Your first question is valid in that three populations versus two is not in itself necessarily a concern. For example if each of the three current populations was as big, or bigger, than each of the original two. But in this case, each of the three populations, and particularly the one in the semi-arid region is small, and the genetic distinctness of the populations suggests there is little if any inter-breeding between them. Small, isolated populations are not genetically healthy, since inbreeding increasing the probability of homozygosity, which means that problems associated with recessive genes are more likely. Small genetically uniform populations are often considered to be at great risk of (local) extinction eg see http://onlinelibrary.wiley.com/doi/10.1046/j.1523-1739.1995.09040792.x/a... Your second question is somewhat vague, and seems to mistakenly project human desires onto nature. It is true however that the progeny of the individual tigers must be experiencing selection pressures that could -- in theory -- make the future tiger populations more adapted to the changing circumstances of their habitats. The reality however is that these changes are occurring so rapidly that 'suitable' adaptations are unlikely to emerge. And inbreeding compounds the problem, since, as noted above, it increases the genetic uniformity of the affected population.