Genes affect ecosystems through fine-root production pathways.
Fischer, Dylan *,1, 2, Hart, Steve1, 2, Rehill, Brian 3, Whitham, Thomas2, Lindroth, Rick4, 1 School of Forestry, Box 15018, Flagstaff, AZ, USA2 Merriam-Powell Center for Environmental Research, Flagstaff, AZ, USA3 Chemistry Department, Annapolis, MD4 Dept. of Entomology, Madison, WI
ABSTRACT- Do genetics of naturally occurring dominant plant species affect root dynamics? Since roots often have gene-specific interactions with other belowground organisms (Hirsch et al. 2003, Phillips et al. 2003), represent an important and dynamic component of nutrient and carbon cycles (Hendrickson and Robinson1984, Hendricks et al. 1993), and can be under strong genetic control (Pregitzer and Friend 1996), the effects of genetics on fine root dynamics in natural systems can not be ignored. We hypothesized that fine root dynamics can be under strong genetic control in nature and thus represent an ideal pathway through which genes can alter ecosystems dynamics. To test this we measured fine root production along a genetic hybridization gradient from Populus fremontii to P. angustifolia in an experimental common garden. Using minirhizotron measurements we found that root production was highly correlated with proportion of P. fremontii RFPL markers (R2 = 0.76, P < 0.0001) and leaf tannin concentration (R2 = 0.66, P< 0.0001). This trend reflects the patterns found by Schweitzer et al. (2004) demonstrating genetic control over tannin concentration in the leaves and nutrient cycling. We hypothesize that our unique finding has two explanations. 1) Genotypes with high leaf tannin content inherently produce more fine roots in order to enable greater foraging ability for nitrogen, or 2) tannin concentration in the leaves reduces nitrogen availability thus influencing higher root growth. Regardless, our finding demonstrates that the effect of genes on ecosystems can also take place through belowground pathways.
Key words: roots, ecosystems, minirhizotron, genetics
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