UC San Diego

Accurately predicting how species respond to climate change is increasingly important as current methods suggest most will be unable to adapt. But can organisms respond to climate change faster than studies of selection alone suggest? Here we investigate potentially extreme phenotypes of heat tolerance resulting from complimentary gene action. We do so by hybridizing two populations in allopatry of Tigriopus californicus with high genetic divergence from similar temperature regimes. Parentals as well as F1, F2 and F6+ generations are subjected to acute heat stress at a sublethal and lethal temperature. We also look at life history traits for these hybrids to understand the overall viability of these populations. 8 of the 20 F6+ lines had survivorships significantly higher than parentals after being stressed at the sublethal temperature. 3 of those 8 had significantly higher survivorship after being stressed at the lethal temperature. Aside from breakdown resulting from hybridization alone, no further degradation of life history traits were seen in the 8 lines exhibiting extreme thermal tolerance. These results suggest that hybrids of populations in allopatry can respond faster to climate change than studies on selection alone have suggested.