Results of testing the comparatory method: The curvature of the shell valve frontal section is inappropriate as a systematic character for the freshwater pearl mussel of the genus Margaritifera

Trace element composition of freshwater pearl mussels Margaritifera spp. across Eurasia: Testing the effect of species and geographic location

“…Most species inhabit only oligotrophic rivers and streams; the optimal mesohabitats include riffles and runs with gravel as the prevalent riverbed substrate (Smith, 2001). In recent decades, all species of Margaritifera have become threatened due to habitat degradation, water pollution and decreased host fish abundance (Arajo et al, 2009;Bolotov et al, 2012;Makhrov et al, 2013).…”

“…It is difficult to determine whether this pattern is a reflection of i) the extinction and contraction of an ancient, formerly widespread margaritiferid fauna; ii) peripheral isolation; iii) fish host dispersal; or even iv) host switching (Huff et al, 2004). The lifespan and shell flexibility of Margaritifera species strongly depend on environmental conditions (Akiyama and Iwakuma, 2009;Bolotov et al, 2013). For example, Margaritifera margaritifera mussels living in the lower reaches of rivers grow faster than those living in the upper reaches, and the maximum size and age differ among sampling sites along the same river (Hastie et al 2000;Akiyama and Iwakuma, 2009).…”

Pearl mussels of the genus Dahurinaia (Bivalvia, Margaritiferidae): Differently sized groups of Margaritifera dahurica Middendorff, 1850

“…The discussion about the number of species in the freshwater pearl mussel M. margaritifera (Sergeeva et al, 2008;Bogatov, 2009Bogatov, , 2013Bolotov et al, 2013;Voroshilova, 2013) appeared within the framework of such terms as morphological species, which, accord ing to Mair (1971, p. 38) does not have any biological or, thus, scientific sense. Two species of this genus (M. elongata and M. borealis), which were singled out based on the morphological differences and contours of the frontal valves section (Bogatov et al, 2003), are not separate, because these differences are associated with interpopulational variations (Sergeeva et al, 2008;Bolotov et al, 2013).…”

“…The contours of the frontal section of valves were not tested as a diagnostic feature, because it is proved that the comparative method is not appropriate for this purpose, especially for large sized shells (Sergeeva et al, 2008;Bolotov et al, 2013;Voroshilova, 2013).…”

“…Among five species of the genus Kurilinaia, separated by Russian malakologists, Margaritifera laevis Haas, 1910, M. middendorffi Rosen, 1926and M. togakushiensis Kondo and Kobajashi, 2005 are valid (Graf, 2007). The number of species of the freshwater pearl mussel M. margaritifera Linnaeus, 1758, which is distributed in the northwestern part of Russia, has been also dis cussed (Sergeeva et al, 2008;Bogatov, 2009Bogatov, , 2013Bolotov et al, 2013;Voroshilova, 2013).…”