MORPHOLOGICAL VARIATION IN THE MONARDELLA ODORATISSIMA – MONARDELLA VILLOSA COMPLEX

In this study, morphological characters were investigated to better characterize the species boundaries between members of the Monardella odoratissima – M. villosa complex (Lamiaeceae). Traditionally, it has been very difficult to identify and separate members of this complex. Monardella linoides, M. purpurea, and M. sheltonii populations are distributed in the overlapping boundaries of these two species (M. odoratissima and M. villosa) and considered within the complex as well. Previous studies and floral manuals have found that the vegetative plant parts from these five Monardella species intergrade with the other taxa in the complex throughout their distribution in California and in the western United States. Many of these vegetative characters are used to differentiate the five species from one another. Furthermore, floral characters have not been studied as a tool for delimiting species in this genus. Univariate and multivariate statistical analyses (ANOVA, Kruskal-Wallis, Principal Components Analysis, Discriminant Analysis, Mantel Tests, and Cluster Analysis) of measurements of nine vegetative and 21 floral characters were used to gain a more accurate idea of relatedness between these five species of Monardella and help strengthen the argument for reclassification of the species’ taxonomic identities. Based on analysis of single characters among the five Monardella species, discontinuities among the taxa were not observed. The multivariate analyses performed in this study were unable to fully segregate Monardella species from one another and did not suggest clearly defined taxa. Overlap and intermingling between all species was seen in all analyses. This study was unable to define consistent floral combinations for detecting and delimiting taxa. In floral morphology, flower length characters were found to be weakly correlated with flower width characters. This study found there was little to no relationships between both morphological distance and geographic location. However, both morphological variation and elevation were found to be more strongly correlated. In general, species boundaries in this complex are difficult to identify