Effects of temperature on survival and preimaginal development rates of Colorado potato beetle on potato and horse‐nettle: potential role in host range expansion

Abstract

AbstractThe effect of temperature on the ability of Colorado potato beetles (Leptinotarsa decemlineata, Say) to use horse‐nettle (Solanum carolinense L.) as a host plant was determined for larvae from colonies originating from two geographically separated populations, one adapted to horse‐nettle (NC) and the other unadapted to horse‐nettle (MA). Survival and developmental rate on horse‐nettle and potato were measured for larvae from both colonies over a range of constant temperatures (12–30 °C) and one fluctuating temperature regime (22 °C to 30 °C). The ability of Colorado potato beetles to use horse‐nettle as a larval host was strongly influenced by temperature, but the effects of temperature differed greatly between beetles from the two colonies. Survival of adapted larvae on horse‐nettle was highest and comparable to that on potato at the constant 30 °C and the fluctuating temperature regime. Below 30 °C, survival of adapted larvae decreased drastically but some larvae survived at all temperatures except the lowest (12 °C). In contrast, survival of unadapted larvae to adult occurred only at 30 °C, and was low (10%). At lower temperatures, all larvae died. On potato, the effect of temperature was less dramatic, and consistent across colonies. At 12 °C, survival to adult was poor (ca. 10%), but at higher temperatures, survival increased sharply and larvae from both colonies survived equally well. On potato, small but statistically significant differences in developmental rates between beetle colonies were detected at the constant but not at the fluctuating temperature regimes. Also, the developmental day degree requirements (DD) and the low temperature development threshold (T0) values for the various developmental stages did not differ between colonies on potato. On horse‐nettle, development times for both colonies were always significantly longer and DD requirements were greater than on potato. At 30 °C, the only constant temperature at which larvae from the unadapted colony completed development, the development rate to adult emergence was similar to that of beetles from the adapted colony. Differences between colonies in performance on horse‐nettle were not a result of host‐independent, genetically based differences in the thermal requirements of the two populations. Our findings are consistent with the hypothesis that adaptation to horse‐nettle by Colorado potato beetle may be facilitated by a genotype × environment interaction involving temperature. These findings have important implications for host plant utilization, host range expansion and selection of pest biotypes adapted to plant resistance traits used in crop protection.