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Hidden biodiversity of the extremophilic Cyanidiales red algae

Authors

  • CLAUDIA CINIGLIA,

    1. Dipartimento di Biologia vegetale, Università‘Federico II’, via Foria 223, 80139 Napoli, Italy,
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    • These authors contributed equally to this work.

  • HWAN SU YOON,

    1. Dipartimento di Biologia vegetale, Università‘Federico II’, via Foria 223, 80139 Napoli, Italy,
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    • These authors contributed equally to this work.

  • ANTONINO POLLIO,

    1. Dipartimento di Biologia vegetale, Università‘Federico II’, via Foria 223, 80139 Napoli, Italy,
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  • GABRIELE PINTO,

    1. Dipartimento di Biologia vegetale, Università‘Federico II’, via Foria 223, 80139 Napoli, Italy,
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  • DEBASHISH BHATTACHARYA

    Corresponding author
    1. Department of Biological Sciences and Center for Comparative Genomics, University of Iowa, 210 Biology Building, Iowa City, Iowa 52242, USA
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Debashish Bhattacharya. Fax: (319) 335 1069; E-mail: dbhattac@blue.weeg.uiowa.edu

Abstract

The Cyanidiales is a group of asexual, unicellular red algae, which thrive in acidic and high temperature conditions around hot springs. These unicellular taxa have a relatively simple morphology and are currently classified into three genera, Cyanidium, Cyanidioschyzon and Galdieria. Little is known, however, about the biodiversity of Cyanidiales, their population structure and their phylogenetic relationships. Here we used a taxonomically broadly sampled three-gene data set of plastid sequences to infer a robust phylogenetic framework for the Cyanidiales. The phylogenetic analyses support the existence of at least four distinct Cyanidiales lineages: the Galdieria spp. lineage (excluding Galdieria maxima), the Cyanidium caldarium lineage, a novel monophyletic lineage of mesophilic Cyanidium spp. and the Cyanidioschyzon merolae plus Galdieria maxima lineage. Our analyses do not support the notion of a mesophilic ancestry of the Cyanidiales and suggest that these algae were ancestrally thermo-acidotolerant. We also used environmental polymerase chain reaction (PCR) for the rbcL gene to sample Cyanidiales biodiversity at five ecologically distinct sites at Pisciarelli in the Phlegrean Fields in Italy. This analysis showed a high level of sequence divergence among Cyanidiales species and the partitioning of taxa based on environmental conditions. Our research revealed an unexpected level of genetic diversity among Cyanidiales that revises current thinking about the phylogeny and biodiversity of this group. We predict that future environmental PCR studies will significantly augment known biodiversity that we have discovered and demonstrate the Cyanidiales to be a species-rich branch of red algal evolution.

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