- •Conducted a comparative study of two closely related invasive fruit fly species, Bactrocera correcta & B. dorsalis in China.
- •The more widespread species B. dorsalis has a higher thermal plasticity than the narrowly distributed species B. correcta.
- •Heat shock survival rates and levels of Hsp gene expression in two species were highly consistent in response to heat.
It is generally believed that widely distributed species differ in their
thermal plasticity from narrowly distributed species, but how
differences in thermal plasticity are regulated at the molecular level
remains largely unknown. Here, we conducted a comparative study of two
closely related invasive fruit fly species, Bactrocera correcta and B. dorsalis, in China. The two species had overlapping distributions, but B. dorsalis had a much wider range throughout the country and a longer invasive history than B. correcta.
We first examined the effects of thermal acclimation on the ability of
the two fruit flies to survive heat stress. The heat shock tolerance of B. dorsalis was significantly enhanced by heat hardening at 35, 37, 39 and 41 °C, but that of B. correcta
was only enhanced by heat hardening at 39 °C and 41 °C. Thus, the more
widespread species has a higher thermal plasticity than the narrowly
distributed species. We then determined the expression of Hsp70 and
Hsp90 during different developmental stages and their responses to
thermal hardening. The expression of both Hsp70 and Hsp90 in larvae was
upregulated in response to heat hardening, starting at 35 °C for B. dorsalis and at 39 °C for B. correcta.
The two species exhibited a highly consistent pattern of thermal
response in terms of their heat shock survival rates and levels of Hsp
gene expression. The results suggest that the difference in thermal
plasticity may be responsible for the different distributions of the two
species and that Hsp expression may be involved in the regulation of
thermal plasticity. Our findings have important implications for the
prediction of the thermal limits and ecological responses of related
species in nature.