The Role of Photobionts as Drivers of Diversification in an Island Radiation of Lichen-Forming Fungi

Speciation in oceanic islands has attracted the interest of scientists since the 19th century. One of the most striking evolutionary phenomena that can be studied in islands is adaptive radiation, that is, when a lineage gives rise to different species by means of ecological speciation. Some of the best-known examples of adaptive radiation are charismatic organisms like the Darwin finches of the Galapagos and the cichlid fishes of the great African lakes. In these and many other examples, a segregation of the trophic niche has been shown to be an important diversification driver. Radiations are known in other groups of organisms, such as lichen-forming fungi. However, very few studies have investigated their adaptive nature, and none have focused on the trophic niche. In this study, we explore the role of the trophic niche in a putative radiation of endemic species from the Macaronesian Region, the Ramalina decipiens group. The photobiont diversity was studied by Illumina MiSeq sequencing of the ITS2 region of 197 specimens spanning the phylogenetic breadth and geographic range of the group. A total of 66 amplicon sequence variants belonging to the four main clades of the algal genus Trebouxia were found. Approximately half of the examined thalli showed algal coexistence, but in most of them, a single main photobiont amounted to more than 90% of the reads. However, there were no significant differences in photobiont identity and in the abundance of ITS2 reads across the species of the group. We conclude that a segregation of the trophic niche has not occurred in the R. decipiens radiation.

Phylogeny, Phylogeography and Population Connectivity of Lessonia (Phaeophyceae)

<p>The brown algal genus Lessonia is distributed in the Southern Hemisphere where it can form dominant kelp beds on the exposed rocky shores of New Zealand, South America and Tasmania. Its disjunct distribution within the West Wind Drift contrasts with the view that it is a poor disperser. Apart from studies in Chile, where it is an economically important genus, little is known about Lessonia and in some areas even the number of species is unknown. Using different genetic markers I examined the phylogeny, phylogeography, and the connectivity of populations in Lessonia. Using the literature, species affiliations and nomenclatural problems have been investigated. Combining the sequences of three mitochondrial, one chloroplast and two nuclear markers, a supermatrix approach was used to investigate the phylogenetic relationship and the timing of speciation for all known Lessonia species. The Australasian Lessonia species form a clade within a paraphyletic grouping of South American species. Radiation in Lessonia occurred about 5 Mya at the beginning of the Pliocene and rapid radiation took place in Australasia 3.5 Mya. The data also revealed cryptic species within a L. variegata species complex. Further analysis within the Australasian clade, using mitochondrial (atp8-sp) and chloroplast (rbc-sp) markers and wider sampling (469 individuals from 57 sample sites) supported four cryptic species and revealed localized distribution for all Australasian lineages. Genetic breaks between Lessonia lineages corresponded well to known biogeographic regions and could be correlated to the geographic structure of New Zealand at the end of the Pliocene. The Cook Strait region was analysed more closely with newly developed microsatellite markers to test the influence of geographic breaks (Cook Strait and Palliser Bay) on the connectivity of populations. The results suggested that connectivity depends on the width of unsuitable habitat, and within inner Cook Strait it is facilitated by sometimes strong tidal flows that create turbulences and unique current patterns. The results implied that rafting is an important mean of dispersal. The study of the early literature on Lessonia supported the new lectotypification of L. flavicans but revealed that L. frutescens and possibly L. ovata (supported by images of rediscovered herbarium material) are synonymous to L. searlesiana and as the older epithets they should have priority. Suggestions have been made for the lectotypification of L. fuscescens and L. ovata. In general Lessonia shows non-overlapping distribution in Australasia but overlapping distribution in South America. Despite being a poor disperser, indicated by fine scale genetic structure, Lessonia is also able to connect populations over wide areas of unsuitable habitats.</p>

Phylogeny, Phylogeography and Population Connectivity of Lessonia (Phaeophyceae)

