Abstract
Three species of Nassella have naturalized in South Africa. Nassella trichotoma and N. tenuissima are declared weeds under category 1b of the National Environmental Management: Biodiversity Act (NEM:BA) and occur mainly in the montane grasslands of the Western and Eastern Cape provinces. Nassella neesiana is not listed in NEM:BA but is naturalized in the Eastern Cape, Western Cape and Free State provinces. Research conducted in the 1970s and 1980s led to vigorous government-funded awareness and control campaigns which ended in 2000. No research on Nassella distribution or control has been undertaken since then. Despite this hiatus, Nassella remains a dangerous genus in southern Africa, given the serious impacts of these species in similar social-ecological systems in Australia and New Zealand. This paper presents a synthesis of available information about Nassella invasions in South Africa and identifies research gaps. It specifically addresses these questions: What identification issues exist? What is the current spatial distribution of Nassella? What is the autecology of the genus? What are the social-ecological impacts of Nassella? What control measures are currently applied and what are their strengths and limitations? What do we know about Nassella distribution and its response to climate change? This paper highlights many knowledge gaps about Nassella, such as the species’ current distribution range, field identification and detection difficulties, and the uncoordinated control efforts that require urgent research to inform an effective management response.
Highlights
This paper collates all available information about Nassella invasions in South Africa and identifies research gaps. It seeks to shed light on these questions: What identification issues exist? What is the current spatial distribution of Nassella? What is the autecology of the genus? What are the social-ecological impacts of Nassella? What control measures are currently applied and what are their strength and limitations? What do we know about Nassella distribution and its response to climate change?
Nassella research in South Africa effectively stopped in the 1980s and no recent scientific research could be found in the literature
Australia and New Zealand have similar socio-ecological systems to South Africa (Pysek et al 2020), and much research on the invasion ecology of the genus has been undertaken in these countries
Summary
Belongs to the grass family, Poaceae (Gramineae), subfamily Pooideae in the tribe Stipeae (spear grasses). Nassella comprises at least 116 species (Barkworth et al, 2008; Soreng et al, 2009; Romaschenko et al, 2012). Species currently placed in this genus were originally included in the genus Stipa s.l. and for many years researchers held mixed views regarding the segregation of these genera. With strong support from molecular studies, their separation appears to be largely settled, save for a few species (Romaschenko et al, 2012; Cialdella et al, 2014). The name ‘Nassella’ comes from the Latin noun nassa which means “a fish basket” (Quattrocchi, 2000), probably because these grasses were used for making fishing baskets
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