Abstract Detail

Conservation Biology

LOCAL ADAPTATION OF THE DOMINANT PRAIRIE GRASS IN RECIPROCAL GARDENS ACROSS THE RAINFALL GRADIENT OF THE US CENTRAL GRASSLANDS: DECADAL PATTERNS.

Local adaptation is a fundamental phenomenon in evolutionary biology with implications for conservation, restoration, and climate change. Populations are said to be locally adapted when populations in their home environment have higher fitness than foreign populations planted in same location. Our focal species Andropogon gerardii (big bluestem), is a dominant, native, foundational grass important for forage, conservation, and restoration in the Great Plains. This grass has a wide distribution across the Great Plains precipitation gradient (500-1200 mm rainfall/yr), leading to formation of distinct dry and wet ecotypes. Using A. gerardii cross-transplanted across a climate gradient, objectives were to identify if ecotypes are locally adapted in realistic competitive settings, how ecotypes respond to experimental drought, and how ecotypes affect the surrounding community. To study local adaptation, we established from seed reciprocal gardens in 2009 in four garden sites (dry to wet: Colby 500, Hays 580 and Manhattan, KS 871 to Carbondale, IL 1200 mm rainfall/yr) and measured the biomass and cover produced by each ecotype and the surrounding community under the natural rainfall gradient. To examine drought effects, precipitation was reduced by 50% using rainout shelters in three sites (excluding the driest site in Colby). We predicted that each ecotype would outperform in their respective home sites compared to the foreign ecotype and the pattern of adaptation would strengthen over the years as succession progresses. We predicted that ecotype cover would be decreased under rainout shelters and that the wet and mesic ecotypes would be the most adversely affected by experimental drought. In terms of community response, we expected that where strong local adaptation of an ecotype was detected, this would result in an “extension of the phenotype” with competitive dominance over the surrounding community. Our results showed that dry and wet ecotypes performed best in their home site, demonstrating local adaptation to precipitation. In contrast, the mesic ecotype had intermediate cover and biomass across sites in all years, suggesting this ecotype is a generalist and can survive well across the precipitation gradient. Experimental drought supported the pattern observed by the natural precipitation gradient. Rainout shelters resulted in decreased cover of the wet ecotype in the dry site and increased dry ecotype cover in the wet site. These results indicate the prominent role of ecotypes across the natural and experimental precipitation gradient and strengthening of patterns of adaptation over time. Notably, local adaptation in some sites was not observed in earlier years, demonstrating the need for long-term study to detect these phenomena. Finally, strong local adaptation resulted in competitive dominance over the neighboring plant communities, indicating ecotypes “extend phenotypes” in the Great Plains. Due to the prediction of more severe, frequent droughts because of ongoing climate change, restoration ecologists should consider utilizing locally adapted ecotypes as tools for mitigating drought and preparing for future climate change.

1 - 1424 McCain Ln, Manhattan , KS, 66502, United States

Keywords:
none specified

Presentation Type: Poster
Number: PCB006
Abstract ID:363
Candidate for Awards:None