'Invasive' species have been around much longer than believed

The DST-NRF Centre of Excellence for Palaeoscience funded researchers based in the School of Geography, Archaeology and Environmental Studies and in the Evolutionary Studies Institute of the University of the Witwatersrand have used fossil pollen records to solve an on-going debate regarding invasive plant species in eastern Lesotho.

Their study, Chrysocoma ciliata L. (Asteraceae) in the Lesotho Highlands: an anthropogenically introduced invasive or a niche coloniser?, published in Biological Invasions, confirms that a shrub believed to be an invasive in the eastern Lesotho Highlands has been growing in the region for over 4,000 years.

Dr Jennifer Fitchett of the School of Geography, Archaeology and Environmental Studies, and her co-authors Professors Marion Bamford (ESI, Wits), Stefan Grab (GAES, Wits) and Anson Mackay (University College London Environmental Change Research Centre and Geography Department) have been investigating the palaeoenvironments of eastern Lesotho through the use of pollen, diatom and sedimentary records.

In a case of ‘accidental science’, the group discovered the pollen of Chrysocoma cilliata at intermittent locations throughout the depth of the sediment profile they were studying. This was unexpected, as Chrysocoma ciliata is believed to be an invasive species introduced to the eastern Lesotho Highlands by cattle herders at the turn of the 20th century. The species was found to extend much further back in the pollen record than the 100 years that it is believed to have been growing in the region.

Read more at University of the Witwatersrand, Johannesburg

Image: This is Chrysocoma ciliata and microscope images of its pollen grain. (Credit: Jennifer Fitchett and Louis Scott)