About Digital Atlas

Virginia Botanical Associates

The Digital Atlas of the Virginia Flora is the online successor to the Atlas of the Virginia Flora, which was published in three hard-copy editions between 1977 and 1992. Although it is still a work in progress in many respects, the Digital Atlas contains the most comprehensive information available on the geographic distribution of vascular plants in the Commonwealth. The data provided in the Digital Atlas and its predecessors is based on the iterative evaluation of voucher specimens housed in both Virginia and out-of-state herbaria. Holdings in the herbaria of Virginia Tech (VPI), The College of William & Mary (WILLI), Longwood University (FARM), George Mason University (GMUF), Lynchburg College (LYN), Virginia Military Institute (VMIL), Old Dominion University (ODU), University of Richmond (URV), Lord Fairfax Community College (LFCC), Virginia Commonwealth University (VCU), James Madison University (JMUH), Randolph-Macon College (RMWC), Radford University (RUHV), Bridgewater College (BDWR), and several smaller institutions total about 574,000 specimens. These, plus the very large Virginia holdings of the Smithsonian Institution United States National Herbarium (US), Harvard University’s Gray Herbarium (GH), the Philadelphia Academy of Natural Sciences (PH), the New York Botanical Garden (NY), the University of North Carolina (NCU), and West Virginia University (WVA) provide the great majority of the documentation for the county distributions now mapped.

With the publication of the Flora of Virginia in December, 2012, The Digital Atlas of the Virginia Flora has become not only an essential phytogeographic companion for users of the manual, but an even more important tool for updating both distributional and taxonomic information. The digital format allows for continual updating of distributional records, as well as numerous issues regarding taxonomy and nomenclature that remain unresolved and subject to change. Both the Flora and The Digital Atlas include numerous subspecific taxa and species splits that were not included in Atlas of the Virginia Flora, 3rd ed. (referred to as Atlas III). While many of these could be mapped with information on hand, many others could not without revisiting the herbarium specimens from which the original records were derived. With Virginia’s herbarium resources being so widely scattered, this endeavor will go on for years. In the meantime, a few maps remain placeholders, while others are only partly populated. New information and taxonomic/nomenclatural changes will be added as they become known.

Taxonomic Concepts

Family designations follow the Flora of Virginia and those of the Angiosperm Phylogeny Group (APG3).

From the initiation of the Digital Atlas, VBA’s goal has been to provide concepts that reflect plants as they exist morphologically and ecologically in Virginia. The authors of the Flora of Virginia made a tremendous effort to bring the taxonomic treatment of the state’s vascular plants in line with contemporary advances in molecular systematics, which are overturning many long-held conventions in classification and phylogeny. Following the Flora’s publication, VBA members systematically compared all treatments in the Flora and Digital Atlas, and identified conceptual and nomenclatural differences. In most cases, treatments in the Digital Atlas are now the same as those of the Flora. However, in a small number of cases, the Digital Atlas has followed an alternative treatment or name. While a fully cohesive treatment might be desirable, some differences are inevitable in this age of rapidly changing botanical concepts and diverse opinions among accomplished taxonomists.

Additionally, the Digital Atlas has maintained maps for a number of poorly known infraspecific taxa that are only included in the Flora as comments, primarily in order to call attention to them for future research. Where differences between the Digital Atlas and Flora occur, the “Comments” field typically provides an explanation. One of the results of the Synthesis of the North American Flora (John T. Kartesz, 1999) and the successive drafts of Weakley’s “Flora of the Southern and Mid-Atlantic States” was to bring to the surface many names that, for our region, had gone out of use for many years, especially at the infraspecific level. Many herbarium specimens are not identified to subspecific or varietal level. The choices of what to recognize and what to lump have been exceedingly difficult. As often as possible, we have made decisions based on how successfully we’ve been able to make the distinctions in our own field and herbarium experience. Again, the “Comments” field may provide some guidance on our experiences and leanings at this point in time.

Virginia Status

The Digital Atlas has traditionally doubled as a checklist of the flora. Consequently, a concerted effort has been made over the years to clean up the list of what is actually known to occur in the state. Numerous attributions have been explored and resolved, yet others remain unresolved. Virginia Flora by A.B. Massey (1961) reported many plants without county designation or vouchered documentation, often based on assumptions about the “Gray’s Manual Range.” The Digital Atlas continues the effort of previous hardcopy editions to resolve these questions. The “Comments” field is used to report the status of many plants, especially where uncertainty exists, but has not yet been populated for all taxa of questionable establishment. This field is also used for a wide variety of other information: taxonomic issues, phytogeographical facts, literature citations, and points of general interest. At present, the information is incomplete, and it’s hoped that much more will be added in coming years. In collaboration with the Flora of Virginia Project, habitat descriptions and assessments of relative abundance for all taxa were completed in 2011. Under a cooperative agreement, these descriptions (or updated versions of them) have been added to the Digital Atlas. These data will be updated continuously as new information becomes available.

Treatment of Waifs and other Species of Questionable Establishment

Selection of criteria for inclusion of species in a floristic treatment is always a difficult and controversial task. The Flora of Virginia took a rather restrictive approach to including non-native species, with fairly tight requirements for establishment and the use of some quantitative measures for plants escaped from cultivation. As a result, the Flora, to some extent, under-represented the introduced flora, although it certainly captures all of the well-established and frequently encountered non-native taxa.

Not being constrained by the same requirements of a published flora, the Digital Atlas has taken a much more inclusive approach and mapped many plants that are known or probable waifs, or species of uncertain establishment. We believe that keeping track of a wider range of introduced flora that will likely change over time is a valid role for the Digital Atlas. In recent decades, globalization has removed many barriers to the worldwide migration of weedy species, and more and more species are being reported as cultivated escapes every year. In addition, there’s a lot of truth in the concept that today’s waif may well become tomorrow’s horrible invasive!

The basic criteria we have attempted to apply for mapping of non-natives are: 1) the occurrences must be vouchered, and 2) the populations must represent something more than mere persistence; at a minimum they must have spread or escaped away from the immediate vicinity of plantings. Plants like Helianthus annuus (common sunflower) or Avena sativa (oats) that are not persistent at a given locality, but appear spontaneously and repeatedly as waifs are accepted. Similarly, garden plants like tomatoes or cucurbits that produce ephemeral populations repeatedly in disturbed alluvial soils and waste ground are likewise included. On the other hand, garden vegetables and cultivated ornamentals that may rarely regenerate from seed in situ are excluded. In some cases where the situation is not clear or known, we have erred on the side of inclusion.

Hybrids were explicitly excluded from the Flora of Virginia, and many are excluded from the Digital Atlas. Nevertheless, we have mapped certain hybrids, particularly of ferns, that may be of interest to taxonomic specialists.

Excluded Taxa List

In order to better keep track of both potentially native species reported for Virginia in error or without known voucher documentation and introduced species reported but not meeting the basic criteria for inclusion, we have created an Excluded Taxa List. This list is annotated with pertinent information and is available on the browsing menus at the top of all Digital Atlas pages. We expect that changes to this list will be frequent, and it will be updated regularly.

Your comments

Our hope is that this atlas will spur others to their own investigations resulting in new and better information than we presently have. Comments, corrections, new data, and any thoughts you may have are most welcome. Please send them to Tom Wieboldt, Massey Herbarium, Virginia Tech, Blacksburg, VA 24061, or by phone at (540) 231-5746 or email. To document new records, click on the “To Contribute New Records” tab.