Phytogeography and Geographic Scope

For centuries, much of the taxonomic community in North America has struggled with problems of phytogeography.  Even in the Northeast, where vascular plant systematics has been an active interest for well over three centuries, and where the amount of botanical exploration is unparalleled anywhere in the Western Hemisphere, a substantial number of newly reported plant distributions are documented annually. Although we must realize that many of of our voucher records are old, they still represent the best documentation we have for assessing phytogeography. Over the past five decades, BONAP has assessed many of these older specimens and historical reports, to determine which are credible and which are false.  In doing so, we have dismissed nearly 6,500 state-level species occurence "records" due to taxonomic problems, misidentifications, erroneous place names, etc. This number represents more plant species occurrences than are currently reported for all of northeastern North America! Unfortunately, it is very likely that numerous other false reports remain.  Rather than to simply ignore them, each false report can be viewed by engaging any subgeneric taxon, then clicking on "See Maps of False Reports", above the state-level map on the TDC. During the course of our study, we have also determined that many of our plant species are more common and widespread than previously thought. Even within some of our most thoroughly understood plant groups, such as trees and shrubs, it's not unusual to find new state-level records. Certain taxa, originally considered to be state-level endemics are now reported from two, three, four, or even more states. Scores of taxa once thought to be extinct have been relocated, reducing our earlier extinction estimates (for not only the vascular flora but for other groups of the biota as well!). Consider for example, of the 33,000 total taxa treated within the current TDC, only 142 taxa (127 species) are now thought to be extinct in North America, 86 taxa (84 species) of which are restricted to Hawaii, and certainly, some of these will ultimately prove to be nothing more than taxonomic synonyms of common species.  We have also noticed unquestionable shifts in our flora due to various factors, including: modification of ecosystems, influences of exotic pests, spread of taxa into new areas via human activities (including the transportation of domestic animals), the germination of latent seeds within soil banks that establish only when environmental conditions become suitable, the transportation of fruits, seeds, and other plant materials by avifauna and other wildlife and humans into new geographic areas, and most recently, the effects of global warming.  The vast majority of "additions" of native plants at both continental and state levels, have resulted from discoveries of long-existing, but previously unreported populations, whereas new reports of exotics are due primarily to  recently established populations.  Based on historical records, it is quite predictable that within the next several decades, between 50-150 taxa could be added to most of our average-sized eastern states, 75-200 in Florida and Texas, and 250 or more in our western states of California and Hawaii.  Although most of these additions would obviously be exotic taxa, it is likely that some 50-100 new, undescribed taxa could be found in the eastern U.S. alone,  primarily from the southeastern coastal plain, while 100 or more new taxa could be described from Texas or other western U.S. states.  With the exception of wetland species, certain rare plants, and a few other plant groups, I believe that most native species populations will not undergo significant change, at least for the next decade or so. However, if global warming continues as predicted for many decades, we are likely to see wholesale shifts in species assemblages. Quite predictably, even if the climate remains relatively stable, with only minor increases in temperature, weedy species, both native and exotic, will continue to thrive and many will increase, while populations of native wetland plants and rare species may perish. BONAP hopes to play an active role in the long-term mapping and monitoring of all our species by incorporating public assistance for detecting increases or decreases of plant populations.  The geographic scope of the Taxonomic Data Center includes North America north of Mexico: the continental United States, Canada, the French islands of St. Pierre and Miquelon, and Greenland (a territory of Denmark), as well as Hawaii and the Caribbean islands of Puerto Rico, Nassau, and the U.S. Virgin Islands. The decision to include plants of the Caribbean islands and Hawaii was made at the request of various U.S. federal government agencies that share jurisdiction over them. Although it certainly could be argued that the floristic affinities that exist between the various islands and the mainland are not strong, especially for Hawaii, where approximately 89% of the native flora is endemic (Wagner, W.L., D.R. Herbst, and S.H. Sohmer, 1990), it is both floristically interesting and phytogeographically valuable for some workers to be able to ascertain the numbers and kinds of taxa within all of the various political subunits of North America. For the determination of occurrence of a given taxon within the range of the TDC, I have relied upon four primary sources: (1) my own field work, (2) existing voucher specimens (see Voucher Specimen), (3) published reports (see Documentation), and (4) reviews by floristic and monographic specialists (see Specialist Review).  In total, some 33,000 unique taxa are known to occur within the geographic area, 24,017 of which are species. These numbers represent the highest counts ever reported for the geographic area under study.  For all U.S. states, there is an average of 2,900 species per state, while in Canada, the average is 1,600 species per province.  It might interest some to know that not a single taxon occurs in all 71 geographic regions.  Within our data files and within our Floristic Synthesis of North America CD-ROM (to be released late in 2013), voucher and bibliographic references are provided for virtually each of our 5,000,000 county-level records, as well as for each of our 500,000 state-level records.  In very few cases, a personal communication references exist without further details. This designation indicates that a specimen has been seen in the wild, or that the taxon has been reported reliably for the particular geographic area designated, but further details do not exist. If a taxon represents a native or naturalized occurrence, or if the taxon represents an exotic taxon that has escaped cultivation, it is included. However, if a taxon is merely mentioned as being cultivated or included within a published list or otherwise included in the literature, without documentation of establishment, it is excluded from the TDC but listed within the excluded section.  All non-cultivated plants reported as exotic within the geographic area of the TDC are clearly indicated (see Map Color Key for details).  When using the North American Plant Atlas (NAPA) portion of our website, it should be apparent that several distributional patterns emerge.  Exotic plants, comprising 18.4% of the North American flora or some 4,410 species, often occur sporadically in a checkerboard pattern across the continent. In most cases, this checkerboard pattern reflects both the sporadic occurrences of many of these exotic taxa, or the historical ambivalence towards collecting them, or both. It may also reflect biased collecting at locations where exotics have been reported previously as escapes: commercial agriculture areas, dumping grounds of contaminated ship ballast, along our coastal seaports, and areas around wool mills, railways, or other ruderal locations.  Doubtless, exotic species are generally undercollected, and are actually more widely distributed than the data reflect.  Examples of this pattern can be seen via the following species:  Althaea officinalis, Ballota nigra, Forsythia suspensa, Geranium columbinum,Geranium sanguineum, Hyssopus officinalis, Iris germanica, Ligustrum ovalifolium,Petroselinum crispum, and Salvia pratensis.  (This pattern is also commonly reflected in the distribution of native hybrids, due primarily to undercollecting.)  Conversely, geographic patterns of native species reflect far more coherent or continual patterns.  As expected, only occasionally do geographic "holes" exist within distributions of our native plants. When this pattern occurs, it is generally due to a lack of available habitat. Far more obvious are the "holes" that exist in the distributions of infraspecific native taxa. In most of these cases, the interrupted patterns nearly always reflect identification or taxonomic difficulties, or undercollecting.