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The genus Adriohydrobia (Hydrobiidae: Gastropoda): polytypic species or polymorphic populations?
Wilke, T.; Falniowski, A. (2001). The genus Adriohydrobia (Hydrobiidae: Gastropoda): polytypic species or polymorphic populations? J. Zoo. Syst. Evol. Research 39(4): 227–234. hdl.handle.net/10.1046/j.1439-0469.2001.00171.x
In: Journal of Zoological Systematics and Evolutionary Research. Wiley-Blackwell: Berlin. ISSN 0947-5745, more
Peer reviewed article  

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Keywords
    Population genetics; Adriohydrobia; Hydrobiidae Stimpson, 1865 [WoRMS]; Marine
Author keywords
    Adriohydrobia; COI; DNA sequencing

Authors  Top 
  • Wilke, T.
  • Falniowski, A.

Abstract
    In molluscs, the shell characters have historically played an important role in discrimination among species. However, because of the paucity, variability and degree of homoplasy of shell characters, their sole use for taxonomic and systematic studies is controversial in many groups. In the present paper the genus AdriohydrobiaRadoman, 1973 is used as a paradigm to test relationships of taxa that were considered to be species, mainly on the basis of the shell size variations. We tested whether the genus consists of several sympatric and polytypic species or a single species with polymorphic populations and whether the reported shell size differences, on which the description of three putative species is mainly based, are intrinsic or extrinsic. A fragment of the mitochondrial cytochrome oxidase I (COI) gene was used as an independent genetic marker. We found very little genetic variability in 40 specimens from four populations studied. The nucleotide-sequence diversity (π) within populations ranges from 0.0017 to 0.0056 and the nucleotide-sequence divergence (Dxy) between populations from 0.0018 to 0.0051. The phylogenetic network is very compact with two ‘groups’ of haplotypes that are separated by only two nucleotide positions. A plot of pairwise nucleotide differences against pairwise shell size differences did not reveal any distinct clusters and a Mantel test did not show any significant associations between the two matrices. Based on the very low genetic diversity, the lack of distinct clusters in the phylogenetic network and the lack of concordance between morphological and genetic differentiation it is concluded that only one species is involved, Adriohydrobia gagatinella. The previously reported morphogroups within Adriohydrobia are probably due to a discrete age structure in these population and/or due to the effect of trematode-induced gigantism. The observed genetic patterns in Adriohydrobia indicate a rapid population growth from an ancestral population of small evolutionary-effective size. The present study stresses the importance of testing species-level hypotheses based on shell characters using one or more independent markers.

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