Atlas of the flora of New England: Pteridophytes and Gymnosperms: Introduction

ABSTRACT. Dot maps are provided to depict the distribution at the county level of the pteridophytes (Lycopodiophyta, Equisetophyta, Polypodiophyta) and gymnosperms (Coniferophyta) growing outside of cultivation in the six New England states of the northeastern United States. The 172 taxa (species, subspecies, varieties and hybrids, but not forms) are mapped at the county level based on specimens in the major herbaria of Maine, New Hampshire, Vermont, Massachusetts, Rhode Island and Connecticut, with primary emphasis on the holdings of the New England Botanical Club Herbarium (NEBC). Brief synonymy to account for names used in recent manuals and floras for the area, habitat and chromosome information and common names also are provided.

Key words: Flora, New England, atlas, distribution, pteridophytes, gymnosperms

This article is the first in a series that will present the distributions of the vascular flora of New England in the form of dot distribution maps at the county level. New England comprises the six northeastern states of the United States: Maine, New Hampshire, Vermont, Massachusetts, Rhode Island and Connecticut. These states range in latitude from 41°N to 47°28'N and in longitude from 67°W to 73°45'W. The elevation of the region extends from sea level to 1,898 m (6,228 ft) at the summit of Mt. Washington, New Hampshire, the highest mountain in eastern North America outside of North Carolina. The total area of the region is 172,515 km² (66,608 miles²) including bodies of water; the total land area is 163,157 km² (62,995 miles²). The effects of continental glaciers, which covered the entire region several times during the Pleistocene, and the last of which did not retreat until about 15,000 years ago, are still clearly evident throughout the area. The state by state statistics on size and elevation are shown in Table 1 (Merriam-Webster, Inc. 1984).

The more southerly states of Massachusetts, Rhode Island, and Connecticut are densely populated (the least densely populated of these three states, Connecticut, had an average of 262 persons per km² in 1990; Hoffman 1992). The northern states of Maine, New Hampshire, and Vermont are mostly rural (the most densely populated of these three states, New Hampshire, had an average of 48 persons per km² in 1990; Hoffman 1992).

This work encompasses all vascular plants (pteridophytes and spermatophytes) at the rank of species, subspecies, and variety growing outside of cultivation in the New England states. Hybrids also will be included, but forms and other ranks below the level of variety will not. The dots are based primarily on voucher specimens in the herbaria of New England representing reproducing populations, or plants persisting after cultivation when it is uncertain that they are actually naturalized. This first installment includes the pteridophytes (Lycopodiophyta, Equisetophyta, Polypodiophyta) and gymnosperms (Coniferophyta). Future accounts will treat the distribution of angiosperms.

We intend to gather this series of articles, together with additional background material, into a separate volume upon completion of all the maps, and to make it available on the Internet as various parts are finished. It is our hope that, in the meantime, these articles will stimulate additional field work to supplement the distributions portrayed in the maps. The New England Botanical Club herbarium, which has proven to be the most important resource for this project, is especially eager to receive specimens documenting range extensions. We also would like to be informed of such specimens in other herbaria. Similarly, because the atlas of the New England flora will be updated continuously as new information becomes available, we are eager to receive notification of published corrections of cytological information and new, documented chromosome counts for taxa in the New England flora.

This atlas grew out of an inventory of the New England Botanical Club vascular plant herbarium. The purpose of the inventory, conducted at the county level, was to serve as a filter for the processing of a large number of unmounted specimens being considered for accession. Consequently, the core of the database for this atlas consists of specimens in the herbarium of vascular plants of the New England Botanical Club (NEBC). The NEBC herbarium, which limits its geographical scope to the New England states, presently comprises more than 253,000 specimens and is the largest collection of plants for the New England region.

In the mid 1980s the herbarium inventory was expanded into an atlas project, since data from the NEBC herbarium essentially depict the distributions of the vascular plants of New England. Additional data from specimens in other major herbaria with large holdings of New England plants have allowed us to portray the distributions more completely.

The data represented currently by specimens in New England herbaria best depict vascular plant distributions when displayed at the county level. Attempting to display such data by the exact geographical coordinates of each collection locality, or even at the township level, distorts the actual distributions. By such detailed mapping, patterns tend to reflect concentrated collecting along major highways and clustering near popular resort areas or botanical hot spots. This was evident from some of the detailed distribution maps produced about 15 years ago by the plant distribution committee (now defunct) of the New England Botanical Club. The distortions portrayed by such detailed mapping are resolved by using data only at the county level.

The counties of New England range in size from Bristol County, Rhode Island (65 km², or 25 mi.²), to Aroostook County, Maine (17,666 km², or 6,821 mi.² - land only). The great majority of counties, however, are between 1,300 km² (500 mi.²) and 3900 km² (1,500 mi.²). To reduce the size disparity at the large end, and to depict distributions more evenly, the largest Maine counties are subdivided. Penobscot, Piscataquis, Somerset, and Oxford counties are divided arbitrarily into roughly equal-sized, north and south sectors along township boundaries. Aroostook County, the largest county, is divided into three sectors. Coös County, New Hampshire, is divided into north and south sectors. The division of Coös County isolates the White Mountains, which harbor an alpine flora associated mostly with New England's highest peak, Mount Washington. Figure 1 shows the location of states and counties of New England and the subdivisions of the largest counties.

