Final answer:
Beta diversity measures the number of unique species not shared between two habitats, quantifying how much they differ in species composition.
Step-by-step explanation:
The comparison of two habitats to count the number of unique species not shared between the two relates to beta diversity. Beta diversity is a measure of species uniqueness between areas and quantifies the difference in species composition. Unlike alpha diversity, which focuses on the diversity within a single habitat or ecosystem, or gamma diversity that refers to overall species diversity within a larger region encompassing multiple ecosystems, beta diversity highlights the variability of species between different ecosystems or habitats. It is an important concept for understanding how species turnover and differentiation contribute to the overall biodiversity of landscapes.
Beta diversity increases when locations differ significantly from one another in terms of the species they contain. This diversity can help support ecosystem services by providing spatial insurance through complementary resource use, as different species that are not present or not important in one habitat might play crucial roles in others. This is particularly key in managing ecological systems and ensuring the sustainability of various ecosystem functions.