Genetic evidence for the occurrence of a cryptic species with the littoral nemerteansLineus ruberandL. viridis(Nemertea: Anopla)

✍ Scribed by A. D. Rogers; J. P. Thorpe; R. Gibson

• Book ID: 104733990
• Publisher: Springer-Verlag
• Year: 1995
• Tongue: English
• Weight: 992 KB
• Volume: 122
• Category: Article
• ISSN: 0025-3162
• DOI: 10.1007/bf00348944

✦ Synopsis

Lineus ruber and L. viridis are common intertidal heteronemerteans found on the coasts of northern Europe and the east coast of North America. The two species resemble each other morphologically and were synonymised for many years prior to being separated on the basis of larval development. In this study, specimens ofL. ruber and L. viridis were collected from sites along the west and southwest coast of Britain, northern France and the east coast of North America. The external morphology and allele frequencies of isozymes of the two species were compared from all sites. The external morphology of L. ruber and L. viridis was similar but they could generally be separated by colour. Allele frequencies for up to 13 enzyme loci between sympatric populations of L. ruber and L. viridis indicated that these two species are genetically very different (Nei's genetic identity= 0.090 to 0.083). Allelefrequency data also indicated the presence of a third genetic type occurring sympatrically with populations of both L. ruber and L. viridis on the coasts of Britain and France but not on the coast of North America. Fixed differences in allele frequencies between populations of the third genetic type and sympatric populations ofL. ruber and L. viridis were observed across multiple loci. Genetic identity between the third genetic type and sympatric populations of L. ruber and L. viridis were extremely tow (Nei's genetic identity = < 0.078). Such large genetic differences between populations indicate a barrier to gene flow and reproductive isolation. The aberrant type, which exhibits sufficient morphological variation to prevent individuals be-Communicated by J.