Molecular phylogeny, phylogeography and population genetics of the red seaweed genus <i>Asparagopsis</i>

The red seaweed genus Asparagopsis Montagne (Bonnemaisoniales) was studied with respect to its taxonomy, phylogeny, phylogeography and population genetics. The representatives of this genus, A. armata Harvey and A. taxiformis (Delile) Trevisan, are notorious invaders. Both species occur worldwide and show disjunct distribution patterns. Such patterns may result from recent jump-dispersal or from fragmentation of once panglobally distributed species. First, a phylogeographic approach was deployed in order to delineate the taxonomic units in local scale and to assess if European populations of each of the species originated from a single introduction or multiple cryptic ones. Results showed that the two species recognized A. armata and A. taxiformis are also genetically distinct. Asparagopsis armata was found to consist of a single species worldwide, whereas A. taxiformis constituted three and probably four morphologically cryptic but genetically distinct lineages. At times, lineages were encountered in sympatry and two of them were detected in the Mediterranean Sea. In order to confirm distinction between lineages and to assess invasive potential and colonization mechanisms of the species along the western Italian coast, eight nuclear micro satellite markers were identified against the invasive lineage 2 of A. taxiformis. The markers cross-hybridised only with lineages I and 2. Moreover, it was demonstrated that carpogonia present on many female thalli can affect microsatellite reading patterns because of external (male) allelic contribution. Even after removal of the carpogonia, gametophyte thalli exhibited multiple allelic patterns, which is indicative for polyploidy. The markers were then used to assess genetic structure and diversity within and among Mediterranean populations of A. taxiformis lineages 1 and 2. Analyses based on statistics developed for polyploid species showed that the lineage l-population (HAW) was distinct from Mediterranean lineage 2 populations. A geographically distant Californian lineage 2· population was genetically distinct from the Mediterranean ones as well. The Mediterranean lineage 2-samples showed panmixia. High genotypic diversity, high gene flow, and low differentiation encountered amongst these populations probably are due to a recent invasion of this lineage into the basin

Molecular phylogeny, phylogeography and population genetics of the red seaweed genus <i>Asparagopsis</i>

The red seaweed genus Asparagopsis Montagne (Bonnemaisoniales) was studied with respect to its taxonomy, phylogeny, phylogeography and population genetics. The representatives of this genus, A. armata Harvey and A. taxiformis (Delile) Trevisan, are notorious invaders. Both species occur worldwide and show disjunct distribution patterns. Such patterns may result from recent jump-dispersal or from fragmentation of once panglobally distributed species. First, a phylogeographic approach was deployed in order to delineate the taxonomic units in local scale and to assess if European populations of each of the species originated from a single introduction or multiple cryptic ones. Results showed that the two species recognized A. armata and A. taxiformis are also genetically distinct. Asparagopsis armata was found to consist of a single species worldwide, whereas A. taxiformis constituted three and probably four morphologically cryptic but genetically distinct lineages. At times, lineages were encountered in sympatry and two of them were detected in the Mediterranean Sea. In order to confirm distinction between lineages and to assess invasive potential and colonization mechanisms of the species along the western Italian coast, eight nuclear micro satellite markers were identified against the invasive lineage 2 of A. taxiformis. The markers cross-hybridised only with lineages I and 2. Moreover, it was demonstrated that carpogonia present on many female thalli can affect microsatellite reading patterns because of external (male) allelic contribution. Even after removal of the carpogonia, gametophyte thalli exhibited multiple allelic patterns, which is indicative for polyploidy. The markers were then used to assess genetic structure and diversity within and among Mediterranean populations of A. taxiformis lineages 1 and 2. Analyses based on statistics developed for polyploid species showed that the lineage l-population (HAW) was distinct from Mediterranean lineage 2 populations. A geographically distant Californian lineage 2· population was genetically distinct from the Mediterranean ones as well. The Mediterranean lineage 2-samples showed panmixia. High genotypic diversity, high gene flow, and low differentiation encountered amongst these populations probably are due to a recent invasion of this lineage into the basin

Dietary supplementation of astaxanthin modulates skin color and liver antioxidant status of giant grouper (Epinephelus lanceolatus)

Giant grouper (Epinephelus lanceolatus) is an emerging aquaculture species in Southeast Asia and Australia with limited knowledge of its nutrient requirements and effects of supplements on its physiology. The present study investigated the effects of astaxanthin, vitamin E, and combinations on growth performance, body coloration, and the antioxidant status of juvenile giant grouper. Nine isonitrogenous (crude protein = 65 % ± 0.7 %) and isolipidic (crude lipid = 10 % ± 0.3 %) diets were formulated using a 3 × 3 factorial design, including three levels astaxanthin (0, 75, and 150 mg/kg) and vitamin E (0, 250, and 500 mg/kg), respectively. Each of the nine diets was fed to triplicate groups of 15 giant grouper (18.04 ± 0.92 g) for 30 days. Giant grouper fed the different diets exhibited no significant differences (p > 0.05) in specific growth rate (4.87 %/day - 5.21 %/day). However, dietary astaxanthin supplementation significantly enhanced the redness (a*), yellowness (b*b*), chroma, and hue values of the fin, regardless of the dose supplemented. Giant grouper fed astaxanthin at 75 and 150 mg/kg diet were more yellow and had three times higher b* values than fish fed non-supplemented diets. Further, total antioxidant capacity (TAC; mmol Trolox equivalent) in liver tissues was significantly increased in fish fed any of the astaxanthin-supplemented diets (p ≤ 0.05). In contrast, TAC levels were not affected by vitamin E supple-mentation. Malondialdehyde (MDA) levels were not significantly (p > 0.05) affected by astaxanthin or vitamin E. Findings from this study will contribute toward a better understanding of the dietary effects of antioxidant and pigment in juvenile giant grouper. We present that dietary treatment can modulate giant grouper pigmentation and may be used in the live fish trade. Further, this study contributes to narrowing the knowledge gap in formulating appropriate diets for giant grouper, which to date is fed diets formulated for other species

