The harsh climate of the glacials was not an obstacle for butterflies

Fig: Agriades optilete; Alaska, Bonanza Creek, Fairbanks (A) and Boloria chariclea; Alaska, Bonanza Creek, Fairbanks (B)

To understand the evolutionary history of widely distributed species, it is desirable to sample their entire distribution ranges. So far, majority of the studies on Holarctic species were restricted to their European or North American range parts. They neglected the fact that the vast areas of Asia must have played very important role in the species’ evolution. The Pleistocene Northern and central Asia was inhabited by large populations of mammalian herbivores, maintaining the mosaic of highly productive grasslands and open forests through the glacial cycles.

Researchers from the Institute of Entomology (J. Marešová, A. Sucháčková, M. Konvička and Z. Faltýnek Fric) and their colleagues explored the biogeographic patterns of four butterflies sampled through the Holarctic region – Boloria chariclea inhabiting tundra, Agriades optilete preferring bogs and humid meadows, temperate grassland species Carterocephalus palaemon and taiga species Oeneis jutta. The study published in Journal of Biogeography combines genetic data and species distribution modelling. The results showed that out of the four species, only B. chariclea originated in the North America and recently spread to Eurasia. This species colonized Greenland several times and probably also survived the glacial periods on the island’s eastern coast. The open habitat species A. optilete and C. palaemon formed widely distributed east-west genetic clusters in continental Asia and clusters separated from them in Europe. On the other hand, the Eurasian populations of taiga species O. jutta were probably fragmented during the Pleistocene, and recently connected again. After deglaciation, North America was recolonized from Beringian and southern refugia by all four species.

The Pleistocene mammoth steppe allowed a widespread continuous distribution of open habitat butterflies, while in contrast the distribution of a taiga-specialist species had to be more limited. In the mostly flat continental Asia, the butterflies of various types of open habitats lived through the ice ages in widely distributed east-west belts. In the mountainous and oceanic regions of Europe, Beringia and west North America, all four species persisted in contracted areas during the glacials. After deglaciation, they expanded their ranges and formed contact zones among populations.

Marešová J., Sucháčková Bartoňová A., Konvička M., Hoye T.T., Gilg O., Kresse J.-C., Shapoval N.A., Yakovlev R.V., Faltýnek Fric Z. (2020) The story of endurance: Biogeography and the evolutionary history of four Holarctic butterflies with different habitat requirements. Journal of Biogeography. Published online: 27 November 2020. DOI: 10.1111/jbi.14022