Western North American Naturalist Volume 64 Number 4 Article 20 10-29-2004 Full Issue, Vol. 64 No. 4 Follow this and additional works at: https://scholarsarchive.byu.edu/wnan Recommended Citation (2004) "Full Issue, Vol. 64 No. 4," Western North American Naturalist: Vol. 64 : No. 4 , Article 20. Available at: https://scholarsarchive.byu.edu/wnan/vol64/iss4/20 This Full Issue is brought to you for free and open access by the Western North American Naturalist Publications at BYU ScholarsArchive. It has been accepted for inclusion in Western North American Naturalist by an authorized editor of BYU ScholarsArchive. For more information, please contact [email protected], [email protected]. Western North American Naturalist 64(4), © 2004, pp. 421–432 EVALUATING THE GEOGRAPHIC DISTRIBUTION OF PLANTS IN UTAH FROM THE ATLAS OF VASCULAR PLANTS OF UTAH R. Douglas Ramsey1,2 and Leila Shultz1 ABSTRACT.—Locations of 73,219 vascular plant vouchers representing 2438 species were digitized from the Atlas of the Vascular Plants of Utah (Albee et al. 1988). Source maps consist of 1:6,000,000-scale shaded relief maps of Utah with points representing collection locations by species. Location points, representing 1 or more specimens, were transposed onto these maps from the approximately 400,000 herbarium records of 3 major universities and federal land manage- ment agencies. These source maps were digitized into an ARC/Info™ database in order to reproduce the atlas in digital form. Analysis of all locations revealed a mapping bias of the original authors to avoid placing sample locations on county boundaries and over major river corridors. A comparison between ecoregions and elevation showed that the Col- orado Plateau and Wasatch/Uinta Mountains have the highest species diversity, and that areas of low elevation (1000–2000 m) have the highest number of unique species in the state. Further, species richness is related to elevation and to ecoregion boundaries. Key words: GIS, vascular plants, Utah, ecoregions, species richness. Biogeographers study the geographical dis- species in Utah. The database represents vouch- tribution of plants and animals. Combining er collections from 3 major research universi- geographic information systems (GIS) and bio- ties (Brigham Young University, University of geography offers a powerful tool to help under- Utah, Utah State University) and from 3 gov- stand the geographic distribution of life forms. ernment agencies (Bureau of Land Manage- This combination is used extensively by bio- ment, U.S. Park Service, U.S. Forest Service). geographers to understand the geography of Original maps, stored in the University of Utah taxa and to evaluate scale dependencies (Neil- Garrett Herbarium archives, show individual son and Marks 1994, Nichol 1994, Stoms 1994, data points color-coded by herbaria in which Ramsey et al. 1995, and Shultz et al. 1998). A specimens are stored. Seven years were re- key component to any biogeographical analy- quired to compile this atlas. It is the most sis using GIS is the availability of accurate complete source for spatial distribution of information describing the spatial distribution individual plant locations for Utah. of plants and animals. Information about the Specimen vouchers examined by the authors geographic distribution of individual plant were generated over more than a century by a species is not readily available. This lack of host of individuals. The authors critically ex- information limits biogeographers to the study amined approximately 400,000 specimens rep- of distribution of vegetation types or to a small resenting 2822 native and introduced species, group of individual taxa. In this paper we use and they mapped multiple sample locations of an extensive database of individual species loca- 2438 species. Where the same species was tions for Utah to evaluate plant collection dis- collected in approximately the same area, a tribution and species richness within the state. single dot represented multiple collections, Our objective is to understand if databases and where the location of a specific voucher like this can provide accurate biogeographical was in question, the voucher was not mapped. information in an ecological context and pro- Further, plants that were collected from only a vide an understanding of sampling bias. single location, usually considered rare, were The Atlas of the Vascular Plants of Utah not mapped. These plants represent an addi- (Albee et al. 1988) is a compilation of herbar- tional 384 taxa and are listed in the appendix ium collection locations for 2438 vascular plant of the published atlas. Including the unmapped 1Department of Forest, Range, and Wildlife Sciences, Utah State University, Logan, UT 84322-5230. 2Corresponding author. 