Predatorregimers påverkan på labiumform och fångstframgång hos nordamerikanska flicksländelarver

Sammanfattning

Damselfly larvae (Zygoptera) live under strong selective pressure from both fish and larger dragonfly larvae (Odonata), which has driven behavioral and morphological adaptations to balance foraging against predation risk. The larvae capture their prey using a specialized labium, a modified lower lip that functions as a protrusible prey-capture organ. This study investigated whether the labium morphology of North American damselfly larvae from the genera Enallagma and Ischnura differs between different predator regimes, and whether shape variation can be linked to capture success. Eight morphological measurements of the labium were analyzed separately for the genera Enallagma and Ischnura using principal component analysis (PCA). The first component (PC1) was interpreted as an indicator of general size, whereas PC2 and PC3 described relative shape variation. Differences in labium shape between predator regimes were analyzed with MANOVA, and capture success was examined using binomial generalized linear mixed models (GLMM). The results showed significant differences in relative labial shape between fish-lake and fishless-lake species in both Enallagma and Ischnura, but the morphological character of these differences was genus-specific. In Enallagma, capture success was linked only to larger head width, a measure used to describe general size. In Ischnura, however, higher PC2 values were associated with significantly higher capture success. The findings provide support for the association between predator regimes and variations in labial morphology but demonstrate that both shape and capture success vary between the genera. The results suggest that factors other than predator regime play a role in variation in the prey-capture organ of damselfly larvae, such as genus-specific or behavioral differences.