Phylogeny of Cirsium spp. in North America: Host Specificity Does Not Follow Phylogeny.

Weedy invasive Cirsium spp. are widespread in temperate regions of North America and some of their biological control agents have attacked native Cirsium spp. A phylogenetic tree was developed from DNA sequences for the internal transcribed spacer and external transcribed spacer regions from native and non-native Great Plains Cirsium spp. and other thistles to determine if host specificity follows phylogeny. The monophyly of Cirsium spp. and Carduus within the tribe Cardinae was confirmed with native North American and European lineages of the Cirsium spp. examined. We did not detect interspecific hybridization between the introduced invasive and the native North American Cirsium spp. Selected host-biological control agent interactions were mapped onto the phylogenic tree derived by maximum likelihood analysis to examine the co-occurrence of known hosts with biological control agents. Within Cirsium-Cardueae, the insect biological control agents do not associate with host phylogenetic lines. Thus, more comprehensive testing of species in host-specificity trials, rather than relying on a single representative of a given clade may be necessary; because the assumption that host-specificity follows phylogeny does not necessarily hold. Since the assumption does not always hold, it will also be important to evaluate ecological factors to provide better cues for host specificity.

High throughput tissue preparation for large-scale genotyping experiments.

A fast, efficient technique is described for the extraction of DNA from a large number of samples. The applications of this method include population genetics, plant breeding, and genetic screening. In the field, samples are collected in premeasured silica gel aliquots in polypropylene blocks, which are later used to grind the dried tissue. This permits naturalists, breeders, and collaborators to collect a large number of samples in a short amount of time and allows the samples to dry quickly during shipping. No phenol or chloroform steps are required to obtain high-quality DNA. Samples representing 12 plant families, three invertebrates, and a mammal were included. Quantities of DNA obtained were consistent with or better than other techniques. The quality of samples was tested by amplification of the internal transcribed spacer region. Test amplifications were successful, confirming the quality of extracted DNA.