The expanding range of Undaria pinnatifida in southern New Zealand: distribution, dispersal mechanisms and the invasion of wave-exposed environments
Russell, LK and Hepburn, CD and Hurd, CL and Stuart, MD, The expanding range of Undaria pinnatifida in southern New Zealand: distribution, dispersal mechanisms and the invasion of wave-exposed environments, Biological Invasions, 10, (1) pp. 103-115. ISSN 1387-3547 (2008) [Refereed Article]
Copyright 2007 Springer Science+Business Media B.V.
Very few studies have addressed how the
invasive kelp Undaria pinnatifida (Harvey) Suringar
spreads beyond initial founding populations in harbours.
Surveys of the harbours and accessible areas of
open coast throughout southern New Zealand were
conducted to determine how far U. pinnatifida
populations had extended since initial incursions.
Our findings clearly demonstrate that U. pinnatifida is
capable of invading native communities and can
establish reproductive populations in locations subjected
to significant and consistent wave action. The
extent of spread from source populations differs
between harbours in which it has established.
Dispersal is greatest in harbours with long established
populations, those where populations have not been
strategically managed, harbours with high water
exchange with surrounding coastal waters, and where
prevailing currents allow establishment of U. pinnatifida
on suitable substrata close to harbour
entrances. Dispersal along the open coast is primarily
achieved by drifting adult sporophytes that are
washed up in the rocky intertidal zone. Founding
populations are most often found in the intertidal
zone, primarily within rockpools. Subtidal transects
and observations indicate that U. pinnatifida is well
adapted to invade exposed coastlines and can establish
within a broad range of niches in wave-exposed
areas including rockpools, the low intertidal, shallow
subtidal, Macrocystis pyrifera kelp forests, and in low
light areas beyond the vertical extent of large native
macroalgae. The current range of U. pinnatifida is
much greater than expected and appears to be
expanding. Due to its ability to grow in a broad
range of environments and to form dense monospecific
stands, U. pinnatifida has the potential to
strongly modify almost all rocky subtidal and intertidal
communities in temperate locations.