No abstract

The kelp Undaria pinnatifida (Phaeophyta: Laminariales), native to Japan, Korea and parts of China, has been found growing subtidally to 7 m depth over a 4 km stretch of the shoreline of Wellington Harbour, New Zealand. In August 1987, some sporophytes were up to 1.3 m tall with fully developed sporophylls. Circumstantial evidence suggests Japanese and Korean fishing vessels may have carried Undaria to New Zealand within the last nine years. This is the second record of Undaria being inadvertently introduced to shores beyond Asia, and it is the first record of its occurrence in the Southern Hemisphere.

Many macroalgae exhibit considerable intraspecific morphological variation, but whether such variation reflects phenotypic plasticity or underlying genetic differences is often poorly understood. We quantified both morphological and genetic variation of 96 plants from seven field sites across eastern South Island, New Zealand, to assess genetic differences between morphotypes of the southern bull kelp Durvillaea antarctica (Cham.) Har. Consistent DNA sequence differentiation across mitochondrial, plastid, and nuclear loci was correlated with two broadly sympatric morphotypes: "cape" and "thonged." These ecologically, morphologically, and genetically distinct bull-kelp lineages were previously considered to be environmentally determined phenotypes with no underlying genetic basis. Interestingly, the sheltered "cape" lineage appears essentially genetically uniform across its South Island range, whereas the exposed "thonged" lineage exhibits marked phylogeographic structure across its range. Results suggest that D. antarctica in New Zealand comprises two reproductively isolated species.

2000. The role of natural dispersal mechanisms in the spread of Undaria pinnalijida (Laminariales, Phaeophyceae). Phycologia 39: 547-553.The Asian kelp Undaria pinnalijida (Laminariales, Phaeophyceae) was first recorded in New Zealand in 1987 and has since' spread via shipping traffic and other vectors to a number of ports and harbours. Here we report the results of laboratory and field studies devised to assess the potential for natural dispersal of Undaria from a founding population. Under laboratory conditions, > 90% of Undaria spores were viable in seawater for at least 5 days, with some viable after 14 days. Spores artificially released into a tidal current resulted later in sporophytes appearing on artificial surfaces positioned 10 m down current of the release point. Field monitoring of a founding popUlation within the Marlborough Sounds, New Zealand, suggested that natural populations spread at least 100 m yr-l. Reasons for the differences between the dispersal distances of the artificially released spores (10 m) and natural populations (100 m) are discussed. We propose that spore dispersal from fixed stands of Undaria results primarily in short-range spread (metres to hundreds of metres), with dispersal of fragments or whole sporophytes facilitating spread at scales of hundreds of metres to kilometres.

At its geographical limits, the distribution of Macrocystis C. Agardh is related to highest summer sea surface temperatures. This paper discusses New Zealand populations of M. pyrifera (Linnaeus) C. Agardh, the distribution of which may be correlated closely with the Southland Current. In New Zealand, M. pyri{era does not persist in areas where maximum temperatures exceed 18-19°C for several days, and where the warmest monthly isothere does not exceed 16-17°C. An apparent easterly retraction of Macrocystis distribution within Cook Strait since 1942 is described, and the possibility that this may reflect slight warming in ambient sea surface temperature over the last forty years is discussed. The intolerance of the kelp to extreme temperatures above 18-19°C was confirmed by experimental transplantation of kelp plants within Queen Charlotte Sound. Collectively these observations suggest M. pyrifera may indicate patches of relatively cool water, and on a very small geographic scale. In an area such as the Marlborough Sounds, clearly close to the plant's limits of distribution, the presence of Macrocystis may be useful in considering potential sites for locating net cages for the commercial "ranching" of chinook salmon. The upper temperature limit for both kelp and salmon appear to be similar.