Algae bring life to the world – species, microbiomes and biodiversity

The first European Phycological Congress was held in Cologne, Germany in 1996. In the last 20-odd years, the meeting has been held every four years from Italy, to Northern Ireland, to Spain and Greece.

This year the meeting was held in London and as a recipient of the FEMS Meeting Attendance Grant and a little bit of field work (see here and here), I was able to attend. Not only is this one of the best meetings to attend, in my opinion, it also served as a chance for me to meet up with friends and colleagues I hadn’t seen since returning to the US in 2013.

The sessions were as varied as Shedding new light on photosynthesis and its role in global biogeochemistry, Algae-microbiome interactions, Phylogenomics and Algae in stressful environments in coastal systems. Thus, it was a very full four days of conference talks, coffee breaks and dinners.
I wanted to highlight some of the excellent presentations, though this is by no means an exhaustive review of the excellent science that was on show in Hammersmith. There’s too much for one post, so I’m going to break it up into two awesome algal posts (Rob Denton, that’s for you)!
If you are a regular reader of TME and I did not highlight your presentation at EPC, by all means contact me for a follow up interview/article highlight!

Christophe Destombe (destombe@sb-roscoff.fr; 1KN.1)
How complementary barcoding and population genetic analyses can help solve taxonomic questions at short phylogenetic distances: the example of the brown alga Pylaiella littoralis.
One problem, especially for phycologists, is the definition of a species. Species may be separated on a temporary or reversible basis. Therefore, a combined phylogenetic (barcoding) and population genetic approach can help shed light on species delimitation.
Using the brown alga Pylaiella littoralis as a model, Destombe and colleagues demonstrated the utility of this approach. P. littoralis has no morphological characters with which to help distinguish different species.

This species, not unlike Ectocarpus (Couceiro et al. 2015, Evolution 69: 1808-1822), has a haploid-diploid life cycle, is capable of both sexual and asexual reproduction and also alternates the substratum upon which it is found depending on the season. Basically, algae are complicated!
The team uncovered different species separated by spatiotemporal patterns. For example, the frequency of the mitotypes depended on the season, while different nuclear groups occupied different hosts (Group 1 was found on  Ascophyllum nodosum, Group 2 mainly on Fucus vesiculosus and Group 3 mainly on F. serratus).
For these species of Pylaiella, reproductive isolation is not complete, but interestingly, ecological specialization (e.g., different hosts used as substratum) can accelerate differentiation.
Aschwin Engelen (aengelen@ualg.pt; 4OR.1)
The microbiome of a seaweed invader across its introduced European range
Seaweeds are pretty prolific invaders, but we don’t know all that much about seaweed invasions. In this vein, Engelen and colleagues explored the impacts of the bacterial microbiome on the invasion process as well as patterns with latitudinal clines.
They measured different zones of the thallus of Sargassum muticum: the tip, receptacle, blade and holdfast.

The microbiomes segregated according to the thallus tissue, with the holdfast exhibiting the most diversity. This is likely due to the differences in longevity of the tissue in which the holdfast is perennial whereas the thallus is short lived. Moreover, the holdfast is also under the influence of the sediment on the hard substratum.
They also found a latitudinal trend from Portugal to Norway, but less pronounced than the thallus zone patterns. In Portugal, S. muticum occurs in very dense pools and is in constant contact with other conspecific thalli. In contrast, in Norway and Morocco, the thalli occur in lower density.
The latitudinal clines may be due to the environment, adaptation or population age (the invasion front vs. older populations). Nevertheless, the microbiome is likely locally obtained in the novel habitats.
Tania Aires (taniaires@gmail.com; 4OR.5)
Differentiation in bacterial communities associated to the red seaweed genus Asparagopsis in the western Atlantic and their potential drivers
The red algal genus Asparagopsis is one of the 100 most invasive species. Depending on the species, there are different number of invasive lineages.

Based on this knowledge, Aires and colleagues addressed the following questions: (i) is the bacterial community lineage specific, (ii) is the bacterial community affected by environmental factors and (iii) are environmental patterns reflected in diversity patterns.
They compared Asparagopsis species from mainland Portugal, Madeira and Cape Verde and found less bacterial diversity on the island populations. More genes associated with housekeeping functions were found on the islands, whereas, mainland Portugal populations exhibited higher bacterial diversity. There were species specific patterns and a higher percentage of strains associated with disturbed habitats on the mainland. For example, seaweeds located near populated areas had more disease-affected bacteria.
The microbiomes are determined by their holobiont hosts, but they may adapt to local conditions by selecting for certain metabolic genes.
Declan Schroeder (dsch@mba.ac.uk; 4OR.8)
Phaeoviruses extend their host range to the kelps
Brown algal viruses are related to viruses affecting animals. In 2010, Cock and colleagues (Nature 465, 617–621) found a viral genome integrated into the Ectocarpus genome. It is the only virus in which genome integration occurs and in which the virus is not lytic.
Viruses likely affect the unicellular stages as there are no cell walls, easing the infection process. After infection, it is possible for the viral genome to be integrated into the host’s genome.
Usually, viruses are species limited, but several variants of phaeoviruses have been found in the Laminariales.

