Differences in larval nutritional requirements and female oviposition preference reflect the order of fruit colonization of Zaprionus indianus and Drosophila simulans

Species coexist using the same nutritional resource by partitioning it either in space or time, but few studies explore how species-specific nutritional requirements allow partitioning. Zaprionus indianus and Drosophila simulans co-exist in figs by invading the fruit at different stages; Z. indianus colonizes ripe figs, whereas D. simulans oviposits in decaying fruit. Larvae feed on yeast growing on the fruit, which serves as their primary protein source. Because yeast populations increase as fruit decays, we find that ripe fruit has lower protein content than rotting fruit. Therefore, we hypothesized that Z. indianus and D. simulans larvae differ in their dietary requirements for protein. We used nutritional geometry to assess the effects of protein and carbohydrate concentration in the larval diet on life history characters in both species. Survival, development time, and ovariole number respond differently to the composition of the larval diet, with Z. indianus generally performing better across a wider range of protein concentrations. Correspondingly, we found that Z. indianus females preferred to lay eggs on low protein foods, while D. simulans females chose higher protein foods for oviposition when competing with Z. indianus. We propose the different nutritional requirements and oviposition preference of these two species allows them to temporally partition their habitat.

多个物种可通过空间或时间维度的营养资源分化共享同一营养资源，但目前鲜有研究探讨物种特异性营养需求如何促成此类资源分化。斑翅果蝇（Zaprionus indianus）与模拟果蝇（Drosophila simulans）在无花果生境中共存，二者通过侵染果实的不同阶段实现共存：斑翅果蝇侵染成熟无花果，而模拟果蝇则在腐烂果实上产卵。二者幼虫均以果实表面生长的酵母作为主要蛋白质来源。由于酵母种群随果实腐烂过程增殖，成熟果实的蛋白质含量低于腐烂果实。据此我们提出假设：斑翅果蝇与模拟果蝇的幼虫在蛋白质膳食需求上存在差异。本研究采用营养几何（nutritional geometry）方法，评估幼虫日粮中蛋白质与碳水化合物浓度对两个物种生活史性状的影响。结果显示，存活率、发育时长与卵巢管数量对幼虫日粮组成的响应存在显著物种差异：斑翅果蝇在更广的蛋白质浓度范围内均表现出更优的适合度。相应地，本研究发现：斑翅果蝇雌虫偏好于在低蛋白质食物上产卵，而当与斑翅果蝇竞争时，模拟果蝇雌虫则选择高蛋白质食物进行产卵。我们认为，这两个物种的营养需求差异与产卵偏好差异，使其能够通过时间维度对栖息生境实现资源分化。