On The Evolution Of Orchids That Never Bloom

AsianScientist (Jun. 25, 2025) – As Charles Darwin once said, “It is hardly an exaggeration to say that Nature tells us, in the most emphatic manner, that she abhors perpetual self-fertilisation,” Self-fertilisation carries genetic risks, causing the accumulation of harmful mutations and reducing genetic diversity in the plant’s population.

Despite this, the ability to self-fertilise has evolved many times in flowering plants, providing the ability to reproduce in environments with few pollinators or sparsely distributed plants. Even so, most plants that mainly self-pollinate occasionally cross-pollinate, introducing some genetic diversity.

Certain orchids on the Northern Ryukyu Islands in Japan are exceptions to this rule. These orchids never open their flowers, reproducing solely by self-pollination.

“I’ve long been captivated by Darwin’s scepticism about plants that rely entirely on self-pollination,” said Professor Suetsugu Kenji, a botanist at Kobe University “When I found those non-blooming orchids, I felt this was a perfect chance to directly revisit this issue. The apparent defiance of evolutionary common sense made me wonder what precise conditions — both environmental and genetic — would allow a purely self-pollinating lifestyle to emerge, let alone persist.”

Intrigued, Suetsugu and his team set out to understand why the orchids evolved in this way. “Our group spent over ten years working with local plant enthusiasts, monitoring more than a hundred individual plants across several islands, so we can say with certainty that these orchids never open their flowers in their natural habitats,” said Suetsugu.

The researchers investigated the evolution of the non-blooming orchid species Gastrodia takeshimensis and Gastrodia kuroshimensis, using sensitive genetic analysis tools that can discern small differences between near-identical plants.

Each species showed extreme genetic uniformity between individuals, confirming that the orchids reproduce purely by self-pollination. They likely evolved from other, insect-pollinated, Gastrodia orchids in the region.

Surprisingly, the insect-pollinated Gastrodia also showed a very low degree of genetic variation, almost identical to the effect of self-pollination.

Insect-pollinated Gastrodia on the Northern Ryukyu Islands are pollinated by fruit flies with limited flight range, which can only pollinate flowers on the same plant or those close by, reducing the benefit of insect pollination. These orchids have a low rate of pollination success, compared to the nearly 100 percent success of self-pollinating orchids.

“Darwin’s statement was motivated by the idea that a purely self-pollinating lineage would accumulate harmful mutations and eventually face an evolutionary dead end,” explained Suetsugu. “Yet our findings show that for the orchid species with open flowers, the real genetic payoff for outcrossing might be marginal, giving the self-pollinating orchids, which are more successful at producing fruit, an evolutionary edge.”

The self-pollinating orchid species are at most 2000 years old – a fleeting amount of time on an evolutionary timescale. There are no other plants in the world known to purely self-pollinate, suggesting that such species may be ephemeral and lending weight to Darwin’s scepticism of self-fertilisation’s effectiveness.

Further studies into other self-pollinating Gastrodia lineages could shed more light into the conditions that make self-pollination a viable evolutionary strategy. “The fact that these orchids truly never outcross raises intriguing questions about their long-term viability, especially under pressures like habitat fragmentation and climate change,” said Suetsugu. “Each new data point, each newly described species, brings me closer to grasping the full spectrum of evolutionary possibilities.”

—

Source: Kobe University; Image: Shutterstock

This study can be found at Genomic signature and evolutionary history of completely cleistogamous lineages in the non-photosynthetic orchid Gastrodia