Using Molecular Markers to Discriminate Lamprey Species and Populations: The Case of the European Brook and River Lampreys

In most lamprey genera, groups of two or more species exist in which the larvae are morphologically similar but the adults adopt different life history types. The European river and brook lampreys, Lampetra fluviatilis (L.) and Lampetra planeri (Bloch), are one of these so called “paired species”. L. fluviatilis is parasitic and anadromous and L. planeri is non-parasitic and freshwater resident. Here we are interested in understanding the relationship of the European brook and river lampreys, exploring the validity of the classification of this species pair as two separate taxa, pointing out the possibility of two ecotypes of a single species instead. Several studies based essentially on allozyme and mitochondrial DNA (mtDNA) markers revealed a notorious lack of differentiation between members of paired species. Microsatellite loci have been used to infer phylogenetic relationships at levels below the species level or for recently diverged species. To explore whether ecological or genetic factors determine the adults’ life-history strategy, the allele frequency differences in about 15 microsatellite markers between sympatric populations of L. fluviatilis and L. planeri are being analysed. The knowledge about the specific status of these taxa will have an important impact on their conservation status. Focusing on the phylogeographic pattern of this species pair, the genetic structure of the genus Lampetra within the Iberian Peninsula was investigated. The Iberian Peninsula has been identified as one of the most important glacial refugia in the European subcontinent during the Pliocene and Pleistocene epochs. We used two mitochondrial DNA markers, and surveyed individuals of L. fluviatilis and L. planeri from 21 sites along their distribution range in the Iberian Peninsula. The results indicate the existence of four highly divergent allopatric evolutionary lineages that evolved by fragmentation during the Ice Ages, and suggest restricted dispersal ability of the anadromous form. Also, the high level of genetic divergence between the four lineages suggests the existence of a complex of incipient or cryptic resident species and allows the definition of discrete population units for L. planeri and L. fluviatilis within the Iberian Peninsula. The morphological differentiation between population units contribute to a better understanding of the taxonomic status and relationships of Iberian populations of the resident form, L. planeri. The results gathered so far provide new insight into the knowledge of the pattern of genetic structure and evolutionary processes that occur in this genus and will have major conservation implications to this threatened species pair.