Of Chenopodium and Man: Covered traces of the most widespread weed today
Supervisor: prof. Mgr. Bohumil Mandák, Ph.D.
Annotation:
Most European species are believed to have been restricted to southern refugia during the Last Pleniglacial (24–15 kyr BP) in the peninsulas of Iberia, Italy and the Balkans. After the Last Ice age (i.e. c. 12 kyr BP), when the climate warmed and the ice retreated, these species expanded their ranges northwards. Certainly Pleistocene climatic oscillations have had strong effects on the genetic structures of populations of many species. Nevertheless, during the Holocene, the distributions of species such as crop weeds, to some extent relate to those of cultivated crop species, and these have been significantly influenced by human activity. Hence, crop weed distributions reflect both the historical expansion of agriculture and also trade and the associated movements of goods into new areas. In Eurasia, human mediated Holocene dispersal (largely from east to west) has been confirmed as the main driver of the genetic diversity of many weed species. Consequently, the genetic diversity of weedy species and their geographical distributions may be correlated with both human-associated and climate-associated migrations. One of the main weedy species group in Europe is Chenopodium album aggregate. As a typical weed species, their distribution is put into relationship with human colonisation of the European continent and the history of its spread could be representative of the spread of the whole group of species with the first Neolithic agriculturalists. Many studies have shown the abundant presence of C. album in archaeobotanical profiles associated with Neolithic settlements in different parts of Europe. However, natural habitats, that precede its shared evolution with humans, are unknown. Hence, there is no consensus regarding their original distribution ranges and hence the origins of the European populations. The species could be an archaeophyte – a non-native species introduced to Europe before the discovery of the American continent. In this case it was likely introduced to Europe from Asia as a weed. The species could also be an apophyte – a native species colonising areas changed by human activity that became widespread due to gathering as food. The western Asian region is considered a cradle of Neolithic agriculture and could, therefore, be an important centre of diversity that could well have been the source for the colonisation of the European parts of C. album aggregate’s distribution range. On the other hand, south-central Asia has been recognised as one of the main centres of diversity for the family Chenopodiaceae and thus this region is another potentially important source for the expansion of the C. album aggregate into Europe.