Effects of temperature and host distribution on gypsy moth growth rates along its expanding population front

Abstract

The gypsy moth, Lymantria dispar (L.), has been a major pest species in North American forests for >100 years and has caused defoliation on >369,000 km2 since 1924. Due to the economic and ecological consequences of gypsy moth, many aspects of its population biology and ecology have been studied. However, much prior work has focused at local spatial scales and in established outbreaking populations. In contrast, gypsy moth invasion dynamics are understudied in newly established populations and across landscape scales. I first analyzed the effect of sub- and supraoptimal temperatures on nascent gypsy moth population growth rates, and the spatial patterns of growth rates, along the expanding invasion front in the eastern United States. Second, I quantified the relationship between primary and secondary host plant fragmentation and gypsy moth population growth rates along the expanding invasion front. The data from this study indicate that there are geographical differences in how temperature and host fragmentation is affecting gypsy moth growth rates, and the spatial structure of those growth rates within expanding populations along the leading edge of the invasion front. Furthermore, the results from this study emphasize the important role that secondary hosts play in establishing populations. The results from this study could help in the development of more accurate risk assessment models pertaining to gypsy moth invasion potential.