Japan Ant Species Has Only Queens—and Clones Itself

A remarkable discovery in Japan reveals a species of ant, Temnothorax kinomurai, where every individual is a queen – and they reproduce by cloning themselves. These ants don’t build their own colonies. instead, they infiltrate the nests of other ant species, taking them over and compelling the existing workers to raise their young. The findings, published February 23 in Current Biology, offer a unique glimpse into the evolution of social parasitism and asexual reproduction.

The unusual ant was first suspected of having a peculiar social structure, lacking both male and worker castes, but confirmation required detailed study. Researchers, led by Keiko Hamaguchi at the Kansai Research Center in Kyoto, Japan, and collaborating with biologist Jürgen Heinze at the University of Regensburg in Germany, investigated colonies of T. Kinomurai found in just nine locations across Japan. Their work confirms that this species consists entirely of reproducing females, a phenomenon previously unknown in the ant world.

A Life of Parasitism and Parthenogenesis

Unlike most ant species, where queens rely on sperm stored from a single mating event to produce both female workers and queens, and short-lived males, T. Kinomurai reproduces asexually through a process called parthenogenesis. This means the queens can create genetically identical copies of themselves without needing to mate. This ability is not unique to ants – sharks have also been observed reproducing this way – but its combination with a fully parasitic lifestyle is unprecedented.

The parasitic strategy involves invading the nests of a closely related species, Temnothorax makora. Young T. Kinomurai queens will sting the host queen and any aggressive workers attempting to defend the colony. If successful, the invading queen then relies on the host workers to forage for food and care for her offspring. “T. Kinomurai needs the host workers for foraging and brood care and cannot produce offspring without them,” explained Heinze via email.

Laboratory Confirmation of a Queen-Only Society

To definitively confirm the absence of workers and males, Hamaguchi’s team reared 43 offspring from six T. Kinomurai colonies in a controlled laboratory setting. Detailed examination of the offspring revealed that all were queens, with no evidence of male or worker development. Further testing showed that seven of these virgin queens successfully invaded new T. Makora colonies, initiating the parasitic cycle and producing a further 57 queen offspring. This high failure rate in colony founding attempts is typical for parasitic ants, reflecting the inherent risks of taking over another species’ nest.

Evolutionary Implications: Combining Strategies

The discovery is significant as it represents the first known species to combine both asexual reproduction and social parasitism. As evolutionary biologist Jonathan Romiguier at the University of Montpellier in France told Live Science, “Despite the intuitive evolutionary logic behind such a combination, no species had been shown to merge both strategies until now.”

The benefits of sexual reproduction typically lie in the genetic diversity it creates, which can enhance a colony’s ability to resist disease and adapt to changing environments. Asexual reproduction, allows an organism to maximize its own genetic contribution to the next generation, potentially leading to faster population growth in stable conditions. However, the loss of workers in T. Kinomurai eliminates the benefits of genetic diversity within the colony.

Daniel Kronauer, a biologist at The Rockefeller University, explained to Live Science that the loss of workers may have tipped the balance in favor of asexual reproduction. “This could shift the balance in favor of asexual reproduction and, the loss of males,” he said. The researchers suggest that the parasitic lifestyle, where the host colony provides all necessary labor, may have reduced the selective pressure for maintaining a diverse workforce.

Understanding the Balance of Reproduction

Both sexual and asexual reproduction have advantages, and disadvantages. Asexual reproduction allows for rapid population growth by producing genetically identical daughters, avoiding the energy expenditure of finding mates and producing males. However, sexual reproduction generates genetic diversity, which can be crucial for adapting to changing environments and resisting pathogens. In the case of T. Kinomurai, the parasitic lifestyle appears to have diminished the benefits of genetic diversity, making asexual reproduction a viable strategy.

The study highlights the complex interplay between reproductive strategies and social organization in ants. Further research is needed to understand the genetic mechanisms underlying parthenogenesis in T. Kinomurai and to investigate the long-term evolutionary consequences of this unique combination of traits.

Looking ahead, researchers plan to investigate the genetic basis of parthenogenesis in T. Kinomurai and explore the potential for similar reproductive strategies in other ant species. Continued monitoring of T. Kinomurai populations in Japan will also be crucial to assess the long-term viability of this remarkable queen-only society and its impact on the host ant species.