Differential Allometric Patterns of Shell Growth in Two Invasive Pomacea Species Amid Water Hyacinth Beds in Central China

Allometric relationships represent common laws of relative growth between size and weight of different organisms, including mollusks. Although allometries between shell size and weight of highly invasive apple snails ( Pomacea spp.) vary globally, food‐source effects on these relationships remain unclear, challenging local conservation for freshwater biodiversity. After successful invasion of Pomacea spp. at the largest lake of Huangshi City, Daye Lake, in central China, allometries between shell size and weight of the mollusk populations feeding on different plants remain unknown. Using this invaded lake as a study system, this study tested whether allometries differed between two Pomacea species and whether body form and scaling factors of their allometric equations were associated with the co‐occurred invasive water hyacinth ( Pontederia crassipes ). Based on the equations built from 197 individuals of Pomacea spp., collected from a block with water hyacinth and outside the block with endemic macrophytes, we found no difference in the scaling factors between P. canaliculata and P. maculata regardless of food sources. However, the snails that fed on water hyacinth showed significantly higher body form factors than those feeding on endemic macrophytes. The observed patterns possibly imply that increased shell weight is associated with the ability to feed on water hyacinth. If no equation built for the populations feeding on water hyacinth existed, 34.02%–38.58% underestimation on shell weight would incur to predictions based on the equations for the populations feeding on endemic macrophytes. This suggests the necessity for considering the impact of food sources on allometries of Pomacea spp. when assessing their biomass and evaluating the control strategies over their invasion.