Data from: Weaving a tangled web: divergent and reticulate speciation in Boechera fendleri sensu lato (Brassicaceae: Boechereae)

Hybrid speciation is relatively common in plants compared to other well-studied groups. Polyploidy and apomixis are strongly associated with hybrid speciation, presumably due to the opportunities they provide for both reestablishing reproductive function in hybrids with incomplete chromosomal homology and creating rapid reproductive isolation in sympatry. Boechera, a species-rich genus closely related to Arabidopsis, is a particularly fertile ground for the study of hybrid speciation. Thirty-eight apomictic triploid hybrid species are currently recognized in Boechera. Recent research has shown that apomictic diploid hybrids, although very rare in angiosperms, are common in Boechera. Given this complexity, focused studies of individual species complexes are critical to understanding speciation and diagnosing biodiversity in Boechera. Here we analyze DNA sequences from seven nuclear loci and multilocus genotypes from 15 microsatellite markers in a group of closely related taxa formerly included in B. fendleri. Our results support the recognition of four species previously segregated from B. fendleri s. l., including three genetically distinct, sexual diploids (B. fendleri, B. spatifolia, and B. texana) and one apomictic triploid hybrid (B. porphyrea). We also identify four novel apomictic diploid hybrid species (B. carrizozoensis, B. centrifendleri, B. sanluisensis, and B. zephyra) and additional apomictic triploid hybrids. Our results reveal a complex network of relationships. Sexual diploid species can hybridize to form apomictic diploids, and members of these two groups can hybridize to form trigenomic, apomictic triploids

Data from: Does hybridization drive the transition to asexuality in diploid Boechera?

Gametophytic apomixis is a common form of asexual reproduction in plants. Virtually all gametophytic apomicts are polyploids, and some view polyploidy as a prerequisite for the transition to apomixis. However, any causal link between apomixis and polyploidy is complicated by the fact that most apomictic polyploids are allopolyploids, leading some to speculate that hybridization, rather than polyploidy, enables apomixis. Diploid apomixis presents a rare opportunity to isolate the role of hybridization, and a number of diploid apomicts have been documented in the genus Boechera (Brassicaceae). Here we present the results of a microsatellite study of 1393 morphologically and geographically diverse diploid individuals, evaluating the hypothesis that diploid Boechera apomicts are hybrids. This genus-wide dataset was made possible by the applicability of a core set of microsatellite loci in 69 of the 70 diploid Boechera species and by our ability to successfully genotype herbarium specimens of widely varying ages. With few exceptions, diploid apomicts exhibited markedly high levels of heterozygosity resulting from the combination of disparate genomes. This strongly suggests that most apomictic diploid Boechera lineages are of hybrid origin, and that the genomic consequences of hybridization allow for the transition to gametophytic apomixis in this genus

Alexander-etal_Boechera-fendleri-sensu-lato_data

Specimen citations, GenBank accessions for novel sequence data (locus: pistillata; cloned from hybrid members of Boechera fendleri sensu lato), and complete microsatellite data (15 nuclear microsatellite loci from 374 individuals) for molecular systmatic investigation of Boechera fendleri sensu lato

96-well_extraction

The associated file describes a plant DNA extraction protocol modified for deep-welled tubes in 96-well racks

1393_diploids_data

Sample information for the 1393 diploids analyzed in this study

Microsatellite genotypes for the 60 samples analyzed in this study.

Microsatellite genotypes for the 60 samples analyzed in this study. Each microsatellite locus is presented in diploid format with the size of each allele in bp. Missing data is noted with a -1. Asterisks denote samples that were exact multilocus duplicates of other samples at resolved loci. DNA#s correspond to Appendix 1

Data from: Searching for diamonds in the apomictic rough: a case study involving Boechera lignifera (Brassicaceae)

The genus Boechera is one of the most difficult species complexes in North America, with about 70 sexual diploids and hundreds of apomictic taxa representing diverse combinations of nearly every known sexual genome. In this study, we set out to clarify the taxonomy of Boechera lignifera, which currently includes a small number of sexual diploid populations in addition to the widespread apomictic diploid upon which the name is based. Using data from cytological studies, microsatellite DNA analyses, geography, and morphology, we demonstrate that the apomictic populations are genetically quite divergent from the sexual diploids. We propose the name Boechera kelseyana to accommodate the sexual diploid taxon, which occurs entirely south of the geographic range of B. lignifera. Boechera kelseyana is consistently separable from B. lignifera based on pollen and seed morphology, the length and proximal orientation of fruiting pedicels, differences in the branching and orientation of trichomes on the lowers stems, and the number of flowers and cauline leaves on unbranched fertile stems