Lack of population structure between trans-Saharan migrants for the butterfly Vanessa cardui revealed by hydrogen and strontium isotope-based geographic assignment and genomics

Tuesday, November 15, 2022

2:20 PM – 2:40 PM PT

Location: Vancouver Convention Centre, Meeting Room 221/222

Presenting Author(s)

Megan Reich

PhD candidate
University of Ottawa
Ottawa, Ontario, Canada

Co-author(s)

DS

Daria Shipilina

Uppsala University
Uppsala, Uppsala Lan, Sweden
VT

Venkat Talla

Uppsala University
Uppsala, Uppsala Lan, Sweden
FB

Farid Bahleman

SOS Savane
Tanguieta, Benin
GT

Gerard Talavera

Institut Botanic de Barcelona
Barcelona, Spain
CB

Clement P. Bataille

Associate Professor
University of Ottawa
Ottawa, Ontario, Canada
NB

Niclas Backström

Uppsala University
Uppsala, Uppsala Lan, Sweden
KK

Khadim Khebe

Cheikh Anta Diop University
Dakar, Senegal

The painted lady butterfly (Vanessa cardui (L.)) is a virtually cosmopolitan species famous for its annual multi-generational migration cycle between the Palearctic and Afrotropical regions. However, the autumnal, southward migration from Europe results in a disjunct population distribution in the winter, with breeding observed on both sides of the Sahara Desert. Here, we investigated the genetic basis of this winter population disjunction by combining isotope geolocation and population genomics. We hypothesized that winter population distributions result from the genetic differentiation between sub-populations with distinct migration strategies (i.e., long-distance migrants in tropical Africa and short-distance migrants in the Maghreb and southern Europe). We first analyzed strontium and hydrogen isotopes in wings and performed isotope-based geographic assignments of 40 specimens collected between September and November from both north (i.e., Portugal, Spain, Malta, Morocco) and south (i.e., Benin, Senegal) of the Sahara. Most painted ladies collected from tropical Africa likely migrated long distances from north of the Sahara Desert, whereas individuals collected north of the Sahara likely migrated shorter distances from Europe. We then performed a genome scan of these individuals with distinct migratory distances. The genomic analysis showed no evidence of population structure or genetic differentiation, suggesting widespread gene flow across the Sahara. Together, these results support the view of a panmictic population of painted lady butterflies with reticular connectivity networks regularly migrating across the Sahara. Future studies should explore the role of regulatory genomics on the observed variations in migratory destination and distance.