Questions 1 and 2 are based on this passage

Some studies have shown that red-backed salamanders (RBS) are scarce in areas with acidic soils and that those present in such conditions have smaller-than-average bodies. Explanations have included the possibility that young RBS are adversely affected by acidic soil, that adult RBS can sense and may avoid acidic soil conditions, or that loss of RBS prey populations due to acidic soil could result in reduced RBS populations. Yet researchers found fairly high densities of large- bodied RBS at Lake Claire Watershed, where soil conditions are acidic.
One hypothesis is that intraspecific geographical variation in acidity tolerance (i.e., local adaptation to an acidic environment) could exist for RBS. Previous studies showed potential local adaptation of some salamander species to acidity.