The Effect of an Insectivorous Lizard Predator (Crotaphytus collaris) on Ozark Glade Orthopteran Assemblages

Abstract. Insectivorous lizards can alter arthropod community structure and composition. Collared lizards (Crotaphytus collaris) are believed to be keystone predators for Ozark glade grasshopper (Orthoptera) communities by increasing species richness on smaller glades. However, the interaction between collared lizard presence and glade area on orthopteran species richness has been inconsistent between studies on glades in southeastern Missouri. In this study, we explored the effects of collared lizard presence on orthopteran abundance, diversity, and assemblage composition in Ozark glades located in northern Arkansas. We found the presence of predatory collared lizard populations significantly affected orthopteran assemblage composition. However, the presence of collared lizards did not affect orthopteran abundance or diversity. Additionally, there were no interaction effects between collared lizard presence and glade area on orthopteran assemblages. We did find that month had the most consistent effect on orthopteran abundance, diversity, and assemblage composition. These results contrast with other studies that indicate collared lizards influence orthopteran species richness on other glade communities within the region. In this study, seasonal effects, glade area, and unmeasured bottom-up effects appear more important for determining orthopteran diversity than predation. Our results provide further evidence that the strength of top-down effects can vary across a predator's range and could have implications for glade restoration plans in the region.