Hitchhiking across the North Atlantic e Insect immigrants, origins, introductions and extinctions Eva Panagiotakopulu School of GeoSciences, University of Edinburgh, Drummond Street, Edinburgh EH8 9XP, UK article info Article history: Available online xxx abstract This paper discusses North Atlantic insect biota and their origins in relation to climate change in the North Atlantic. The debate concerning biotic survival in refugia or immigration to a clean slate is argued from a fossil insect point of view. The hypothesis for the survival of the fauna during the last Ice Age is challenged by the lack of endemics on the North Atlantic islands and the bulk of the fossil data point towards immigration onto a tabula rasa. The mechanisms involved, coupled with the climate dynamics of the North Atlantic region and the climatic tolerances of pre-human impact Coleoptera assemblages, from the Faroe Islands, Iceland and Greenland point to early Holocene introductions via ice rafting perhaps from Scandinavia, as the initial “en bloc” event of dispersal. Post human settlement introductions are dominated by synanthropic species and a range of local extinctions, which could be a direct result of human impact, exacerbated in the post medieval period by the Little Ice Age. Ó 2014 Elsevier Ltd and INQUA. All rights reserved. 1. Introduction The contemporary insect fauna of the North Atlantic islands mirrors the processes which determined the dispersal of biota onto the islands. Russell Coope in his 1986 overview of the problem highlighted the use of the palaeoentomological record for under- standing the biogeography of the North Atlantic. Buckland et al. (1986) discussed early Holocene immigration to Iceland in the light of the fossil record and suggested that it was a rapid event which took place around 10,000 (radiocarbon) years ago with the warming following the end of the Younger Dryas, 12,800 to 11,700 cal BP (Walker et al., 2009). Their views contradicted the- ories brought forward by botanists who vouched for survival of plants in refugia, in ice free areas on the islands (Steindórsson, 1963). Nunataks have been thought to be critical in this argu- ment, with conditions which could allow a few remnants of the biota to continue from interglacials through glacials (Gjærevoll, 1963, but for an alternative view see Birks, 1993, 1996). Work on fossil faunas from the North Atlantic islands, coupled with better understanding of processes linked with climate change, for example, ocean thermohaline circulation, carbon and water cycles, and rates of deglaciation, have provided new data, and application of DNA studies to botanical material have added new perspectives to the ongoing debate about the origins of both flora and fauna. This debate about the origins and subsequent introductions of the faunas still goes on after over a century and remaining uncertainties serve to fire up further debates. The aim of this paper is to provide an overview of North Atlantic biota introductions, to discuss mechanisms of dispersal of the in- sect faunas to the North Atlantic islands from a fossil insect point of view, and by using already collected data from a range of sites to look into the history of introductions and the role of climate change and human impact in shaping the modern fauna of the islands. The North Atlantic islands discussed here are the Faroe Islands, Iceland, and Greenland, and the fossil record is that of Coleoptera and Diptera, excluding chironomids. The latter are essentially distrib- uted in the aerial plankton with many other weakly flying species, and are as a result largely Holarctic (cf. Gislén, 1948). 2. Tabula rasa and survival in refugia The origins of biota on the North Atlantic Islands have been discussed in terms of two opposing theories: introductions onto a clean slate, tabula rasa, a theory with origins in the 19th century, and survival in ice free areas, proposed by botanists such as Blytt (1882) in Norway and developed by Ostenfeld (1926) for Greenland, and by the entomologist Carl Lindroth (1931) in Iceland. Refugia in ice free areas provided a much needed explanation for the uniqueness of high alpine faunas in Scandinavia and the hy- pothesis was embraced particularly by botanists in Iceland (e.g. Óskarsson, 1961; Steindórsson, 1963) and more recently by paly- nologists (Caseldine et al., 2004). E-mail address: eva.p@ed.ac.uk. Contents lists available at ScienceDirect Quaternary International journal homepage: www.elsevier.com/locate/quaint 1040-6182/$ e see front matter Ó 2014 Elsevier Ltd and INQUA. All rights reserved. http://dx.doi.org/10.1016/j.quaint.2014.01.005 Quaternary International xxx (2014) 1e10 Please cite this article in press as: Panagiotakopulu, E., Hitchhiking across the North Atlantic e Insect immigrants, origins, introductions and extinctions, Quaternary International (2014), http://dx.doi.org/10.1016/j.quaint.2014.01.005