Abstract
Invasive alien species are routinely moved around the world as horticultural specimens. An additional route through the traditional medicine trade may exist, especially where cultures from different continents coalesce. South African traditional medicine, for example, has a long history of association with its Indian Ayurvedic equivalent via migration of people from the sub-continent as either slaves or indentured labour. This study investigated the occurrence and viability of alien species in South African traditional medicine markets and shops. Forty-two species of alien plants were found, of which 26 species were propagules and 22 were viable. Seven of the viable species are listed as invasive in South Africa. However, all but one of the 22 species that were tested and identified are known to be invasive somewhere in the world. Most of the viable alien species were sold as seeds, seedpods or nuts (64%, n=14 of 22 species) from Indian-owned shops, while mainly tubers, stems and rhizomes were found in African-run markets. Alien plant species moving within this trade route have circumvented all dispersal barriers and may have exerted propagule pressure over at least a century, and should therefore be considered as candidates for monitoring.
Highlights
This paper investigates the viability of plant parts sold as traditional medicine, as propagules of potentially invasive alien taxa
This is in contrast to the trade in indigenous species on the Witwatersrand, around Johannesburg, where most of the species sold are in the form of plant parts that are not reproductive structures and seeds comprised b1% of the total flora traded (Williams et al, 2000; Williams et al, 2001; Williams, 2007)
Mean residence time in the country of introduction is considered to be one of the principal indicators of invasiveness (Richardson and Pyšek, 2006), it is a massively variable metric ranging from 147 years for woody species (Kowarik, 1995), 14 years for tropical woody species and only five years for herbaceous species (Daehler, 2009). Whatever status these medicinal species are eventually given, we suggest assigning them to a ‘watch list’ given that they qualify in all three criteria, namely history of invasion, environmental suitability, and propagule pressure (Faulkner et al, 2014)
Summary
This paper investigates the viability of plant parts sold as traditional medicine, as propagules of potentially invasive alien taxa. Many invasive alien plants are regarded as conflict of interest species (Beinart and Wotshela, 2011) that simultaneously create problems and benefits for different members of human communities or natural ecosystems. Invasive alien plant species (IAS) cost South Africa at least R6.5 billion per year, which if unmanaged will multiply by a factor of six (Van Wilgen et al, 2008; De Lange and Van Wilgen, 2010). The National Resource Management Programme of the Department of Environmental Affairs [formerly known as Working for Water (WfW)], manages IAS in South Africa through an extensive clearing programme that is combined with the biological control of 48 plant species (Moran et al, 2013). The NRMP funds a unit of the South African National Biodiversity Institute's Invasive Species Programme (SANBI ISP), which
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