Similar phylogeographic history in a fig species and its obligate pollinators forms parallel genetic structure

Closely related and co-distributed species usually share a common phylogeographic history, but it remains unclear whether ecologically interacting species can respond synchronously to historical climate changes. Here, we focused on a fig-pollinator mutualism comprising Ficus pumila var. pumila and its obligate pollinators (morphospecies Wiebesia pumilae), and collected samples across most of their distribution ranges. We employed cytoplasmic DNA sequences and nuclear microsatellite loci to reveal the species composition within the pollinators and to test whether the two mutualists exhibited similar postglacial phylogeographic patterns. We identified three cryptic pollinator species, with two dominant cryptic species exhibiting parapatric distributions in the northern and southern parts of the plant's range, respectively. Similar current spatial genetic structures were detected in the two dominant cryptic pollinator species and the host plant, with both showing eastern and western genetic clusters. Moreover, evidence for postglacial expansion was found for all three species, and their potential refugia during the Last Glacial Maximum were located in the eastern and western parts of their distribution ranges. These results suggest synchronous responses to historical climate changes. Our study demonstrates congruent phylogeographic patterns between obligate mutualists and highlights the role of biogeographic factors in shaping the current biodiversity across trophic levels.