What is a fitness landscape and how does population genetics view local vs global optima?

• A. A map of environmental variables affecting survival
• B. A simple measure of genetic distance between populations
• C. A mapping of genotypes to fitness values; populations may be trapped on local optima; selection and drift determine trajectories across the landscape
• D. A landscape that always leads to global optimum

Answer: (C)

A fitness landscape is a conceptual map in population genetics where each genotype is assigned a fitness value, plotted as heights on a landscape. As mutations create new genotypes and selection acts to increase reproductive success, populations tend to move uphill. But the landscape can be rugged, with many peaks (local optima) separated by valleys. A population can climb to a local peak and become stuck there if the nearby mutational steps would lower fitness, making it hard to reach a higher, global peak. Random fluctuations from genetic drift—especially in small populations—can help populations explore the landscape, potentially crossing valleys or shifting to different peaks. Because of this, there isn’t always a single best global optimum; different populations can end up on different high peaks depending on starting point and chance. The best description, then, is a mapping of genotypes to fitness values, with local optima and trajectories shaped by selection and drift. The other ideas miss essential parts: fitness landscapes aren’t just environmental maps, they aren’t simple genetic-distance measures, and they don’t guarantee a move to the global optimum.