Cymbella affinis Kuetz, 1844

Silva, Weliton Jose da, Jahn, Regine, Ludwig, Thelma Alvim Veiga, Hinz, Friedel & Menezes, Mariangela, 2015, Typification and taxonomic status re-evaluation of 15 taxon names within the species complex Cymbella affinis / tumidula / turgidula (Cymbellaceae, Bacillariophyta), PhytoKeys 53, pp. 1-25 : 3

Cymbella affinis Kuetz Figs 1-7

Cymbella affinis Kütz., Bacill., 80, Pl. 6 Fig. 15, 1844.

Lectotype.

3rd figure from the left in Kützing (1844, pl. 6, Fig. 15) designated by Tuji (2007).

Type locality.

"Falaise (France): De Brébisson! Herb. Binder., Schleswig: Herb. Binder.!"

Epitype.

An individual on preparation BM18530, from Kützing packet 333, in the Natural History Museum (BM), designated by Tuji (2007, Fig. 9).

Epitype locality.

Falaise, France, coll. De Brébisson.

Valvae lanceolate, dorsiventral, dorsal and ventral margins convex; ends barely protracted, rounded, to slightly subrostrate or subcapitate; length 22.5-26.5 µm, breadth 7.0-8.5 µm, L/B ratio 2.9-3.4; axial area narrow, linear-arched, indistinct central area; striae 9-12 in 10 µm, becoming 11-18 towards ends, one isolated pore at end of central striae on ventral side; 19-27 punctae in 10 µm.

Remarks.

Although Krammer (2002, p. 41) used material sampled by the same collector and from the same locality and related his new preparation to the type locality, his effort did not constitute a typification of Cymbella affinis as ruled by the ICN (Art. 7.10, McNeill et al. 2012). On the other hand, Tuji (2007) was the first to consider the original material of this taxon and performed a lectotypification and epitypification, and as such, must be followed according to Articles 9.19 and 9.20 ( McNeill et al. 2012).

The lectotype valve of Cymbella affinis is similar to the lectotype valve of Cymbella excisa , except for the excision in the middle part of the valve present in the majority of specimens (Figs 8-21 ). Populations of this complex from different parts of the world may or may not have excisions, but this character is present in the majority of specimens from the populations examined ( Krammer 2002). Therefore, we consider Cymbella excisa and Cymbella affinis as belonging to the same species with differences at the varietal rank based on phenotypic expression and ecological modifications. Genetic studies are still to be completed.

The two taxa were both proposed by Kützing (1844, p. 80) and therefore have the same priority. In similar cases, Article 11.5 of the ICN rules that "the first such choice to be effectively published establishes the priority of the chosen name".

Grunow (1882) proposed the new combination and the new status of Cymbella excisa for Cymbella affinis var. excisa ( Kütz.) Grunow. This was the first publication that defined the priority of the epithet affinis over excisa at the specific level. Therefore, the name Cymbella affinis must be considered to be the name of the species when Cymbella excisa and Cymbella affinis are considered to be the same species, in conformity with Article 11.5 of the ICN ( McNeill et al. 2012).

Cymbella affinis valves sensu Patrick and Reimer (1975, p. 57) have similar outlines as Cymbella affinis in the type population, but higher range of length and breadth values (length: 20-50 vs. 22.5-26.5 µm; breadth: 7-12 vs. 7.0-8.3 µm, respectively). However, these authors ( Patrick and Reimer 1975), included representatives of different localities that could encompass different varieties subscribed to this taxon. The density of striae in the material from USA was similar in the middle part of the valve compared to the type material (9-11 vs. 9-12 striae in 10 µm, respectively) and lower when comparing them close to the ends of the valvae (12-14 vs. 11-18 striae in 10 µm, respectively) ( Patrick and Reimer 1975).

Cymbella excisa var. procera Krammer (Figs 22-28 ), Cymbella excisa var. angusta Krammer (Figs 39-35 ) and Cymbella excisa var. subcapitata Krammer (Figs 36-42 ) also appear to be conspecific with Cymbella affinis , but the types show slight differences in their outlines and metric characteristics (Table 1 ). Thus, all these taxa are here transferred to Cymbella affinis using their respective infraspecific epithet.

Figures

Figures 1 - 28. Cymbella affinis species complex 1 - 7 Cymbella affinis Kuetz. var. affinis 8 - 14 Cymbella affinis var. excisa (Kuetz.) Grunow, specimens from Trieste in preparation BM 18543 11 Lectotype, designated here 15 - 21 Cymbella affinis var. excisa [- Cymbella excisa sensu Krammer], specimens from Trieste in preparation 1131 IOK 16 Isolectotype, designated here 22 - 28 Cymbella affinis var. neoprocera W. Silva, specimens from Germany in preparation 212 A IOK, holotype 22 Lectotype, designated here. Scale bar: 10 µm.

Figures 29 - 42. Cymbella affinis species complex 29 - 35 Cymbella affinis var. angusta (Krammer) W. Silva, specimens from Croatia in preparation 752 IOK, holotype 29 Lectotype, designated here 36 - 42 Cymbella affinis var. subcapitata (Krammer) W. Silva, specimens from Hungary in preparation 717 IOK, holotype 39 Lectotype, designated here. Scale bar: 10 µm.