Latitudinal diversity of the symbiotic dinoflagellate symbiodinium in New Zealand

Abstract

This study determined the diversity of zooxanthellae (Symbiodinium sp.), harboured by the sea anemone Anthopleura aureoradiata, along a temperate latitudinal gradient in New Zealand. The anemone was collected from various sites around the three main islands of New Zealand - North Island, South Island and Stewart Island, expanding the reported range. Restriction fragment length polymorphisms (RFLPs) using the digest Taq I on 18S rDNA showed clade A zooxanthellae to be present, which is in agreement with the only other previous genetic study of zooxanthellae in New Zealand (Birkenstock 2001). 30 samples were genetically sequenced, 10 each from the far north, middle and far south of New Zealand, respectively. After alignment no genetic diversity was found within or between populations. When compared to other international clade A zooxanthellar sequences from various hosts, including two temperate north Pacific sea anemones, the sequences of this study and Birkenstock (2001) grouped together into a distinct group. There are many possible reasons for clade A being harboured, and the low diversity found. Clade A zooxanthellae are hardy, adapted to high light and fluctuating environments. They are predominantly found in the shallows of tropical reef settings but are also harboured by temperate sea anemones that experience comparatively little light. A. aureoradiata experiences dramatic changes and harsh environmental conditions living in an estuarine environment, with its tentacles exposed to full sunlight; clade A may be optimal for this type of environment. The low diversity observed may be due to the lack of environmental niches or other symbiotic donors, maternal inheritance and host-symbiont specificity, isolation and genetic bottlenecks, or a combination of the previous factors. New Zealand's zooxanthellae may be endemic but further study using other genes is necessary.