The florivory could disrupt reproductive success of plants by feeding flower, and plants also have some defense mechanisms against florivory. In Kyushu, the alien slugs (Lehmannia valentiana) that originated from the Iberian Peninsula preferred feeding on the capitula of the native dandelion (Taraxacum japonicum), but the sympatric hybrid dandelion with recurved phyllary and longer sepals were immune. In this study, we try to understand the function of the specialized bracts of Taraxacum through observing the slug behavior. Result show the recurved phyllary can extend the handling time for slugs and the longer sepals can protect the nutritious reproductive tissue of capitula. Thus, these morphological differences between dandelion species lead to the feeding preference of slugs. Our result supports that these specialized bracts of dandelion are the effective defense against florivory. Finally, we find the relationship between floral traits and climate. The dandelions with recurved phyllary dominate in Iberian Peninsula but don’t in East Asia monsoon region. We could infer that the evolution of floral defenses of Taraxacum evolved in response to differences in plant-animal interactions underlying variable phenology.