Malod Kevin, Archer C Ruth, Hunt John, Nicolson Susan W, Weldon Christopher W
Department of Zoology and Entomology, University of Pretoria, Hatfield, South Africa.
Institute for Evolutionary Ecology and Conservation Genomics, University of Ulm, Ulm, Germany.
Front Insect Sci. 2023 May 17;3:1166753. doi: 10.3389/finsc.2023.1166753. eCollection 2023.
A changing environment can select on life-history traits and trade-offs in a myriad of ways. For example, global warming may shift phenology and thus the availability of host-plants. This may alter selection on survival and fertility schedules in herbivorous insects. If selection on life-histories changes, this may in turn select for altered nutrient intake, because the blend of nutrients organisms consume helps determine the expression of life-history traits. However, we lack empirical work testing whether shifts in the timing of oviposition alter nutrient intake and life-history strategies.
We tested in the marula fruit fly, , how upward-selection on the age of female oviposition, in comparison with laboratory adapted control flies, affects the sex-specific relationship between protein and carbohydrate intake and life-history traits including lifespan, female lifetime egg production and daily egg production. We then determined the macronutrient ratio consumed when flies from each selection line and sex were allowed to self-regulate their intake.
Lifespan, lifetime egg production and daily egg production were optimised at similar protein to carbohydrate (P:C) ratios in flies from both selection lines. Likewise, females and males of both lines actively defended similar nutrient intake ratios (control =1:3.6 P:C; upward-selected = 1:3.2 P:C).
Our results are comparable to those in non-selected , where the optima for each trait and the self-selected protein to carbohydrate ratio observed were nearly identical. The nutrient blend that needs to be ingested for optimal expression of a given trait appeared to be well conserved across laboratory adapted and experimentally selected populations. These results suggest that in , nutritional requirements do not respond to a temporal change in oviposition substrate availability.
变化的环境能够以多种方式选择生活史特征及权衡取舍。例如，全球变暖可能会改变物候，进而影响寄主植物的可利用性。这可能会改变对草食性昆虫生存和繁殖时间表的选择。如果生活史的选择发生变化，这可能反过来会选择改变营养摄入，因为生物体消耗的营养成分组合有助于决定生活史特征的表达。然而，我们缺乏实证研究来检验产卵时间的变化是否会改变营养摄入和生活史策略。
我们以马鲁拉果蝇为研究对象，测试与实验室适应的对照果蝇相比，对雌蝇产卵年龄进行向上选择如何影响蛋白质和碳水化合物摄入量与包括寿命、雌蝇一生的产卵量和每日产卵量在内的生活史特征之间的性别特异性关系。然后，我们确定了每个选择品系和性别的果蝇在能够自我调节摄入量时所消耗的常量营养素比例。
两个选择品系的果蝇在相似的蛋白质与碳水化合物（P:C）比例下，寿命、一生的产卵量和每日产卵量都达到了最优。同样，两个品系的雌蝇和雄蝇都积极维持相似的营养摄入比例（对照 = 1:3.6 P:C；向上选择品系 = 1:3.2 P:C）。
我们的结果与未经过选择的果蝇的结果相当，在未经过选择的果蝇中，观察到的每个性状的最优值以及自我选择的蛋白质与碳水化合物比例几乎相同。在实验室适应的种群和经过实验选择的种群中，为使给定性状得到最优表达而需要摄入的营养成分组合似乎得到了很好的保留。这些结果表明，在马鲁拉果蝇中，营养需求不会对产卵底物可利用性的时间变化做出反应。
