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We use population genetic, traditional quantitative genetics, association genetics, and greenhouse and field studies to understand evolutionary process shaping diversity in natural populations.

At present we are primarily working on questions related to the population genomics and evolution in legume-rhizobia  symbioses and local adaptation to urban environments.  

Genomic diversity in Medicago truncatula and Association Mapping of symbiosis genes in Medicago and Sinorhizobia

As part of a multi-investigator project that is developing resources for association mapping in the model plantMedicago truncatula we are investigating the evolutionary forces shaping nucleotide diversity as well as evaluating association mapping approaches. We are particularly interested in identifying and characterizing the evolutionary history of genes responsible for intra specific variation in interactions with Medicagos rhizobiamutualists. We have previously used data on nucleotide variants to conduct association mapping and to characterize the evolutionary history of Medicago.  Collaborators and I have recently expanded that work to examine structural variation segregating in Medicago and the potential phenotypic consequences of copy number variants.  We also have been conducting functional assays to evaluate phenotypic effects of candidate genes identify by our earlier association analysis -- thus far the results look great and validate and point to several previously uncharacterized genes with functional roles in nodule formation.

We are conducting similar work in the Sinorhizobia mutualists of Medicago and have collected full genome sequence data for nearly 200 strains of Sinorhizobia (in addition to 48 strains we had earlier analyzed).  We are now using these data to characterize genomic diversity in Sinorhzibia, understand the evolutionary history of the species, and conduct association mapping to identify functional importance of genes.  

For more information please visit our project website.

Adaptation and evolution in urban environments

Urban environments are interesting habitats to investigate evolutionary processes and provide an opportunity to investigate how species are affected by heavily altered environments.  We have been investigating whether and how plant populations have adapted to urban environments and how fragmentation and population structure may affect such adaptation.  

Recent research

Population Genomics and in Populus balsamifera

Matt Olson (Univ. of Alaska, Fairbanks) and I used population genetic analysis to identify genes and characterize the evolutionary history of genes likely involved in adaptation of Populus to northern latitudes.  We have also collaborated with Miki Balint and Imke Schmitt in characterizing the foliar fungal microbiome of this species, and the relative importance of the environment and host genotype in shaping that microbiome. 

Ecological and Evolutionary Limits to Species Range Expansion

Monica Geber at Cornell University, Vince Eckhart at Grinnell College, and Dave Moeller at University of Georgia. and I are using Clarkia xantiana (an annual plant native to the southern Sierra Nevada Mountains) to investigating the geographic limits to species range, a fundamental and long-standing problem in ecology and evolution. We are using i) demographic censuses and seed bank experiments to investigate demographicstochasticity, ii) GIS-based niche modeling to characterize suitable habitat; molecular population genetics to evaluate historical population structure, effective population sizes, and gene flow, and iv) reciprocal common-garden experiments to quantify selection and genetic variance across a species range. The results from this series of experiments will provide insight into the basic processes that determine species ranges and provide an opportunity to evaluate predictions from theoretical models predicting limits to local adaptation.

Peter Tiffin
612 624-7406

Dept. of Plant Biology
Univ. of Minnesota
250 Biosciences
St. Paul, MN 55108

Graduate Faculty:
Ecology, Evolution, and Behavior, and Plant Biology