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One group of termites are habitual seafarers, suggests new research. The wood-munching insects crossed the world鈥檚 oceans at least 40 times over the past few tens of millions of years. The termites probably set sail accidentally, rafting inside pieces of wood washed out to sea.

Drywood termites make up the second-largest termite family, the Kalotermitidae, with more than 400 species found throughout the tropics and subtropics. Unlike many other termite groups, members of drywood termite colonies don鈥檛 forage between wood resources, instead subsisting within a single tree, log or branch. This largely hidden existence has made these termites difficult to collect, says at the Okinawa Institute of Science and Technology in Japan.

Because drywood termites are relatively understudied and their lifestyle has been considered a primitive trait among termites, Bu膷ek and his colleagues were interested in the group鈥檚 evolutionary history.

The team analysed the DNA of drywood termites belonging to about 120 different species, about 27 per cent of the family鈥檚 total diversity. Bu膷ek and his colleagues then used differences in the DNA to map the evolutionary relationships between the species. Using termite fossils and knowledge of the modern species鈥� geographical locations, the team could determine where and when drywood termite lineages moved between continents.

The team found that drywood termites travelled across oceans at least 40 times, with most crossings occurring within the past 50 million years. Once on a new continent, they diversified into new species.

The evolutionary relationships also reveal that the very oldest lineages of drywood termite don鈥檛 nest in single pieces of wood, so the researchers think this lifestyle isn鈥檛 ancient after all, but a more recently evolved specialisation.

However, this nesting approach may have helped the termites cross oceans. Drywood termite nests are often contained in relatively hard or even partially living wood 鈥� a sturdy vessel protected from the elements.

鈥淭hat鈥檚 probably one of the factors which helped [the termites] in their transoceanic voyages, because this piece of wood is like a nice ship,鈥� says Bu膷ek.

Also, in contrast to many termites, the non-reproducing members of a drywood termite colony can become reproductive later on, says Bu膷ek. This would make seeding new colonies after a sea voyage far easier.

鈥淵ou don鈥檛 need the whole colony with the king and queen floating,鈥� he says. 鈥淵ou can have just a small fragment with maybe only a limited number of workers.鈥�

at the University of Florida notes it is actually a conservative estimate that there were 40 ocean crossings given the study included less than a third of the total drywood termite species.

鈥淭here are most likely countless other lineages that made the trip, died in the process or made it but went extinct later for other reasons,鈥� says Chouvenc.

There is plenty left to learn about these termites, says Bu膷ek, particularly in regards to their ecology and secretive, wood-bound lives. Such information may help researchers understand more about how the group evolved into such prolific dispersers, and what types of traits might help invasive species spread.

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