February brought me a new and exciting job, but also two publications that happen to represent the opposite ends of the spectrum of my research interests.
Churi Tepui, Venezuela (photo by Dr. Jan Kastovsky)
The first article, published in the journal Phytotaxa, is a collaborative study I worked on with my friends and colleagues at the University of South Bohemia. The paper describes two new species of Cyanobacteria, two new species of diatoms, and one new genus and species of green algae, Ekerewekia churiensis. These likely endemic algae were collected on top of Churi Tepui, a table mountain in Venezuela. Now, table mountains have fascinated scientists for a long time, as they harbor unique floras and faunas that have been isolated from the rest of the world for millions of years. Still, the diversity of microscopic organisms of table mountains largely remains to be explored.
The newly discovered Ekerewekia with its long, branched filaments is unique among its relatives. Even though other filamentous forms exist in this group of green algae (called the Prasiola clade), they are not closely related to Ekerewekia, suggesting that the multicellular, filamentous form evolved twice in the Prasiola clade.
The newly described green alga Ekerewekia was also examined with the use of molecular phylogenetic methods and was found to belong to a diverse group of green algae called the ‘Prasiola clade’. This group mostly contains single-celled organisms, among which Ekerewekia stands out as very unusual. However, another subgroup of the Prasiola clade contains filamentous forms (though very different looking from Ekerewekia), but is not closely related to Ekerewekia, suggesting two evolutionary origins of multicellularity in this algal group. This finding underscores how studying and exploring biodiversity goes hand in hand with understanding evolution.
Kaštovský J, Veselá J, Bohunická M, Fučíková K, Štenclová L, Brewer-Carías C. 2016. New and unusual species of cyanobacteria, diatoms and green algae, with a description of a new genus Ekerewekia gen. nov. (Chlorophyta) from the table mountain Churí-tepui, Chimantá Massif (Venezuela) Phytotaxa 247: 153-180.
The second paper was published in the journal Molecular Phylogenetics and Evolution and describes the phylogenetic relationships in the green algal order Sphaeropleales as inferred by chloroplast genome data. We found that the outcome really depends how one analyzes the data, and this might be caused by a variety of biases in the sequence data themselves. Thus, it is essential to apply the most appropriate analysis methods that will account for such biases as much as possible.
Amino acid data yield a different tree topology than nucleotide data – even though these data sets originate from the same genes (amino acid data are merely translated nucleotide data). One possible explanation is that some species have highly biased codon and amino acid composition relative to what we would expect solely based on nucleotide composition.
The paper is part of the Green Algal Tree of Life project, which was funded by the National Science Foundation. In addition, a more in-depth description and comparative analysis of the chloroplast genomes will be coming out soon in the journal Data in Brief.
Fučíková K, Lewis PO, Lewis LA. In press. Chloroplast phylogenomic data from the green algal order Sphaeropleales (Chlorophyceae, Chlorophyta) reveal complex patterns of sequence evolution. Molecular Phylogenetics and Evolution. pdf preprint