Scientists have found something unusual to a butterfly from Nairobi, Kenya where two subspecies of African Queen butterflies are thriving but mostly females.
There is a microbe common in African Queen butterflies known as Spiroplasma, which seems to be the primary cause why these females are killing males even before they hatch. But no other subspecies infected with this microbe have ever displayed this type of behavior.
A team of researchers conducted a study to understand better this process, and they came to the conclusion that this behavior change originates from a chromosomal anomaly which usually occurs in Nairobi butterflies.
The sex of humans is determined by an X and Y chromosome, but the sex of butterflies is established by a ZW system. ZW is for females, whereas ZZ is for males. But all problems begin when a non-sex chromosome fuses with the W and forms the so-called „neo-W,” a chromosome which determines the African Queen butterflies killing males before they hatch.
According to David Smith, lead author of the research formerly from the Natural History Museum at Eton College, the neo-W is the leading cause why the African Queen populations in Nairobi consist mostly of females.
In other words, Spiroplasma causes the chromosome genetic mutation, and this mutation affects butterflies’ behavior making them aggressive especially towards males. However, there is still a mystery regarding the fact that Spiroplasma affects only African Queen butterflies from Nairobi and not from other African areas as well.
Scientists explained that the only possibility for these butterflies to mate is when a male arrives in Nairobi during the migration. When this happens females lay eggs but then they kill males before they even hatch. There are two subspecies of African Queen butterfly in Nairobi, but they are unable to mate with each other because the populations are made of females.
According to Richard Ffrech-Constant, co-author from the Centre for Ecology and Conservation at the University of Exeter, researchers have to continue their investigation to understand more about this chromosomal anomaly that increases the risk for the subspecies to die eventually if no males will find their way in Nairobi during the migration.
Hopefully, scientists will find a solution to deal with Spiroplasma or at least to understand why Nairobi butterfly populations suffer this mutation compared to other subspecies.