Competition between Lemna minuta, Lemna minor and Azolla filiculoides
Alien aquatic plant species can have negative impacts on native plant species and higher trophic levels, as well as the habitats they invade, for example ponds, streams, rivers and wetlands. Such species can alter ecosystem processes and have negative impacts on the ecosystem services that aquatic habitats provide. Lemna minuta (Lemnoideae) is a non-native species to the EPPO region and often occurs in the same habitat to that of the native Lemna minor and the invasive North America aquatic plant Azolla filiculoides (Azolloideae). The presence, abundance and growth rates of all three species were monitored in 24 natural ponds in Ireland. The field monitoring showed that the distribution of all three species was relatively uniform across the study sites and their occurrences were not associated with nutrient or light levels. In a controlled experiment, mesocosms were established that contained either one of each species or a mixture of the species allowing all possible combinations. When L. minuta and L. minor were grown in the presence of A. filiculoides the relative growth rate of the Lemnaceae species was reduced. When the two Lemnaceae were grown together both species had lower relative growth rates compared to when they were grown apart. In the study area A. filiculoides is relatively rare and thus the study suggests that the invasiveness of the species is not always reflected under natural conditions. The study concludes that several factors determine the abundance and heterogenous distribution of the three species and these include growth under winter conditions and dispersal following disturbance.
Sources
Paolacci S, Jansen MAK, Harrison S (2018) Competition between Lemna minuta, Lemna minor, and Azolla filiculoides. Growing fast or being steadfast. Frontiers in Chemistry 6, DOI: 10.3389/fchem/2018.00207.