Biogeographical dynamics of the Spanish Marbled White Melanargia ines (Lepidoptera: Satyridae) in the Western Mediterranean: does the Atlanto-Mediterranean refuge exist?

Abstract

Climatic changes can cause severe range shifts of biota over time. During climatically challenging periods, many organisms often persist in suitable refugia. One rather important refuge area of thermophilic species of the Palaearctic region includes the Iberian Peninsula and the Maghreb region, known as the ‘Atlanto-Mediterranean’ refuge. In order to study this postulated refugium, we computed species distribution models to reconstruct the past potential distribution of Melanargia ines (Hoffmannsegg, 1804) during the last glacial maximum. We also sampled individuals from populations of this butterfly species at its distribution margins (Iberia, and western and eastern Maghreb), and performed allozyme electrophoresis to assess the biogeographical patterns. The projected continuity of a conductive climate from Iberia to the eastern Maghreb, and the lack of genetic differentiation across the entire distribution range of M. ines, is in favour of the existence of one Atlanto-Mediterranean refugium for this species. A relatively constant climate over the Atlas Mountains over long periods of time, as predicted by species distribution models and observed genetic diversity patterns displaying an accumulation of intraspecific variability in this area, supports the idea of an important stronghold of M. ines in this mountain range, as has already been shown for several other species. The lower genetic diversity of the Iberian and Tunisian population might be the result of a rapid range expansion originating from the Atlas region or the survival of smaller relict populations in the eastern Maghreb (which is underpinned by geographically restricted climatically suitable retreats in this area, computed using species distribution models). In general, these findings highlight the importance of the Atlas massif as a refugium for thermophilic species on the Palaearctic scale. © 2011 The Linnean Society of London, Biological Journal of the Linnean Society, 2011, 104, 828–837. ADDITIONAL KEYWORDS: allozyme electrophoresis – climatic stability – climatic oscillations – differentiation centre – range shifts – refugia – species distribution modelling.