Vertebrata fruticulosa (Wulfen) Kuntze, 1891

Piñeiro-Corbeira, Cristina, Maggs, Christine A., Rindi, Fabio, Bunker, Francis, Baldock, Lin & Díaz-Tapia, Pilar, 2020, Molecular assessment of the tribes Streblocladieae and Polysiphonieae (Rhodomelaceae, Rhodophyta) in the British Isles reveals new records and species that require taxonomic revision, Cryptogamie, Algologie 20 (8), pp. 55-72 : 60

Vertebrata fruticulosa (Wulfen) Kuntze

MOLECULAR IDENTIFICATION

In total 18 rbc L sequences, 16 newly determined, are available for specimens morphologically identified as Vertebrata fruticulosa from the United Kingdom, the Atlantic Iberian Peninsula and the Mediterranean. They were resolved in the rbc L phylogeny ( Fig. 2 ) in a fully supported clade that also included sequences of V.thuyoides (Harvey) Kuntze , V. tripinnata (Harvey) Kuntze , V. subulifera (C.Agardh) Kuntze and V. furcellata (C.Agardh) Kuntze.Within this clade, specimens assigned to V. fruticulosa formed two clades that diverged by 3-3.3% (21-24 bp) and that are labelled in Figure 2 as V. fruticulosa and V. martensiana . Two haplotypes of V. fruticulosa were 0.6% (4 bp) divergent. Specimens of the V. fruticulosa clade were only found in the Mediterranean, including the Adriatic Sea, its type locality. Vertebrata martensiana has a wider distribution including the Adriatic Sea, the Atlantic Iberian Peninsula and the United Kingdom. Two haplotypes were found in the Atlantic and a third one in the Mediterranean and they diverged by 0.3-0.4% (4-6 bp).

MORPHOLOGICAL OBSERVATIONS

Specimens that were initially identified as Vertebrata fruticulosa ( Fig. 4 ) were predominantly erect, attached to the substratum by short prostrate axes that bear rhizoids cut off from the pericentral cells. Thalli were composed of several main axes that bear branches pseudodichotomously at wide angles (>30°) ( Fig. 4A, E, I ). They were 250-900 in diameter in mid-parts of the thallus. Trichoblasts were absent or scarcely developed. Axes had 8-12 pericentral cells and were corticate ( Fig. 4D, H, L ). Specimens of the V. fruticulosa and V. martensiana clades can be distinguished by the morphological characters indicated below.

Specimens placed in the V. fruticulosa clade had main axes of indeterminate growth that were alternately branched at regular intervals and bore alternate branches of determinate growth ( Fig. 4A, B ). Determinate branches, in turn, bore 2-3 orders of branches mostly every 3 segments ( Fig. 4C ) and were 7-9 mm in length. Axes had 11-12 pericentral cells ( Fig. 4D ).

The specimens in the V. martensiana clade had main axes branched at irregular intervals and bore branches of determinate growth ( Fig. 4E, F, I, J ). Mediterranean specimens had simple or once-branched determinate branches that were 1.5 mm in length ( Fig. 4G ). Axes had 8-10 pericentral cells ( Fig. 4H ). Atlantic specimens had determinate branches 3-5 mm in length that were simple or bore up to 2 branching orders ( Fig. 4K ) and axes with 8-12 pericentral cells ( Fig. 4L ).

Figures

FIG. 2. — Phylogenetic tree estimated with ML analysis of rbcL sequences. Values at nodes indicate bootstrap support (BP) (only shown if ≥70). Species analysed in this study are grey-shaded and species or haplotypes found in the British Isles are in bold. For P. morrowii Harvey, the number (n) of sequences available for each haplotype is indicated. Codes for countries/regions: AD, Adriatic Sea; AR, Argentina; AUS, Australia; BC, British Columbia; CH, Chile; EN, England; FR, France; GUE, Guernsey; IR, Ireland; JA, Japan; KO, Korea; LG, Ligurian Sea; NZ, New Zealand; PO, Portugal; SP, Spain.

FIG. 4. — Vertebrata fruticulosa (Wulfen) Kuntze: A, habit; B, lateral branch bearing determinate branches; C, determinate branches bearing two-three branching orders; D, cross-section of an axis with 11 pericentral cells. Vertebrata martensiana (Kützing) Piñeiro-Corbeira, Maggs & Díaz-Tapia from the Mediterranean Sea: E, F, habit; G, upper part of an erect axis with alternate determinate branches that are once branched; H, cross-section of an axis with eight pericentral cells. Vertebrata martensiana from the British Isles: I, J, habit; K, upper parts of erect axes with alternate determinate branches that are once or twice branched; L, cross-section of an axis with ten pericentral cells. Scale bars: A, B, E, F, I, J, 10 mm; C, D, H, K, L, 100 µm; G, 1000 µm.