These trait measurements were taken on four different species at two different study sites. Column descriptions: Site = Organ Pipe National Monument (OPNM) or Tumamoc Hill (TH). Species = ERLA (Eriophyllum lanosum), ERTE (Erodium texanum), PERE (Pectocarya recurvata) or STMI (Stylocline micropoides). ID = unique id # assigned to each individual in the field. RelFitness = the relative fitness of each individual, calculated as individual biomass/population mean. stdRGR = relative growth rate, standardized within each population by subtracting the mean and dividing by the standard deviation. stdSLA = specific leaf area, also standardized as described above. stdRMR = root mass ration, standardized stdN = leaf nitrogen content, standardized stdDELTA = delta, a measure of carbon isotope discrimination, standardized Missing cases are designated with a Ò.Ó