Effects of an Invasive Alien Poaceae on Aquatic Macrophytes and Fish Communities in a Neotropical Reservoir

Abstract

We investigated the potential effects of an invasive alien Poaceae (Urochloa arrecta) on the abundance, richness, and composition of native macrophytes and fish. Samples were collected in patches of macrophytes dominated by the invasive species and in others dominated by a native macrophyte (Eichhornia azurea). We assessed the potential effects of these two species on macrophyte and fish abundance and richness, as well as in fish assemblage composition. The effects of both macrophytes did not differ when they were in similar, low biomasses. Consistent with our expectations, however, the abundance of native macrophytes and fish decreased with increasing U. arrecta biomass, and both assemblages were eliminated at the extreme high levels of biomass attained by this species. In contrast, E. azurea did not affect the assemblages because this native species never reached levels of biomass as high as those recorded for the invasive species. Competition for space and light most likely determines the elimination of macrophytes in patches that are extensively colonized by U. arrecta, whereas fish assemblages do not occupy these patches due most likely to the limited space available for movement and foraging. Thus, U. arrecta is a source of concern for biodiversity conservation because it has negative influences on both assemblages when it is well developed, which is true in the later stages of the invasion process.

Poaceae em uma planície de inundação no Brasil: distribuição espacial e conservação

“…Atualmente, estas porções são ocupadas por pastagens abandonadas, espécies exóticas e vegetação nativa em diferentes estágios de sucessão (Souza et al 2009) (Kawakita et al 2016). Urochloa arrecta foi registrada em lagoas da PIAP e em outros ambientes ripários da bacia do Rio Paraná (Mormul et al 2010, Carniatto et al 2013, Michelan et al 2013. Diante disso, ressalta-se a necessidade da continuidade do monitoramento e manejo das populações de Urochloa arrecta, tendo em vista o seu potencial invasor em ambientes lênticos, principalmente em lagoas.…”

Aquatic macrophyte mats as dispersers of one invasive plant species

“…The macrophyte Urochloa arrecta (Hack. ex T. Durand & Schinz) Morrone & Zuloaga (in previous investigations identified as Urochloa subquadripara; e.g., Thomaz et al, 2009) is a highly invasive Poaceae native to Africa that reduces diversity and changes the composition of macrophytes and fish assemblages in Neotropical regions (Carniatto et al, 2013;Amorim et al, 2015). This species grows quickly from fragments (Michelan et al, 2010a), it roots in the shores and its stems extend toward limnetic regions, thus exhibiting a typical "rooted with floating stems" life form.…”

Status of the Invasion of a Poaceae Species in Tropical Semiarid Reservoirs

“…Changes in the communities of native species is commonly associated to the formation of exotic macrophytes populations with high density, distributed in monospecific banks in rivers, margins of supply reservoirs, flooded rice areas and irrigation canals (Mormul et al, 2010;Carniatto et al, 2013). Thus, the reduction of the richness of native species may occur due to the biotic interactions with exotic macrophytes, such as interspecific competition and, consequently, competitive exclusion (Thomaz et al, 2009b).…”