Does the Cosmopolitan Diatom <i>Gomphonema parvulum</i> (Kützing) Kützing Have a Biogeography?

<div><p>Diatom cultures of the <i>G. parvulum</i> species complex were established from seven different sites in the Faroe Islands, Sweden, Germany, Mexico and Korea, and were studied in detail. Eight morphodemes were identified which corresponded to the descriptions of the cosmopolitan taxon <i>G. parvulum</i> (Kützing) Kützing sensu lato: its nominate variety (var. <i>parvulum</i>), <i>G. parvulum</i> var. <i>exilissimum</i> Grunow and <i>G. parvulum</i> f. <i>saprophilum</i> Lange-Bertalot & Reichardt, <i>G. [parvulum</i> var.] <i>lagenula</i> Kützing plus four unidentifiable morphodemes. The concatenated analysis of the sequences of the markers 18SV4, <i>rbc</i>L, and ITS as well as morphological data resulted in a separation of four taxa based on their biogeography in Mexico, Korea, central Continental Europe and Northern Atlantic Europe. Mantel tests showed a significant correlation between molecular and geographical distances. The diagnoses of two taxa, <i>G. parvulum sensu stricto</i>, and <i>G. lagenula</i>, were emended, G. <i>saprophilum</i> elevated to species rank and epitypes designated. One species was newly described.</p></div

LM photos of strains.

<p>Figs. 2.1–22. <i>Gomphonema parvulum</i> (Kützing) Kützing var. <i>parvulum</i>. Figs. 2.1–3. Strain D16_042, Figs. 2.4–6. Strain D16_044, Fig. 2.7. Strain D16_005, Fig. 2.8. Strain D16_009, Figs. 2.9–11. Strain D16_008, Figs. 2.12–15. Strain D16_004, Figs. 2.16–18. EPITYPE Strain D16_045. Figs. 2.19–20. Strain D13_034, Fig. 2.21. Strain D16_030, Fig. 2.22. Strain D16_027. Figs. 2.23. Strain D16_026, <i>Gomphonema parvulum</i> var. nov.? Figs. 2.24–25. Strain D12_022, <i>Gomphonema parvulum</i> var. <i>parvulum</i> [morphodeme exilissimum]. Figs. 2.26–28. <i>Gomphonema lagenula</i> Kützing. Figs. 2.26–27. Strain D33_006. Fig. 2.28. EPITYPE Strain D33_024. Figs. 2.29–34. <i>Gomphonema parvulum</i> var. nov.? Figs. 2.29. Strain D16_028. Figs. 2.30–34. Strain D16_011. Figs. 2.35–43. <i>Gomphonema saprophilum</i> (Lange-Bertalot & Reichardt) Abarca et al. comb. nov. Figs. 2.35–38. EPITYPE Strain D36_003. Figs. 2.39–41. Strain D20_027, Figs. 2.42–43. Strain D03_167. Figs. 2.44–49. <i>Gomphonema narodoense</i> R. Jahn et al. sp. nov. Figs. 2.44–46. HOLOTYPE Strain D23_012. Figs. 2.46–49. Strain D23_009. Scale bars represent 10 µm.</p

Morphometrics of the studied strains.

1<p>Morphometric measurements were performed at least on 10 oxidized specimens per culture.</p

Strict consensus tree of the ML analysis of the combined dataset (molecular markers 18SV4, internal transcribed spacer ITS, and <i>rbc</i>L) including Genbank sequences with the results of the SAMS analysis (arrows), bootstrap values (>75) of MP (PB) and ML (LB) as well as Bayesian posterior probabilities (PP) (>0.75).

<p>Split names indicate the splits from <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0086885#pone-0086885-g007" target="_blank">Fig. 7</a>.</p

<i>Gomphonema parvulum</i> strains from Genbank with accession number and country of origin.

2<p>also registered as <i>G.</i> cf. <i>lagenula</i> in Genbank.</p

SEM morphology of studied strains; external valve view.

<p>Frustule outline. Apices: rostrate (Fig. 3.1), capitate (Fig. 3.4) and subrostrate to subcapitate (Fig. 3.2). External raphe fissure: head pole: hooked (Fig. 3.1), strongly hooked (Fig. 3.2), undulate (Fig. 3.3), slightly deflected (Fig. 3.4) and foot pole: hooked (Fig. 3.5), strongly hooked (Fig. 3.6), undulate (Fig. 3.7), slightly deflected (Fig. 3.8, 3.9). Fig. 3.1. Strain D16_026, <i>Gomphonema parvulum</i> var. nov.?. Fig. 3.2. Strain D16_008, <i>Gomphonema parvulum</i> var. <i>parvulum</i>. Fig. 3.3. Strain D13_034, <i>Gomphonema parvulum</i> var. <i>parvulum</i>. Fig. 3.4. EPITYPE Strain D33_024, <i>Gomphonema lagenula</i>. Fig. 3.5. Strain D20_027, <i>Gomphonema saprophilum</i>. Fig. 3.6. Strain D16_008, <i>Gomphonema parvulum</i> var. <i>parvulum</i>. Fig. 3.7. Strain D16_042, <i>Gomphonema parvulum</i> var. <i>parvulum</i>. Fig. 3.8. Strain D12_022, <i>Gomphonema parvulum</i> var. <i>parvulum</i> [morphodeme exilissimum]. Fig. 3.9 Strain D23_009, <i>Gomphonema narodoense</i> R. Jahn et al. sp. Nov. Scale bars usually represent 2 µm; the bar for Fig. 3.4 represents 5 µm.</p

SEM morphology of studied strains, internal valve view.

<p>Central raphe endings: hooked (Fig. 5.2), deflected (Fig. 5.1), strongly hooked (Fig. 5.4) and parrot head-shape (Fig. 5.5). Alveoli: rectangular separated by silica struts (Fig. 5.6) and oval elongated separated by opened silica struts (Fig. 5.7). Stigma opening in internal view: short slit (Fig. 5.3), slit (Fig. 5.1), sperm-shape (Fig. 5.4) and round (Fig. 5.2). Scale bars represent 2 µm; only in Figs. 5.3 and 5.7 it represents 1 µm. Fig. 5.1. HOLOTYPE Strain D36_003, <i>Gomphonema saprophilum</i>. Fig. 5.2. Strain D23_009, <i>Gomphonema narodoense</i>. Fig. 5.3. Strain D20_027, <i>Gomphonema saprophilum</i>. Fig. 5.4. Strain D16_026, <i>Gomphonema parvulum</i> var. nov.? Fig. 5.5. Strain D12_022, <i>Gomphonema parvulum</i> var. <i>parvulum</i> [morphodeme exilissimum]. Fig. 5.6. Strain D33_006, <i>Gomphonema lagenula</i>. Fig. 5.7. D16_028, <i>Gomphonema parvulum</i> var.nov.?</p