The Afrotropical breeding grounds of the Palearctic-African migratory painted lady butterflies (Vanessa cardui)

Abstract

Migratory insects are key players in ecosystem functioning and services, but their spatiotemporal distributions are typically poorly known. Ecological niche modeling (ENM) may be used to predict species seasonal distributions, but the resulting hypotheses should eventually be validated by field data. The painted lady butterfly ( Vanessa cardui ) performs multigenerational migrations between Europe and Africa and has become a model species for insect movement ecology. While the annual migration cycle of this species is well understood for Europe and northernmost Africa, it is still unknown where most individuals spend the winter. Through ENM, we previously predicted suitable breeding grounds in the subhumid regions near the tropics between November and February. In this work, we assess the suitability of these predictions through i) extensive field surveys and ii) two-year monitoring in six countries: a large-scale monitoring scheme to study butterfly migration in Africa. We document new breeding locations, year-round phenological information, and hostplant use. Field observations were nearly always predicted with high probability by the previous ENM, and monitoring demonstrated the influence of the precipitation seasonality regime on migratory phenology. Using the updated dataset, we built a refined ENM for the Palearctic-African range of V. cardui . We confirm the relevance of the Afrotropical region and document the missing natural history pieces of the longest migratory cycle described in butterflies.

Isotope geolocation and population genomics inVanessa cardui:Short- and long-distance migrants are genetically undifferentiated

“…In contrast, V. cardui individuals captured in the circum-Mediterranean region in the same season had either undertaken shorter migrations or had isotopic signatures compatible with their capture area (Fig 1). Despite the increasing evidence that V. cardui was involved in regular trans-Saharan crossings as part of its annual migratory cycle, this evidence was limited to the monitoring of migratory arrivals in the sub-Sahara (9,10) and δ²H-based geolocation (8,36). We have expanded this isotope-based evidence with the addition of 87 Sr/ 86 Sr, narrowing down the potential geographical sources of these long-distance migrants and confirming that distinctive migration strategies are displayed by V. cardui found north and south of the Sahara during the autumn months.…”

“…As part of a migratory cycle covering between 8 and 10 generations and involving both the Palearctic and Afrotropical regions, late summer and autumn generations migrate southward from temperate Europe towards more suitable breeding grounds. While a substantial portion of these southward migrating butterflies journey across the Mediterranean Sea and Sahara to subsequently breed in sub-Saharan Africa (8)(9)(10), others migrate to the circum-Mediterranean region (11,12). The factors driving these differences in migratory behaviour, resulting in the disjunct winter distribution of V. cardui across the Sahara, remains unknown.…”

Struggling to survive: A comparison of Vanessa cardui larval survivorship on putative host plants

“…As previously described, we assessed pupation success and survival of each larva. C. vulgare was selected for these tests because it is a key host plant in the sub‐Saharan range of the Palearctic‐African V. cardui migration (Stefanescu et al, 2017; Talavera et al, 2023). Additionally, C. vulgare is commonly found in California sage scrub despite being non‐native.…”

A hydrogen isoscape for tracing the migration of herbivorous lepidopterans across the Afro‐Palearctic range

“…1 Unlike bird or mammal species, insect species breed across multiple generations at different places and times throughout the year. [3][4][5] When studying insect population connectivity across the Afro-tropical Palearctic range, insect population ecologists need to investigate the sequential and back-and-forth connectivity between tropical and subtropical, subtropical and temperate, and temperate and boreal regions, instead of focusing solely on the direct connectivity between tropical and boreal realms as observed in bird studies. 6 Despite insects being the most diverse and abundant group of animals on earth, the spatiotemporal connectivity of most migratory and highly dispersive species is poorly understood.…”

“…Among insects, many species of dragonflies, locusts, flies, moths and butterflies are known to actively migrate 1 . Unlike bird or mammal species, insect species breed across multiple generations at different places and times throughout the year 3–5 . When studying insect population connectivity across the Afro‐tropical Palearctic range, insect population ecologists need to investigate the sequential and back‐and‐forth connectivity between tropical and subtropical, subtropical and temperate, and temperate and boreal regions, instead of focusing solely on the direct connectivity between tropical and boreal realms as observed in bird studies 6 .…”