Hybridization is a critical driver in biological evolution, yet the ecological conditions that favor it remain uncertain. To gain insight into the circumstances under which hybridization occurs, researchers from the Xishuangbanna Tropical Botanical Garden (XTBG) conducted a study involving two closely related fig species with an extensive longitudinal contact belt spanning Southeast Asia.
The researchers focused on Ficus heterostyla and Ficus squamosa, two dioecious fig species, and aimed to uncover patterns of interspecific hybridization and introgression along a latitudinal gradient. Using nuclear microsatellites and extensive population sampling across their shared contact range, they examined spatial signatures of hybridization.
Surprisingly, the study revealed that these closely related figs exhibited reproductive isolation within their core contact range, with hybridization signatures only emerging at the climatic extremes in the north. The prevalence of hybridization significantly increased toward higher latitude climatic margins.
Detailed natural history data, including factors such as growth form, phenology, and population density, provided further insights into the direction of interspecific gene flow. The findings suggest that climatic margins may serve as hotspots for hybridization, potentially leading to speciation events.
This research contributes to our understanding of how hybridization operates in the context of geographical contact zones and offers valuable insights into the role of ecological factors in shaping patterns of gene flow among closely related species.