Final answer:
Island Biogeography Theory discusses the species richness balance due to colonization and extinction on isolated islands, whereas Forest Fragments also consider the influence of the surrounding landscape―including altered species interactions and other ecological processes―after habitat fragmentation.
Step-by-step explanation:
The major difference between islands hypothesized by Island Biogeography Theory and Forest Fragments lies in the dynamics of species richness and their physical and biological interactions with the surrounding landscape. While island biogeography focuses on the balance between colonization and extinction rates of species on actual islands, forest fragments are influenced by land use changes and habitat quality in the wider landscape. With forest fragments, their proximity to similar habitats and the nature of surrounding land uses can affect species movements and lead to varied ecological processes, such as species interactions and biophysical changes that occur after isolation.
For example, forest fragments can experience an 'ecological meltdown' where changes in species dynamics, such as the loss of predators and overabundance of certain species, drastically alter the local ecosystem. Conversely, island biogeography often considers islands in isolation, where species diversity is primarily influenced by immigration, speciation, and extinction processes, with island size and distance from the mainland being crucial factors. Therefore, while both concepts apply the principles of species-area relationship, the importance of the matrix surrounding forest fragments introduces additional layers of complexity not present in traditional island biogeography.