The ability of populations to adapt, persist, and thrive in changing environments may depend on the genetic diversity present in a given population. Climate change affects the length and timing of seasons, which can alter or limit the time available for populations to complete their life cycles and successfully reproduce. These environmental constraints can especially impact the fitness of populations that reside at the edge of their geographic range, where environmental conditions are likely to be more extreme. Edge populations also tend to be smaller, more isolated, and often suffer from bottlenecking and/or inbreeding depression. Admixture can alleviate genetic load and increase fitness in such populations. Here, we assess the ability of admixed vs. non-admixed populations to adapt to novel life history constraints by using the red flour beetle, Tribolium castaneum, as a model system. We created populations likely to differ in diversity by crossing two to five distinct laboratory beetle strains together. We then compared the fecundity of these populations when reared under a shortened generation time.
Results/Conclusions
After only two generations, our results indicate that admixed populations were able to achieve a higher growth rate, and that growth rate increased with the number of strains included in each mix. These effects of diversity per se were compared with the effects of the presence of a beneficial strain in the mix (the strain with the highest fecundity), and diversity was shown to be the stronger predictor of population growth. This indicates that outcrossing alone, likely through the reduction of genetic load, may be sufficient to facilitate population adaptation to a shortened generation time. Rapid adaptation to changes in seasonality, therefore, can be facilitated by increasing gene flow from other populations, which do not need to be adapted to the constraints present in the new environment. This has implications for both the conservation of susceptible edge populations as well as the prevention of new outbreaks of invasive species, which can be aided by the increase or decrease of admixture from outside populations, respectively. Future steps will involve investigating the effects of a harsher environment on population adaptation rates to test the ability of population adaptation to overcome life history constraints as well as challenging environmental conditions.