Geographical subdivision is lacking in both species, even though recurrent gene flow by both pollen and seed is severely limited. These mutations exist as dominant cytotypes across populations and species. Only successful 'surfing mutations' reach very high frequencies and occupy a large portion of a species range. Conclusionįates of newly derived mutations of cycads follow Klopfstein et al.'s surfing model where the majority of new mutations do not spread geographically and remain at low frequencies or are eventually lost by genetic drift. Molecular dating estimated that mt- and cp DNA lineages coalesced to the most recent common ancestors (TMRCA) about 327 (mt) and 204 MYA (cp), corresponding with the divergence of cycad sections in the Mesozoic. The lack of reciprocal monophyly between these long isolated sections is likely due to persistent shared ancestral polymorphisms. Phylogenetic analyses revealed paraphyly of both loci in the two species and also in the section Asiorientales.

The phylogenies of ribosomal ITS region of mtDNA and the intergenic spacer between atpB and rbcL genes of cpDNA were reconstructed. revoluta is found in the Ryukyu Archipelago and on mainland China. taitungensis is limited to Taiwan whereas C. Fossil evidence indicates divergence of the section from the rest of Cycas at least 30 million years ago. taitungensis, species that constitute the section Asiorientales and represent a unique, basal lineage of the Laurasian genus Cycas. This study addresses the apportionment of genetic diversity between Cycas revoluta and C.

Ancestral polymorphism and gene flow