Monday, September 10, 2012

Quid pro quo

It is a bustling, vivacious world out there, is a thought I cannot evade every single time I am out in the wild. One could walk ten steps and observe a hundred different things happening at the same time. At sundown, a huge flock of Bee-eaters chirping, or a lone Pitta calling out mean the same thing - they are prepping to roost and retire for the day. But, that Nightjar clucking aloud at the same moment has just begun its day. A skittish Bulbul perching on a shrub could be very random behavior, but a Mormon picking a particular shrub to settle down on could mean something else. A bunch of Ants going up and down a blade of grass are definitely there for a reason and so is that Calotes hanging around an Ant's nest. For every unrelated event, there are a dozen related behaviors and for every behavior we think we understand, there are a dozen that we don't see or comprehend.

Relationships in the wild are mostly either obligate (where both species completely depend upon each other) or facultative (where they can, but they don't have to live together).

I once came across dozens of little insects, each the size of a mustard, clumped together under a leaf. They had some pretty red ants for company. I was later told that they are sap sucking insects called Aphids or Plant Lice. They are probably one of the most destructive insect pest species. The red ants belonged to the genus Camponotus and are commonly called Carpenter Ants. Aphids pierce leaves and feed on sap. Excess sap concentrates as honeydew, which attracts ants. In a display of Mutualism, the ants provide aphids protection from predators.The next time you see plant lice on a leaf in your garden, look around before you toss the leaf out. You might see the entire life cycle of a species on that very leaf!

Ants and Aphids

Mutualism is a co-operative interaction between two organisms of different species where they biologically interact and derive some positive benefit out of the interaction. However, this is not an obligatory relationship. Both species can function normally without this relationship. 

Watching ants and aphids peacefully co-exist together built enough curiosity in me to observe ants more. And that is how I was introduced to Mealybugs and Treehoppers. Mealybugs are scale insects, considered as pests since they feed on plant juices and can induce leaf drop when they occur in large numbers. They become very serious pests in the presence of some ants, as these ants protect them from predators - again, a display of mutualism.

Ant tending to a Mealybug

Ants and a Mealybug

Treehoppers belong to the family Membracidae, a group of insects related to Cicadas and the Leafhoppers. Some treehoppers have also developed mutualistic relationships with Wasps.

Ant tending to a Treehopper

Unlike mutualism, Parasitic relationships are non-mutual, where one organism benefits at the expense of the other. Mistletoe, strangler figs, leeches, fleas fall into this category.
Insects like fleas are external parasites, they are wingless and have mouthparts adapted for piercing skin of mammals and birds to suck blood. Leeches are also blood suckers, they feed on blood from vertebrate and invertebrate animals. 

Some members of the Mistletoe family are partial parasites. When birds like Flowerpeckers feed on the fruit of this plant, a sticky substance present in the fruits ensures that the seeds get stuck to their body. To get rid of these seeds, the birds rub their body against a tree, thus enabling seed dispersion - the roots penetrate the branch of the tree and the plant is born. The plant has green leaves and can photosynthesize, but absorbs nutrients from the host tree instead. Although the Mistletoe is a partial parasite, it is beneficial to the ecosystem, with a wide variety of species depending on the fruits. The plant is also a larval host for the very pretty butterfly, Common Jezebel.

Mistletoe Flowers

I find Strangler Figs fascinating, I think they add charm to a forest. Mostly found in dense, tropical forests, these plants begin life as epiphytes. Birds and other arboreal animals act as seed dispersers for these Ficus plants and they grow on top of other trees, by germinating in crevices on branches. The seedlings then begin their journey downwards, looking for necessary nutrients and simultaneously grow upwards into the sky, in the quest for sunlight. In the process, the original host tree is enveloped and often dies. As they grow, the fractals these roots and branches assume look eerily beautiful. I have seen the most spectacular specimen of Strangler Figs in Bhadra Tiger Reserve and Jim Corbett National Park.  

Strangler Fig from Bhadra

A Symbiotic relationship, on the other hand, takes place between two species where they completely depend on each other for survival.
Symbiotic relationships can be broadly classified into Ectosymbiosis - where one organism lives on another (mistletoe, lice, cleaner fish) and Endosymbiosis - where one partner lives inside the other (zooxanthelles in corals, lactobacilli in humans)

Lichen, for example, is a composite organism which is formed as a result of a symbiotic relationship between fungi (mycobiont) and a photosynthetic partner, usually green algae (phycobiont). Algae can photosynthesize by virtue of being a plant. Carbohydrates are produced during photosynthesis, which in turn serve as food for the fungi. 


Lichens (rock flower) are some of the oldest living organisms on Earth and can survive in varied climates and altitudes. They grow on any undisturbed surface that receives ample light - leaves, branches, bare rocks, walls and exposed soil surfaces. Many lichens are vulnerable to environmental disturbances and their growth is inhibited in such cases. So, they can be observed to assess air pollution. They are used to prepare dyes, masalas and some medicines too.

Cattle Egrets following a herd of grazing cattle is a common sight in most suburban parks and villages. In forests, we see these Egrets around herds of Elephants, Deer and Gaur. They spend time around these large mammals feeding on insects and other small prey that are disturbed while they graze.
This type of a relationship is called Commensalism. The word originates from the term 'Commensal' which means 'sharing of food'. Here, one organism benefits but the other doesn't - and it is caused no harm either. 

Cattle Egrets with a herd of Elephants

All bonds in the ecosystem are delicate and sensitive, they hang by a thin silken thread. The loss of one species in a relationship can spell disaster for the other species too. They give and take, but just the right amount, to maintain and enrich that critical equilibrium. While we know of and understand some of these connections and inter-dependencies between species around us, there are many that aren't even visible to the naked eye, that are still being studied. Many of these relationships have heavily influenced evolution.

We humans are social in nature and live in a sea of relationships - we are born into many, we build several, we are forced into some, we love being in a few that we care about and hate being in those we become hostages of. We are capable of developing close bonds with anything or anyone we spend a considerable amount of time with. We are constantly wriggling in and out of relationships, pretty much like all other forms of life we share this planet with. However, there is a difference. Humans can never achieve the kind of complexity in relationships that non-human forms of life can.

P.S Thank you, Karthik for helping me put mind and matter in a reasonable order :)