RT Journal Article SR Electronic T1 Temperature change has the same effect as genetic variation on a morphological trait involved in reproductive isolation between Drosophila sister species JF bioRxiv FD Cold Spring Harbor Laboratory SP 2020.01.20.911826 DO 10.1101/2020.01.20.911826 A1 Alexandre E. Peluffo A1 Mehdi Hamdani A1 Alejandra Vargas-Valderrama A1 Jean R. David A1 François Mallard A1 François Graner A1 Virginie Courtier-Orgogozo YR 2020 UL http://biorxiv.org/content/early/2020/01/20/2020.01.20.911826.abstract AB Phenotypic plasticity, the capacity of one genotype to generate distinct phenotypes in different environments, is usually thought to facilitate species divergence by opening novel ecological niches to plastic individuals. Here we reveal a case of speciation where this “plasticity first” scenario might not hold. Male genitalia are usually extremely divergent between closely related species, but relatively constant within one species. Under the lock-and-key hypothesis, rapid morphological evolution is associated with a high match between male and female genitalia of the same species and a low match between male and females of closely related species. Previous studies have suggested plasticity of genitalia to be a proof against the lock-and-key hypothesis since the environmentally triggered phenotypic change could modify the “key”. Here we examine the effect of temperature on the shape of the ventral branches, a male genital structure involved in reproductive isolation, in the sister species Drosophila santomea and D. yakuba. We designed a semi-automatic measurement pipeline that can reliably identify curvatures and landmarks based on manually digitized contours of the ventral branches. With this method, we observed that ventral branches are not plastic in D. yakuba but that in D. santomea temperature change phenocopies interspecific genetic variation between both species for ventral branches shape. Our results suggest that speciation of D. santomea and D. yakuba was associated with a gain of plasticity and that genitalia plasticity can be compatible with the lock-and-key hypothesis.QTLQuantitative Trait LocusSTspine thrust