specimens barcoded:  19862
species barcoded:  858
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Mammals are not particularly speciose, compared to many other Animal classes (with approximately 5500 species currently recognized). However, because of their unique evolutionary position (as a taxon including the human species) and their immense economical value, they have received consistent attention from varied scientific disciplines. Needless to say, mammals play a vital role in most ecological communities and the very existence of some of these communities (e.g., prairies and savannas) imperatively requires mammals as a key component. It is also notorious that all but a few mammal species are becoming endangered and extirpated, due to human activities, such as hunting, urbanization, and agriculture.

The extent of our knowledge of mammalian diversity is still to be determined. In just over a decade, between 1992 and 2006, more than 300 new species have been discovered, and numerous previously described forms have been raised to species status, with a nearly 1/5th overall increase in documented species diversity (Reeder et al., 2006). [ new mammals OPTTU final.pdf].

Some estimates propose that an additional 2000 species of mammals are still awaiting description and/or formal recognition, thus potentially raising the total species count to 7500. Most of these are cryptic genetic lineages, which could be morphologically distinguished from their sister species only (if at all) by a few experts. Much of this work has been achieved due to the active use of molecular methods in taxonomic research and would have been impossible based on morphological characters alone. However, even for many commonly recognised species morphological distinction is only possible for specially prepared collection material and with specialised training, which makes them elusive for identification during faunistic surveys and ecological monitoring. Such are, for example, many species of shrews and muroid rodents, which form the bulk of small mammal communities in many temperate and tropical ecosystems. Hence, another challenge facing mammalogists is to make the wealth of up-to-date taxonomic information readily usable by the broad scientific community with limited taxonomic expertise in mammals and to further extend its use into practical applications. Coping with these challenges requires an approach that is precise, time-efficient, and readily usable by non-expert users.

As a response to these challenges, an initiative to perform a first-pass alpha-taxonomic screening of mammals using the standard DNA barcoding marker has been launched by the Biodiversity Institute of Ontario (BIO) at the University of Guelph, in collaboration with a number of leading research institutions worldwide. DNA barcoding is a scientific proposition based on the premise that a short, standardized segment of the genome can enable species identification and discovery. A series of studies involving a wide range of taxonomic groups provided clear evidence that a ca. 650 base pair segment positioned near the 5' terminus of the mitochondrial cytochrome c oxidase subunit I (COI) gene is effective in discriminating the vast majority of species within the animal kingdom, allowing reliable identification of known taxa and provisional delimitation of new ones. This gene has been adopted as the standard DNA barcode marker for animals.

Mammals are no exception to this. Moreover, they have a history of use of mitochondrial genes in taxonomic research, although the marker traditionally used in mammal studies is the mitochondrial cytochrome b gene (Cyt-b). The advantage of COI DNA barcoding as a tool for large-scale alpha-taxonomic screening is that it offers a standardized approach, thus making the basic taxonomic information readily comparable across broad taxonomic entities. Today the existing reference database for COI is larger, compared to any other single gene, thus offering the broadest context for taxonomic and biodiversity studies. The nearly 32000 mammalian COI sequences accumulated to date (including GenBank data) comprise a conservative 23% of species and 44% of genera recognized in Wilson & Reeder (2005). The majority of these sequences are associated with voucher specimens preserved in nationally and internationally recognized collections. This makes the existing reference database already applicable in a wide range of practical tasks. As an example, DNA barcoding offers a tool which will enable non-experts in mammal taxonomy to verify field identifications of their study objects, thus significantly raising the confidence levels in results obtained by studies normally relying solely on field identifications, such as catch-and-release surveys.

Development of a comprehensive DNA barcode library for all mammal species will allow the use of DNA barcoding for varied diagnostic needs from ecological surveys and taxonomic revisions to forensics and management of genetic resources collections. Existing data have already demonstrated the utility of barcodes as an ancillary tool for the curation of museum collections, a valuable quality control mechanism for field ecological surveys, and an excellent way of determining the taxonomic position of morphologically unidentifiable mammal remains. It has also allowed taxonomic experts from different museums across the planet to collaborate online on resolving the taxonomy of the most challenging mammal groups without the need for large-scale transfer of collection voucher specimens. These benefits are expected to multiply as more experts become involved and as the taxonomic and geographic coverage scales up.

Collecting barcodes for mammals is not the ultimate, but rather a minimalistic goal of the mammal barcoding campaign. It is envisioned that large-scale screening of mammalian DNA barcodes will highlight intriguing taxonomic questions that may have been overlooked by either conventional morphological approaches or in-depth molecular research of limited taxonomic samples. For instance, cryptic species can be readily separated into distinct groups on the DNA tree, whereas other named forms may need to be synonymized. DNA barcoding is not intended to attain a final verdict on complex taxonomic questions. Instead, it is proposed as a basis to properly formulate these questions and instigate in-depth research involving the entire gamut taxonomic, phylogenetic, ecological, and other research approaches.