Final answer:
Increasing regional diversity likely increases the intercept (c) of the species-area relationship, which suggests higher base levels of local species richness. Factors such as landscape heterogeneity and both natural and human-induced constraints influence species richness and the specifics of the species-area relationship.
Step-by-step explanation:
Increasing regional diversity is likely to increase the intercept of the species-area relationship. The species-area relationship is a well-documented ecological pattern where the number of species increases with the area surveyed. This pattern is often represented as S = cAz, where S is species richness, A is area, and c is the y-intercept reflecting intrinsic levels of diversity. Increasing regional species richness could enhance local diversity, which in turn elevates the c value assuming a Type I relationship where local richness is proportional to regional richness.
Increased heterogeneity in the landscape, as seen in the Madrid region of Spain with varied land-uses, is strongly correlated with assemblage richness. This points to regional diversity as a driver for local biodiversity richness. On the other hand, where natural or semi-natural habitats are fragmented, as in the case of woodland-dependent birds in Australia, the total habitat extent is a more critical factor influencing species richness.
Moreover, geographical constraints and human activities, such as in catchment areas, play a role in shaping species distributions and richness. This suggests that not only the intrinsic biological interactions (like biotic resistance demonstrated in mesocosm experiments with native fish diversity limiting effects of invasive carp) but also extrinsic factors such as habitat diversity, human disturbance, and geographical features influence the position of the y-intercept in species-area curves.