Researchers have used genome-wide DNA data to identify a new insect species on the Ogasawara Islands, a remote Japanese archipelago roughly 900 to 1,000 kilometres south of Tokyo. The findings suggest that evolution among island insects is more intricate than appearances imply. The study is published in the open-access journal ZooKeys.
The Ogasawara Islands are a UNESCO World Natural Heritage site, celebrated for their endemic land snails and plants. Their insects, of which some 440 endemic species are known, have received far less evolutionary attention.
Jun Souma, of Hirosaki University’s Shirakami Research Center for Environmental Sciences, and Naoyuki Nakahama, of the Graduate School of Agriculture at Osaka Metropolitan University, examined Omoplax, a genus of lace bugs found nowhere else and thought to have diversified rapidly across the islands.
Analysing 52 specimens with a genetic method known as MIG-seq, the team found that an insect previously regarded as a single species, Omoplax desecta, in fact comprised two. Populations on the Chichijima and Hahajima island groups were genetically distinct, and subtle differences in male genitalia confirmed the split. The Hahajima population is now described as Omoplax sandoru, named after the local name of its host plant.
Souma was first drawn to Omoplax desecta by its unusual diet:
“The reason I took a particular interest in Omoplax desecta is that it feeds on both the native plant Rhaphiolepis indica var. tashiroi and the introduced plant Calophyllum inophyllum in the Chichijima island group.
This is quite unusual for lace bugs, which typically exhibit high host specificity. I was also intrigued by the fact that it is distributed across multiple island groups, which is different from other Omoplax species.”
The Hahajima population posed its own puzzle:
“I had wondered why it fed exclusively on Rhaphiolepis indica var. tashiroi and why there were no individuals with dark brown to black pronotum, which are sometimes seen in the Chichijima island group.
After conducting population genetic and phylogenetic analyses, I began to suspect that this population might be a distinct species. Upon closely observing their morphological characteristics, I was certain of this.”
The evolutionary tree also overturned expectations:
“The most surprising finding of my research was that species feeding on the same plant and appearing very similar are not necessarily sister groups.
Adaptive radiation among insects on oceanic islands may be more complex than comparisons of morphological characteristics and life histories would suggest at first glance.”
The results point to both geographic isolation and shifts between host plants as drivers of speciation.
Of particular interest is the insect’s adoption of Calophyllum inophyllum, a tree introduced by people. The data indicate that this host shift occurred once, and recently.
“I also find it interesting that the introduction of Calophyllum inophyllum by humans may have led to a budding of future speciation in Omoplax desecta.”
Jun Souma
The authors note that DNA could not be obtained from two rare species, leaving parts of the story unresolved. Further sampling will be needed to trace how these insects reached the islands and diversified.
Original source:
Souma J, Nakahama N (2026) Genome-wide SNP data reveal phylogenetic relationships and further new species of lace bugs (Hemiptera, Heteroptera, Tingidae) endemic to the Japanese oceanic islands (the Ogasawara Islands), providing insight into their speciation. ZooKeys 1294: 175-203. https://doi.org/10.3897/zookeys.1294.205145
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