Mossive Disjunctions are from the Birds

Though we may not think about it, plants have migratory capacity. Their migrations are not like those of a wildebeest or neotropical warblers. Instead of moving as individuals, plants migrate via seeds, spores, or pieces of the parent plant that can then grow into a new, albeit genetically identical individual. Either way, long distance dispersal events have long puzzled ecologists. It has been demonstrated time and again that even modest barriers can inhibit propagule movement. Still, it would seem that over the course of time, plants have managed to overcome such boundaries. One way or another, plants have made some impressive migrations.

Some species have really managed to confuse ecologists. Certain mosses and lichens have very curious distributions. There are species that are found only in the Arctic and the very southern tip of South America. Nowhere in between. Why is this? There have been hypotheses regarding wind currents but the genera to which these plants belong originated in the Miocene and Pleistocene, while the Intertropical Convergence Zone (a major barrier between northern and southern wind currents) was already in place.

Recently, researchers have looked towards long-distance fliers like plovers to explain these distributions. These birds breed in the Arctic and overwinter in South America. Could these be the vessels by which these plants migrate? It has long been known that seeds passing through the gut of a bird often have high germination rates. Many plant species gear their fruit specifically for this reason. Birds travel great distances in their search for food and breeding territory, much greater than the average plant can. But birds aren't necessarily eating mosses and lichens. However, they do use them in their nests. Spores and bits of vegetative material can then get stuck in their feathers. After breeding, the birds migrate to South America and begin their molt. The feathers containing spores and plant material are now shed into the wild where they can germinate and grow.

Considering the size of these migrations, it is likely that these migratory shore birds, and possibly many other species of migratory birds, play a significant role in the dispersal of these plant species.

Photo Credit: barloventomagico (http://bit.ly/1p1X2WC)

Further Reading:
https://peerj.com/articles/424/