Variation in cold hardiness among geographic populations of the ragweed beetle, Ophraella communa LeSage (Coleoptera: Chrysomelidae), a biological control agent of Ambrosia artemisiifolia L. (Asterales: Asteraceae), in China

Abstract

The ragweed beetle, Ophraella communa, is a potential biological control agent of common ragweed that appeared in Nanjing City in 2001 and has since dispersed throughout southeast China. We compared the cold hardiness of five different O. communa populations by measuring the supercooling point (SCP), water and glycerol contents of adult beetles. All indices of cold hardiness varied significantly among the sampled populations. Male beetles from the most northerly population (Nanjing) had the lowest water content of any sampled and, although female beetles from Nanchang and Miluo had water content similar to those from Nanjing, they were still lower than those of females from Fuzhou and Wuchang. Beetles from the most southerly population (Fuzhou) had the highest SCP, although Nanchang males were not significantly different from Fuzhou males. Glycerol content yielded resolution of populations as follows: Nanjing [ Wuchang = Miluo = Nanchang [Fuzhou, with beetles from Nanjing yielding twice the glycerol content of Fuzhou beetles. These results suggest that overwintering O. communa use freeze avoidance to survive winter cold and that geographically separated populations of O. communa are diverging with respect to their baseline cold hardiness in accordance with the severity of low temperatures experienced during the coldest winter months in each locality. The apparent ability of O. communa to rapidly adapt to different climatic conditions is predicted to facilitate its continued range expansion across mainland China, with consequent benefits in terms of fortuitous biological control of common ragweed.

Cold Temperatures Increase Cold Hardiness in the Next Generation Ophraella communa Beetles

“…This results in bettles to have lower supercooling points when parents experienced colder temperatures. It has been demonstrated that cold hardiness, via changes in the relative composition of their body fluids and fats, is a plastic trait that can be influenced by fluctuations in abiotic factors (e.g., temperature) throughout the breeding season of O. communa [37], [38]. The present experiment is in line with the idea that O. communa has strong environmentally-driven phenotypic plasticity to cold adaptation, and this can be transmitted to the next generation.…”

“…Insects living in temperate regions have to cope with low winter temperatures, which may strongly influence the establishment and persistence of perennial populations in the field [37], [38], [58]. In general, survival rates of insects decrease with decreasing temperatures [23], [25], [27], [59], and this phenomenon has been also observed in O. communa [17], [23], [42].…”

“…The whole-body glycerol content of beetles was determined using an enzymatic assay (337-40A, Sigma Chemical Company, St. Louis, MO, USA) as in [38]. Briefly, twelve hours-starved individual adults were homogenized in 25 mM sodium phosphate buffer (pH 7.4) and then centrifuged at 12,000 g for 10 min at 25°C.…”

“…Resistance to cold temperatures, or cold hardiness of insects, is reflected by four variables relating to insect physiology including; water content, accumulation of glycerol or other low molecular weight polyols and sugars (cryoprotectants), supercooling point (SCP), and survival capacity under low temperature [28], [30], [31], [32], [33], [34]. Previous studies revealed that better cold hardiness is typically associated with lower SCP, lower water content, and higher glycerol content in the insect [28], [30], [31], [35], [36], [37], [38], [39], [40].…”

Winter hosts ofAphalara itadori(Hemiptera: Psyllidae), a classical biological control agent ofFallopia japonica(Polygonaceae), in the UK

“…For A. itadori to overwinter successfully in the UK, the climatic conditions must fall within the fundamental tolerances of the species and there must be suitable overwintering sites available. There will be a natural variation in the coldhardiness of any species depending on the conditions of the native region (Zhou Guo, Michaud, Li, & Wan, 2010). This can influence the selection of a particular population, not just the species identity, of a biological control agent to ensure the best match between the native and introduced regions.…”