Data from: Sexual selection in true fruit flies (Diptera: Tephritidae): transcriptome and experimental evidences for phytochemicals increasing male competitive ability

In male tephritid fruit flies of the genus Bactrocera, feeding on secondary plant compounds (sensu lato male lures = methyl eugenol, raspberry ketone and zingerone) increases male mating success. Ingested male lures alter the male pheromonal blend, normally making it more attractive to females and this is considered the primary mechanism for the enhanced mating success. However, the male lures raspberry ketone and zingerone are known, across a diverse range of other organisms, to be involved in increasing energy metabolism. If this also occurs in Bactrocera, then this may represent an additional benefit to males as courtship is metabolically expensive and lure feeding may increase a fly's short-term energy. We tested this hypothesis by performing comparative RNA-seq analysis between zingerone-fed and unfed males of Bactrocera tryoni. We also carried out behavioural assays with zingerone and cuelure-fed males to test if they became more active. RNA-seq analysis revealed, in zingerone-fed flies, up regulation of 3183 genes with homologues transcripts to those known to regulate inter-male aggression, pheromone synthesis, mating and accessory gland proteins, along with significant enrichment of several energy metabolic pathways and GO terms. Behavioural assays show significant increases in locomotor activity, weight reduction and successful mating after mounting; all direct/indirect measures of increased activity. These results suggest that feeding on lures leads to complex physiological changes, which result in more competitive males. These results do not negate the pheromone effect, but do strongly suggest that the phytochemical-induced sexual selection is governed by both female preference and male competitive mechanisms.

针对实蝇科果实蝇属（Bactrocera）的雄性实蝇而言，取食广义植物次生代谢物（即雄性引诱剂，包括甲基丁香酚、覆盆子酮与姜酮）可提升其交配成功率。被摄入的雄性引诱剂会改变雄性的信息素混合组分，通常使其对雌性更具吸引力，这被认为是交配成功率提升的核心机制。然而，现有研究表明，在多种其他生物类群中，雄性引诱剂覆盆子酮与姜酮可参与增强能量代谢的过程。若该现象在果实蝇属（Bactrocera）物种中同样存在，则可能为雄性带来额外益处：求偶行为本身代谢成本高昂，而取食引诱剂可提升果蝇的短期能量储备。本研究以趋源果实蝇（Bactrocera tryoni）的雄性个体为实验对象，通过对比取食姜酮与未取食姜酮的雄性个体的转录组测序（RNA-seq）数据，对上述假说进行验证。此外，本研究还针对取食姜酮与诱蝇酮（cuelure）的雄性个体开展行为学实验，以检测其活动能力是否有所提升。转录组测序分析结果显示：取食姜酮的果蝇体内共有3183个基因呈现上调表达，这些基因的同源转录本已知可调控雄性间攻击行为、信息素合成、交配过程及副腺蛋白的表达；同时，多条能量代谢通路及基因本体（GO）术语显著富集。行为学实验结果表明：取食组果蝇的运动活性显著提升、体重出现下降，且挂载后的成功交配比例上升——上述指标均为活动能力增强的直接或间接衡量依据。上述结果表明，取食引诱剂会引发果蝇复杂的生理变化，最终使其成为更具竞争优势的雄性个体。本研究结果并未否定信息素的调控作用，但强有力地指出：植物次生代谢物诱导的性选择，同时受到雌性偏好与雄性竞争机制的共同调控。