PgmNr P2031: Detecting patterns of microgeographical adaptation to a patchy saline environment of a single popupation of Medicago truncatula.

Authors:
w. vu 1 ; P. Chang 1 ; K. Moriuchi 4 ; E. von-Wettberg 2 ; M. Friesen 3 ; S. Nuzhdin 1


Institutes
1) Univ Southern California, University Park Campus, Los Angeles, CA 90089; 2) Florida International university 11200 SW 8th St, Miami, FL 33199; 3) Michigan State University 220 Trowbridge Rd, East Lansing, MI 48824; 4) University of California, Davis 1 Shields Ave, Davis, CA 95616.


Abstract:

Divergent selective pressures across a heterogeneous environment can result in the maintenance of genetic variation and adaptation to local environmental conditions. While this process has been well documented at larger geographical scales, it remains unknown whether micro-environmental variation can result in the maintenance of genetic variation. Therefore we aim to understand the genetic basis of plant response to micro-environmental variation.  Our study examines the patterns of micro-scale adaptation to a saline habitat within a single population of Medicago trucatula—an annual selfing legume that is native to Mediterranean regions.

Early flowering is a predictor of increased plant performance and reproductive output in saline conditions. We observe that flowering time is negatively correlated with soil salinity levels in the field, indicating that the variability in soil patches can maintain phenotypic variation and potentially genetic variation. This suggests that variable selective pressure between soil patches is likely driving divergent flowering time responses within a single selfing population. Furthermore, SNP frequency is strongly associated with latitude, longitude, elevation and soil salinity levels. Some of the polymorphisms correlated with environmental variability cause functional changes in genes associated with flowering time, disease resistance, salt and osmotic stress. Overall, these results suggest that micro-scale environmental variation can potentially shape patterns of adaptation to heterogeneous environments.