Methods: We hypothesize that physiological homeostasis, the maintenance of physiological traits at a stable level despite environmental differences, allows tetraploids to survive in a diverse range of habitats, and so occupy a larger range. We identified clones of 205 tetraploid C. douglasii by sequencing 16 microsatellite loci. Currently we are collecting microsatellite data from more individuals in order to better test whether clones maintain a similar level of fitness in a variety of environments. Fitness is being estimated from pollen stainability, while environmental variation was estimated at the localities where specimens were collected from climate data, habitat composition, soil characteristics, and proximity to disturbance factors.
Results: Some polyploid clones live in a variety of environments. This implies that some mechanism, such as physiological homeostasis, allows C. douglasii tetraploids to survive in these diverse conditions. If clonal individuals living in different environments are able to maintain similar levels of fitness, this will be consistent with the idea that C. douglasii tetraploids tolerate varied conditions. However, if clonal individuals have varying levels of fitness across environments, this may indicate that physiological homeostasis is not operating, and other factors, such as high dispersal ability or increased adaptability account for the wide geographic range of tetraploids.
Conclusions: Not only do C. douglasii tetraploids inhabit a wider geographic range than diploids, there is also evidence that single clones occupy a variety of environments. This allows us to investigate whether the fitness of identical genotypes varies among these habitats and so test for evidence of physiological homeostasis as one possible mechanism of polyploid success.