Climate Change, Succession, and Reproductive Success of a Praying Mantid

Abstract

AbstractWe examined the adult phase of the Chinese praying mantid, Tenodera aridifolia sinensis (Saussure) (Mantodea: Mantidae) at the end of five growing seasons spanning two decades (1999–2018) in a successional old field. Sex ratio, which is generally male-biased by the time all members of a cohort are adults, exhibited a steady decline in proportion of males and eventual reversal by 2016, even though the calendar time of the study did not vary among years. Increasing length and warmth of the growing season resulted in earlier maturation, so we were seeing later portions of the adult phase at the same calendar time over successive years. This result is consistent with the earlier-published hypothesis that global warming can reduce fitness by warming and extending the growing season: earlier maturation results in earlier oviposition, which in turn causes eggs to hatch before onset of winter, thereby dying before egg diapause can occur. This may push the latitudinal distribution of this, and of other univoltine semelparous insects, farther north as the climate continues to warm. Reproductive output for the population, measured as total number of eggs produced by a cohort, peaked in 2004 at 8,514 and then fell to 226 by 2018, as did estimated numbers of adults. This decline was probably due to shrinkage of the open field area where prey were more abundant, by more than 2/3 as cedar trees replaced herbaceous vegetation during plant secondary succession. This is consistent with the hypothesis that succession limits the residence time in a habitat for these mantids.