Living in a cloud: intraspecific facilitation by allelochemical mediated grazing protection 1 2

Abstract 23 Dinoflagellates are a major cause of harmful algal blooms, with consequences for coastal marine 24 ecosystem functioning and services. Alexandrium tamarense is one of the most abundant and 25 widespread toxigenic species in the temperate northern and southern hemisphere, and produces 26 paralytic shellfish poisoning toxins as well as lytic allelochemical substances. These bioactive 27 compounds may support the success of A. tamarense and its ability to form blooms. Here we 28 investigate grazing of highly (Alex2) and moderately (Alex4) allelochemical active A. tamarense 29 strains and a non-allelochemical active conspecific (Alex5) by the heterotrophic dinoflagellate 30 Polykrikos kofoidii in monoclonal and mixed experimental set-ups. While Alex4 and particularly 31 Alex5 were strongly grazed by P. kofoidii in monoclonal set-ups, both strains did grow well in 32 the mixed assemblages (Alex4+Alex5 and Alex2+Alex5). Hence, the allelochemical active 33 strains facilitate the non-active strain by protecting the population against grazing. This 34 allelochemical mediated facilitation resembles associational resistance observed in various 35 macroalgal and plant communities. Occurring intraspecifically it may partly explain the high 36 genotypic and phenotypic diversity of Alexandrium populations. It is furthermore conceivable 37 that these diverse populations comprise multiple cooperative traits that may support mutual 38 intraspecific facilitation, which in turn will promote the success of this notorious harmful algal 39 bloom species. 40 4

High Genetic Diversity and Fine-Scale Spatial Structure in the Marine Flagellate Oxyrrhis marina (Dinophyceae) Uncovered by Microsatellite Loci

Free-living marine protists are often assumed to be broadly distributed and genetically homogeneous on large spatial scales. However, an increasing application of highly polymorphic genetic markers (e.g., microsatellites) has provided evidence for high genetic diversity and population structuring on small spatial scales in many free-living protists. Here we characterise a panel of new microsatellite markers for the common marine flagellate Oxyrrhis marina. Nine microsatellite loci were used to assess genotypic diversity at two spatial scales by genotyping 200 isolates of O. marina from 6 broad geographic regions around Great Britain and Ireland; in one region, a single 2 km shore line was sampled intensively to assess fine-scale genetic diversity. Microsatellite loci resolved between 1–6 and 7–23 distinct alleles per region in the least and most variable loci respectively, with corresponding variation in expected heterozygosities (He) of 0.00–0.30 and 0.81–0.93. Across the dataset, genotypic diversity was high with 183 genotypes detected from 200 isolates. Bayesian analysis of population structure supported two model populations. One population was distributed across all sampled regions; the other was confined to the intensively sampled shore, and thus two distinct populations co-occurred at this site. Whilst model-based analysis inferred a single UK-wide population, pairwise regional FST values indicated weak to moderate population sub-division (0.01–0.12), but no clear correlation between spatial and genetic distance was evident. Data presented in this study highlight extensive genetic diversity for O. marina; however, it remains a substantial challenge to uncover the mechanisms that drive genetic diversity in free-living microorganisms

Patterns of post-glacial genetic differentiation in marginal populations of a marine microalga

Peer reviewe

FIGURE 5 in A new species of Trimma of the T. taylori species group (Teleostei: Gobiidae) from the Red Sea, Indian Ocean

