Ga Hun Boo

Complex phylogeographic patterns in the freshwater alga Synura provide new insights into ubiquity vs. endemism in microbial eukaryotes

The global distribution, abundance, and diversity of microscopic freshwater algae demonstrate an ability to overcome significant barriers such as dry land and oceans by exploiting a range of biotic and abiotic colonization vectors. If these vectors are considered unlimited and colonization occurs in proportion to population size, then globally ubiquitous distributions are predicted to arise. This model contrasts with observations that many freshwater microalgal taxa possess true biogeographies. Here, using a concatenated multigene data set, we study the phylogeography of the freshwater heterokont alga Synura petersenii sensu lato. Our results suggest that this Synura morphotaxon contains both cosmopolitan and regionally endemic cryptic species, co‐occurring in some cases, and masked by a common ultrastructural morphology. Phylogenies based on both proteins (seven protein‐coding plastid and mitochondrial genes) and DNA (nine genes including ITS and 18S rDNA) reveal pronounced biogeographic delineations within phylotypes of this cryptic species complex while retaining one clade that is globally distributed. Relaxed molecular clock calculations, constrained by fossil records, suggest that the genus Synura is considerably older than currently proposed. The availability of tectonically relevant geological time (107–108 years) has enabled the development of the observed, complex biogeographic patterns. Our comprehensive analysis of freshwater algal biogeography suggests that neither ubiquity nor endemism wholly explains global patterns of microbial eukaryote distribution and that processes of dispersal remain poorly understood.

Supermatrix data highlight the phylogenetic relationships of photosynthetic stramenopiles.

Molecular data had consistently recovered monophyletic classes for the heterokont algae, however, the relationships among the classes had remained only partially resolved. Furthermore, earlier studies did not include representatives from all taxonomic classes. We used a five-gene (nuclear encoded SSU rRNA; plastid encoded rbcL, psaA, psbA, psbC) analysis with a subset of 89 taxa representing all 16 heterokont classes to infer a phylogenetic tree. There were three major clades. The Aurearenophyceae, Chrysomerophyceae, Phaeophyceae, Phaeothamniophyceae, Raphidophyceae, Schizocladiophyceae and Xanthophyceae formed the SI clade. The Chrysophyceae, Eustigmatophyceae, Pinguiophyceae, Synchromophyceae and Synurophyceae formed the SII clade. The Bacillariophyceae, Bolidophyceae, Dictyochophyceae and Pelagophyceae formed the SIII clade. These three clades were also found in a ten-gene analysis. The approximately unbiased test rejected alternative hypotheses that forced each class into either of the other two clades. Morphological and biochemical data were not available for all 89 taxa, however, existing data were consistent with the molecular phylogenetic tree, especially for the SIII clade.

Highly conserved mitochondrial genomes among multicellular red algae of the Florideophyceae

Two red algal classes, the Florideophyceae (approximately 7,100 spp.) and Bangiophyceae (approximately 193 spp.), comprise 98% of red algal diversity in marine and freshwater habitats. These two classes form well-supported monophyletic groups in most phylogenetic analyses. Nonetheless, the interordinal relationships remain largely unresolved, in particular in the largest subclass Rhodymeniophycidae that includes 70% of all species. To elucidate red algal phylogenetic relationships and study organelle evolution, we determined the sequence of 11 mitochondrial genomes (mtDNA) from 5 florideophycean subclasses. These mtDNAs were combined with existing data, resulting in a database of 25 florideophytes and 12 bangiophytes (including cyanidiophycean species). A concatenated alignment of mt proteins was used to resolve ordinal relationships in the Rhodymeniophycidae. Red algal mtDNA genome comparisons showed 47 instances of gene rearrangement including 12 that distinguish Bangiophyceae from Hildenbrandiophycidae, and 5 that distinguish Hildenbrandiophycidae from Nemaliophycidae. These organelle data support a rapid radiation and surprisingly high conservation of mtDNA gene syntheny among the morphologically divergent multicellular lineages of Rhodymeniophycidae. In contrast, we find extensive mitochondrial gene rearrangements when comparing Bangiophyceae and Florideophyceae and multiple examples of gene loss among the different red algal lineages.

