Influence of seasonality and climate on captures of wood-boring Coleoptera (Bostrichidae and Curculionidae (Scolytinae and Platypodinae)) using ethanol-baited traps in a seasonal tropical forest of northern Thailand

Abstract

ABSTRACT Insects in the tropics usually have continuous generations throughout the year. We reanalyzed published data of wood-boring beetles, belonging to three taxonomic groups (Bostrichidae; Curculionidae: Scolytinae, Platypodinae), that were captured by ethanol-baited traps continuously set for three years and collected every two weeks in the lowland montane forest in northern Thailand. Because trap captures seemed to have 1-yr cycle, we hypothesized that 1-yr cycle of climate had caused 1-yr cycle in the trap captures. To test this hypothesis, cycles of both total trap captures (TTC) and of each species, synchrony in time-series trap captures, and causality of temperature and rainfall to the TTC were determined. Eighty-nine species were captured over the three years. Among 55 species (>2 individuals), 30 species showed the greatest peak of spectral density at 1-yr, but only three were significant. Some species had (a) cycle(s) shorter than one year. However, 20 species making up 69.7% of TTC and 38 species making up 91.1% of TTC showed significant synchrony with TTC diagnosed by the Phillips-Ouliaris cointegration test and Pearson’s correlation function, respectively. Temperature, rainfall, and season (solar elevation angle) showed significant causalities, the effect of season being the strongest. Both temperature and rainfall positively influenced TTC with lags. These results indicate that seasonality in temperature and rainfall caused a 1-yr cycle in flying beetles of a majority of the more abundant species, and synchrony among species, which resulted in the 1-yr cycle of TTC. The revolution and tilt of the earth was a likely driving force.