Importance of natural history collections
The present study highlights the necessity of close linkages between historical museum specimens and actual biological patterns and processes including refinement of the taxonomic placement and biogeographic ranges. Therefore, it further contributes to a general recognition of taxonomy as a central biological discipline with high integrative potential for multipurpose applications. This is not the first case in which a study of historical specimens in museum collections can be applied to retrieve past species records and to reconstruct historical base lines regarding the distribution ranges of species, which can produce relevant information for the conservation of these species and their habitats (e.g. Shaffer et al., 1998; Pyke and Ehrlich, 2010; Rainbow, 2009; Drew, 2011; Ellis et al., 2011; Hoeksema et al., 2011; Lips, 2011; Hoeksema, 2015). The historical records of the present study should stimulate researchers to survey Gullmar Fjord and other localities for the present occurrence of D. velifer and for additional rarely encountered species that may be locally threatened.