Mitogenomes from type specimens, a genotyping tool for morphologically simple species: ten genomes of agar-producing red algae

DNA sequences from type specimens provide independent, objective characters that enhance the value of type specimens and permit the correct application of species names to phylogenetic clades and specimens. We provide mitochondrial genomes (mitogenomes) from archival type specimens of ten species in agar-producing red algal genera Gelidium and Pterocladiella. The genomes contain 43–44 genes, ranging in size from 24,910 to 24,970 bp with highly conserved gene synteny. Low Ka/Ks ratios of apocytochrome b and cytochrome oxidase genes support their utility as markers. Phylogenies of mitogenomes and cox1+rbcL sequences clarified classification at the genus and species levels. Three species formerly in Gelidium and Pterocladia are transferred to Pterocladiella: P. media comb. nov., P. musciformis comb. nov., and P. luxurians comb. and stat. nov. Gelidium sinicola is merged with G. coulteri because they share identical cox1 and rbcL sequences. We describe a new species, Gelidium millariana sp. nov., previously identified as G. isabelae from Australia. We demonstrate that mitogenomes from type specimens provide a new tool for typifying species in the Gelidiales and that there is an urgent need for analyzing mitogenomes from type specimens of red algae and other morphologically simple organisms for insight into their nomenclature, taxonomy and evolution.

A novel phylogeny of the Gelidiales (Rhodophyta) based on five genes including the nuclear CesA, with descriptions of Orthogonacladia gen. nov. and Orthogonacladiaceae fam. nov.

Although the Gelidiales are economically important marine red algae producing agar and agarose, the phylogeny of this order remains poorly resolved. The present study provides a molecular phylogeny based on a novel marker, nuclear-encoded CesA, plus plastid-encoded psaA, psbA, rbcL, and mitochondria-encoded cox1 from subsets of 107 species from all ten genera within the Gelidiales. Analyses of individual and combined datasets support the monophyly of three currently recognized families, and reveal a new clade. On the basis of these results, the new family Orthogonacladiaceae is described to accommodate Aphanta and a new genus Orthogonacladia that includes species previously classified as Gelidium madagascariense and Pterocladia rectangularis. Acanthopeltis is merged with Gelidium, which has nomenclatural priority. Nuclear-encoded CesA was found to be useful for improving the resolution of phylogenetic relationships within the Gelidiales and is likely to be valuable for the inference of phylogenetic relationship among other red algal taxa.

Complete mitochondrial genome of the agarophyte red alga Gelidium vagum (Gelidiales)

Abstract We describe the first complete mitochondrial genome of Gelidium vagum (Gelidiales) (24,901 bp, 30.4% GC content), an agar-producing red alga. The circular mitochondrial genome contains 43 genes, including 23 protein-coding, 18 tRNA and 2 rRNA genes. All the protein-coding genes have a typical ATG start codon. No introns were found. Two genes, secY and rps12, were overlapped by 41 bp.

Distribution patterns and introduction pathways of the cosmopolitan brown alga Colpomenia peregrina using mt cox3 and atp6 sequences

Colpomenia peregrina is an annual brown macroalga found in temperate waters worldwide. To understand population differentiation and to reconstruct pathways of colonization/introduction, we analyzed variation in two mitochondrial protein-coding genes, cytochrome c oxidase subunit III (cox3) and ATP synthase F0 subunit 6 (atp6), and cp RuBisCO spacer. A total of 359 cox3, 342 atp6, and 38 RuBisCO spacer sequences from Colpomenia peregrina were obtained for samples collected at 28 sites from 12 countries. The combined cox3 + atp6 sequences (1,231 bp) revealed 99 polymorphic sites and 69 haplotypes. An mt haplotype network revealed four distinct groups, separated by 7 to 26 mutation steps. NW Pacific populations were present in each group (but dominant in one), whereas SW Pacific and the Atlantic populations each were present in one group. The network and phylogenetic analyses, along with patterns of genetic diversity, suggested a NW Pacific center of origin, expanding first to the SW Pacific, then the NE Pacific, and most recently to the north Atlantic. A generalized skyline plot revealed a dramatic population expansion of the species ca. 20 kya.

