Читать книгу Biogeography in the Sub-Arctic - Группа авторов - Страница 40

It has traditionally been suggested that the NALB had become unavailable for animal and plant migration in the course of the Oligocene (McKenna 1983). However, both new subsidence models (e.g. Poore et al. 2006) and palaeobotanical data (Denk et al. 2011 and references in their Chapter 12) suggest that this link persisted much longer than previously thought, providing a functioning ‘land bridge’ particularly for plants (see also recent reviews by Tiffney and Manchester 2001; Tiffney 2000, 2008). The exceptionally rich Neogene record of Iceland allows distinguishing directions of transatlantic migration during the Miocene and Pliocene. The oldest floras of Iceland are characterized by taxa that had a markedly widespread northern hemispheric distribution during large parts of the Cenozoic (Glyprostrobus, Sequoia, Cercidiphyllum, Platanus, Liriodendron, Sassafras, etc.). These taxa may have migrated to Iceland either from the east or from the west. A similar pattern is seen in the early late Miocene floras, where less common taxa such as Rhododendron section Pontica have closely similar related taxa in the modern floras of eastern North America and western Eurasia. At the same time, a number of late Miocene taxa recovered from Iceland clearly migrated from Europe (Fagus gussonii Massalongo emend. Knobloch and Velitzelos, Trigonobalanopsis). Similarly, the pollen record suggests that Quercus sect. Quercus/Lobatae migrated to Iceland from the west as late as between 7 and 6 and 5.5 Ma (Denk et al. 2010a). Younger floras record a stepwise loss of ‘exotic’ taxa until the complete extinction of the (warm) temperate elements of the ancient Icelandic flora during the cold phases of the Pleistocene. Interglacial and postglacial plant colonization of Iceland occurred predominantly from the east.