421 422 WESTERN NORTH AMERICAN NATURALIST [Volume 64 species, there were 2822 species cataloged in instructed to digitize the center of the mapped Utah when the atlas was published in 1988. sampling point. Each species distribution map This paper deals only with the 2438 mapped was individually digitized and stored in its species. own GIS layer. Attribute information consists The authors of the Atlas of the Vascular of genus, species, lowermost elevation limit, Plants of Utah used a shaded relief map of and uppermost elevation limit for each species Utah scaled at approximately 1:6,000,000 to as stated in the atlas. All taxa are named locate vouchers. Accompanying each map is according to standard Natural Resources Con- the species’ scientific name, authority, com- servation Service (NRCS; SCS 1993) genus/ mon name, brief habitat description, growth species acronyms and are stored in individual habit, indigenous status, blooming time, and family workspaces. elevation range. The purpose of publishing In order to spatially evaluate sampling and the atlas was to document areas that have mapping bias, all points for each species are been sampled for individual species and eluci- combined in family-wide databases and in a date biogeographic patterns, to identify sam- collection-wide coverage. Family-wide data- pling gaps, and to direct future activities in bases contain all digitized points for each those areas with little or no sampling. species within that family. The collection-wide This database, in its original published form, coverage contains all points digitized for the represents an important body of work depict- entire atlas. Each point maintains its original ing distribution of plant species throughout attribution in all coverages. the state. The atlas can be used by ecologists, The spatial distribution of voucher speci- evolutionary botanists, morphologists, physiol- mens was evaluated according to ecoregions, ogists, reproductive biologists, and others to elevation, and a 649-km2 hexagonal map tessel- understand the distribution of plants along lat- lation of the state to determine landscape level itudinal, elevational, and ecoregional bound- representation of samples and to help evaluate aries. As a GIS database, the atlas can be used species richness. The Utah portion of the in conjunction with other ecological data sets national ecoregion map produced by Omernik to provide biogeographical information, poten- (1987) was used to delineate ecologically dis- tial range distribution, and sampling adequacy. tinct zones in the state. There are 5 Omernik While the atlas is an important piece of ecoregions that fall within the state bound- work and is voluminous in its coverage of plant aries: Northern Great Basin (NGB), Southern distribution, like all geographic data sets it Great Basin (SGB, which in Utah represents makes assumptions and has limitations that the eastern extension of the Mojave Desert preclude certain types of analysis. This paper floristic province), Colorado Plateau (CP), will detail the process of converting the atlas Wasatch-Uinta Mountains (WUM), and Wyo- to digital form, provide an understanding of ming Plateau (WP). An elevation zone map the limitations of using small scale (large area) was generated from a statewide, 30-m resolu- databases, and evaluate sampling adequacy tion, digital elevation model and was catego- and species distribution across ecoregion and rized into 500-m elevation zones. Elevation elevation boundaries. zones began at 500 m (msl) and terminated with a zone of elevation above the 3500-m METHODS (msl) mark (Fig. 1). The Environmental Pro- tection Agency (EPA) Emap-based, hexagonal The atlas was digitized over the span of 1 sampling frame (Carr et al. 1992) was used to year by 3 student technicians. To reduce digi- evaluate species richness (as a function of the tizing variation between technicians, a menu collections) across the state. interface was created using ARC/Info™ menu and Arc Macro Language tools. Control points RESULTS were positioned at each corner of a state boundary map to reference each distribution The atlas provides collection locations for map to the same GIS state boundary layer. 2438 species, representing 117 families. A Technicians worked together to maintain con- total of 73,219 sample points describe the dis- sistency with the database and were each tribution of species. Figure 2 shows the digital 2004] DIGITAL ATLAS OF THE VASCULAR PLANTS OF UTAH 423 Fig. 1. Elevation zone map of Utah using 500-m increments. 424 WESTERN NORTH AMERICAN NATURALIST [Volume 64 Fig. 2. Digital distribution map of sego lily (Calochortus nuttallii T. & G.) from the Atlas of the Vascular Plants of Utah. 2004] DIGITAL ATLAS OF THE VASCULAR PLANTS OF UTAH 425 Fig. 3. Distribution of sampling points for the collection-wide database. version of the sego lily distribution map. Figure tion shows that there was no obvious bias in 3 shows the distribution of sampling points for mapping of points for the individual species the collection-wide coverage. (Fig. 2). However, when the collection-wide While there are areas within the state where database is displayed (Fig. 3), there is a decided a species does exist but has not been docu- mapping bias. When all 73,219 points are mented, cursory examination of point distribu- simultaneously displayed, political boundaries 426 WESTERN NORTH AMERICAN NATURALIST [Volume 64 Fig.