Molecular identification of gelidioid algae (Gelidiales, Rhodophyta) from Singapore with a description of Gelidium sentosaense sp. nov.

Abstract: Gelidioid specimens from Singapore were analyzed using sequences of cox1 and rbcL to identify the species. Both datasets revealed the presence of four species: Gelidiella acerosa, Pterocladiella bartlettii, Pterocladiella caerulescens and Gelidium sentosaense sp. nov., described here. Gelidium sentosaense formed small tufts up to 1 cm high and occurred in monospecific patches on cement beds at the outlet of drainpipes at intertidal areas. A morphological investigation of fresh specimens collected from Singapore revealed that G. sentosaense was similar to Gelidium pusillum, which is limited to North Atlantic coasts. However, it was distinguished by longitudinal striations present on the surface of branches and rhizines scattered in the inner cortex and medulla. Phylogenetic analyses of rbcL and cox1 sequences revealed that G. sentosaense consistently formed a clade with Gelidium sp. from Oman and Gelidium pluma from Hawaii but it was distinct from previously described Gelidium species.

Genetic segregation and differentiation of a common subtidal alga Pterocladia lucida (Gelidiales, Rhodophyta) between Australia and New Zealand

Pterocladia lucida (Gelidiales), an important agar source in New Zealand, commonly occurs subtidally in Australia and New Zealand and is very variable in morphology. In the present study, the genetic diversity of P. lucida was investigated for 33 specimens collected in Australia and New Zealand. Phylogenetic analyses of mitochondrial cox1 and plastid rbcL sequences revealed that P. lucida specimens formed a monophyletic clade but consisted of four distinct genealogical lineages: one from Australia and three from New Zealand. The pairwise divergences between these four lineages are equal to or higher than those between other species of the family. The Australian lineage is recognized as Pterocladia lucida sensu stricto because the type of the species is from southern Australia. Our results suggest that an ancestor of the P. lucida complex from New Zealand was segregated from the Australian species and then has likely diverged into three species.

Genomic and phylogenetic analysis of Ceramium cimbricum (Ceramiales, Rhodophyta) from the Atlantic and Pacific Oceans supports the naming of a new invasive Pacific entity Ceramium sungminbooi sp. nov.

Abstract The filamentous marine red alga Ceramium cimbricum was described from Denmark, but the name has since been applied to populations worldwide. To determine if C. cimbricum from the Pacific is conspecific with C. cimbricum from the Atlantic, we (1) deciphered an authentic rbcL sequence for the lectotype specimen of C. cimbricum, (2) performed phylogenetic analysis on Pacific and Atlantic C. cimbricum, and (3) assembled and analyzed the complete mitochondrial and plastid genomes of specimens of C. cimbricum from Denmark and California. The lectotype sequence of C. cimbricum was unique and fully resolved with other Atlantic Ceramium species, however, the specimens of C. cimbricum from Denmark, Norway, California, Oregon, and Korea formed a clade with Pacific species. The plastid and mitochondrial genomes of C. cimbricum from Denmark and California were similar in length and gene content, differing by only 67 SNPs and nine gaps for the plastid, and by 100 SNPs and 31 gaps for the mitochondrial genomes. These results support the continued application of the name C. cimbricum to specimens from Denmark, and warrant the naming of a new species, Ceramium sungminbooi sp. nov., native to Asia and introduced to the northeastern Pacific and Europe.