Herbivory on freshwater macrophytes from the perspective of biological invasions: a systematic review

The previously neglected herbivore-aquatic macrophyte interaction has received more attention among scientists in the recent decades, especially in the context of biological invasions. However, there is still a great deal of work needed to improve scientific knowledge about this relationship and to improve biological management and control techniques. This systematic review provides an overview of temporal and spatial trends and the methodological approaches, habitats, and species most studied concerning this interaction. We evaluated scientific articles published in journals indexed to Web of Science that measured the consumption or other direct effects of herbivores on freshwater macrophytes, including non-native species. From 1992 to 2017, there was a growth rate of approximately three times in the publication of such articles, although they are concentrated in the temperate and subtropical zones, neglecting tropical and subpolar environments. We have also noticed a simple general pattern in most of the topics evaluated here, such as the low preference for using tests of multiple hypotheses and for applying both experimental and fieldwork methods together. Deep lakes and rivers were the most studied ecosystems, while shallow lakes, ponds, streams and wetlands had less attention. Non-native macrophytes were more studied than non-native herbivores. The macrophyte life forms most studies were rooted submerged, free-floating and emergent species, while the herbivore taxa most often examined in these studies were fish, molluscs and crustacea. We suggest performing studies that are more complex, using multi-species biological communities, with a focus on the unexplored pointed areas to advance scientific knowledge regarding herbivory on macrophytes, especially in tropical areas.