The pattern of morphological and mtDNA cytochrome b diversity of three calanoidcopepod species belonging to the diaptomid genus Hemidiaptomus has been investigated with the aim of checking the reliability of the morphological characters currently used for species identification, and thepossible presence of cryptic taxa. A sharply different molecular structuring has been observed in the studied species: while Hemidiaptomus amblyodon exhibits a remarkable constancy throughout theEuropean range of its distribution area (maximum inter-populations cytochrome b divergence of 3%), observed distances between presumed conspecific lineages of Hemidiaptomus gurneyi (maximum divergenceof 21.5%) and Hemidiaptomus ingens (maximum19.1%) suggest that under these binomens arein fact included complexes of cryptic, or currently just unrecognized, independent evolutionary lineages. The application of the ‘‘4x rule’’ shows that the two lineages singled out within H. ingens are in fact independent evolutionary units, while the complex molecular structure observed in H. gurneyi s.l. could not be resolved based on the currently available data. Applying standard crustacean mtDNA evolutionaryrates to the observed divergence values, the separation of the main lineages within both H. ingens and H. gurneyi might dates back to the Miocene; however, it has also to be considered that the rate of mtDNA evolution might be accelerated in copepods,as already observed in other arthropod taxa.Present results gives further evidences of the high potential for copepod speciation with no or little morphological changes, and stress the need of a revision of the most controversial Palaearctic diaptomid genera.
|Numero di pagine||11|
|Stato di pubblicazione||Published - 2010|
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