Tracking provenance of Painted Ladies from Kenya in winter and in summer using hydrogen isotopes
Sana Ghouri, Clément Bataille
Department of Earth and Environmental Sciences, University of Ottawa
Sana Ghouri, Clément Bataille
Department of Earth and Environmental Sciences, University of Ottawa
The painted lady butterfly (Vanessa cardui) is the most widely distributed lepidopteran worldwide that does the longest multigenerational migration in the insect world. This research goal is to increase knowledge about migration and spatial temporal origins of individuals across Africa. In this research, we collected painted lady individuals across winter (N=23) and summer (N=18) in tropical Africa (i.e. Kenya) because painted ladies have two distinct annual abundance peaks during these seasons in Kenya. However, the actual origin of individuals in these two abundance peaks remains largely unknown. Are these two population peaks from a single population or from two distinct populations? I assessed the origin of each individual collected within each season over three years (Summer = May to July and Winter= November to February) by analyzing stable hydrogen isotopes values in their wings. I then used isotope values, monthly specie distribution models and isoscapes (i.e. spatial predictions of isotope variation) to calculate the probability of geographic origin of each individual over Europe and Africa. Geographic assignments show that most of the individuals from the winter abundance peak are highly compatible with a circum-Mediterranean origin and incompatible with local origins in Kenya. These results suggest the winter individuals are migrating from Southern Europe to Tropical Africa to escape cold climate and limited resources in Europe. In contrast, painted ladies collected in the early summer show a much broader range of hydrogen isotope values suggesting a variety of origins. Within this summer group, we identified 3 clusters, one of likely local individuals (N=3), one of individual potentially migrating from southern African regions (N=7) and the last migrating possibly from western Africa or Sahel (N=8). Long-distance migrants from Africa probably escape limited resources during the dry season in their region of origins. We conclude that these two populations are likely separated by space and time (allopatric) and provide interesting examples to investigate the controls of migrations in insect species, in particular how distinct environmental stimuli (i.e. dry vs. cold) control the migratory behaviour.