Gone

Volovnik, Semyon V., 2025, Phytochory - the dispersal of animals by terrestrial and aquatic plants, Journal of Natural History 59 (21 - 24), pp. 1469-1539 : 1478-1480

Gone with the wind

Sometimes, plants are moved across land by air currents. Some small invertebrates are associated with them and are transferred in this way also.

In 1981–1990, I studied the habitats of weevils in Southern Ukraine. On the shores of the Sea of Azov, dry stems of the sea-kale Crambe spp. were carried away by wind to a distance of some 1.5 km from the sea coast where they had vegetated. Inside these stems, I found live adults (or, less frequently, pupae) of the weevil Lixus canescens ( Figure 3 ). Notably, its larvae build their pupal chamber in the root crown or near it. Presumably, this facilitates the detachment of stems by gusts of wind. It cannot be excluded that other inhabitants of the aboveground part of Crambe spp. ( Korneyev et al. 2015) are also sometimes dispersed inside the plant by air currents.

In general, the tumbleweed strategy is based on some specific properties of the plants that use it. The above-ground parts of Crambe and some other plants contain high concentrations of phytotoxins. They are accumulated in the ground under the plants and inhibit the germination of all seeds, including those of the plants themselves. The toxins retain their activity for a long period ( Grodzinskii 2016). In other cases, the accumulation of the dead organic matter inhibits the natural regeneration of plants mechanically, and ‘self-cleaning’ of the parent plot of land is required ( Alyokhin 1986). In any case, displacement is a necessity for the ripe seeds of a new crop. However, this may also be beneficial for the insects transported in the stems. The tumbleweed moves the insects away from the place where seeds of their host plants cannot germinate. This may give rise to a new plant population and increase the survival chances of new insect generations. Dispersal by tumbleweed is common for some endobionts ( Table 4).

In deserts, some small and fragile gall gnats ( Diptera ) are dispersed by winds inside dry fruits of host plants, where they are possibly safe from extreme heat ( Beknazarova 1989). Both air currents and gravity are active dispersal vectors for the invertebrates living in the pods and ripe samaras of maples ( Figure 4 ).

Figures

Figure 3. Dispersal of the weevil due its host plant and wind as active vector: (1) Sea-kale, Crambe pontica; (2) Fragment of sea-kale transported by wind with inhabitants inside; (3) Newly emerged adult weevil Lixus canescens; (4) Exit opening of emerged adult; (5) Adults in the topsoil where they overwinter. Note that there are other endobionts of the stems and fruits of Crambe (Zerova 1978, 1981; Volovnik 1994; Korneyev et al. 2015). So, they can also be dispersed inside the plant by air currents.

Figure 4. Dry ripe pods of honey locust Gleditsia triacanthos are long, broad and flat. Because of this, strong winds break them off the branches and can carry them up to 50 m from the parent tree. This becomes the first air journey for seed beetles Megabruchidius dorsalis developing inside the pods, and, possibly, for their parasitoids (Zerova and Fursov 2015) also. The pictures were taken in spring, after overwintering of some individuals within seeds: (1) larva, (2) pods with exit openings of the overwintered adults. Personal observation and photo by S.V. Volovnik.