Frank T. van Manen Joseph D. Clark John R. Boetsch 2003 <p>We investigated the applicability of biometric habitat modeling to rare plant inventory and conservation by developing and field testing a geographically explicit model for <i>Cardamine clematitis Shuttleworth</i> ex A. Gray (mountain bittercress), an endemic plant of the southern Blue Ridge Mountains, USA. For each of 187 confirmed coordinates for <i>C. clematitis</i> in Great Smoky Mountains National Park, 13 habitat variables were measured with a geographic information system. These data were used to calculate Mahalanobis distances for each 30-m x 30-m pixel within the study area; small values of Mahalanobis distance represented site conditions similar to those of known locations of <i>C. clematitis</i>, whereas larger distance values represented dissimilar conditions. Following model development, we tested model performance by sampling 120 randomly distributed plots for<i> C. clematitis</i> presence. Logistic regression showed that Mahalanobis distance values were strongly related to C. clematitis occurrence (P = 0.039). Overall, 75% of all known occurrences of <i>C. clematitis</i> had associated Mahalanobis distance values below 17.7, and 95% of all occurrences were below 33.8; the median Mahalanobis distance value for the study area as a whole was 40.0. A habitat suitability cutoff value was defined which identified roughly 23,640 ha (19.5% of the study area) as suitable habitat. Although the model successfully predicted species absence in test plots with high Mahalanobis distance values, many sites with low values did not contain <i>C. clematitis</i>. Only 16.2% of test plots below the habitat suitability cutoff contained <i>C. clematitis</i>. The absence of <i>C. clematitis</i> from sites with low Mahalanobis distance values (low specificity) is not necessarily indicative of a poor model; metapopulation processes (e.g., recolonizations, local extinctions) have been shown to play a major role in presence or absence of many plant species. That may be partially the case with our model as evidenced by a relationship between <i>C. clematitis</i> presence and habitat patch size. <br /><br /></p> application/pdf en Natural Areas Association Predicting rare plant occurrence in Great Smoky Mountains National Park, USA article