associated with 2-hydroxyphenylacetic acid (2HPAA). We asked if allelopathy and light availability interact to give Guinea grass a competitive advantage during seedling establishment in its introduced range. We used a fully factorial greenhouse experiment in which allelochemical concentrations and light availability treatments were based on empirical measurements of these variables at an invaded site in South Texas. Seedling recruitment and growth were assessed for three native species and for Guinea grass itself. We also described the metabolome (the complete set of small molecules) of an invasive grass for the first time to facilitate a comparison of the effect of the known allelochemical 2HPAA with that of the whole-plant chemical extract. Shading and allelochemistry each reduced recruitment and growth by themselves, and a significant interaction of these stressors exacerbated the negative effects in the shade, resulting in short plants, low biomass, and ultimately decreased seedling recruitment. The whole-plant metabolomic extract had significantly stronger effects than pure 2HPAA, and these negative effects were intensified in

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The dilemma of Guinea grass (Megathyrsus maximus): a valued pasture grass and a highly invasive species

Cited by 23 publications

References 96 publications

Understanding patterns and pathways of exotic perennial grass invasion in South‐eastern Australian grassy communities

Understanding patterns and pathways of exotic perennial grass invasion in South‐eastern Australian grassy communities

Identifying the geographic origins of invasiveMegathyrsus maximusin the United States using molecular data

Adding insult to injury: Light competition and allelochemical weapons interact to facilitate grass invasion

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