Glacial refugia influence plant diversity patterns in the Mediterranean Basin

Abstract

Aim The aims of this study were to assess the distribution of putative Mediterranean refugia of plants, to compare the locations of refugia and those of regional hotspots of plant biodiversity, and to provide a critical analysis of the Mediterranean refugium paradigm. Furthermore, we consider how biogeographical and genetic results can be combined to guide global conservation strategies.Location The Mediterranean region.Methods We started from a detailed analysis of the scientific literature (1993)(1994)(1995)(1996)(1997)(1998)(1999)(2000)(2001)(2002)(2003)(2004)(2005)(2006)(2007) in order to identify refugia in the Mediterranean region, based on intraspecific phylogeographical studies of plant species. We used population locations together with gene-pool identity to establish the database, comparing patterns of phylogeographical concordance with the locations of Mediterranean refugia. We then tested the biogeographical congruence between two biodiversity components, namely phylogeographical refugia and regional hotspots. ResultsWe identified 52 refugia in the Mediterranean bioclimatic region and confirmed the role played by the three major peninsulas, with a shared total of 25 refugia. We emphasize the importance of areas that have previously been attributed a lesser role (large Mediterranean islands, North Africa, Turkey, Catalonia). Of the 52 refugia identified, 33 are situated in the western Mediterranean Basin and 19 in the eastern part. The locations of the phylogeographically defined refugia are significantly associated with the 10 regional hotspots of plant biodiversity, with 26 of these refugia (i.e. 50%) occurring within the hotspots.Main conclusions The locations of refugia are determined by complex historical and environmental factors, the cumulative effects of which need to be considered because they have occurred since the Tertiary, rather than solely during the last glacial period. Refugia represent climatically stable areas and constitute a high conservation priority as key areas for the long-term persistence of species and genetic diversity, especially given the threat posed by the extensive environmental change processes operating in the Mediterranean region. The refugia defined here represent 'phylogeographical hotspots'; that is, significant reservoirs of unique genetic diversity favourable to the evolutionary processes of Mediterranean plant species.

Population genetic structure of Juniperus phoenicea (Cupressaceae) in the western Mediterranean Basin: gradient of diversity on a broad geographical scale

“…The center of the species occurrence, however, covers the western part of the Mediterranean, especially the Iberian Peninsula and North-West Africa (Amaral Franco, 1986;Charco 2001;Farjon 2005). At the same time, the J. phoenicea contemporary geographical range is congruent with the area of several Pleistocene refugia of tertiary floras in the Mediterranean region (Médail and Diadema 2009). The highest taxonomic, morphological, biochemical, and genetic diversities of J. phoenicea were described from the Iberian Peninsula (Amaral Franco, 1986;Lebreton and Rivera 1989;Adams et al 2002;Farjon 2005;Boratyński et al 2009;Mazur et al 2010).…”

A long hard road… Reviewing the evidence for environmental change and population history in the eastern Adriatic and western Balkans during the Late Pleistocene and Early Holocene

“…In the Balkans, the vegetation during the Pleistocene was composed of periglacial tundra, steppe, and boreal forest, as well as refugial populations of broad-leaved deciduous taxa (Rossignol-Strick et al, 1992, Willis, 1994, Médail and Diadema, 2009). Even at the Last Glacial Maximum (hereafter LGM), the southern extent of permafrost reached no further than 45° latitude (Bailey, 2000).…”

Fine-scale spatial patterns of the Tertiary relict Zelkova abelicea (Ulmaceae) indicate possible processes contributing to its persistence to climate changes

“…Zelkova in Europe became restricted to refugia as the result of the cold and aridity during the Pleistocene. Refugia, providing suitable habitats during adverse climate periods, appear to have limited species extinction as well as favouring the emergence of new taxa (Médail and Diadema 2009). The genus eventually disappeared from continental Greece during the middle Pleistocene ( Van der Wiel and Wijmstra 1987), but persisted longer in central Italy until ca.…”