The expanding range of Undaria pinnatifida in southern New Zealand: distribution, dispersal mechanisms and the invasion of wave-exposed environments |
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Authors: | Lisa K Russell Christopher D Hepburn Catriona L Hurd Michael D Stuart |
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Institution: | (1) Department of Botany, University of Otago, P.O. Box 56, Dunedin, 9010, New Zealand;(2) Kingett Mitchell Ltd, P.O. Box 1087, Dunedin, New Zealand |
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Abstract: | 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. |
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Keywords: | Dispersal Disturbance Exotic Incursion Introduced macroalgae Kelp Marine invasion New Zealand Sporophytes Undaria pinnatifida Wave exposure |
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