| Summary: | Volatile organic compounds (VOCs) released by the receptive syconia of <i>Ficus</i> species play a vital role in attracting highly species-specific pollinating fig wasps. The components of VOCs vary considerably among <i>Ficus</i> species, but are generally dominated by a few common terpenoid compounds or specific proportions of several compounds. Terpene synthase (<i>TPS</i>) is the main source of specific and diverse terpenoids, but the evolution of the <i>TPS</i> gene family in <i>Ficus</i> and the potential functions of the <i>TPS</i> genes in species-specific pollination remain largely unelucidated. In this study, using transcriptomes of ostiole bracts of receptive male figs from 24 <i>Ficus</i> species collected from South China and Southeast Asia, we comprehensively scanned and investigated the composition and evolutionary characteristics of all <i>TPS</i> genes in all 24 species. We identified 248 <i>TPS</i> genes, including 33 orthologous genes and six singletons. Sequence and phylogenetic analysis showed that a majority of the 248 <i>TPSs</i> contained the DDXXD and DTE motifs, rather than the DXDD motif, and involved all subfamilies (<i>TPS-a,b,c,e/f</i> and <i>g</i>) known in other angiosperm genomes, suggesting a very diverse and complex composition of class I <i>TPSs</i> during the receptive phase. In addition, compared to <i>TPS-a</i>, which is generally the largest subfamily in some plants, the <i>TPS-b</i> subfamily contained the highest number of genes in <i>Ficus</i> species. Expression profile comparison showed that the distribution and expression levels of different <i>TPSs</i> among different <i>Ficus</i> species differed considerably, but a few <i>TPS</i> genes were common across most species. Positive selection analysis showed that the <i>Ficus TPS</i> genes were mainly under purifying selection, with only four genes having positive selection signals and two genes having positive selection sites, and two genes having relatively fast-evolving rates. The present study demonstrates the basic evolutionary characteristics of <i>TPS</i> genes in <i>Ficus</i> and reveals the roles of <i>TPSs</i> in shaping the diversity and specificity of the fig–fig wasp symbiotic relationship.
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