Final answer:
The question refers to the study of population genetics, which is a combination of evolutionary theory and Mendelian genetics focusing on genetic variability and phenotypic differences across populations due to geographic isolation.
Step-by-step explanation:
Genetic Variability and Geographic Separation in Populations
When populations of the same species are separated by geographic barriers such as rivers or mountains, it can lead to an increase in genetic differences among them. These differences are more pronounced as the physical distance between populations increases, a concept studied in the field of population genetics. This branch of biology combines evolutionary theory and Mendelian genetics to understand how populations evolve over time. By studying populations in terms of their genetic variability and phenotypic characteristics, scientists can observe patterns such as clines, where species exhibit gradual changes across an ecological gradient.
Latitudinal and altitudinal clines are examples of how populations can adapt to their environment in different geographic locations. For instance, warm-blooded animals may develop larger body sizes in colder climates to retain heat more effectively, demonstrating a latitudinal cline. Similarly, the timing of flowering in plants may vary with altitude, showing an altitudinal cline. These traits reflect the adaptations of populations to their specific ecological niches and conditions.
Geographic isolation can eventually lead to speciation, where new species arise due to the lack of gene flow and resulting genetic drift. Variations in environmental factors such as climate, food sources, and interactions with other species also drive this process. Thus, the statement about salmon species differing genetically across distances pertains to population genetics and can be illustrative of the broader evolutionary patterns seen in nature.