Darwin famously warned against perpetual self-fertilization, but Kobe University botanist SUETSUGU Kenji encountered a real-world challenge to that notion. On several Japanese islands, including Kuroshima, Takeshima, and Yakushima, he found orchids that never open their flowers and reproduce only via self-pollination. "When I found those non-blooming orchids, I felt this was a perfect chance to directly revisit this issue," said Suetsugu.
Suetsugu's team collaborated with local plant enthusiasts over more than a decade to monitor over 100 orchids. Their genetic analyses confirmed the plants do not outcross, and the populations exhibit extreme genetic uniformity. These purely self-pollinating orchids, the study reveals, descend from insect-pollinated ancestors that already had minimal genetic variation.
Adding to this picture, the team found that these orchids' relatives depend on fruit flies with poor mobility, limiting the effectiveness of cross-pollination. "The real genetic payoff for outcrossing might be marginal," Suetsugu noted. In contrast, the self-pollinating orchids produce fruit more successfully, potentially offering a short-term evolutionary advantage.
Yet this advantage may not last. The study estimates that these lineages are no more than 2,000 years old and could be fleeting. "The fact that these orchids truly never outcross raises intriguing questions about their long-term viability," said Suetsugu, pointing to threats like climate change and habitat fragmentation. He added, "Each new data point... brings me closer to grasping the full spectrum of evolutionary possibilities."
Research Report:Genomic signature and evolutionary history of completely cleistogamous lineages in the non-photosynthetic orchid Gastrodia
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Kobe University
Darwin Today At TerraDaily.com
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