Effects of temperature on life histories of three endangered Japanese diving beetle species

Abstract

To elucidate population‐increasing factors in the diving beetle Cybister tripunctatus lateralis (Fabricius) (Coleoptera: Dytiscidae) in Japan in recent years, life histories and oviposition patterns were compared among three endangered diving beetle species, Cybister brevis Aubé (qualified by the Japanese Red Data List as ‘near threatened’), Cybister chinensis Motschulsky (vulnerable), and C. tripunctatus lateralis (vulnerable). Oviposition in C. brevis, C. chinensis, and C. tripunctatus lateralis was observed from late April to mid‐June, from late April to early July, and from late May to mid‐August, respectively, under semi‐outdoor conditions. There were no interspecies differences in total hatchling production during the reproductive season. In rearing experiments at various temperatures (20, 23, 25, 28, and 30 °C), the mortality of C. tripunctatus lateralis larvae was higher at 20 °C, and gradually lower with increasing temperature up to 30 °C. Adult body size of females in C. tripunctatus lateralis is larger than that of males but there were no significant differences among temperatures (25–30 °C). Cybister brevis had a higher emergence rate at 23–28 °C than at 20 and 30 °C. In C. brevis, the body size of adults reared at 25 or 28 °C was significantly larger than at other temperatures. Cybister chinensis did not differ in emergence rate and adult body size among the five temperature conditions. The developmental zero (i.e., the lower developmental threshold) from the first instar to adult emergence was 11.1 °C for C. brevis, 8.7 °C for C. chinensis, and 16.8 °C for C. tripunctatus lateralis. We speculate how the influence of global warming may have a positive impact on the growth and survival of C. tripunctatus lateralis.

Life history of Laccophilus lewisioides Brancucci, 1983 (Coleoptera: Dytiscidae) and the ecological significance of the larval period of five Laccophilus species

“…The known case studies of Dytiscidae include Copelatus Erichson, 1832 (Watanabe & Ohba 2022), wherein the habitat adaptation was considered based on the duration of larval period, and Cybister Curtis, 1827, in which adult emergence rates at different temperatures were examined (Ohba et al . 2020).…”

“…The rearing-based method is suitable for a comparison between closely related species, because it is possible to rear target species under the same environmental conditions. The known case studies of Dytiscidae include Copelatus Erichson, 1832 (Watanabe & Ohba 2022), wherein the habitat adaptation was considered based on the duration of larval period, and Cybister Curtis, 1827, in which adult emergence rates at different temperatures were examined (Ohba et al 2020).…”

Life history of Copelatus zimmermanni Gschwendtner, 1934 (Coleoptera: Dytiscidae) and the ecological significance of the larval period of three Copelatus species

“…Ohba et al . 2020). This allows a comparison of different habitats utilized for reproduction between closely related species via observation of immature stages.…”

“…An additional advantage of laboratory methods is that they allow comparisons of life history between related species when reared under the same conditions (e.g. Ohba et al 2020). This allows a comparison of different habitats utilized for reproduction between closely related species via observation of immature stages.…”

Biological notes on immature stages of Hydaticus pacificus conspersus (Coleoptera: Dytiscidae)

“…To assess the larval period in detail, quantitative and temporal data produced from experimental rearing are required. Insights into life histories and development of immature stages will contribute to ex situ and in situ conservation approaches to preserve biodiversity in aquatic ecosystems, such as those inhabited by this species (e.g., Vahrushev 2011;Ohba et al 2020).…”