Population Genetic Structure of the Mycoheterotroph <i>Monotropa hypopitys</i> L. (Ericaceae) and Differentiation between Red and Yellow Color Forms

Abstract

The mycoheterotroph Monotropa hypopitys L. has been used as a model organism for evolutionary ecology studies of nonphotosynthetic plant species. However, the species has perplexed plant biologists for centuries owing to confusion over taxonomic placement of two discrete color forms (red and yellow). The purpose of this study was to characterize the population genetic structure of M. hypopitys using 11 microsatellite markers and to determine levels of genetic differentiation between these two color forms. Results from this analysis demonstrated relatively low to moderate levels of genetic variation across populations in Ohio and Indiana (eastern United States), with levels of variation differing between color forms. Substantial genetic differentiation was detected among populations of the yellow color form and between the red and yellow color forms. Additionally, analyses showed genetic structuring of sympatric and allopatric populations of M. hypopitys by color form, a distinction that may support a taxonomic revision at the subspecific level. This study offers conclusive evidence of genetic divergence among populations and color forms of M. hypopitys, possibly arising from habitat fragmentation and limitations in gene flow associated with a mycoheterotrophic life history.