Understanding the ecological and genetic mechanisms of adaptation remains one of the central goals of evolutionary biology. What is the extent of geographic adaptation? What traits contribute to adaptive differentiation? What is the genetic basis of adaptive traits? How many traits and genes are required for major adaptations? Is geographic adaptation an important first step in the origin of species?
Studies of geographic adaptation in plants have long provided some of our best examples of adaptive evolution. I will discuss three research projects that illustrate different approaches to the study of plant adaptation. Experimental studies of hybrids between the perennial plant Lobelia cardinalis collected from Michigan and its close relative L. graminea collected from Panama reveal that rosette production is a major factor contributing to winter survival in Michigan. A genetic mapping study found that a single, major QTL controlled rosette production, and a field study of experimental evolution indicated that plants homozygous for the Michigan allele at the rosette QTL had much higher survival than the heterozygous genotype.
We are in the early stages of investigating the ecological genetics of geographic adaptation in natural populations of the model plant Arabidopsis thaliana. We find evidence of striking geographic adaptation from reciprocal transplant experiments conducted in Sweden and Italy. Laboratory studies are underway to investigate the genetic basis of freezing tolerance and flowering time, and field experiments of experimental evolution have identified major QTL for fitness.
Field and greenhouse studies of two closely related, Neotropical gingers (Costus spp.) indicate that local adaptation to edaphic factors has played an important role in adaptation and speciation. Costus allenii inhabits dense forest understory along streams while C. viollosissimus is found along forest edge in full sun. The two species are easily crossed to produce fully...