114 Phytologia (June 2006) 88(1) BIOGEOGRAPHICAL OBSERVATIONS ON LOUISIANA AND TEXAS RARE AND ENDEMIC PLANTS Michael H. MacRoberts and Barbara R. MacRoberts Bog Research, Shreveport, LA 71 104 and Herbarium, Museum of Life Sciences, Louisiana State University in Shreveport, Shreveport, LA 71115. ABSTRACT Using state rare and endemic plant lists, we document the North American distribution of Louisiana and Texas rare plants and the distribution of Texas endemic plants. Because the Louisiana and Texas rare plant lists have been developed using different criteria, the North American distribution maps of each are distinctly different. Texas endemics are concentrated in the center of the state. KEY WORDS: Louisiana. Texas, rare plants, endemic plants. Because of conservation concerns, state agencies such as the Natural Heritage programs. Parks and Wildlife departments, and The Nature Conservancy produce rare and endemic plant lists. However, listed plants generally have not been subjected to biogeographical analysis. In this paper, we examine the Texas rare and endemic plant lists and the Louisiana rare plant list inorder to place listed taxa in a broader biogeographical context. We do not question what is on the lists, nor do we question taxonomic status. We simply use the lists as data. THE LISTS The Louisiana rare plant list is produced by the Louisiana Natural Heritage Program. The 2004 edition consists of 368 taxa (Reid 2004) and includes both globally rare (G1-G3/T1-T3) and locally rare taxa (SI -S3) that might not be rare elsewhere but that are rare in Louisiana. The Texas rare plant list is produced by the Texas Parks and Wildlife Department and The Nature Conservancy of Texas. The 2004 edition
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