Evolutionary relationships and an investigation of sympatric speciation within Limnanthaceae.

摘要

Limnanthes floccosa ssp. floccosa and L. floccosa ssp. grandiflora are two of five subspecies, within the Limnanthes floccosa complex, endemic to vernal pools in southern Oregon and northern California. Three seasons of monitoring natural populations have quantified that L. floccosa ssp. grandiflora is always found growing sympatrically with L. floccosa ssp. floccosa and that their flowering times overlap considerably. Despite their close relationship, greenhouse crossing experiments have confirmed that their F1 hybrids are sterile. An analysis of twelve microsatellite markers, with unique alleles in each taxon, also shows almost no evidence of gene flow between populations of the two subspecies. Due to the lack of previous phylogenetic resolution within the L. floccosa complex, we used Illumina next generation sequencing to identify single nucleotide polymorphisms from genomic DNA libraries of L. floccosa ssp. floccosa and L. floccosa ssp. grandiflora. These data were used to identify single nucleotide polymorphisms in the chloroplast, mitochondrial, and nuclear genomes. From these variable loci, a total of 2772 bp was obtained using Sanger sequencing of ten individuals representing all subspecies of the L. floccosa complex and an outgroup. The resulting phylogenetic reconstruction was fully resolved. Our results indicate that although L. floccosa ssp. floccosa and L. floccosa ssp. grandiflora are closely related, they are not sister taxa and therefore likely did not diverge as a result of a sympatric speciation event.;The results of this phylogenetic portion of this study confirm the monophyly of two sections within Limnanthes and also suggest that Limnanthaceae may contain as few as four species of Limnanthes and the monotypic genus Floerkea proserpinacoides. Additionally, these results do not support taxonomic recognition of an anomalous 4-petaled Limnanthes population located in Half Moon Bay, California, U.S.A., rather it is likely part of a highly polymorphic Limnanthes douglasii sensu lato.;Lastly, from the results of this study we have determined that L. floccosa ssp. grandiflora and L. floccosa ssp. pumila are a species complex distinct from L. floccosa. Therefore, as part of a revision of L. floccosa we designate these taxa L. pumila ssp. grandiflora and L. pumila ssp. pumila.