Human Fragmentation Effects Are Genetically Detectable After 6 Years in an Island-Endemic Plant.

Anthropogenic disturbances have long been acknowledged to be one of the primary threats to biodiversity worldwide; however, little is still understood about how human-built infrastructure affects gene flow and phylogeographic structure of plants. Such information is helpful for the conservation and restoration of human-disturbed ecosystems. Here we studied the effects of a large reservoir and two expressways on (Gesneriaceae), a short-lived herb endemic to Hainan Island (China), one of the key areas of the globally important Indo-Burma biodiversity hotspot. By applying comparative phylogeography using one nuclear ribosomal DNA and two chloroplast DNA sequences, we estimated the levels of genetic diversity and differentiation in 176 and 117 individuals collected, respectively, before (in 2016) and after (in 2022) the construction of two expressways in Hainan Island, from the same eight populations of . We found that this species significantly increased nuclear genetic differentiation during the period 2016-2022, which coincides with the opening of the two expressways. Also notably, the sharing of ribotypes among the three groups of populations separated by the expressway network diminished greatly for the same period. Moreover, the changes in the significance of genetic barriers before and after road construction suggest that geographic isolation caused by human constructions is key for understanding the present phylogeographical patterns of . We provide direct evidence that large anthropogenic infrastructures are capable of increasing genetic differentiation and, thus, modifying the phylogeographical pattern of , in just a six-year period (or two generations of the study plant). We suggest establishing ecological corridors to enhance gene exchange between the two sides of these artificial barriers.