An Atlas of Past and Present Pollen Maps for Europe: 0-13000 Years Ago, and The Overlay Maps.

The relative importance of contemporary climate and history as controls of geographical diversity patterns is intensely debated. A key example is the controversy over the extent to which temperate tree distributions and diversity patterns reflect postglacial dispersal limitation. Here, we focus on Central and Northern Europe, and show that recent estimates of tree migration rates < 100 m year(-1) imply that many species have probably not reached equilibrium with climate in this region. We then demonstrate that geographical accessibility from glacial refuges explains 78% of the geographical variation in the region's tree diversity and is a much stronger diversity predictor than climate. Finally, we show that realistic estimates of migration rates can be derived from the observed tree diversity pattern by assuming it to be purely dispersal driven. In conclusion, the tree diversity pattern in Central and Northern Europe could, to a large extent, be a result of postglacial dispersal limitation.

Could the tree diversity pattern in Europe be generated by postglacial dispersal limitation

Aim: The southern European peninsulas (Iberian, Italian and Balkan) are considered to have been refugia for many European species of plants and animals during the climatic extremes of the Pleistocene ice ages. A number of recent studies (fossil and genetic), however, have provided evidence for full-glacial survival of some species beyond these peninsulas. Here we explore the biogeographical traits of these species, and ask whether they possessed certain characteristics that enabled them to persist in more northerly refugia.
 
Location: Europe.
 
Methods: Fossil and genetic evidence for refugial localities of species that survived in Europe during the last full-glacial was obtained from the literature (totalling 90 species: 34 woody plants and 56 vertebrates). Forty-seven of these species (23 woody plants and 24 vertebrates) had fossil evidence, whereas the remaining 43 species (11 woody plants and 32 vertebrates) had only genetic evidence. All species were scored according to their present geographical distribution, habitat preference and life-history traits. The species were classified on the basis of these traits using hierarchical cluster analysis. Analysis of similarities was used to examine differences in vertebrate and woody plant species groups that survived only in southerly refugia and those that also persisted
in more northerly locations. Non-metric multi-dimensional scaling was used to examine patterns observed between and within groups.
 
Results: Results from our analysis of species with fossil and genetic evidence for survival in refugia reveal that species that survived only in southerly refugia were large-seeded trees or thermophilous vertebrates. In contrast, species that had a full-glacial distribution, including more northerly locations, were wind-dispersed, habitat-generalist trees with the ability to reproduce vegetatively, and habitatgeneralist mammals with present-day northerly distributions.
 
Main conclusions: Analysis of the geographical distribution, habitat preference and life-history traits of the species studied suggests that underlying biogeographical traits may have determined their response to Pleistocene glaciation. The traits most commonly found in present populations with a northerly distribution in Europe enabled the same species to exist much farther north than the southern European peninsulas during the full-glacial. It is possible that many of these species are now in restricted populations, within the ‘warm stage’ refugia of the current interglacial. The northerly full-glacial survival of a number of woody plants and vertebrate species has significant implications for understanding migration rates of these species in response to climate change. It also has important implications for understanding current patterns of genetic diversity of European species. We suggest that both fossil and genetic evidence should be used to identify and prioritize for conservation of refugial localities in southern and northern Europe.

https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1365-2699.2007.01861.x

Species persistence in northerly glacial refugia of Europe: a matter of chance or biogeographical traits?

The history of Castanea sativa (sweet chestnut) cultivation since medieval times has been well described on the basis of the very rich documentation available. Far fewer attempts have been made to give a historical synthesis of the events that led to the cultivation of sweet chestnut in much earlier times. In this article we attempt to reconstruct this part of the European history of chestnut cultivation and its early diffusion by use of different sources of information, such as pollen studies, archaeology, history and literature. Using this multidisciplinary approach, we have tried to identify the roles of the Greek and Roman civilizations in the dissemination of chestnut cultivation on a European scale. In particular, we show that use of the chestnut for food was not the primary driving force behind the introduction of the tree into Europe by the Romans. Apart from the Insubrian Region in the north of the Italian peninsula, no other centre of chestnut cultivation existed in Europe during the Roman period. The Romans may have introduced the idea of systematically cultivating and using chestnut. In certain cases they introduced the species itself; however no evidence of systematic planting of chestnut exists. The greatest interest in the management of chestnut for fruit production most probably developed after the Roman period and can be associated with the socio-economic structures of medieval times. It was then that self-sufficient cultures based on the cultivation of chestnut as a source of subsistence were formed.

/pdf/the-cultivation-of-castanea-sativa-mill-in-europe-from-its-4awy6wqgv6.pdf

The cultivation of Castanea sativa (Mill.) in Europe, from its origin to its diffusion on a continental scale

Chorological maps for the main European woody species.

Knowledge about the glacial refugia of the thermophilous European Castanea sativa Mill. (sweet chestnut) is still inadequate. Its original range of distribution has been masked by strong human impact. Moreover, under natural conditions the species was probably admixed with other taxa (such as Quercus, Fraxinus, Fagus, Tilia) and thus possibly represented by low percentages in pollen records. In this paper we try to overcome the difficulties related to the scarcity and irregularity of chestnut pollen records by considering 1471 sites and extending the palynological approach to develop a Castanea refugium probability index (IRP), aimed at detecting possible chestnut refugia where chestnuts survived during the last glaciation. The results are in close agreement with the current literature on the refugia of other thermophilous European trees. The few divergences are most probably due to the large amount of new data integrated in this study, rather than to fundamental disagreements about data and data interpretation. The main chestnut refugia are located in the Transcaucasian region, north-western Anatolia, the hinterland of the Tyrrhenian coast from Liguria to Lazio along the Apennine range, the region around Lago di Monticchio (Monte Vulture) in southern Italy, and the Cantabrian coast on the Iberian peninsula. Despite the high likelihood of Castanea refugia in the Balkan Peninsula and north-eastern Italy (Colli Euganei, Monti Berici, Emilia-Romagna) as suggested by the IRP, additional palaeobotanical investigations are needed to assess whether these regions effectively sheltered chestnut during the last glaciation. Other regions, such as the Isere Departement in France, the region across north-west Portugal and Galicia, and the hilly region along the Mediterranean coast of Syria and Lebanon were classified as areas of medium refugium probability. Our results reveal an unexpected spatial richness of potential Castanea refugia. It is likely that other European trees had similar distribution ranges during the last glaciation. It is thus conceivable that shelter zones with favourable microclimates were probably more numerous and more widely dispersed across Europe than so far assumed. In the future, more attention should be paid to pollen traces of sporadic taxa thought to have disappeared from a given area during the last glacial and post-glacial period.

/pdf/quaternary-refugia-of-the-sweet-chestnut-castanea-sativa-4v8h2ptvuq.pdf

Markus Felber

Papers

Quaternary refugia of the sweet chestnut (Castanea sativa Mill.): an extended palynological approach