Morphological and genetic polymorphism in two North American reindeer lichens: Cladonia arbuscula and C. rangiferina

Cladonia arbuscula and C. rangiferina are two reindeer lichen species, which are widely distributed in northern climates and have not been shown to be monophyletic, suggesting incomplete lineage sorting and speciation. The wide species distribution may suggest strong adaptive potential and an outcrossing reproductive life style, which might explain the lack of monophyly and success of these two species. The current study examined the genetic diversity of mycobiont ascospore colonies within and between apothecia of two species, C. rangiferina and C. arbuscula s. l. using Randomly Amplified Polymorphic DNA (RAPD)-PCR, estimates of gene flow, morphology, and colony growth rates. Cladonia rangiferina showed higher rates of growth than C. arbuscula but more variability in growth between apothecia was observed in C. arbuscula than C. rangiferina. Both species showed levels of genetic variation within and among apothecia that was consistent with heterothallism and recombination. AMOVA analyses provided evidence for gene flow among apothecia in both species. It is hypothesized that higher genetic variation in C. arbuscula than in C. rangiferina may give C. arbuscula an adaptive advantage over C. rangiferina.