Invertebrate colonization and plant architecture: The influence of two non-native milfoil species

The purpose of this study was to determine if the complexity and surface area of a macrophyte’s structure has an influence on invertebrate colonization, and to determine the influence of two non-native species on invertebrate colonization. Three plant architectures were compared. Floating leaved plants were represented by the following species: Nuphar lutea, Nymphaea odorata, and Brasenia schreberi. Moderately dissected leaved plants were represented by Potamogeton natans, and highly dissected leaved plants were represented by two non-native species, Myriophyllum spicatum and Myriophyllum heterophyllum. The number of invertebrates/g dry biomass and the number of individuals/m², diversity, evenness, and richness were calculated for comparison. The density of invertebrates was significantly different among the different plant architecture types for both individuals per m² and individuals per/g dry biomass (ANOVA, F=33.53, p \u3c 0.0001; ANOVA, F=194.41, p \u3c 0.0001). The highly dissected milfoils had the greatest density of individuals per gram dry plant biomass compared to the moderately dissected plants, and the moderately dissected plants had a greater density of individuals per gram dry mass than floating leaved plant. There were also differences in terms of invertebrate community diversity (H\u27), (ANOVA, F=l7.08, p \u3c 0.001), and richness (ANOVA, F= 35.52, p \u3c 0.001), but not evenness (ANOVA, F = 1.83, p = .0961). When the number of invertebrates/g dry plant biomass was examined in lakes where the highly dissected plants were ”rare/not observed , there was a lower density of invertebrates per gram dry biomass. This was significantly lower than in lakes where the highly dissected plants were both ”common” and ”dominant” (ANOVA, F=3.31, p = 0.0393). Data analysis was strongly affected by the density of the oligochaete Sty/aria and the amphipod Hyallela azteca, as evident in the Principle Component Analysis. Parameters associated with the two axes, principle component 1 and principle component 2, explained 86% of the variation in epiphytic invertebrate density