Invasive harlequin ladybirds reproduce early in life and their reproduction is spread over a longer lifespan than their native counterparts, reports a study published this week in Nature Communications. This strategy may help explain how they have become one of the most successful invasive species worldwide.
Life history is the sequence of important events in an organism's lifetime, such as the onset of reproduction and lifespan, and it can be shaped by natural selection, sexual selection or both. Understanding how life history changes in response to a new environment is central in understanding the success of an invasive species. Invasive species have long been thought to exhibit a fast end of the life history spectrum, with early reproduction and short life. The harlequin ladybird has to-date invaded a wide range of climatic and ecological conditions and is an ideal subject to study life history changes in response to invasion.
Benoit Facon and colleagues compare adult life histories of different harlequin ladybird populations (native, biocontrol and invasive) in a common environment to determine how life history evolves during invasions. While biocontrol populations (populations reared in a predator-free environment and fed freely for 100 generations) show shorter lifespan and reduced reproductive lifespan, invaders invest more resources in reproduction and their reproduction is spread over a longer lifespan. This strategy might be an adaptation to variable environments because reproduction can be attempted over more years. This study shows that life history can evolve rapidly, and that the changes in life history over the course of an invasion are modulated by the conditions experienced by the invader in the new environment.