Development of microsatellite markers for the apomictic triploid fern Myriopteris lindheimeri (Pteridaceae)

PREMISE OF THE STUDY

Microsatellite markers were developed for investigating the population dynamics of Myriopteris lindheimeri (Pteridaceae), an apomictic triploid fern endemic to deserts of the southwestern United States and Mexico.

METHODS AND RESULTS

Using 454 sequencing, 21 microsatellite markers were developed. Of these, 14 were polymorphic with up to five alleles per locus and eight markers amplified in one or more congeneric close relatives (M. covillei, M. fendleri, M. aurea, and M. rufa). To demonstrate marker utility, M. lindheimeri samples from three Arizona populations were genotyped at nine loci. For each population, diversity measures including percent polymorphic loci, frequency of heterozygotes across all loci, and genotypic diversity were calculated. Across the three populations, on average, 63% of loci were polymorphic, the average frequency of heterozygotes (across all loci) was 0.32, and average genotypic diversity was 0.34.

CONCLUSIONS

These markers provide a foundation for future studies exploring polyploidy and apomixis in myriopterid ferns.

Toward a monophyletic Cheilanthes: The resurrection and recircumscription of Myriopteris (Pteridaceae)

The fern genus Cheilanthes (Pteridaceae) has perplexed taxonomists for more than two centuries. Complex patterns of evolution involving rampant morphological convergence, polyploidy, hybridization, and apomixis have made the taxonomy of this group especially difficult. Fortunately, recent phylogenetic analyses have helped to clarify relationships among cheilanthoid taxa. Based on these findings, we here formalize an updated taxonomy for one monophyletic clade comprising 47 primarily North and Central American taxa usually included in Cheilanthes. Because the type species of Cheilanthes (Cheilanthes micropteris) is only distantly related to this clade, we resurrect the genus Myriopteris to accommodate these taxa, and present a revised circumscription for the group, including 36 new combinations.