Tremough biologist charts rise of male butterflies
A biologist on the Tremough Campus in Penryn has helped to
discover a remarkable example of natural selection in a tropical
butterfly. Along with scientists from London, Toronto and
California, Dr Nina Wedell of the University of Exeter's
Tremough Campus has tracked the amazingly rapid recovery of
male butterflies in the species Hypolimnas bolina, commonly
known as the 'blue moon' butterfly.
The blue moon butterfly, which lives on the South Pacific
island of Savaii, has been affected by the Wolbachia bacteria,
which is passed down from the mother and kills males before
they have a chance to hatch. Males had been reduced to just
one percent of the population of the species, but this has
risen to 39 percent in less than ten years and within just
ten generations. The researchers credited this increase to
the rise of a suppressor gene that holds bacteria in check.
"To my knowledge, this is the fastest evolutionary
change that has ever been observed in the wild,"
said Dr Nina Wedell of the University of Exeter's Tremough
Campus. "This study shows that when a population
experiences very intense selective pressures, such as an extremely
skewed sex ratio, evolution can happen very fast."
It is not yet clear whether the suppressor gene emerged from
a chance mutation from within the local population, or if
it was introduced by migratory Southeast Asian butterflies
in which the mutation had already been established. Bacteria
that selectively kill male offspring are found among a range
of arthropods, so what was seen in this study may not be unusual,
despite the fact that it has never before been observed.
"In essence, organisms must evolve to stay in the
same place, whether it's a predator-prey relationship,
or a parasite-host interaction," said Dr Wedell.
"In the case of H. bolina, we're witnessing an
evolutionary arms race between the parasite and the host.
This strengthens the view that parasites can be major drivers
The researchers tested for the continued presence of Wolbachia
in the butterflies. By mating infected females with males
from a different island that did not have the suppressor gene,
they also confirmed that the bacteria were still effective
at killing male embryos. The male-killing ability of the bacteria
emerged again after three generations. Thus, they could rule
out a change in the bacteria as an explanation for the resurgence
of the males in the butterfly populations studied.
This study has been published in leading journal Science.
The US National Science Foundation, the UK Natural Environment
Research Council and the Natural Sciences and Engineering
Research Council of Canada helped support this research.
The £100 million Tremough campus is a Combined Universities
in Cornwall initiative of which the University of Exeter and
University College Falmouth are two of the founding partners.
It is funded mainly by the European Union (Objective One),
the South West Regional Development Agency, and the Higher
Education Funding Council for England, with support from Cornwall
County Council. Set in 70 acres of countryside, but close
to the waterside towns of Penryn and Falmouth, the campus
offers a lively student community. The University of Exeter
now offers degrees in Biology, Cornish Studies, English, Geology,
Geography, History, Law, Mining Engineering, Politics and
Renewable Energy on its Tremough Campus, which has expanded
rapidly as part of the Combined Universities in Cornwall initiative.
For further information contact Sarah Hoyle, Press Officer,
University of Exeter on 01392 262062/07989 446920 or email
The Objective One Programme for Cornwall and the
Isles of Scilly has invested in the Combined Universities
in Cornwall (CUC) project, both Phase 1 and Phase 2, through
the European Regional Development Fund (ERDF) and the European
Social Fund (ESF). University of Exeter is a partner of the
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