Mimulus gemmiparus Populations: Current Status and Extended Search

Summary To more accurately assess the current conservation status of the rare plant Mimulus gemmiparus (Phrymaceae), we visited all previously known sites of occurrence and documented the location, size, and condition of populations, and we searched for additional populations in nearby areas. In 84 searcher-hours of intensive search, we found at least 15 new populations/sites of occurrence (separated from other populations by at least 30 m), 13 in Middle Saint Vrain Canyon (Roosevelt National Forest), and 2 in Horseshoe Park (Rocky Mountain National Park (RMNP)). Some additional populations or patches at other locations in RMNP are likely new, as well. Two previously known populations in RMNP (the type locality near Fall River Road, and the Alluvial Fan population) were not found, and may not persist. The newly discovered populations and patches increase the estimated total abundance of M. gemmiparus by approximately 21,000 plants (to a total of ~126,000 plants), with the majority of these newly found plants (~14,000) in Middle Saint Vrain Canyon. Our search results indicate that more occurrences of M. gemmiparus are likely, and we recommend the following actions: 1) The search for additional populations of M. gemmiparus in areas with suitable habitat should be continued and expanded. 2) Efforts to minimize adverse human impacts on existing populations should be expanded. For instance, the Hankins Gulch Trail in the Pike National Forest should be rerouted to eliminate trampling of plants. 3) Fine-scale demographic and genetic analyses of populations and patches should be undertaken to provide information on population dynamics and genetic structure. 4) A reintroduction program (with ex situ propagation) to establish new experimental populations seems feasible, and should be undertaken.