Effects of Temperature on the Developmental and Reproductive Biology of North American Bean Thrips, Caliothrips fasciatus (Pergande) (Thysanoptera: Thripidae: Panchaetothripinae)

Simple Summary North American bean thrips, Caliothrips fasciatus, native to California (U.S.), is a regular contaminant of navel oranges exported from California. Despite more than 100 years of accidental shipments overseas, this polyphagous thrips has not established outside of its native range. Understanding why this thrips has not successfully invaded other parts of the world may be explained, in part, by the effects of temperature on fitness. This study investigated the effects of nine fluctuating temperatures that averaged 8, 10, 15, 20, 25, 30, 32, 35, and 37 & DEG;C over a 24 h period on the developmental and reproductive biology of C. fasciatus to better understand the effects of temperature on these critical life history characters and how temperature may influence the invasion potential of this thrips. North American bean thrips, Caliothrips fasciatus, native to California U.S., has been detected inside the navels of navel oranges exported from California for more than 120 years. Despite this long history of accidental movement into new areas, this thrips has failed to establish populations outside of its native range. The cold accumulation hypothesis postulates that increasing levels of cold stress experienced by thrips overwintering inside navels is compounded when harvested fruit is shipped under cold storage conditions. Consequently, the fitness of surviving thrips is compromised, which greatly diminishes invasion potential. At the time this study was conducted, the effects of temperature on C. fasciatus fitness were unknown. To address this shortcoming, the effects of nine fluctuating temperatures that averaged 8, 10, 15, 20, 25, 30, 32, 35, and 37 & DEG;C over a 24 h period on the developmental and reproductive biology of C. fasciatus were evaluated. One linear and five nonlinear regression functions were fit to egg-to-adult development rate data for parent and offspring thrips to characterize thermal performance curves. Estimates of minimum, optimal, and maximum temperature thresholds for development were in the ranges of -4.37-6.52 & DEG;C (i.e., T-min), 31.19-32.52 & DEG;C (i.e., T-opt), and 35.07-37.98 & DEG;C (i.e., T-max), respectively. Degree day accumulation to complete development, estimated from linear regression, ranged 370.37-384.61. Average development times for eggs, first and second instar larvae, propupae, pupae, and adult longevity, and mean lifetime fecundity of females were significantly affected by temperature. These biological responses to temperature may provide insight into how this abiotic variable affects the invasion potential of C. fasciatus.