New Study Sheds Light on Spread of Sexually Transmitted Disease in Ladybirds

The impact of the spread of sexually transmitted infection in a wider population of ladybirds cannot be predicted without sampling the infection at small spatial scales, according to a new study.

A team of researchers from the University of Liverpool, U.K., studied a virulent form of infection in the central and northern European populations of the two-spot ladybird, in order to figure out the conditions that favor the spread of the disease.

They found that there were significant differences in disease epidemics in two locations of the same habitat - the lime tree - despite the places being located close to each other. It is expected that disease epidemics will vary over space, but surprisingly researchers noticed that the variation in the disease impact occurred at a very local level.

The differences between disease outbreak sites were caused by differences in mating rates across habitats, said the researchers. The study showed that a healthy supply of food increased the mating frequency of the ladybirds. This caused a rise in the spread of disease to other ladybirds. However, ladybirds with less food supply mated less frequently and did not experience high rate of infection.

"This means that the infection, which causes sterility in females, will reduce ladybird reproduction in habitats with good food supply, the very places that should be important drivers of population growth. It highlights the significance of looking very carefully at local differences in the spread of infection before predicting disease impact," professor Greg Hurst, from the University of Liverpool, said in a statement.

Information about food supply and mating habits of the local ladybird population is needed to understand the impact of the sexually transmitted infection in the wider population, Hurst said

The findings of the study are published in the journal Behavioural Ecology.