FIGURE 5. Various examples of freshly collected Trimma taylori from throughout its geographic range. Group numbers ("Gr.1 x") denote haplogroups. A: Marquesas, Gr. 1a. B: Helen Reef, Palau, Gr. 1b. C: Raja Ampat, Indonesia, Gr. 1b. D: Oahu, Hawaiian Islands, Gr. 1b. E: Hithadhoo, Maldives, Gr. 1d. F: Sonsorol I., Palau, Gr. 1e. G: St. Joseph's Atoll, Seychelles, Gr. 1f. H: Chagos Archipelago, Indian Ocean, Gr. designation unassigned. Photos: A—J.T. Williams. B, C, F and H—R. Winterbottom. D—J.E. Randall. E—M.V. Erdmann. G—R. Daly.Published as part of Winterbottom, Richard, Bogorodsky, Sergey V. & Alpermann, Tilman J., 2023, A new species of Trimma of the T. taylori species group (Teleostei: Gobiidae) from the Red Sea, Indian Ocean, pp. 250-264 in Zootaxa 5353 (3) on page 259, DOI: 10.11646/zootaxa.5353.3.3, http://zenodo.org/record/842741

FIGURE 1. Trimma nubarum. A in A new species of Trimma of the T. taylori species group (Teleostei: Gobiidae) from the Red Sea, Indian Ocean

FIGURE 1. Trimma nubarum. A: Left lateral view of caudal fin and peduncle showing the wedge-shape fin, SMF 35730 (holotype), 15.8 mm SL, female. B: Dorso-lateral view of right first gill arch and gill rakers, SMF 35734, 16.3 mm SL, male. Specimens stained with cyanine blue. Photos: R. Winterbottom.Published as part of Winterbottom, Richard, Bogorodsky, Sergey V. & Alpermann, Tilman J., 2023, A new species of Trimma of the T. taylori species group (Teleostei: Gobiidae) from the Red Sea, Indian Ocean, pp. 250-264 in Zootaxa 5353 (3) on page 255, DOI: 10.11646/zootaxa.5353.3.3, http://zenodo.org/record/842741

A new species of Trimma of the T. taylori species group (Teleostei: Gobiidae) from the Red Sea, Indian Ocean

Winterbottom, Richard, Bogorodsky, Sergey V., Alpermann, Tilman J. (2023): A new species of Trimma of the T. taylori species group (Teleostei: Gobiidae) from the Red Sea, Indian Ocean. Zootaxa 5353 (3): 250-264, DOI: 10.11646/zootaxa.5353.3.3, URL: http://dx.doi.org/10.11646/zootaxa.5353.3.

FIGURE 3 in A new species of Trimma of the T. taylori species group (Teleostei: Gobiidae) from the Red Sea, Indian Ocean

FIGURE 3. Trimma nubarum, head papillae of SMF 35734, 19.6 mm SL, female. Left lateral (A) and dorsal (B) views of head to show head papillae. Papillae in any given row connected by a thin green line. Specimen stained with cyanine blue. Photo: R. Winterbottom.Published as part of Winterbottom, Richard, Bogorodsky, Sergey V. & Alpermann, Tilman J., 2023, A new species of Trimma of the T. taylori species group (Teleostei: Gobiidae) from the Red Sea, Indian Ocean, pp. 250-264 in Zootaxa 5353 (3) on page 257, DOI: 10.11646/zootaxa.5353.3.3, http://zenodo.org/record/842741

FIGURE 6 in A new species of Trimma of the T. taylori species group (Teleostei: Gobiidae) from the Red Sea, Indian Ocean

FIGURE 6. Maximum likelihood tree based on mitochondrial COI barcoding sequences of members of the Trimma taylori group including the new species T. nubarum and sequences from T. filamentosus, T. flavicaudatum, T. mendelssohni and T. quadrimaculatum as the outgroup. Group assignment (Groups 1a – 1e) follows Winterbottom et al. (2020) with Group 1f from Seychelles added accordingly. Values on branches indicate bootstrap support from 1,000 replicates in percent; bootstrap support values below 50 percent are not shown. The bar shows the average rate of nucleotide substitutions.Published as part of Winterbottom, Richard, Bogorodsky, Sergey V. & Alpermann, Tilman J., 2023, A new species of Trimma of the T. taylori species group (Teleostei: Gobiidae) from the Red Sea, Indian Ocean, pp. 250-264 in Zootaxa 5353 (3) on page 260, DOI: 10.11646/zootaxa.5353.3.3, http://zenodo.org/record/842741