These viruses are capable of infecting not only different species, but also different orders!
Lar Gamfeldt (lars.gamfeldt@gu.se; 8KN.1)
The consequences of changes in algal biodiversity

The first experimental manipulations of biodiversity began to emerge in the 1990’s and since then, there has been an exponential increase in the amount of empirical studies.
Species occupy different niches. They can be complementary in their use of different resources. Therefore, biodiversity can be an important factor influencing how ecosystems work.
Generally, communities with many species (high biodiversity) have greater biomass and use resources more efficiently. In contrast, communities with fewer species (low biodiversity) have lower biomass and less efficient use of resources.
This presentation provided an overview of the current state of this field, in terms of the research investigating the function consequences of changes in algal biodiversity. More importantly, it highlighted future directions.
Many experiments are conducted with a limited number of species in an assembly-like experiment. Species are put together and then we sit back and see what happens. Other studies, remove species (e.g., Stachowicz et al. 2008, Ecology 89:3008-3019) and as more are removed, the percent cover of algae decrease (upwards of 20% in some cases).
In a nutshell, the more diverse the community, the more multifunctionality. Yet, there is a need to move beyond the use of several species in a bottle in the lab. These experiments are great, but it is necessary to increase the realism of these studies.
James Murphy (james.murphy@nuigalway.ie; 8OR.6)
Modeling the population dynamics of invasive Undaria pinnatifida using an individual-based approach
Along with Mark Johnson and Frédérique Viard, they developed an individual-based modelling approach in order to understand the impact of wakame, or the kelp Undaria pinnatifida, on the native biodiversity in European coastal waters.
A detailed life history model, including both the microscopic gametophytes and macroscopic sporophytes was developed based on empirical data. This model was integrated with a spatio-temporal model of a coastal environment in order to make predications about potential growth dynamics under different environmental conditions.

Comparing the model predictions and field studies, they found a quantitative agreement in terms of the relative abundance, recruitment rates and the life expectancy of adult sporophytes.
This model can be adapted to explore the potential future spread of wakame in Europe as well as how these populations will respond to changing climatic conditions.

Phylogenetic and biogeographical patterns of allopolyploid speciation in an intertidal fucoid seaweed assemblage
Studies of allopolyploid speciation are best known from plants and a few vertebrate examples, however, expanding the models across the tree of life can elucidate the underlying factors leading to allopolyploid formation, establishment and evolutionary success.
Using three types of molecular markers (nDNA, mtDNA and microsatellites), João and colleagues investigated the evolutionary history of the Hesperophycus/Pelvetiopsis species complex.

They found evidence for allopolyploidy: gene paraphyly, cyto-nuclear conflict, fixed heterozygosity and allele states.
They also found evidence for the co-existence of allopolyploids with their diploid parents due to ecological divergence.

Elucidating unresolved invasion history with genome-wide sequencing approach: the case of the global invader Sargassum muticum
Sargassum muticum is a successfully established, global invader. In Europe, for example, it is found over a large latitudinal gradient of strong environmental pressures.

Over 2500 individuals were analyzed at 14 microsatellite loci. In the native range in the Pacific Northwest, there were 60 multilocus genotypes (MLG) and strong genetic differentiation, all consistent with partial selfing. By contrast, in the introduced range, there was only a single MLG!!
The team turned to RADseq and genotyped European, North American and Japanese populations. They were able to genotype 270 individuals from 20 populations over 4500 polymorphic SNPs.
They compared the microsatellites and SNPs and found consistent results in the Japanese populations. In North America and European populations, Le Cam and colleagues were able to detect some diversity and found these two regions share a similar genetic background – a significant advance from the monomorphism with the microsatellites.
Strong homozygote excess was found in the native range as well as some important sites in the introduced range.
Moreover, combining microsatellite and RADseq data, they were able to map the invasive history. S. muticum likely came from Japan through North America to Europe.
Interestingly, low genotypic diversity, even with the SNPs, in the introduced range has not limited this alga. Its invasion has been incredibly successful and could be driven by epigenetics rather than a huge repository of genetic diversity.
 
Stay tuned for highlights from the final two days of the conference next week!