Temperature fluctuation effects on the demography and fitness of Xyleborus bispinatus (Coleoptera: Curculionidae: Scolytinae): thresholds and growth rates.

Abstract

Understanding the demography of Xyleborini ambrosia beetles and accurately estimating their optimal growth temperatures remains a challenge due to their cryptic behavior and complex reproductive habits. In this study, we reared the ambrosia beetle Xyleborus bispinatus at five distinct temperatures (17 °C, 20 °C, 26 °C, 29 °C, and 35 °C) over a 36-d period. Population dynamics, growth rates, and life cycle durations were assessed through destructive sampling every 4 d for each temperature treatment. To analyze temperature-dependent growth and development, a nonlinear model was fitted to the intrinsic growth rate values at each temperature, allowing us to determine the species' optimal temperature and corresponding maximum growth rate. In the laboratory, X. bispinatus exhibited optimal growth rates between 26 °C and 29 °C, with rates of 0.10 and 0.12, individuals/individuals/day, and life cycle durations of 20 and 16 d, respectively. However, based on the fitted growth curve, the thermal optimum was estimated at 26.2 °C, where the maximum intrinsic growth rate reached 0.13 individuals/individuals/day. Given its potential to transmit Harringtonia lauricola, these findings provide valuable insights into the thermal effects on X. bispinatus throughout its life cycle and offer a practical approach for estimating growth rates and thresholds in species with cryptic behavior or where cohort tracking is challenging for demographic assessments.