Littorina neglecta Bean: ecotype or species?

Abstract

The taxonomic status of the littoral prosobranch Littorina neglecta has been investigated using animals from the northeast coast of England. Rough periwinkles were collected from barnacle-covered rock platforms near the northern (Ness Point) and southern (Old Peak) ends of Robin Hood's Bay, and from small and large boulders at the southern end. Shape was analysed in shells from all sites, and the activity levels and heat stability of aspartate aminotransferase (Aat) and alanine aminotransferase (Alat) were determined in samples from Peak Steel and a nearby boulder habitat. Of the shells from Ness Point, 98% could be separated visually, using colour, sculpturing and banding, into three categories (the oviparous L. arcana, and the ovoviviparous L. saxatilis and L. neglecta). The categories were confirmed using discriminant analysis on shell measurements and cross-validation indicates at least 70% accuracy. On Peak Steel L. saxatilis breeds at a small size and its shells are visually quite distinct from those of Peak Steel L. neglecta. In discriminant analysis 84% of the latter classify with the Ness Point L. neglecta. The enzyme studies clearly indicate that the activity level of Aat after 1 min exposure to 56°C is significantly different between Peak Steel L. saxatilis and L. neglecta. In general, it appears that there are different physiological responses in the different groups of animals depending on the zone, microhabitat and taxonomic category. The relationship between the 2 barnacle-dwelling, brooding periwinkles is discussed. It is considered that the existence of two distinct, sympatric ecotypes is unlikely, and that there is a true barnacle-dwelling ecotype of L. saxatilis that is morphologically and biochemically distinct from L. neglecta. The possibility of gene flow between these forms is currently being investigated.

Keywords :

• Prosobranchia
• Littorina
• taxonomy
• England