Natural history museums as repositories of endangered diversity: the case of the United States Unionida in the Museo di Zoologia

The importance of natural history museums is often underappreciated, but they provide society with a number of services. Among these, they are a fundamental tool for assessing extinction rates and range contractions, or the only way to access species extinct in historical times. In this perspective, we describe here the collection of Unionida of the Museo di Zoologia dell’Università di Bologna, containing one extinct (Epioblasma haysiana) and nine threatened species, plus another 47 species. The collection was built in the mid-19th century and potentially provides baseline information for specialists. In the fragmented natural history museum system of Italy, this might be just the tip of the iceberg of a significant and important amount of material collected in the 19th and early-20th century.


Introduction
Natural history museums provide society with a number of indispensable, although often underappreciated, services in the fields of homeland security, public health and safety, agriculture, monitoring of environmental change, traditional taxonomy and systematics (Suarez and Tsutsui 2004). They are also indispensable for the study of the state and trends of biodiversity, providing baseline information useful to assess change at the genetic, species, community and landscape level. They are sometimes the only repositories of specimens of taxa which have gone extinct in historical times, and allow studies on endangered taxa avoiding new captures.
The 'Museo di Zoologia dell'Università di Bologna' is no exception. In its present form, it dates back to the 1930s, but it actually contains specimens dating back to the 16 th century (collected by Ulisse Aldrovandi, 1522-1605). It was then enriched by the collections of F. Cospi (1609-1686) and L.F. Marsigli (1658Marsigli ( -1730, and further developed during the 19 th century, mainly due to the work of its directors C. Ranzani (1775-1841) and G.G. Bianconi (1809Bianconi ( -1878, and 20 th century, due to the commitment of A. Ghigi (1875A. Ghigi ( -1970. The value of the museum as repository of specimens of extinct or endangered species has been already recognized for vertebrates; for example it contains a head of a great auk, Pinguinus impennis (Linnaeus, 1758), which became extinct in the mid-19 th century. However, no recognition was ever given to the value of its invertebrate collections, of which here we present the North-American Unionida.
The Unionida is a diverse order of bivalves with ca. 840 species worldwide. The Neartic (especially the SE United States) has the highest concentration of Unionida diversity in the world, comprising ca. 300 species alone Cummings 2007, Bogan 2008). However, this richness has been threatened by the construction of dams, pollution and sediment toxicity, wetland drainage and channelization, sedimentation and siltation resulting from poor agricultural and silvicultural practices, highway and bridge construction, interbasin transfer schemes, habitat loss through dredging, and other land-use activities (Lydeard et al. 2004). At present, 235 species have been assessed, of which 27 (11%) are considered extinct, 50 (21%) critically endangered, 31 (13%) endangered and 11 (5%) vulnerable (IUCN Red List, last accessed July 2013).
Our work recovered the collection of Unionida in the Museo di Zoologia dell'Università di Bologna, Italy, a collection dating back to the 19 th century. This collection is likely to be only the tip of the iceberg among many other collections, hidden in the Italian fragmented natural history museum system. Our aims are therefore to highlight the value of historic natural history collections as repositories of specimens of extinct or endangered species. In a time of increased awareness of global biological changes, museums are valuable reservoirs of baseline information. Moreover, we wish to bring to the attention of the international scientific community the hidden treasures in the Italian museums, and foster research on their material.

Methods
We recovered the collection of North American Unionida, cleaned all specimens, labels and original boxes, and transferred them into zip-lock plastic bags along with all original labels. Also the original boxes, likely to belong to early 20 th century were preserved. The most interesting lots were photographed. Identification was checked, nomenclature updated following the MUSSELp database (Graf and Cummings 2013), which proved particularly useful in tackling old names, and the conservation status of each species was recorded on the basis of published assessments (IUCN Red List, U.S. Fish and Wildlife Service). Samples were databased, and research into the biography of the main contributors to the collection performed. The collection also contains several lots from Europe, as well as samples from South America, Africa and Asia, which were cleaned, but not analysed in detail.

Results
Eighty-six specimens of North-American Unionida are preserved in the Museum (Table 1 gives a list) in 76 lots, representing two families (Unionidae and Margaritiferidae) and 57 species. The condition of specimens is generally very good, with most valves being paired, and only a few having cracks or other defects. The collection comprises further 34 lots (104 specimens and 22 valves) from Europe, 21 lots (31 specimens and two valves) from the Central and South America, three lots (three specimens) from sub-Saharan Africa, and two lots (two specimens) from New Zealand, which will not be further commented upon here.
Most of the lots were received from M.E. Moricand (1779-1854) (Fig. 2 A-B), a Swiss collector, in the mid-1800s. His collection was particularly rich, especially of land shells: his son M.J. Moricand catalogued his collection in 1859 censing 5,950 species and about 25,000 specimens (Cailliez, 1983). A few more lots from the Mississippi River are dated 1863 and belonged to the Capellini collection (Fig. 2 C). Giovanni Capellini (1833Capellini ( -1922 was a professor of geology at the University of Bologna, and travelled in 1863 to the United States (Vai, 2002).

Discussion
Museum collections are increasingly becoming the only source of information on extinction rates and range contractions, or the only way to access species extinct in historial times (Allmon 1994). The case study here reported shows that the effort to recover an historical 19 th century collection allowed the recognition of an extinct species and of several endangered species, belonging to one of the most imperiled groups of molluscs worldwide. The specimens themselves, and the data accompagnying them, provide researchers with a historic record of where extinct and endangered species once lived. Notwithstanding natural history collections are then a vital resource for conservation research, the recognition of their importance is often lacking.
Even when the value of natural history collections as sources of long-term or past datasets is recognized (Lister et al. 2011), locating material of interest is often difficult due to the fragmentation of the museum system in some countries, the lack of computerization of collection data, or the lack of availability to the public (e.g. via internet) (O'Connell et al. 2004). The Museo di Zoologia dell'Università di Bologna does not have permanent personnel, and all curatorial work is carried out by university researchers and students in the framework of their research assignments or on voluntary basis. The malacological collection is partly databased, but the database is not readily available to the public. Publishing the results of this work will hopefully contribute to arise consciousness on the value of natural history collections, and start spreading information to the scientific community on the Italian invertebrate historical collections. Indeed, the Italian museum system had its golden years in the second half of the 19 th century and early 20 th century (see for a narrative on vertebrate collections Gippoliti (2005)). Therefore, further collections of interest can be expected when digging into the old cabinets of the Italian museums. Cyprogenia stegaria (Rafinesque, 1820) ( Fig. 1 A,