Termite salinity tolerance and potential for transoceanic dispersal through rafting

Abstract

1. Oceanic rafting through driftwood has been hypothesized to be a mechanism underlying the transoceanic distribution of termites (Order: Blattodea). To test this hypothesis, we examined the salinity tolerance of 12 termite species from eight genera and three families, namely Archotermopsidae, Kalotermitidae, and Rhinotermitidae.2. Our results revealed that the survival rates of Incisitermes inamurai (Oshima), Cryptotermes domesticus (Haviland), Prorhinotermes flavus (Bugnion and Popoff), P. simplex (Hagen), and Heterotermes sp. are not affected by treatment with 3.5% saline water, strongly supported that oceanic rafting may be a mechanism underlying the insects' transoceanic distribution.3. By contrast, Hodotermopsis sjostedti Holmgren, Glyptotermes satsumensis (Matsumura), Coptotermes formosanus Shiraki, Co. gestroi (Wasmann), Reticulitermes virginicus (Banks), R. leptomandibularis Hsia and Fan, and R. kanmonensis Takematsu treated with saline water showed dehydration symptoms, and their mortality rates increased significantly within 12 days after treatment. These results indicate that these species are less likely to be dispersed through oceanic driftwood and that their transoceanic dispersal is rather more likely to occur through human transportation or land bridges.4. Phylogenetic positions and habitats of salinity-tolerant termites implied that the acquisition of salinity tolerance may relate to both phylogeny and coastal living.

Desiccation tolerance of Termitidae termites in relation to their nest type

“…Body shrinkage during the desiccation process is a common phenomenon observed in insects, including fruit flies (Thorat et al 2016) and termites (Chiu et al 2021). This shrinkage directly affects the surface area of the insect's body and may consequently influence the rate of water loss.…”

Molecular Phylogeny Reveals the Past Transoceanic Voyages of Drywood Termites (Isoptera, Kalotermitidae)

“…Species of Cryptotermes possess three biological traits that enhanced their invasiveness and have allowed them to disperse around the world with human assistance: they are wood-feeders, nesting in wood pieces, and easily produce secondary reproductives ( Evans et al 2013 ). In addition, C. domesticus is tolerant to saline water, a biological trait that presumably increases its ability to survive long-distance oceanic dispersal in wood pieces and possibly human-assisted journeys ( Chiu et al 2021 ). Additional life-history traits might contribute to the invasiveness of Cryptotermes , but the physiology and ecology of Kalotermitidae have not been fully elucidated, preventing us from comprehending what may also aid their suitability for such passive dispersal.…”

Neoisoptera repeatedly colonised Madagascar after the Middle Miocene climatic optimum

“…Our ancestral range reconstructions also revealed one long‐distance over‐water dispersal event within the Madagascan realm, that of P. canalifrons between Madagascar and the Reunion Island 2.1 Ma (95% HPD: 1.3–3.0 Ma; Supporting information). This species is also known from Mauritius, Comoros and Seychelles (Krishna et al 2013), potentially indicating additional over‐water dispersals among islands of the Madagascan realm for this genus with high dispersal abilities and tolerance to salinity (Emerson 1955, Chiu et al 2021). Two other species, C. truncatus and Microcerotermes subtilis , as well as the nasutitermitine genus Kaudernitermes , are also known from Madagascar and several neighbouring islands (Krishna et al 2013), indicating further dispersals between islands.…”