Effects of Microhabitat Heterogeneity on the Spatial Dispersion of Small Plant-Associated Invertebrates

The spatial dispersion of invertebrates living on leaves of the floating-leaf plant Ludwigia peploides was observed in a small pond in South-central Texas. Seventy-two individual leaves were collected and invertebrate taxa were examined in relation to visually recognizable stages of leaf physiological condition and filamentous algal accumulation. The chydorid cladoceran Ephemeroporus acanthodes, ostracods, the amphipod Hyalella azteca, the naidid oligochaete Pristina sp., nematode worms, and chironomid and heleid larvae were more abundant on leaves having dense growth of filamentous algae than on leaves with sparse algal growth. Abundance of the daphniid cladoceran Ceriodaphnia quadrangula was inversely related to the amount of algae on the leaves. The small chydorids Alona spp. were more abundant on decaying or senescent leaves than on leaves in good condition, and cyclopoid copepods were most abundant on senescent leaves with dense algae.