Question

6.) How are geography, niche, and genetics related to subpopulation structure?

Answer 1

Answer -

Many species are rare or can be rare at some point during their existence. Various species maintain this rarity over the course of their existence; thus, a question arises that is how can rare species maintain their population sizes when demographic challenges appear. Ecological and genetic explanations to rarity have been suggested. It is proposed that rarity should be considered in three ways: geographic range (wide or narrow), habitat specificity (broad or restricted) and local abundance. Further, species could be rare in different senses, having many forms of rarity. Only one possible combination of the wide range, broad habitat specificity and somewhere large local abundance is classified as common species and all other combinations are different forms of rarity.

The niche breadth is one of several suggested mechanisms to explain species commonness and rarity; species that maintain populations in more varied environments may have a wide geographic distribution. Niche and geographic distribution can be correlated with genetic variability. Species that present small population sizes and a restricted geographic range are expected to have reduced levels of genetic diversity. Insufficient variability would lead species to restrict their geographic range and be more vulnerable to extinction under novel selection pressure. However, whether and how the population would be affected by demographic processes, particularly genetic drift, depend on gene flow within and among populations , mating systems, pollen and seed dispersal, and effective population sizes. Small populations might also experience higher levels of inbreeding, which might maximize the effect of genetic drift.