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Modern Range (modern + range)
Selected AbstractsIsozyme variation and recent biogeographical history of the long-lived conifer Fitzroya cupressoidesJOURNAL OF BIOGEOGRAPHY, Issue 2 2000A. C. Premoli Abstract Aim Palaeoenvironmental records of Pleistocene glaciation and associated vegetation changes in Patagonia have led to the hypothesis that during the last glacial maximum (LGM) tree species survived locally in favourable habitats. If present populations originated from spread from only one refugium, such as an ice-free area of coastal Chile (Single Refugium hypothesis), we would expect that eastern populations would be genetically depauperate and highly similar to western populations. In contrast, if the ice cap was not complete and tree species persisted in forest patches on both slopes of the Andes (Multiple Refugia hypothesis), we would expect a greater degree of genetic divergence between populations either on opposite sides of the Cordillera (Cordillera Effect scenario) or towards its present-day southern distributional limit where the ice sheet reached its maximum coverage (Extent-of-the-Ice scenario). Location We tested this refugia hypothesis using patterns of isozyme variation in populations sampled over the entire modern range of the endemic conifer Fitzroya cupressoides (Mol.) Johnst. (Cupressaceae) in temperate South America. Methods Fresh foliage was collected from twenty-four populations and analysed by horizontal electrophoresis on starch gels. Results Twenty-one putative loci were reliably scored and 52% were polymorphic in at least one population. Populations from the eastern slope of the Andes were genetically more variable than those from the western slope; the former had a greater mean number of alleles per locus, a larger total number of alleles and rare alleles, and higher polymorphism. Genetic identities within western populations were greater than within eastern populations. Discriminant analyses using allelic frequencies of different grouping schedules of populations were non significant when testing for the Single Refugium hypothesis whereas significant results were obtained for the Multiple Refugia hypothesis. Main conclusions Our results indicate that present Fitzroya populations are the result of spreading from at least two, but possibly more, glacial refugia located in Coastal Chile and on the southern flanks of the Andes in Argentina. [source] Population structure in the Atlantic salmon: insights from 40 years of research into genetic protein variationJOURNAL OF FISH BIOLOGY, Issue 2005E. Verspoor Electrophoretic studies of proteins remain a primary source of insight into genetic diversity in many species including the Atlantic salmon Salmo salar, one of the most culturally and economically important fish species of the North Atlantic region. Since 1966, >350 scientific papers on protein variation have been published encompassing 25 000+ salmon from over 400 locations in >200 river systems across the species' distribution. Variation has been detected at 30% of the 110 protein loci screened, though most studies examine <40. The method has been applied largely to the investigation of population structure and differentiation, but work has also led to the systematic revision of the genus Salmo and remains the primary source of insight into hybridization in the wild with brown trout Salmo trutta. Spatial patterns of differentiation show temporal stability, both within and among river systems, and strongly support structuring of the species into river and tributary specific populations and the designation of European and North American populations as distinct sub-species. They also show widespread regional differentiation within both continents, beyond the marked subcontinental differences between Baltic Sea and Atlantic Ocean populations in Europe. Most of the differentiation probably reflects gene flow and founder events associated with colonization following the retreat of the glaciers from much of the species' modern range. However, variation at MEP-2* shows strong correlations with environmental temperature, both within and among rivers, and associations with phenotypic performance. This suggests selection is acting on the locus and provides compelling evidence for the local adaptation of populations. Protein studies have led to more population centred management of the species and have been exploited in the discrimination of regional stocks in mixed stock analysis in high seas fisheries, particularly in the Baltic Sea, and as markers for the assessment of stocking success. They have also advanced insight into how the genetic character of populations can be changed in cultivation and the potential impact of salmon aquaculture and stocking on wild populations. The method