What's In Our Back Yard? Developing An Inventory of U.S. Native and Naturalized Crop Germplasm.

Modeling studies suggest that global climate change will negatively impact the distribution and abundance of crop wild relatives (CWR) in many regions, compounding habitat modification, urbanization, and invasive species stresses already threatening populations. Anticipated changes in species distribution, an increasing appreciation for the value of these resources in breeding, and constantly improving methods for identifying, conserving, and utilizing CWR are catalyzing efforts to conserve economically important taxa that are native or naturalized in the United States.  Compiling a comprehensive inventory is a starting point to develop a national conservation strategy. We developed a national inventory containing over 2600 CWR taxa, native or naturalized to the United States. We included species used for food, fiber, forage, medicine, esthetics, restoration and timber. To help prioritize the list we included data on conservation status and use. We identified 364 taxa useful for breeding 65 different crops. Sixty of these taxa were naturalized species. Species in the genus Helianthus were the most abundant. Other important genera included Frageria, Lupinus, Prunus, Ribes, Rubus, Vaccinium and Vitis. CWR genera of domesticated crops that had particularly limited representation in U.S. ex situ collections included Gossypium, Lactuca, Prunus, Ribes (gooseberry), Saccharum, Vaccinium (cranberry), Tripsacum and Zizania, although for many  genera gaps existed either at the taxon or population level.  Most taxa in the inventory were for crops that are wild or minimally domesticated. The main uses of these crops were for revegetation and esthetics. In terms of conservation status, 2300 of the taxa were globally secure or apparently secure. A total of 102 taxa were globally vulnerable or imperiled. Eight taxa were critically imperiled, including two species of Helianthus and Juglans hindsii, a close wild relative of walnut. We conclude the paper by discussing our next steps for developing a national conservation strategy for crop wild relatives.