Adaptations, associations and Co-evolution Loranthus: The Hardy Survivor

 Adaptations, associations and Co-evolution 

Loranthus: The Hardy Survivor

On the first day, during our trail through the scrub forest we were surprised to see many of the scrub vegetation patches occupied by Loranthus sp. (mistletoe), a stem parasite common in these locations. They establish themselves on the host tree through parasitic roots known as haustoria. The haustoria penetrates the host's circulatory system and sucks water and other nutrients from the host plant. This reduces the host’s growth. 

   

Even more interesting was the co-evolution of Loranthus with a group of small-bodied birds called flowerpeckers. The plant and the bird have co-evolved to an extent that only when the bird teases the tip of the flower with its beak will it open up, revealing the pollen laden anthers and path to get to the nectar inside. Apart from pollination the birds also aid in seed dispersal. We learnt of a very interesting mechanism through which the Loranthus ensures her seeds get deposited on to the right spot. The fruits have a sticky mucous coating and once it passes through the digestive system of birds the remaining seed and the mucous sticks to their anus. The irritated birds will fly off and rub their hind portion in different branches of different trees. This way the sticky seeds latch on to new host plants and germinate there. Even though Loranthus is a partial stem parasite, occurrences of them killing host plants are infrequent in natural systems, whereas they can have devastating effects in monoculture plantations. Another member associated with this plant is the Jezebel butterfly who lay their eggs on the loranthus. The caterpillars hatch to feed on the leaves and so keep the Loranthus population control. Thus we learnt the story of a tight co-evolution between a parasite, her host trees, her bird disperser and a member of the insect community all of whom co- exist.

We came across two common flora of the region, Morinda citrifolia, a tree, and Calotropis gigantia. Soon they turned into interesting ecological puzzles. Soubadra told us to look at the whilte flowers of the Morinda and asked us to guess who must pollinate them. When we came up with random guesses she asked us to pay attention to the tube-like neck of the flower and its white colour. The right answer was Moths. Many flowers that are pollinated in the night tend to be white to attract visitors and moths are night time pollinators with proboscis to reach into thin tubular flowers. 

 

Who then pollinated the sturdy looking Calotropis flowers? RG sir gave us the answer. Carpenter bees. These giant bees come and land on the flowers who almost seem to have a flat landing pad for them. When the bees buzz against the flowers, the pollen which is held with tiny sacks latch on to them using small stick pads. We observed these minute wonderful adaptations with the help of RG sir field magnifying glass.