Genetic diversity within dominant species can affect ecosystem functioning and community processes. It is unknown if climate change causes a loss of genetic diversity by creating conditions that favor some genotypes over others, and whether loss of genetic diversity within a dominant species impacts community and ecosystem processes. 

Using an on-going climate change experiment-the Rainfall Manipulation Plots (RaMPs) at Konza Prarire, KS-we investigated the effect of more variable precipitation patterns, a key aspect of climate change, on genotypic diversity of the dominant C4 grass, Andropogon gerardii. The RaMPs experiment, which consists of twelve rainfall manipulation plots, was established in intact tallgrass prairie. Since 1998, six plots have received ambient growing season rainfall (ambient) and the other six plots have received the same amount of rainfall but in more variable pattern consisting of a 50% increase in the timing between rainfall events (altered). To assess the effects of more variable precipitation patterns on genotypic diversity, we sampled 40 tillers of A. gerardii within permanent 2 x 2 m plots located in each RaMP.  For comparison, we also sampled the same number of tillers in 2 x 2 m plots established adjacent to the RaMPs in an identical spatial array.  We then used amplified fragment length polymorphisms (AFLP) analysis to distinguish between genotypes within and between sample plots.

Results/Conclusions

Overall, many genotypes had a small spatial range, found only within one plot. Five genotypes had a much larger spatial range, extending across at least three plots. We found no difference the number of genotypes in a plot or the dominance of genotypes in a plot between RaMP treatments (altered and ambient), or between the RaMPs and intact prairie. However, two genotypes appear to benefit from the altered rainfall treatments, more frequent in the altered-rainfall plots, than the ambient-rainfall plots or intact prairie. The alteration of genetic diversity within the dominant species could have consequences for community level processes including diversity and productivity.