Community Research and Development Information Service - CORDIS

Periodic Report Summary 1 - MIGRATION (The most cosmopolitan animal migration: phylogeography and population genomics of the butterfly Vanessa cardui)

Animal migration is an evolutionary response to heterogeneity in both space and time, since it functions as a strategy for exploiting temporary resources associated with non-permanent habitats. Insects of several taxonomic groups are well-known migrators, and have relevant consequences for the global economy, with examples including the pollination of agricultural systems, the association with pest outbreaks and the spread of infectious diseases. A special feature of insect migration is the involvement of several generations during roundtrip routes. However, insect migration is still poorly understood, partly because of the difficulty of globally tracking continuous migratory movements. The MIGRATION project aims to bring together genomic-based phylogeography and ecology to understand the population dynamics of the most cosmopolitan of the insects that performs long-range migrations, the painted lady butterfly Vanessa cardui.

MIGRATION started on 1st of February 2015, through collaboration between the Institute of Evolutionary Biology (CSIC-UPF) in Barcelona, Spain (IBE) and Harvard University, USA. The primary goal of the project was to unravel what are the zones where the main migratory pools occur along the planet, and how these temporary interact with the changing environment. During the first 24 months, through intensive field work and support from numerous colleagues, the scientists have first gathered the most comprehensive dataset of specimens ever assembled for V. cardui, with ~2500 samples involving ~60 countries worldwide. This dataset likely represents the largest population study ever assembled for natural populations of a widely distributed species, excluding humans.

Next, the researchers have conducted exhaustive molecular work to assess the genetic connectivity of the different populations collected over the world. To do that, ddRAD libraries for ~1200 specimens from ~60 countries have been sequenced at 2x125 bp in Illumina, constituting a unique reference dataset in population genomics both for its size and diversity. Also, ~200 specimens of closely related Vanessa species with variate distributional ranges and biology have been sequenced for population structure comparisons. On a following phase, genomic-based phylogeographic approaches are being performed to deeply understand how genetic diversity is maintained in a highly mobile species, and how this is shaped geographically.

The population genomics data is complemented by the ecological study, including natural history data, ecological niche modelling, stable isotope ecology and behavioural tests. In this regard, the work conducted by the researchers has led to the discovery that European autumn migrants travel into Africa massively crossing the Sahara Desert and breed in the African savannah (Talavera & Vila 2016; Stefanescu, Soto, Talavera, Vila & Hobson 2016). These migrations entail distances of >4000 km in single flights and a migration range twice the size than was previously held. Such a scenario elucidates a new spatiotemporal model where the species’ latitudinal migratory range encompasses the temperate region (with seasonality determined by temperature) from March to September and the tropical region (with seasonality determined by rainfall) from September to March. This model broadly coincides with the Palaearctic-African bird migration system, where approximately 350 species and c. 3000 million birds annually migrate between tropical Africa and Europe. This situation suggests potential evolutionary convergence between birds and insects in adopting synchronic migratory routes to exploit the same temporary resources and climatic conditions in tropical Africa, or possibly for the insectivore birds to feed on the migrating insects. Patterns equivalent to those between Africa and Europe are being investigated in North America and Asia.

Through the worldwide RAD libraries assembled, MIGRATION will provide a high resolution map of genetic diversity for an insect with a huge distributional range and large population sizes. This dataset represents a very valuable resource and has numerous applications, ranging from the study of insect demography in pest control, the evolutionary understanding of the transitioning between migratory and non-migratory states, to the identification of preferential hotspots for migrants concentrating highest genetic diversity values.

The MIGRATION project has been disseminated in conferences, seminars and public outreach, and has been highlighted by renowned publishers as National Geographic, BBC Earth, ScienceNews and The Guardian. A divulgation video showing the research and the main findings done so far have been created and made public through different channels (e.g. https://www.youtube.com/watch?v=4E9Wb35_t6I). The project website can be visited at: http://carduimigration.weebly.com.

Reported by

AGENCIA ESTATAL CONSEJO SUPERIOR DE INVESTIGACIONES CIENTIFICAS
Spain

Subjects

Life Sciences
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