Around the world in 40 million years: Phylogeny and biogeography of Tecomeae (Bignoniaceae).

Intercontinental disjunct distributions can arise from vicariance, long distance dispersal, or both. Tecomeae (Bignoniaceae) are a nearly cosmopolitan clade of flowering plants providing us with an excellent opportunity to investigate global distribution patterns. While the tribe contains only about 57 species, it has achieved a distribution that is not only pantropical, but also extends into the temperate zones in both the Northern and Southern hemispheres. This distribution is similar to the distribution of its sister group, a clade of about 750 spp. that includes most remaining taxa in Bignoniaceae. To infer temporal and spatial patterns of dispersal, we generated a phylogeny of Tecomeae by gathering sequence data from chloroplast and nuclear markers for 41 taxa. Fossil calibrations were used to determine divergence times, and ancestral states were reconstructed to infer its biogeographic history. We found support for a South American origin and a crown age of the tribe estimated at ca. 40 Ma. Two dispersal events seem to have happened during the Eocene-Oligocene, one from South America to the Old World, and another from South America to North America. Furthermore, two other dispersal events seem to have taken place during the Miocene, one from North America to Asia, and another from Australia to South America. We suggest that intercontinental dispersal via land bridges and island hopping, as well as sweepstakes of long distance dispersal from the Eocene to the present explain the global distribution of Tecomeae.

What is the "modified" CTAB protocol? Characterizing modifications to the CTAB DNA extraction protocol.

Cetyltrimethylammonium bromide (CTAB)-based methods are widely used to isolate DNA from plant tissues, but the unique chemical composition of secondary metabolites among plant species has necessitated optimization. Research articles often cite a "modified" CTAB protocol without explicitly stating how the protocol had been altered, creating non-reproducible studies. Furthermore, the various modifications that have been applied to the CTAB protocol have not been rigorously reviewed and doing so could reveal optimization strategies across study systems. We surveyed the literature for modified CTAB protocols used for the isolation of plant DNA. We found that every stage of the CTAB protocol has been modified, and we summarized those modifications to provide recommendations for extraction optimization. Future genomic studies will rely on optimized CTAB protocols. Our review of the modifications that have been used, as well as the protocols we provide here, could better standardize DNA extractions, allowing for repeatable and transparent studies.

Optimizing the lysis step in CTAB DNA extractions of silica-dried and herbarium leaf tissues.

Premise: The use of cetyltrimethylammonium bromide (CTAB) is an effective and inexpensive method of extracting DNA from plants. The CTAB protocol is frequently modified to optimize DNA extractions, but experimental approaches rarely perturb a single variable at a time to systematically infer their effect on DNA quantity and quality. Methods and Results: We investigated how chemical additives, incubation temperature, and lysis duration affected DNA quantity and quality. Altering those parameters influenced DNA concentrations and fragment lengths, but only extractant purity was significantly affected. CTAB and CTAB plus polyvinylpyrrolidone buffers produced the highest DNA quality and quantity. Extractions from silica gel-preserved tissues had significantly higher DNA yield, longer DNA fragments, and purer extractants compared to herbarium-preserved tissues. Conclusions: We recommend DNA extractions of silica gel-preserved tissues that include a shorter and cooler lysis step, which results in purer extractions compared to a longer and hotter lysis step, while preventing fragmentation and reducing time.