Abstract:
Floating aquatic weed infestations have negative socio-economic and environmental conse-
quences to the ecosystems they invade. Despite the long history of invasion by macrophytes, only a few
studies focus on their impacts on biodiversity, while the ecological benefits of biological control pro-
grammes against these species have been poorly quantified. We investigated the process of biotic
homogenization following invasion by Pistia stra- tiotes on aquatic biodiversity, and recovery provided
by biological control of this weed. Biotic homoge-nization is the increased similarity of biota as a result
of introductions of non-native species. The study quantified the effect of P. stratiotes, and its biological control through the introduction of the weevil, Neo- hydronomus affinis on recruitment of benthic macroin-
vertebrates to artificial substrates. Mats of P. stratiotes altered the community composition and reduced
diversity of benthic macroinvertebrates in comparison to an uninvaded control. However, reduction in
percentage cover of the weed through biological control resulted in a significant increase in dissolved
oxygen, and recovery of the benthic macroinvertebrate community that was comparable to the uninvaded
state. This highlights the process of homogenization by an invasive macrophyte, providing a justification
for sustained ecological and restoration efforts in the biological control of P. stratiotes where this plant is
problematic
