Abstract
Invasive species often face significant challenges when they encounter new and fluctuating environmental conditions. One critical factor influencing the establishment and spread of invasive species is the ability to find and exploit suitable nutritional resources. This article investigates the interactions between morphotype, nutrition, and temperature, and their collective impact on the fitness of an invasive fly, Drosophila suzukii. The findings from this study, conducted by Rendon et al. (2019), provide insight into the ecological and evolutionary dynamics of this pest species, with implications for developing more effective management strategies.
Introduction
The spotted-wing drosophila, Drosophila suzukii, is an invasive fruit fly native to Southeast Asia that has spread to North America and Europe, causing significant damage to soft-skinned fruit crops. This species differs from other Drosophila in that it can lay eggs in unripe fruit, giving it a unique niche but also making it a considerable agricultural pest (Walsh et al., 2011). In their study published in ‘Ecology and Evolution,’ Rendon et al. (2019) examined how the fitness traits of D. suzukii, such as lifespan, fecundity, pre-oviposition periods, and body nutrient contents, respond to dietary protein and carbohydrate (P:C) ratios at variable low temperatures. The study’s focus on the winter morph (WM) and summer morph (SM) of the fly sheds light on phenotypic plasticity’s role in the species’ invasive success.
Background
Phenotypic plasticity is the ability of an organism to alter its physiology, morphology, or behavior in response to environmental challenges. This adaptability can be critical for invasive species to survive and thrive in new environments (Fordyce, 2006). Nutrition, particularly the balance of macronutrients such as proteins and carbohydrates, plays a significant role in the fitness of organisms, influencing their growth, reproduction, and survival (Lee et al., 2015). For invertebrates like D. suzukii, which experience diverse climates and fluctuating food resources, the ability to optimize nutrient intake is essential (Bruce et al., 2013).
Drosophila suzukii exhibits seasonal polyphenism with two distinct morphotypes adapted to different environmental conditions. The winter morph is acclimated to colder temperatures, showing characteristics like increased fat storage and stress resistance (Shearer et al., 2016). These adaptations are presumed to be critical for overwintering success in temperate regions (Tochen et al., 2014; Wallingford et al., 2016). Meanwhile, the summer morph thrives in warmer conditions and is geared toward reproduction and rapid population growth (Ryan et al., 2016). By exploring these morphotypes, Rendon and colleagues aimed at uncovering whether their different adaptations also affect their nutritional needs, particularly in challenging conditions, such as during overwintering periods.
Methodology
The research team collected both WM and SM of D. suzukii and subjected them to various P:C ratios in their diet at different low temperatures. The diets ranged from protein-rich to carbohydrate-rich, reflecting the diversity of conditions the flies might encounter in the wild. They then measured the impact of these diets on several fitness parameters: lifespan, fecundity, pre-oviposition period, and body nutrient content (Rendon et al., 2019). The authors hypothesized that there would be an interaction between diet and morphotype that influences the fitness of D. suzukii, especially under temperature stress.
Key Findings
Rendon et al. (2019) reported notable differences between the WM and SM in terms of adapting to different nutritional environments. At low temperatures, WMs showed increased longevity when consuming diets with higher carbohydrate content. Conversely, SMs did not show the same clear preference or benefit, indicating distinct nutritional requirements and adaptive strategies between morphs for coping with cold stress.
The study also revealed that dietary P:C ratio influenced fecundity, with both WM and SM showing higher egg production on protein-rich diets. However, the WMs delayed oviposition under colder conditions, suggesting that temperature might drive the morphs to prioritize survival over immediate reproduction when resources are scarce (Rendon et al., 2019).
Implications for Ecology and Pest Management
Understanding the nutritional ecology of D. suzukii can inform pest management practices. The different dietary preferences and tolerances of WM and SM highlight the need for seasonally adjusted strategies that consider the flies’ life history stages and morph-specific needs (Grassi et al., 2018). For instance, baiting and trapping methods could be optimized by targeting the preferred macronutrients of each morph at various times of the year.
In addition, the findings suggest that environmental changes affecting food availability could select for certain morphs over others, potentially altering the population dynamics and spread of D. suzukii (Jaramillo et al., 2015). As climate change introduces more variability in weather patterns, it is essential to anticipate how these shifts may impact the distribution and invasiveness of this species (Dos Santos et al., 2017).
Conclusion
This study provides a deeper understanding of the relationship between nutrition, temperature, and fitness in D. suzukii, demonstrating that morphotype-specific adaptations can significantly impact the species’ ability to survive and reproduce in new environments. By considering the roles of nutritional ecology and phenotypic plasticity in invasive species success, researchers and pest managers can develop more nuanced and effective strategies to mitigate the impact of pests like D. suzukii on agricultural systems.
References
1. Rendon, D., et al. (2019). Interactions among morphotype, nutrition, and temperature impact fitness of an invasive fly. Ecology and Evolution, 9(5), 2615–2628. DOI: 10.1002/ece3.4928
2. Walsh, D. B., et al. (2011). Drosophila suzukii (Diptera: Drosophilidae): Invasive pest of ripening soft fruit expanding its geographic range and damage potential. Journal of Integrated Pest Management, 2, G1–G7. DOI: 10.1603/ipm10010
3. Fordyce, J. A. (2006). The evolutionary consequences of ecological interactions mediated through phenotypic plasticity. Journal of Experimental Biology, 209, 2377–2383. DOI: 10.1242/jeb.02271
4. Shearer, P. W., et al. (2016). Seasonal cues induce phenotypic plasticity of Drosophila suzukii to enhance winter survival. BMC Ecology, 16, 11. DOI: 10.1186/s12898-016-0070-3
5. Lee, K. P., et al. (2015). Dietary protein:carbohydrate balance is a critical modulator of lifespan and reproduction in Drosophila melanogaster: A test using a chemically defined diet. Journal of Insect Physiology, 75, 12–19. DOI: 10.1016/j.jinsphys.2015.02.007
Keywords
1. Drosophila suzukii fitness
2. Invasive fly nutrition
3. Phenotypic plasticity adaptation
4. Temperature impact on pest
5. Morphotype-specific pest management
Data Availability
The datasets generated for this study can be found in the Dryad digital repository, DOI: 10.5061/dryad.84jr187.