Competition between invasive Lemna minuta and native L. minor in indoor and field experiments

Abstract

The invasion of aquatic ecosystems by introduced invasive alien species (IAS) has become a worldwide phenomenon, and often leads to competitive interactions with native species. At high-nutrient levels, native species mostly are outcompeted by the introduced species. We performed an outdoor competition experiment between IAS free-floating Lemna minuta and native Lemna minor in a eutrophicated pond to examine whether the invasive species is the better competitor. We additionally performed an indoor experiment resembling mesotrophic phosphorus (P) conditions to investigate both species' competitiveness in low P availability and compared with previous experiments at high-nutrient levels. Our results showed that in field conditions, the alien L. minuta was the better competitor. In the mesotrophic indoor condition, however, the native L. minor was the better competitor. Both species produced longer roots in the indoor experiment compared to field conditions. The species' relative growth rates were also lower in the indoor experiment. A P reduction to mesotrophic condition in the water column thus might reduce invasive L. minuta growth and competitive performance. Additionally, introduction and recovery of L. minor could reduce L. minuta cover, but only following P reduction. Field experiments in mesotrophic ponds are needed to confirm these indoor findings.

Negative frequency‐dependent growth underlies the stable coexistence of two cosmopolitan aquatic plants

“…Likewise, the few studies (including our own) to address this question in submerged and floating macrophytes agree with this finding (Keddy , McCreary et al. , Kautsky , Barrat‐Segretain and Elger , Gérard and Triest ). That we found no increase in the strength of negative frequency‐dependent growth between static and fluctuating temperatures, and that contributions of the temporal storage effect were minimal, implies that stabilization in this system acts primarily in a fluctuation‐independent manner.…”

The importance of local environmental, hydrogeomorphological and spatial variables for beta diversity of macrophyte assemblages in a Neotropical floodplain

“…For example, we did not measure sediment granulometry (De Wilde, Puijalon, & Bornette, ; Sand‐Jensen & Søndergaard, ) or flow direction (Chambers, Prepas, Hamilton, & Bothwell, ; Crossley, Dennison, Williams, & Wearing, ), which can influence macrophytes. The inclusion of temporal variation (Marchetti & Scarabotti, ) and predictors of biological interactions, like facilitation (Hao, Wu, Shi, Liu, & Xing, ), competition (Gérard & Triest, ; Nunes & Camargo, ) and herbivory (Wood, Stillman, Clarke, Daunt, & O′Hare, ), would probably help to improve the explanation of β‐diversity. However, as found in another subtropical floodplain (Boschilia, Oliveira, & Thomaz, ), we suspect that part of the unexplained variation suggests a degree of stochasticity in the community organization, which may be the result of a random process of species colonization and extinction.…”

New occurrences of small aquatic duckweeds (Araceae, Lemnoideae) in Maranhão state, northeastern Brazil

“…The record of the occurrence of L. valdiviana in Maranhão extends the knowledge of its geographical distribution and will also aid studies regarding its potential as an invasive species-various species of duckweeds are invasive, as in the case of L. minuta (Gérard and Triest 2016;Paolacci et al 2016). Lemna valdiviana is not on the IUCN Red List (Maiz-Tome 2016).…”