GENETIC-CONTROL OF ISOZYME SYSTEMS AND HETEROGENEITY OF POLLEN CONTRIBUTION IN BEECH (FAGUS-SYLVATICA L)

International audienc

GENETIC-CONTROL OF ISOZYME SYSTEMS AND HETEROGENEITY OF POLLEN CONTRIBUTION IN BEECH (FAGUS-SYLVATICA L)

International audienc

A new scenario for the Quaternary history of European beech populations: palaeobotanical evidence and genetic consequences

Here, palaeobotanical and genetic data for common beech (Fagus sylvatica) in Europe are used to evaluate the genetic consequences of long-term survival in refuge areas and postglacial spread. Four large datasets are presented, including over 400 fossil-pollen sites, 80 plant-macrofossil sites, and 450 and 600 modern beech populations for chloroplast and nuclear markers, respectively. The largely complementary palaeobotanical and genetic data indicate that: (i) beech survived the last glacial period in multiple refuge areas; (ii) the central European refugia were separated from the Mediterranean refugia; (iii) the Mediterranean refuges did not contribute to the colonization of central and northern Europe; (iv) some populations expanded considerably during the postglacial period, while others experienced only a limited expansion; (v) the mountain chains were not geographical barriers for beech but rather facilitated its diffusion; and (vi) the modern genetic diversity was shaped over multiple glacial-interglacial cycles. This scenario differs from many recent treatments of tree phylogeography in Europe that largely focus on the last ice age and the postglacial period to interpret genetic structure and argue that the southern peninsulas (Iberian, Italian and Balkan) were the main source areas for trees in central and northern Europ

A novel class of herpesvirus with bivalve hosts

Ostreid herpesvirus 1 (OsHV-1) is the only member of the Herpesviridae that has an invertebrate host and is associated with sporadic mortality in the Pacific oyster (Crassostrea gigas) and other bivalve species. Cryo-electron microscopy of purified capsids revealed the distinctive T=16 icosahedral structure characteristic of herpesviruses, although the preparations examined lacked pentons. The gross genome organization of OsHV-1 was similar to that of certain mammalian herpesviruses (including herpes simplex virus and human cytomegalovirus), consisting of two invertible unique regions (UL, 167·8 kbp; US, 3·4 kbp) each flanked by inverted repeats (TRL/IRL, 7·6 kbp; TRS/IRS, 9·8 kbp), with an additional unique sequence (X, 1·5 kbp) between IRL and IRS. Of the 124 unique genes predicted from the 207 439 bp genome sequence, 38 were members of 12 families of related genes and encoded products related to helicases, inhibitors of apoptosis, deoxyuridine triphosphatase and RING-finger proteins, in addition to membrane-associated proteins. Eight genes in three of the families appeared to be fragmented. Other genes that did not belong to the families were predicted to encode DNA polymerase, the two subunits of ribonucleotide reductase, a helicase, a primase, the ATPase subunit of terminase, a RecB-like protein, additional RING-like proteins, an ion channel and several other membrane-associated proteins. Sequence comparisons showed that OsHV-1 is at best tenuously related to the two classes of vertebrate herpesviruses (those associated with mammals, birds and reptiles, and those associated with bony fish and amphibians). OsHV-1 thus represents a third major class of the herpesviruses

Roches ornées, roches dressées

Jean Abélanet peut être considéré comme le pionnier de l'archéologie actuelle sur les terres nord-catalanes. Ce rôle de précurseur dans la découverte de sites majeurs, mais aussi sa contribution savante à l'avancée des études préhistoriques, tant sur le mégalithisme en Pyrénées que sur l'art rupestre post-glaciaire en Europe occidentale, justifient l'hommage qui lui est rendu par la communauté des chercheurs. Cet hommage a pris la forme d'un colloque placé sous l'égide de l'Association Archéologique des Pyrénées-Orientales, dont il fut membre fondateur, et de l'Université de Perpignan, dont il fut le premier enseignant en Préhistoire. Sont rassemblées dans cet ouvrage les contributions de 74 auteurs et co-auteurs. Ces 576 pages, abondamment illustrées par près de 300 figures, abordent des sujets très divers qui reflètent les différents champs d'études balayés par son insatiable et humaniste curiosité. Une première partie, remontant aux sources des arts et des mythes, éclaire certains aspects de l'art rupestre et du mégalithisme, depuis leurs origines jusqu'à nos jours, à partir de recherches récentes menées dans l'Ancien monde, des terres australes d'Afrique jusqu'en Europe de l'Ouest. Le second thème, tout en laissant une large place à l'étude des arts et des traditions funéraires, rassemble des travaux pluridisciplinaires menés à l'orient des Pyrénées, travaux d'historiographie, de palynologie, de géologie, d'archéologie préhistorique et historique, d'histoire ou d'ethnologie