has been largely superseded by DNA based analyses, but the results remain highly relevant to Atlantic salmon management and conservation and are an irreplaceable data set for studying genetic stability of populations over time. [source] A new Lyrodiscus (Mollusca, Gastropoda) assemblage from Saint-Acheul (Somme Valley): a reappraisal of MIS 11 malacofaunas from northern FranceBOREAS, Issue 4 2006NICOLE LIMONDIN-LOZOUET Recent studies undertaken at Saint-Acheul in the Somme Valley (France) have provided an opportunity to recover malacological assemblages from a tufa deposit located at the top of a Middle Pleistocene fluvial sequence. Molluscan communities are rich and, although dominated by open grassland species, contain up to 23 forest taxa. This high diversity of thermophilous molluscs allows the recognition of fully temperate climatic conditions. Moreover, the occurrence of an extinct zonitid belonging to the genus Retinella (Lyrodiscus), along with several species beyond their modern range (Platyla polita, Ena montana, Ruthenica filograna Clausilia pumila, Clausilia dubia, Macrogastra ventricosa, Perforatella bidentata, Monachoides incarnatus, Belgrandia marginata, Hygromia limbata) allows correlation of the Saint-Acheul assemblage with malacofaunas recovered in other MIS 11 tufa deposits from the Somme and Seine valleys. This age attribution is reinforced at Saint-Acheul by stratigraphy and an ESR date on quartz of 403 9/73 kyr from the underlying fluvial deposits. In addition, old collections containing R. (Lyrodiscus) specimens have been rediscovered, allowing taxonomic reassessment of the species. This shows that Retinella (Lyrodiscus) skertchlyi Kerney, 1976 is a junior synonym of Retinella (Lyrodiscus) elephantium (Bourguignat, 1869) and that at least two extinct species of R. (Lyrodiscus) occurred in western Europe during the Quaternary. Finally, reappraisal of these French molluscan assemblages shows that they are similar to British malacofaunas of Hoxnian age. These new results strengthen the uniqueness and biostratigraphical value of the ,Lyrodiscus assemblage'. [source] Virtual study of the endocranial morphology of the matrix-filled cranium from Eliye Springs, KenyaTHE ANATOMICAL RECORD : ADVANCES IN INTEGRATIVE ANATOMY AND EVOLUTIONARY BIOLOGY, Issue 2 2004Günter Bräuer Abstract This paper provides the first endocranial description of the matrix-filled archaic Homo sapiens cranium from Eliye Springs, Kenya. Using CT-based 3D reconstruction, the virtually cleaned endocranial surface allowed for the assessment of more than 30 metrical and nonmetrical features, most of which are considered of phylogenetic importance. The VOXEL-MAN program used was most valuable in describing and analyzing the morphological conditions. Since many of the features have not been widely or virtually studied, a small sample of late Pleistocene/early Holocene skulls from East Africa was similarly analyzed for insight into recent variation. The comparisons between Eliye Springs and the modern African specimens showed that the endocranial morphology of this probably later Middle Pleistocene hominid falls into, or close to, the modern ranges of variation for most features. This study also addresses the problems of variation and phylogenetic significance of many of the features, and highlights the need for basic studies on the variability and relevance of such endocranial traits in human evolution. Anat Rec Part A 276A:113,133, 2004. © 2004 Wiley-Liss, Inc. [source] Pleistocene Plant Fossils in and near La Selva Biological Station, Costa Rica1BIOTROPICA, Issue 3 2003Sally P. Horn ABSTRACT Radiocarbon dating and 40Ar/39Ar analysis of overlying tephra indicate that plant fossil assemblages exposed by stream erosion and well construction in and near La Selva Biological Station in eastern lowland Costa Rica are Pleistocene in age. We identified plant taxa based on wood, leaves, fruits, seeds, pollen, and spores examined from three sites at ca 30 m elevation. Extrapolating from modern ranges and surface temperature lapse rates suggests paleotemperatures 2.5,3.1°C cooler than at present RESUMEN Dataciones radiocarbónicas y análisis de argon (40Ar/39Ar) de la tefra sobrepuesta indican una edad Pleistocénica para las asociaciones de plantas fósiles expuestas por erosión fluvial y por la construcción de un pozo dentro y cerca de la Estación Biológica La Selva en la bajura oriental de Costa Rica. Se identificaron los táxones vegetales con base en madera, hojas, frutas, semillas, polen, y esporas de tres sitios ubicados a unos 30 m sobre el nivel de mar. Los resultados, basados en la extrapolación de los ámbitos geográficos y del gradiente vertical de la temperatura superficial modernos, sugiere paleotemperaturas 2.5,3.1°C mas frescas que en el presente. [source] | |||||||||||||