Scientists discover microscopic living organisms which kill butterflies

Insect scientists from Nairobi-based International Centre for Insect Physiology and Ecology (ICIPE) and their partners from Britain have discovered a male-killing microbe - a microscopic living organism that kills butterflies around Nairobi.

In most parts of Africa this microbe, called Spiroplasma, infects African Queen Butterflies but has no effect on their offspring.

"But in Nairobi, where two sub species of butterfly live and breed, we noted that the microbe infection caused all their son's death," Professor Richard Ffrench-Constant, from the Centre for Ecology and Conservation at the University of Exeter's said in a statement on Tuesday.

The male eggs never hatch and are often consumed by their hungry sisters adding that the chromosomes of the females in which male-killing occurs have changed dramatically with a non sex chromosome fusing with a sex chromosome to form a new chromosome.

"We tend to think of new species coming about due to environmental changes but here it is clearly the microbe that is driving these two sub species apart," Professor Ffrench-Constant observed.

She said that they do not understand the precise molecular mechanisms behind this chromosomal merger, since no males are made in the hybrid zone, and that mating success in the zone is effectively zero, thereby creating a barrier with a new species on either side.

The scientist said that the breakthrough came when female butterflies from the all- female zone were sent to Germany to have their chromosomes examined and were discovered that two of the chromosomes had fused.

"This is like a smoking gun for the way in which species become distinct. It is rare that we can find the molecular basis for how species develop," he said.

This study reveals the work done in the field in which the sex and colour pattern of butterflies around Nairobi has been recorded for over 30 years by scientists.

Ffrench-Constant added that the findings show that the butterfly's susceptibility to the male-killing microbe is driving the separation of the two butterflies into two true species.

"These tiny microbes are therefore having a major effect on sex and death in this fascinating butterfly," he noted.

The butterfly populations around Nairobi are nearly all female, hence demonstrating a complex interplay between sex, colour pattern, male-killing and chromosomes that has set up a genetic 'sink' that keeps two subspecies apart.Dr Jeremy Herren from ICIPE said that the study nicely demonstrates the complexity of interactions between insects and maternally-inherited bacteria that manipulate their reproduction.

"Many researchers believe these bacteria might be useful as a strategy to control insects that transmit diseases and destroy crops and therefore it is very important that we better understand how they affect their hosts," he added.

Kennedy Saitoti, from the National Museums of Kenya (NMK) observed that many scientists are aware of the incredible biology of the North American Monarch Butterfly, but few know that the African Monarch/African Queen is just as fascinating.

He said that scientists will be taking keen interest in the natural biodiversity of Kenya and how it relates globally.

"This study shows how much we can learn from insects and the natural world and from butterflies in particular," he added.

According to Steve Collins of the African Butterfly Research Institute (ABRI) the study shows new ways of thinking about evolutionary processes in animals, and highlights how amazing butterflies are as a model for this type of basic, cutting edge research.

In this study, some of the field data came from students at the University of Nairobi who collected and reared wild butterfly eggs in the 1980's during their coursework in Evolutionary Biology.

Nairobi is home to two of the largest and most important collections of African butterflies housed at the Entomology Section of the NMK and at ABRI. Endit