Covarying phenotypic traits can limit natural selection’s ability to modify these traits. Most evolutionary studies on trait covariation use the comparative method to study complex traits of multicellular organisms. Simpler traits have the advantage of being amenable to experimental evolution. Here we study such a simple molecular system, the TEM-1 beta-lactamase protein, a promiscuous enzyme t...

fifteen yarrow populations from different species achillea millefolium l., a. biebersteinii l. and a. nobilis, from different geographical areas of iran were studied using 24 morphological traits and peroxidase profiles. comparison of mean values of different phenotypic traits show a. millefolium and a. biebersteinii l. had higher plant height and crown diameter; however, a. nobilis had higher ...