Tuesday, August 7, 2018
ESA Exhibit Hall, New Orleans Ernest N. Morial Convention Center
Andrea M. Keeler, Department of Evolution, Ecology, and Organismal Biology, University of California, Riverside and Nicole E. Rafferty, Department of Evolution, Ecology, and Organismal Biology, University of California, Riverside, CA
Background/Question/Methods
Species are shifting in space in response to global climate change and these shifts can expose species to novel environments and alter their mutualistic interactions with other species. Legumes, plants of the Fabaceae family which often have deeply entwined mutualisms with rhizobia, may require exposure to soils that have been inoculated with compatible microbial symbionts to establish and persist. It is unknown how rhizobial species will respond to global climate change and how these changes will impact their plant symbionts. We investigated whether the upward elevational shifts of two bumble bee pollinated legume species (Lathyrus lanszwertii var. leucanthus and Vicia americana) in the Rocky Mountains in Colorado, USA, may be facilitated by the soil microbial symbionts of a third, well-distributed legume species (Lupinus argenteus), which is known to harbor a diverse rhizobial community. Soils were collected from sites where all three legume species co-occur (3200 m elevation) and from sites containing only L. argenteus (3700 m elevation). We tested whether germination of L. leucanthus and V. americana is contingent upon rhizobia. We also tested if germination of L. leucanthus and V. americana is possible in the soils past their current elevational range due to rhizobial inoculation by L. argenteus.
Results/Conclusions
Germination of L. leucanthus and V. americana was not contingent upon the rhizobial symbionts of L. argenteus as they were able to successfully germinate in sterilized soils. However, the onset of germination in soils lacking rhizobia was greatly delayed compared to natural soils. Both legumes were able to germinate in soils from beyond their range and germinated at the same time as individuals planted in soils from the current range. This suggests that if the necessary bacteria are present and active in novel soils at the time of germination, upward range expansion of L. leucanthus and V. americana should be able to occur; if the rhizobia are dormant during the germination and early growth period of seedlings, the establishment of L. leucanthus and V. americana will be slowed. This is potentially detrimental as water or nutrients could be difficult to obtain later in the season when competition may be higher. These data suggest that upward range expansion of these legumes is not limited to sites where L. argenteus occurs. L. argenteus and their rhizobia may facilitate a more optimal onset of germination of L. leucanthus and V. americana as these species colonize novel elevations beyond their current ranges.