<p>The brown algal genus Lessonia is distributed in the Southern Hemisphere where it can form dominant kelp beds on the exposed rocky shores of New Zealand, South America and Tasmania. Its disjunct distribution within the West Wind Drift contrasts with the view that it is a poor disperser. Apart from studies in Chile, where it is an economically important genus, little is known about Lessonia and in some areas even the number of species is unknown. Using different genetic markers I examined the phylogeny, phylogeography, and the connectivity of populations in Lessonia. Using the literature, species affiliations and nomenclatural problems have been investigated. Combining the sequences of three mitochondrial, one chloroplast and two nuclear markers, a supermatrix approach was used to investigate the phylogenetic relationship and the timing of speciation for all known Lessonia species. The Australasian Lessonia species form a clade within a paraphyletic grouping of South American species. Radiation in Lessonia occurred about 5 Mya at the beginning of the Pliocene and rapid radiation took place in Australasia 3.5 Mya. The data also revealed cryptic species within a L. variegata species complex. Further analysis within the Australasian clade, using mitochondrial (atp8-sp) and chloroplast (rbc-sp) markers and wider sampling (469 individuals from 57 sample sites) supported four cryptic species and revealed localized distribution for all Australasian lineages. Genetic breaks between Lessonia lineages corresponded well to known biogeographic regions and could be correlated to the geographic structure of New Zealand at the end of the Pliocene. The Cook Strait region was analysed more closely with newly developed microsatellite markers to test the influence of geographic breaks (Cook Strait and Palliser Bay) on the connectivity of populations. The results suggested that connectivity depends on the width of unsuitable habitat, and within inner Cook Strait it is facilitated by sometimes strong tidal flows that create turbulences and unique current patterns. The results implied that rafting is an important mean of dispersal. The study of the early literature on Lessonia supported the new lectotypification of L. flavicans but revealed that L. frutescens and possibly L. ovata (supported by images of rediscovered herbarium material) are synonymous to L. searlesiana and as the older epithets they should have priority. Suggestions have been made for the lectotypification of L. fuscescens and L. ovata. In general Lessonia shows non-overlapping distribution in Australasia but overlapping distribution in South America. Despite being a poor disperser, indicated by fine scale genetic structure, Lessonia is also able to connect populations over wide areas of unsuitable habitats.</p>

Organelle Genome Variation in the Red Algal Genus Ahnfeltia (Florideophyceae)

The agarophyte Ahnfeltia (Ahnfeltiales, Rhodophyta) is a globally widespread genus with 11 accepted species names. Two of the most widespread species in this genus, A. plicata and A. fastigiata, may have diverged genetically due to past geographic changes and subsequent geographic isolation. To investigate this genomic and genetic diversity, we generated new plastid (ptDNAs) and mitochondrial genomes (mtDNAs) of these Ahnfeltia species from four different regions (A. plicata - Chile and UK and A. fastigiata - Korea and Oregon). Two architecture variations were found in the Ahnfeltia genomes: in ptDNA of A. fastigiata Oregon, the hypothetical pseudogene region was translocated, likely due to recombination with palindromic repeats or a gene transfer from a red algal plasmid. In mtDNA of A. fastigiata Korea, the composition of the group II intronic ORFs was distinct from others suggesting different scenarios of gain and loss of group II intronic ORFs. These features resulted in genome size differences between the two species. Overall gene contents of organelle genomes of Ahnfeltia were conserved. Phylogenetic analysis using concatenated genes from ptDNAs and mtDNAs supported the monophyly of the Ahnfeltiophycidae. The most probable individual gene trees showed that the Ahnfeltia populations were genetically diversified. These trees, the cox1 haplotype network, and a dN/dS analysis all supported the theory that these Ahnfeltia populations have diversified genetically in accordance with geographic distribution.

Endoplura jejuensis sp. nov. and Endoplura koreana sp. nov. (Ralfsiales, Phaeophyceae) from Korea based on molecular and morphological analyses

The crustose brown algal genus Endoplura has been known as a monotypic genus characterized by its intercalary plurangial reproductive structures composed of 2–4 separate parallel filaments terminated by 2–5 sterile cells and by containing several to many chloroplasts per cell. In this study, Endoplura jejuensis sp. nov. and E. koreana sp. nov. from Korea are newly described based on molecular and morphological analyses. Our phylogenetic analyses of the rbcL gene reveal that E. jejuensis sp. nov. and E. koreana sp. nov. are placed in the same clade with “E. aurea” from Japan with a strong bootstrap supporting value. E. jejuensis is characterized by small and light to dark brown crustose thalli of less than 1 cm diameter, tufts of hairs arising from the basal disc, plurangia composed mostly of two separate parallel reproductive filaments terminated by 2–4 sterile cells, and sessile unangia each with a single paraphysis. E. koreana is distinguished by olive or yellowish-brown crustose thalli of up to 3 cm diameter, tufts of hairs arising from the basal disc, and apical parts of erect filaments, plurangia with 2–5 separate reproductive filaments terminated by 2–8 sterile cells, and sessile unangia with 1–2 paraphyses. Our studies also show that “E. aurea” specimens from Japan may be recognized to be a different species from other Endoplura species.

