High microsatellite genetic diversity fails to predict greater population resistance to extreme drought

There is intense debate whether genetic diversity measured via neutral molecular markers can be used as a surrogate for fitness and as an indirect estimate of the amount of genetic variation for fitness-related traits in a population. Here, we measured microsatellite DNA genetic diversity (before the onset of drought) and mortality after prolonged drought in 15 populations of Banksia hookeriana in the species-rich southwestern Australian flora, to test the relationship between population genetic diversity and resistance to extreme climate fluctuations. Number of alleles per locus varied from 5.2 to 8.2 at eleven microsatellite loci among 30 individuals in each population. Mortality varied from 25 to 50% in individual populations after prolonged drought. Lower mortality was not observed in populations with higher genetic diversity, but in populations with lower genetic diversity. Thus, higher microsatellite genetic diversity fails to predict lower population mortality during extreme drought in B. hookeriana. Our results imply that it may be misleading to use studies of neutral genetic variation exclusively as the basis for inferring population and species capacity for resisting extreme climate events and for species conservation and management decisions.