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

Authors: RENDON, DALILA - Oregon State University; WALTON, VAUGHN - Oregon State University; TAIT, GABRIELLA - Fondazione Edmund Mach; BUSER, JESSICA - Oregon State University; LEMOS SOUZA, IVANA - Federal University Of Lavras; WALLINGFORD, ANNA - Cornell University; LOEB, GREG - Cornell University; Lee, Jana

Submitted to: Ecology and Evolution
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/2/2019
Publication Date: 2/4/2019
Citation: Rendon, D., Walton, V., Tait, G., Buser, J., Lemos Souza, I., Wallingford, A., Loeb, G., Lee, J.C. 2019. Interactions among morphotype, nutrition, and temperatures impact fitness of an invasive fly. Ecology and Evolution. 9(5):2615-2628. https://doi.org/10.1002/ece3.4928.
DOI: https://doi.org/10.1002/ece3.4928

Interpretive Summary: Invasive animals need a balanced diet to enable them to colonize, survive, and reproduce in new environments. This can be challenging during cold temperatures and food scarcity. We examined how dietary protein and carbohydrate ratios and low temperatures affected the lifespan, egg laying, and energetic reserves of an invasive fly, spotted wing drosophila (SWD). This was tested with winter morph and summer morph SWD, each morph is adapted to survive at cold or warm temperatures, respectively. We found that high protein diet reduced lifespan and egg laying, whereas a low protein diet enhanced egg laying compared to high protein or carbohydrate-only diets in both morphs. Carbohydrate-only and low protein diets resulted in longer lifespans for both morphs at intermediate temperatures. Winter morphs in general lived longer and had higher fecundity than summer morphs. Both morphs receiving high protein diets had lower sugar, lipid, and glycogen body content compared to flies on low protein and carbohydrate-only diets, but had similar body protein content regardless of diet. This suggests that excess dietary protein is excreted and not used. Winter morphs flies had higher protein, lipids, and sugar content than summer morphs, which may be linked to longer lifespan and higher egg laying. SWD use up their glycogen, sugar, and lipid stores during the overwintering period. This study suggests that having both a winter and summer morphotype enables SWD to colonize new environments, as winter morphs had high survival and egg laying during challenging conditions. Furthermore, finding adequate carbohydrate sources to compensate protein intake is essential for the successful persistence of SWD during suboptimal temperatures.

Technical Abstract: 1. Invasive animals depend on finding a balanced nutritional intake to colonize, survive, and reproduce in new environments. This can be especially challenging during periods of cold temperatures and food scarcity. We examined how dietary protein and carbohydrate (P:C) ratios and low temperatures affected lifespan, fecundity, pre-oviposition periods, and body nutrient content in two morphs of an invasive fly, Drosophila suzukii. 2. Winter morph (WM) flies that survived a simulated overwintering period, and summer morph (SM) flies received diets with variable P:C ratios (0:0, 0:1, 1:4, 1:2, 1:1) at low temperatures (7, 9, 12, 14, and 17°C), simulating early spring and autumn conditions, crucial periods for survival. 3. We found that high protein diet reduced lifespan and fecundity, whereas low protein diet enhanced fecundity compared to high protein or carbohydrate-only diets in both morphs. Carbohydrate-only and low protein diets resulted in longer lifespans for both morphs at intermediate temperatures. Both morphs had higher fecundity and shorter pre-oviposition periods at higher temperatures. At intermediate temperatures both morphs had longer pre-oviposition periods on carbohydrate-only diet. Temperature did not have an effect on lifespan, fecundity, or pre-oviposition period on flies fed detrimental high protein diets. 4. WM in general lived longer and had higher fecundity than SM. Both morphs receiving high protein diets had lower sugar, lipid, and glycogen body content compared to flies on low protein and carbohydrate-only diets, but had similar body protein content regardless of diet. This suggests that excess dietary protein is excreted, affecting lifespan and fecundity. WM flies had higher protein, lipids, and sugar contents than SM, which may be linked to longer lifespan and higher fecundity. Nutrient assays on post-overwintering WM revealed that glycogen, sugars, and lipids (but not proteins) were reduced but not depleted during the overwintering period. 5. This study suggests that phenotypic plasticity can confer an advantage to colonize new places.