Competitive effects and responses of the invasive grass Eragrostis plana in Río de la Plata grasslands

Abstract

The ability of an invasive species to establish is mostly determined by its biotic interactions with native species from the recipient community. Here, we evaluate the competitive effects and responses of the invasive Eragrostis plana when interacting with native species, in order to identify possible mechanisms driving invasion in Río de la Plata grasslands. A pairwise competition experiment was performed consisting of treatments that varied in the identity of neighbour plant species: (i) control (no interaction); (ii) intraspecific interaction; (iii) interspecific interaction between native and invasive species; and (iv) interspecific interaction between two co‐occurring native species. Data analysis was separated into the effect of E. plana on the performance of three native perennial grasses (target species: Aristida laevis, Eragrostis neesii and Paspalum notatum) and the response of E. plana to natives (target species: E. plana). Separately for each target species, components of plant performance were compared between neighbouring species treatments. We found that the strength of competitive interactions depended on both target and neighbour species identity. Regarding natives, interspecific competition was stronger than intraspecific. Native species showed distinctive responses to whether the neighbour was the invasive or a co‐occurring native (Eragrostis lugens). Competition between E. plana and native species was stronger than between co‐occurring natives. We demonstrated E. plana had a greater negative effect on native's species performance than the native congener E. lugens. Regarding E. plana, intraspecific competition was stronger than interspecific, and its response was positive or neutral when interacting with natives, suggesting its high tolerance to grow in competition with neighbours. We conclude E. plana's negative effects on native species performance, and its positive or neutral responses to neighbouring native plants demonstrate its strong competitive ability in the recipient community. This may explain its invasion success in southern Brazil and in the encompassing Río de la Plata grasslands.Abstract in Spanish is available with online material.

¿Las gramíneas invasoras Cynodon dactylon y Eragrostis plana son más fitotóxicas que una nativa coexistente?

“…Including a donor native species as a species origin control was crucial for disentangle the relative effect of both invasive species. This consideration has been already suggested in other experimental designs for testing and relativizing the invasive species impact (Vilà and Weiner 2004;Del Fabbro et al 2013;Dresseno et al 2018;Guido et al 2019), but it is still often ignored. In our experiment, the donor native species provided a comparison about how novel was the effect of the invasive species (i.e., phytotoxicity) in the recipient community (i.e., introduced range).…”

“…Furthermore, it is known that almost all species could be phytotoxic at some level in laboratory assays (Silva et al 2017), thus phytotoxicity can be considered meaningful if compared among others donor species (e.g., Del Fabbro et al 2013). Regarding invasion process, including a common native plant as a donor origin control is crucial to disentangle the relative effect of an invader in the recipient community (i.e., invasive vs. native effect; Vilà and Weiner 2004;Del Fabbro et al 2014;Dresseno et al 2018;Guido et al 2019). Therefore, if the phytotoxic effect of an invasive species is greater than the effect of a native species in the introduced range, this may provide evidence that effects could be related to species origin and co-evolutionary history, enhancing plant invasiveness.…”

Análise da biodiversidade vegetal de pomares no Bioma Pampa

“…This species is considered an indicator of compacted, acidic soil with low fertility (Junqueira et al, 2013). When analyzing the two strata together (Table 2), Eragostris plana, a typical succession-activating pioneer exotic species with a high degree of invasion and seed bank formation (Ferreira, Medeiros & Favreto, 2008;Guido, Hoss & Pillar, 2019;Pagnussat & Bonetti, 2019) stands out in frequency in Q1TA and Q2. As seen in division happened due to the variation in slope and soil density, which resulted in different environmental conditions and, consequently, in different species from those found in Q1TA.…”

Disentangling by additive partitioning the effects of invasive species on the functional structure of communities

“…It is also invasive and with a high potential of spreading to other regions of South America, including Uruguay and northeastern Argentina (Masciadri et al, 2010;Barbosa et al, 2013). The invasiveness of E. plana is mostly associated with its production of a high number of viable seeds which germinate faster than those of native grasses , and its great competitive ability (Guido et al, 2019). Once established, it can survive and spread in adverse abiotic conditions (Guido et al, 2016) due to the anatomical and histological characteristics of its leaves (i.e.…”

“…The invasiveness of E . plana is mostly associated with its production of a high number of viable seeds which germinate faster than those of native grasses (Guido et al, 2017), and its great competitive ability (Guido et al, 2019). Once established, it can survive and spread in adverse abiotic conditions (Guido et al, 2016) due to the anatomical and histological characteristics of its leaves (i.e.…”