Plant Migration: Wings, Hairs and Humans
Seed and the Ocean
Unlike animal fossils of ancient times, plant fossils are more readily available in the very many archaeological layers of earth for the perusal of scientists. Hence Palaeobotany has evolved as a significant field. Still there are many complex factors in action when one considers the history of plant migration. For example, consider a seed falling into the ocean. It will have a destiny decided by the ocean currents, its edibility to sea creatures, the hardness of its outer shell that enables it to float for many days without rotting, and the like. It is an intricate game of nature driven by the food chain and some degrees of chance.
In Search of Carriers
Trees have their own natural mechanisms for seed dispersal and migration and these are mainly, seeds having wings, having hairs, delicious and plump fruits to attract carrier animals, seeds having a shape and texture to be able to roll on ground, having tasty nuts and sometimes the ability of the seedpods to explode! Mistletoes and sandbox trees have such exploding fruits. There are many insects and small animals that bury their fruit harvest and often forget about it. Obviously, another trick of nature to preserve the nuts and let them germinate when the time comes.
Guests are Not Welcome
Do you know it is difficult for a newcomer plant to get acceptance in a forest ecosystem? This is not because forest plants and trees are conservative or narrow minded. The reason is that there are many perennial trees in a forest which have well-developed root systems. All the roots of all the trees work as a single net covering the top soil that prevents new saplings from taking root. Grass lands which have extensive root networks though much minuscule in scale, also resist new entries.
Over the Mountains, Above the Seas
The ferns migrate at the scale of a Siberian Crane or an Arctic Turn. Its spores travel thousands of kilometers, borne by air. The qualities that allow this magnitude of migration are more than one- the infinitesimal size of the spores, their ability to germinate many months after they are produced by the mother fern. Each spore after sprouting can grow into a bisexual fern and hence reproduction on a new land is not a problem at all.
Story of the Ocean as Told by Sea Lettuce
Sea lettuce grows on sea shores and their seeds get carried away by the ocean. Then, up to period of one year, the seeds may float in the sea. What things those seeds could tell about the life in the sea if only they have a voice! Imagine, the chronicles of sea lettuce inhabited by whales and pirate ships, ephemeral sunsets and the limitless sky! After experiencing all these, the seeds settle on a shore and still retain their germination potential. On a new land, they anchor their tiny roots. Coconuts and mangrove seeds also make such amazing sea voyages seeking a chance to sustain the species.
Colonize and Capture
There is a profound connection between migratory birds and seeding plants. The birds eat the fruits of the plants and then fly to far off lands. The seeds thus carried to new lands in their stomachs usually have hard outer shells, the feature that helps them be safe from getting digested.
There is a big category of colonizing species to explore, when we discuss plant migration. These are the plant species that have adaptability to different geographies, climates and long gestation periods. An example could be Pond Apple, which is a small tree that is capable of invading a rain forest and turning it into just a species thin patch of vegetation.
A premeditated Chaos?
Plant migration through agriculture is another sub topic of this discourse. Take the case of Barley. The earliest reported cultivation of Barley is from the region of the Middle East that is called the fertile crescent. That was 10000 years back in history. Gradually Barley migrated to South Asia, indeed with the help of the farmers of those times. One very popular Barley variety was found by scientists to have travelled from South Asia to Europe via human sea routes.
Nature has made many plants in such a way that they are pre-adapted to make use of human migration and other human activities for their dispersal over the planet. So, what do you think? Had nature planned the kind and scale of ecological disturbances and habitat destruction that were to accompany the evolution of Homo Sapiens on earth? I leave it an open question.
Encyclopaedia Britannica: Falling Far from the Tree: 7 Brilliant Ways Seeds and Fruits are Dispersed.
Invasive Plant Species of the World, 2nd Edition: A Reference Guide to Environmental Weeds by Ewald Weber.
On the Origin and Domestication History of Barley (Hordeum vulgare) by A. Badret al., Molecular Biology and Evolution, Oxford Academic.
Plant Migration: The Dynamics of Geographic Patterning in Seed Plant Species by Jonathan D. Sauer.
Plant Migration Studies by Charles E. Bessy.
© 2018 Deepa