Interactions among morphotype, nutrition, and temperature impact fitness of an invasive fly

Abstract

Invasive animals depend on finding a balanced nutritional intake to colonize, survive, and reproduce in new environments. This can be especially challenging during situations of fluctuating cold temperatures and food scarcity, but phenotypic plasticity may offer an adaptive advantage during these periods. We examined how lifespan, fecundity, pre‐oviposition periods, and body nutrient contents were affected by dietary protein and carbohydrate (P:C) ratios at variable low temperatures in two morphs (winter morphs WM and summer morphs SM) of an invasive fly, Drosophila suzukii. The experimental conditions simulated early spring after overwintering and autumn, crucial periods for survival. At lower temperatures, post‐overwintering WM lived longer on carbohydrate‐only diets and had higher fecundity on low‐protein diets, but there was no difference in lifespan or fecundity among diets for SM. As temperatures increased, low‐protein diets resulted in higher fecundity without compromising lifespan, while high‐protein diets reduced lifespan and fecundity for both WM and SM. Both SM and WM receiving high‐protein diets had lower sugar, lipid, and glycogen (but similar protein) body contents compared to flies receiving low‐protein and carbohydrate‐only diets. This suggests that flies spend energy excreting excess dietary protein, thereby affecting lifespan and fecundity. Despite having to recover from nutrient depletion after an overwintering period, WM exhibited longer lifespan and higher fecundity than SM in favorable diets and temperatures. WM exposed to favorable low‐protein diet had higher body sugar, lipid, and protein body contents than SM, which is possibly linked to better performance. Although protein is essential for oogenesis, WM and SM flies receiving low‐protein diets did not have shorter pre‐oviposition periods compared to flies on carbohydrate‐only diets. Finding adequate carbohydrate sources to compensate protein intake is essential for the successful persistence of D. suzukii WM and SM populations during suboptimal temperatures.

Seasonal morphotypes of Drosophila suzukii differ in key life‐history traits during and after a prolonged period of cold exposure

“…For instance, in our assay, flies of both morphotypes were gradually acclimated to both cold and spring‐like conditions, contrary to Rendon et al who assigned overwintered WM and noncold acclimated SM to different diet and temperature treatments without transition temperatures. Furthermore, our WM were reared at 10°C whereas developmental temperatures used to induce the winter morphotype were higher (14 and 15°C) in other studies (Rendon et al., 2018, 2019; Stockton et al., 2018). Thermal responses of acclimated laboratory adult flies to heat and cold exposure, greatly depend on their developmental temperature (Hoffmann, 2010; Hoffmann, Sørensen, & Loeschcke, 2003; Schou, Loeschcke, & Kristensen, 2015).…”

Comparing apples and oranges (and blueberries and grapes): fruit type affects development and cold susceptibility of immature Drosophila suzukii (Diptera: Drosophilidae)

“…We expect that D. suzukii reared on cornmeal-based diets likely experience more (and different) nutrient stress compared to our fruit diets. We have observed poor performance of D. suzukii when reared in cornmeal-based diet (Y.J.-P., unpublished observations) and nutrient balance is important in overwintering of adult D. suzukii (Rendon et al 2019). This among-diet variation in laboratory phenotype is increasingly acknowledged in Drosophila research (e.g., Ormerod et al 2017;Rendon et al 2019) and is important when extrapolating pest management decisions to new crops.…”

“…Protein is also a source of proline and arginine, which have significant cryoprotective effects in D. melanogaster (Koštál et al 2012(Koštál et al , 2016. However, high-protein diets reduce lifespan and fecundity of winter morph D. suzukii (Rendon et al 2019). Interactions with microbes may also mediate the effects of diet on cold tolerance.…”

Differential Impacts of Yeasts on Feeding Behavior and Development in Larval Drosophila suzukii (Diptera:Drosophilidae)

“…For many frugivorous species of Drosophila , yeasts provide a source of dietary protein otherwise absent from ripening fruit, a carbohydrate-rich resource 11 . While these carbohydrates are important for many aspects of adult Drosophila fitness, including their life span, fecundity, and survivorship 12–14 , yeast-associated protein also plays a critical role in fitness, particularly during the larval life stage. In general, Drosophila larvae exhibit lower survivorship in yeast-free or low yeast substrates 15–17 , and increasing the ratio of dietary protein to carbohydrates within the larval diet improves survivorship, reduces larval development time, and increases adult body mass 18–20 .…”