Modeling the growth and sporulation dynamics of the macroalga Ulva in mixed-age populations in cultivation and the formation of green tides

Ulva is a widespread green algal genus with important ecological roles and promising potential as a seagriculture crop. One of the major challenges when cultivating Ulva is sudden biomass disappearance, likely caused by uncontrolled and unpredicted massive sporulation. However, the dynamics of this process are still poorly understood. In this study, we propose a mathematical model describing the biomass accumulation and degradation of Ulva, considering the potential impact of sporulation inhibitors. We developed a differential equation model describing the time evolution of Ulva biomass. Our model simulates biomass in compartments of different Ulva ‘age’ classes, with varying growth and sporulation rates. Coupled with these classes is a differential equation describing the presence of a sporulation inhibitor, produced and secreted by the algae. Our model mimics observed Ulva dynamics. We present Ulva's biomass accumulation under different initial algae population age distributions and sporulation rates. Furthermore, we simulate water replacement, effectively depleting the sporulation inhibitor, and examine its effects on Ulva's biomass accumulation. The model developed in this work is the first step towards understanding the dynamics of Ulva growth and degradation. Future work refining and expanding our results should prove beneficial to the ecological research and industrial growth of Ulva.

Discovery of a novel brown algal genus and species Setoutiphycus delamareoides (Phaeophyceae, Ectocarpales) from the Seto Inland Sea, Japan

We describe a new genus and species of brown algae from the Seto Inland Sea, Japan. This species is similar to Delamarea in gross morphology and anatomy, but distinctive in having longer thalli with rare branching and shorter cortical cells. In culture, pluri-zoids derived from plurilocular zoidangia on the erect thalli developed into filamentous gametophytes bearing ectocarpoid plurilocular zoidangia, but also formed parenchymatous erect thalli of sub-sympodial growth similar to Trachynema often having branches, and formed lateral and terminal plurilocular zoidangia. Molecular phylogenies using concatenated chloroplast and mitochondrial gene sequences showed the new alga nested in the clade composed of ectocarpalean genera with diffuse growth, parenchymatous thalli, and multiple chloroplasts, but this species is distinctive. Therefore, we propose Setoutiphycus delamareoides gen. & sp. nov. for this new alga, and provisionally place it in Chordariaceae, Ectocarpales. The Seto Inland Sea repeatedly dried during sea level regressions during glacial periods, and the present sea level recovered after the last glacial maximums (LGM), ca. 10,000 years ago. Therefore, it is unlikely that the species evolved within this area. Its distribution in the area may be explained as a remnant population that survived in refugia in southern Japan during the LGM.

First Molecular Record and Distribution of Padina pavonica (Linnaeus) Thivy from the Southern Black Sea

Padina is a brown algal genus widely distributed in warm-temperate and tropical regions. Species-level identification of specimens is often difficult due to intraspecific and interspecific morphological plasticity. This study reveals the results of the phylogenetic relationships of specimens, by analyzing the cytochrome oxidase subunit 3 (Cox3) and RuBisCO large subunit (rbcL) gene sequences. A total of 144 new sequences were analyzed together with other Padina sequences obtained from GenBank. Phylogenetic inference identified one well-resolved clade. All of these analyses showed that this genus has only one species in the Black Sea. This is the first study on the molecular diagnosis of macroalgae in the Black Sea, and it contains the first molecular records of Padina in the Black Sea Region.

Molecular data reveals two new species of Hypnea (Cystocloniaceae, Rhodophyta) from India: Hypnea indica sp. nov. and Hypnea bullata sp. nov.

We used three molecular markers (COI-5P, rbcL and UPA) to investigate the diversity of Hypnea spp., an economically important red algal genus, collected from India. Our concatenated tree (COI-5P and rbcL) supported the monophyly of two new species, Hypnea indica sp. nov. and Hypnea bullata sp. nov. H. indica diverged from its closest two sister species, Hypnea cervicornis and Hypnea tenuis (by 15.9 and 11.2%, respectively, in COI-5P; and 3.4 and 3.2% in rbcL). We describe H. indica as a new species characterised by an erect, percurrent main axis with spine-like branchlets in acute angles, straight and forked apices, axial cells surrounded by large periaxial cells or two cells similar in size to the axial cell, and the presence of lenticular thickening in the cross-section of the thallus. H. bullata diverged from its closest sister species, Hypnea brasiliensis (by 10.9% in COI-5P and 3.3% in rbcL). H. bullata is characterized by a prostrate thallus up to 1.5 cm in height, highly anastomosed, with an axial cell surrounded by similar sized, or smaller, periaxial cells, tetrasporangia present near the base of branchlets, and the presence of lenticular thickening.