A deadly war at the genetic level

Butterflies and parasitoids, their arch enemies, co-evolve in the battle for survival.

Butterflies and parasitoids, their arch enemies, co-evolve in the battle for survival.  

Butterflies and parasitoids, their arch enemies, co-evolve in the battle for survival

: There is something magical about butterflies in different colours flitting around from one flower to another. India is home to 1,800 species and subspecies that are increasingly being valued for aesthetic reasons. But what we overlook is that these beautiful creatures are flagship species for biodiversity conservation and indicators of a healthy ecosystem. For generations, butterflies have been waging a deadly and long-drawn-out war with their natural enemy, parasitoids, insects, who in their egg and larval stage, live in the tissue of a host and feed on it. Death of the host, in this case the butterfly, is the only eventuality.

Scientists have found that this war is waged even at the genetic level. Entomologists at Bengaluru’s ICAR-National Bureau of Agricultural Insect Resources (NBAIR) have, for the first time, been able to systematically document how these parasitoids pose a serious threat to the butterfly endangered species through its different life stages.

Dr. Ankita Gupta, an NBAIR scientist told The Hindu that evolutionary studies have found that these parasitoids and the butterflies co-evolve in the battle for survival, wherein both try to change at the gene level, besides changing the food host plant preference. “We are now trying to document ‘host shifts’ and ‘host expansion’ in relation to the co-evolution of butterflies and their associated parasitoids. This is important to understand evolutionary science, biodiversity and speciation,” she said.

NBAIR has discovered a new species of wasps parasitic on butterflies in Goa, Maharashtra, Kerala and Karnataka. A majority of these parasitoids are just 2mm in size, sometimes even smaller. They are usually specific to one particular species of butterfly. These parasitoids sometimes lay their eggs within the butterfly eggs, or even in the caterpillar or pupa itself. “The eggs get parasitised, preventing the butterfly to move on to the next stage in its life cycle,” Dr. Gupta explained.

There are many factors that are detrimental to the conservation of butterflies, such as pesticide drifts, industrial pollution, deforestation, encroachment of natural habitat, lack of appropriate flora and even illegal butterfly trade. But what is ignored is the role of the natural enemies of butterflies, the parasitoids

Abraham Verghese, Director of NBAIR, said that such a study was the missing link in understanding the co-evolution of butterflies and their associated parasitoids in India. “There is still much to be gained from close attention to natural history, meticulous time-intensive rearing and taxonomic investigations. This is essential to maintain the natural balance between butterflies and parasitoids and will go a long way in diversity documentation,” he added.

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