Experimental evolution of S. cerevisiae X S. uvarum hybrids under increasing temperature (A) and ethanol (B). Six replicate populations, founded by the same genetically diverse hybrid pool (see Figure 1), were selected for 200 days (~500 generations) under glucose-sufficient, nitrogen-limiting conditions. Population size was estimated as viable cells mL-1. The dashed line represents dilution rate, D, in h-1; the solid red line represents vessel temperature (A), the solid blue line represents ethanol content of the medium fed to evolving populations (B) (Mean ± S.E.).