Cochlostoma asturicum ( Raven, 1990 )

Gofas, Serge, 2001, The systematics of Pyrenean and Cantabrian Cochlostoma (Gastropoda, Cyclophoroidea) revisited, Journal of Natural History 35 (9), pp. 1277-1369 : 1313-1315

Cochlostoma asturicum ( Raven, 1990)

(®gures 25±28) Obscurella (Cantabrica) asturicum Raven, 1990: 52 ±54, ®gure 45±46. Type locality: Lago de

la Ercina near Covadonga. HOLOTYPE, RMNH 56141 ; PARATYPES RMNH 56140 (Lago

de la Ercina), RMNH 56138 and UPV (Lago Enol), RMNH 56136 (Covadonga), RMNH

56139 (1 km SSE of Beyos), RMNH 56137/alc. 9117 (Des®ladero de Beyos).

Description

Shell up to 13 Ö 5.4 mm with 7 to 8 quite rounded whorls. Early whorls with a peripheral angle which is slightly apparent next to it; body whorl slightly constricted, well rounded. Sculpture weak, wrinkled, on the ®rst embryonic half whorl, then grading to crowded (25±30/mm) ribs on the second whorl. Spire whorls with quite strong, ¯exuous ribs (6±11 ribs/mm) on third to ®fth whorls; ribs slightly thickened at their termination along the suture.

Aperture strongly thickened and expanded into a collar, with a very distinct rim forming a sharp angle inside the outer lip. Peristome distinctly auriculated, gradually narrowing at the columellar insertion; collar commonly somewhat distorted.

Shell colour of a uniform reddish brown. Peristome white, more or less tinged with brownish inside.

Genitalia as in C. hidalgoi .

Remarks

Cochlostoma asturicum is always sympatric with a population of C. hidalgoi with very little, if any, diOEerentiation in microhabitat. Individuals of both species occur normally together on the same rock surfaces ( Raven, 1990: 26 and my observations). Around Lago Enol, the sympatric specimens identi®ed as C. hidalgoi are much larger and smooth and can be easily recognized. The morphological diOEerence is not so clearcut at Covadonga where C. hidalgoi is smaller and ribbed, and C. asturicum has a slight angle on the peri-umbilical part of the body whorl.

The electrophoretic data provide evidence that sympatric C. asturicum and `C. hidalgoi ’ are reproductively isolated. The sympatric populations in Covadonga and Lago Enol diOEer in ®xed or nearly ®xed alternative alleles of LAP (LAP B and LAP C respectively), IDH (IDH B and IDH A respectively) and also show important diOEerences at the ODH and PGD loci. However, the locally ®xed alleles are not exclusive to C. asturicum , but are found in monospeci®c populations of C. hidalgoi elsewhere (IDH A in all the central part of the species’ area; LAP C in most populations of C. hidalgoi where C. asturicum is absent). Paradoxically, C. hidalgoi from Enol and Covadonga resemble more, from the overall electrophoretic pro®le, the sympatric C. asturicum (Nei’s D of 0.15 to 0.25, versus more than 0.3 between distant populations of C. hidalgoi ) than the supposedly conspeci®c but more remote populations.

The results at the PGD locus are puzzling. All C. asturicum are monomorphic for PGD A, which is the normal PGD allele in C. hidalgoi elsewhere, whereas the sympatric C. hidalgoi show a unique expression with a double band on PGD gels. The current taxonomic treatment of C. asturicum as a distinct species relies mainly on the fact that it can be characterized by a de®nite morphological divergence. An alternative view would be to consider the populations with the duplicate PGD as a diOEerent species, and C. asturicum as the local representatives of C. hidalgoi with displaced morphological characters. However, this is not su ciently supported by the other data to hand and would need a much more detailed understanding of the genetic relationships between populations in the Picos de Europa area and the surroundings.