Data were collected primarily from herbarium specimens of major herbaria in New England. The herbaria used to compile data for this work were those of the New England Botanical Club (NEBC), , Harvard University (A, AMES, GH), University of Maine (MAINE), University of Massachusetts (MASS), University of New Hampshire (NHA), University of Rhode Island (KIRI), University of Vermont (VT) and Brown University (BRU). Records from the herbaria at the University of Connecticut (CONN), Connecticut Botanical Society (NCBS), and Yale University (YU) were accessed from data compiled by Leslie Mehrhoff. Lastly, the notebooks of Harry Ahles at the University of Massachusetts were consulted. Ahles visited these same herbaria, plus one or two others, in the 1960s and 1970s to gather locality information at the county level. We obtained some records from systematic treatments where the information on voucher specimens was specific enough to provide county data and the name of the herbarium where the specimens were deposited.

In recording the collection data no attempt was made to verify the accuracy of the identification of every specimen, but obvious misidentifications were annotated with corrections. Even though the basis for a particular dot might be a misidentified specimen, for plants common within New England, our view is that the taxon most likely occurs within the county. Specimens documenting disjunct or marginal occurrences (or otherwise rare, endangered or threatened taxa) usually have received greater scrutiny, because of a heightened interest in rare plants nationwide, and are less likely to be misidentified.

The data were entered into a simple computer database using one of several letters in the county field as a code to indicate the herbarium in which the voucher specimen is deposited. The letter code indicates the first herbarium where a voucher specimen was seen. No letter codes were added for subsequent voucher specimens at other herbaria, because our primary objective has been to plot the distribution of the taxon, not to inventory the holdings of any particular herbarium. While such information might be of value for some purposes, we felt that our time at other herbaria was best devoted to searching for data not found in the New England Botanical Club herbarium, or in each subsequently searched herbarium, to fill in gaps in distribution.

The data in the database were converted to dot distribution maps using a method devised by Angelo (1994).

The taxonomy and nomenclature adopted for this work essentially follow the Flora of North America (Flora of North America Editorial Committee 1993). With the exception of the arrangement for the major divisions within the pteridophytes (Lycopodiophyta, Equisetophyta and Polypodiophyta), which follows the Flora of North America (Flora of North America Editorial Committee 1993) sequence, the families are ordered alphabetically. The genera are alphabetical within families, as are species within genera. Named and unnamed hybrid taxa are placed alphabetically at the end of the genus. Unnamed hybrids combine the names of the parents alphabetically by epithet.

Species deemed to be introduced, that is, not native in New England at the time of European contact with North America, are indicated by the use of all upper case type for the scientific name. No single source of information was used in determining introduced species. For most taxa there is little dispute as to nativity. Where differences of opinion exist in the literature, we have used our own judgment based on the evidence available.

A common name is supplied when it appears to be a name in general use. Names used in New England have been given preference.

Cited chromosome numbers are taken from indices prepared by Cave (1958a, !958b, 1959a, 1959b, 1960, 1961, 1962, 1963, 1964, 1965), Goldblatt (1981, 1984, 1985, 1988, ), Goldblatt and Johnson (1990, 1991, 1994), Moore (1973, 1974, 1977), Ornduff (1967, 1968, 1969), and reports by Takamiya and Kurita (1983), Taylor (1970), Tryon (1978), Tryon and Tryon (1982), and Wagner (1971). Very few of the counts are based on material from New England, but instead reflect counts made from throughout the range of the taxon.

The habitat data are distillations from a variety of sources augmented by our own field observations. An attempt was made to indicate habitat information as it applies to a particular taxon in New England rather than to the entire range of the taxon.

Synonymy is provided primarily with respect to names used in the standard manuals covering New England published from 1950 onward, including Fernald (1950), Gleason (1952), Gleason and Cronquist (1963, 1991), and Seymour (1969a, 1982).

A selection of references, including many not cited above, is provided. This list consists of the standard manuals published from 1950 to date, regional and county floras and checklists produced after 1950, and what we believe to be the key articles and books on the pteridophytes and gymnosperms pertinent to New England. We would appreciate being notified of papers we may have overlooked.

ACKNOWLEDGMENTS. We thank the curators and directors of the herbaria of Brown University, Harvard University, the University of Maine, University of Massachusetts, the University of New Hampshire, the University of Rhode Island, and the University of Vermont for allowing us access to their collections. We particularly appreciate the kindness of David Barrington, Chris Campbell and Karen Searcy for allowing use of the collections in their care outside of normal hours of operation. We are grateful also to Karen Searcy for allowing access to the notebooks of Harry E. Ahles at the University of Massachusetts. Leslie J. Mehrhoff was very generous in sharing data on pteridophytes and gymnosperms that he has collected from the herbaria at the University of Connecticut and Yale University. James Hinds assisted by checking the University of Maine herbarium for some discrepancies in the Harry Ahles data. Thomas Vining, at the University of Maine, checked additional specimen data for us at that institution. David Barrington, David S. Conant, and James Hickey made many helpful comments on various versions of the manuscript and Warren H. "Herb" Wagner was particularly helpful and encouraging. Lastly, we thank Bruce A. Sorrie for collecting data from the Harvard University herbaria in the early stages of this project.