Do thermal tolerances and rapid thermal responses contribute to the invasion potential of Bactrocera dorsalis (Diptera: Tephritidae)?

Abstract

Bactrocera dorsalis (Hendel) (Diptera: Tephritidae) has shown remarkable range expansion over the past 10years and invaded several new continents including Africa. Here we report results of a detailed assessment of acute high and low temperature survival ability and the plasticity thereof, to test the hypothesis that traits of the thermal niche have contributed to the species' invasion ability. We also assess life-stage-related variation of thermal tolerances to determine potential stage-related environmental sensitivity. The temperatures at which c. 20% of the population survived of B. dorsalis were determined to be -6.5°C and 42.7°C, respectively, when using 2h exposures. Further, four life stages of B. dorsalis (egg, 3rd instar larvae, pupae and adults) were exposed to high and low discriminating temperatures to compare their thermal survival rates. The egg stage was found to be the most resistant life stage to both high and low temperatures, since 44±2.3% survived the low and 60±4.2% survived the high discriminating temperature treatments respectively. Finally, the potential for adult hardening responses to mediate tolerance of extremes was also considered using a diverse range of acute conditions (using 2h exposures to 15°C, 10°C and 5°C and 30°C, 35°C, 37°C and 39°C as hardening temperatures, and some treatments with and without recovery periods between hardening and discriminating temperature treatment). These showed that although some significant hardening responses could be detected in certain treatments (e.g. after exposure to 37°C and 39°C), the magnitude of this plasticity was generally low compared to two other wide-spread and more geographically-range-restricted con-familial species, Ceratitis capitata and C. rosa. In other words, Bactrocera dorsalis adults were unable to rapidly heat- or cold-harden to the same extent as the other Ceratitis species examined to date. These results suggest a narrower thermal niche in B. dorsalis compared to these Ceratitis species - in both basal and plastic terms - and suggests that its geographic distribution might be more restricted in consequence.

Comparative transcriptome analysis of Glyphodes pyloalis Walker (Lepidoptera: Pyralidae) reveals novel insights into heat stress tolerance in insects

“…Several insect species, such as Drosophila melanogaster ( D. melanogaster ) and Bombyx mori ( B. mori ), are sensitive to heat stress, and the mass mortalities of these insects are often caused by high temperature [ 3 , 4 ]. Conversely, many pests have evolved outstanding capability to adapt to high-temperature stimulations [ 5 ]. In recent years, many studies have focused on the effect of temperature on these insects because of their adaptability to a broad range of temperature [ 6 ].…”

Imaginal disc growth factor 4 regulates development and temperature adaptation in Bactrocera dorsalis

“…B. dorsalis has shown a remarkable range expansion over the past 10 years and has invaded several new continents 5 . With global warming in recent years, B. dorsalis , poses a significant risk to both agriculture and the environment.…”

“…The oriental fruit fly Bactrocera dorsalis is an important invasive Tephritid pest that causes major financial losses in the fruit and horticultural industries because of its high reproductive capacity and invasiveness 2–4 . Over the past 10 years, B. dorsalis has shown remarkable range expansion and invaded several new continents 5 . As noted in recent studies, four major pest species, B. dorsalis , B. philippinensis , B. papayae and B. invadens , belong to a B. dorsalis complex, which makes it more widely distributed and a higher risk than previously thought 6 .…”

Comparative demography ofBactrocera dorsalis(Hendel) andCeratitis capitata(Wiedemann) (Diptera: Tephritidae) on deciduous fruit

“…The K-selected traits of B. dorsalis on deciduous fruit indicate the latter would possibly out-compete C. capitata. Growth of populations of B. dorsalis would however be limited by temperature (Pieterse et al, 2017) and the latter would possibly be the determining factor in competitive outcomes between the two species. The demographic parameters of B. dorsalis on deciduous fruit obtained in this study are similar to those obtained on mango (recorded by Ekesi et al, 2007), the preferred host of this fruit fly species (Ekesi et al, 2006).…”