Abstract
Symbiotic dinoflagellates (genus Symbiodinium) shape the responses of their host reef organisms to environmental variability and climate change. To date, the biogeography of Symbiodinium has been investigated primarily through phylogenetic analyses of the ribosomal internal transcribed spacer 2 region. Although the marker can approximate species-level diversity, recent work has demonstrated that faster-evolving genes can resolve otherwise hidden species and population lineages, and that this diversity is often distributed over much finer geographical and environmental scales than previously recognized. Here, we use the noncoding region of the chloroplast psbA gene (psbAncr) to examine genetic diversity among clade C Symbiodinium associating with the common reef zoantharian Palythoa tuberculosa on Okinawa-jima Island, Japan. We identify four closely related Symbiodinium psbAncr lineages including one common generalist and two potential specialists that appear to be associated with particular microhabitats. The sea surface temperature differences that distinguish these habitats are smaller than those usually investigated, suggesting that future biogeographic surveys of Symbiodinium should incorporate fine scale environmental information as well as fine scale molecular data to accurately determine species diversity and their distributions.
Highlights
Symbiodinium is an important genus of dinoflagellate photosymbionts found in tropical and subtropical marine ecosystems
Based on ITS2 sequence analyses of Symbiodinium within P. tuberculosa in Southern Japan, we previously reported that subclade C1 or closely related types are dominant (Reimer, Takishita & Maruyama, 2006)
The highest observed sea surface temperature (SST) in any year was at Uken (30.9 C in 2001), and the lowest was at Bise (18.7 C in 2015) and lineage 1 a
Summary
Symbiodinium is an important genus of dinoflagellate photosymbionts found in tropical and subtropical marine ecosystems. These “zooxanthellae” transfer energy to their invertebrate hosts in nutrient-poor environments, enhancing the growth of reef-building corals and other reef organisms such as zoantharians (Muscatine & Cernichiari, 1969; How to cite this article Noda et al (2017), A preliminary survey of zoantharian endosymbionts shows high genetic variation over small geographic scales on Okinawa-jima Island, Japan. They serve a key role in establishing the thermal tolerance of coral colonies and shaping the adaptive response of reef organisms to climate change (Sampayo et al, 2008; Thornhill et al, 2014). As climate change intensifies and diversity patterns are expected to alter, it is increasingly important to map marine species distributions on scales both large (McClanahan et al, 2014; Reimer et al, 2017) and small (Mieszkowska & Lundquist, 2011)
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