Molecular phylogeny, phylogeography and population genetics of the red seaweed genus 'Asparagopsis'

EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Testing cophylogeny between coral reef invertebrates and their bacterial and archaeal symbionts

Marine invertebrates harbour a complex suite of bacterial and archaeal symbionts, a subset of which are probably linked to host health and homeostasis. Within a complex microbiome it can be difficult to tease apart beneficial or parasitic symbionts from nonessential commensal or transient microorganisms; however, one approach is to de- tect strong cophylogenetic patterns between microbial lineages and their respective hosts. We employed the Procrustean approach to cophylogeny (PACo) on 16S rRNA gene derived microbial community profiles paired with COI, 18S rRNA and ITS1 host phylogenies. Second, we undertook a network analysis to identify groups of microbes that were co-occurring within our host species. Across 12 coral, 10 octocoral and five sponge species, each host group and their core microbiota (50% prevalence within host species replicates) had a significant fit to the cophylogenetic model. Independent assessment of each microbial genus and family found that bacteria and archaea af- filiated to Endozoicomonadaceae, Spirochaetaceae and Nitrosopumilaceae have the strongest cophylogenetic signals. Further, local Moran's I measure of spatial auto- correlation identified 14 ASVs, including Endozoicomonadaceae and Spirochaetaceae, whose distributions were significantly clustered by host phylogeny. Four co-occurring subnetworks were identified, each of which was dominant in a different host group. Endozoicomonadaceae and Spirochaetaceae ASVs were abundant among the subnet- works, particularly one subnetwork that was exclusively comprised of these two bacterial families and dominated the octocoral microbiota. Our results disentangle key microbial interactions that occur within complex microbiomes and reveal long- standing, essential microbial symbioses in coral reef invertebrates

Diversity of marine-derived fungal cultures exposed by DNA barcodes: the algorithm matters

Marine fungi are an understudied group of eukaryotic microorganisms characterized by unresolved genealogies and unstable classification. Whereas DNA barcoding via the nuclear ribosomal internal transcribed spacer (ITS) provides a robust and rapid tool for fungal species delineation, accurate classification of fungi is often arduous given the large number of partial or unknown barcodes and misidentified isolates deposited in public databases. This situation is perpetuated by a paucity of cultivable fungal strains available for phylogenetic research linked to these data sets. We analyze ITS barcodes produced from a subsample (290) of 1781 cultured isolates of marine-derived fungi in the Bioresources Library located at the Australian Institute of Marine Science (AIMS). Our analysis revealed high levels of under-explored fungal diversity. The majority of isolates were ascomycetes including representatives of the subclasses Eurotiomycetidae, Hypocreomycetidae, Sordariomycetidae, Pleosporomycetidae, Dothideomycetidae, Xylariomycetidae and Saccharomycetidae. The phylum Basidiomycota was represented by isolates affiliated with the genera Tritirachium and Tilletiopsis. BLAST searches revealed 26 unknown OTUs and 50 isolates corresponding to previously uncultured, unidentified fungal clones. This study makes a significant addition to the availability of barcoded, culturable marine-derived fungi for detailed future genomic and physiological studies. We also demonstrate the influence of commonly used alignment algorithms and genetic distance measures on the accuracy and comparability of estimating Operational Taxonomic Units (OTUs) by the automatic barcode gap finder (ABGD) method. Large scale biodiversity screening programs that combine datasets using algorithmic OTU delineation pipelines need to ensure compatible algorithms have been used because the algorithm matters

Diverse coral reef invertebrates exhibit patterns of phylosymbiosis

Microbiome assemblages of plants and animals often show a degree of correlation with host phylogeny; an eco-evolutionary pattern known as phylosymbiosis. Using 16S rRNA gene sequencing to profile the microbiome, paired with COI, 18S rRNA and ITS1 host phylogenies, phylosymbiosis was investigated in four groups of coral reef invertebrates (scleractinian corals, octocorals, sponges and ascidians). We tested three commonly used metrics to evaluate the extent of phylosymbiosis: (a) intraspecific versus interspecific microbiome variation, (b) topological comparisons between host phylogeny and hierarchical clustering (dendrogram) of host-associated microbial communities, and (c) correlation of host phylogenetic distance with microbial community dissimilarity. In all instances, intraspecific variation in microbiome composition was significantly lower than interspecific variation. Similarly, topological congruency between host phylogeny and the associated microbial dendrogram was more significant than would be expected by chance across all groups, except when using unweighted UniFrac distance (compared with weighted UniFrac and Bray-Curtis dissimilarity). Interestingly, all but the ascidians showed a significant positive correlation between host phylogenetic distance and associated microbial dissimilarity. Our findings provide new perspectives on the diverse nature of marine phylosymbioses and the complex roles of the microbiome in the evolution of marine invertebrates