Environmental influence on interspecific and intraspecific variation within the genus Osmorhiza in northern Michigan.

Abstract

Three species of the genus Osmorhiza are commonly found growing together in Northern Michigan and exhibit a number of similar morphological characters. The objective of our study was to determine if the variation between the three species was influenced by non-genetic environmental factors, and what effect the pH and soil moisture content had on morphological variation within each species. We surveyed approximately 35 individuals from each Osmorhiza species at the Headlands, a preserve in northwestern Lower Michigan, and recorded specific morphological features of each individual. We also took soil measurements of pH and moisture content. Our results showed significant distinction between the three species on the basis of bract length, bract width, and style length (p<0.000), pubescence, (p<0.000), scent (p<0.000), and presence or absence of purple along the stem (p<0.000). The results showed significantly different preferences for pH and moisture levels between each of the three species (pH: p<0.000; soil moisture: p=0.001). Environmental conditions were also shown to have an effect on several morphological characters, including pH and pubescence (leaf: p=0.04; petiole: p=0.001), moisture and petiole pubescence (p=0.052) and moisture and the presence of a leaflet-like bract (p=0.054). These results provided interspecific delineation and demonstrated the effect of pH and soil moisture on intraspecific morphological variation and species preference for moisture and pH.