Revealing the scale of marine bioinvasions in developing regions: a South African re-assessment

Abstract

As recently as 2009 the number of introductions recorded for South Africa comprised 22 marine and estuarine species. This review aims to reassess the diversity and scale of introduced marine and estuarine species in the region. Accurate taxonomic and systematic work, broad review of historical records and new sampling surveys across selected marine habitats conducted by a team of local and international experts has effectively revealed the presence of previously misidentified, overlooked, or new introductions. A total of 86 introduced and 39 cryptogenic species are recognized, increasing known numbers four and twofold respectively within 1 year, although the current assessment is far from fully comprehensive. Additional species were revealed within the historic literature (76%), from surveys conducted post-2005 (11%) and following taxonomic resolution (13%). Temporal analyses confirmed discovery rates were increasing over time. Ship fouling and ballast water were the dominant vector pathways, accounting for 48 and 38% respectively. Spatial analyses revealed patterns of bioinvasion to be significantly higher on the west coast compared to the other coastal regions. Overall, 53% of introductions were concentrated within harbour areas with only 4 opencoast invaders detected at present. Introduced species found in the cool and warm-temperate provinces of the west and south coast mainly originated from the northern hemisphere (65%). In contrast, introductions located in the sub-tropical and tropical provinces of the east coast mainly originated from the southern hemisphere (18%), with the remaining 17% of introduced species being of unknown origin. The research approach described has proven pivotal, contributing massively toward revealing the true scale and patterns of bioinvasion for a developing region within a relatively short period of time.

Seagrass-associated macrobenthic functional diversity and functional structure along an estuarine gradient

“…This system supports the largest area of seagrass (some 350 ha) and highest macrofaunal biodiversity of any South African estuary (Turpie et al, 2002;Bandeira and Gell, 2003), with >100 macrobenthic species in its Zosterella capensis beds (Barnes and Ellwood, 2012), although almost 10% of these are on Mead et al's (2011) and other lists of introduced aliens. As seen in other estuaries (e.g.…”

Macroalgas exoticas en la costa de Chile: patrones espaciales y temporales en el proceso de invasion

“…Por esta razón, Cartlon (2009) ha propuesto que la cantidad de especies exóticas en sistemas que históricamente han sido considerados prístinos (e.g., costa sudafricana, costa argentina, costa chilena) se encontraría subestimada, y tras un análisis más profundo podría aumentar de 5 a 10 veces el número registrado. El ejemplo más emblemático lo constituye la costa sudafricana, en donde en primera instancia, se habían estimado 22 especies exóticas y 18 especies criptogénicas (Robinson et al, 2005;Griffiths et al, 2009), pero tras una exhaustiva revisión de registros históricos, análisis taxonómicos y muestreos en lugares poco estudiados, dichas cantidades se cuadriplicaron (Mead et al, 2011a(Mead et al, , 2011b.…”

Myosotella myosotis (Mollusca: Ellobiidae) — an overlooked, but well-established introduced species in South Africa

“…In a recent re-assessment of the extent of marine bioinvasions in South Africa, Mead et al (2011) demonstrated that the number of introductions of marine and estuarine species in the region was four times greater than previously recorded. Through a combination of more exhaustive literature searches, taxonomic re-appraisal and targeted field work, they increased the number of recorded introductions from 22 (Griffiths et al 2009a) to 86, with a further 39 cryptogenic species, at the same time acknowledging that their assessment was still 'far from fully comprehensive' (Mead et al 2011(Mead et al , p. 1991.…”