How different levels of genetic variance affect the rate of evolutionary change within populations has also been intensively studied. Such changes were originally studied using phenotypic markers: variation among individual plants in traits, such as leaf shape or flower color (Ward et al., 2008). Subsequently the detection of genetic variation has become more sensitive, firstly through the utilization of variation in enzymes (allozymes) and then through PCR-based marker systems allowing direct examination of DNA sequence variation. The precise detection of genetic variation/diversity has greatly enhanced studies of evolution
