Genetic Variation in Endemic and Widespread Plant Species

Population genetic theory and methodology were applied to the study of endemic plant species. Levels of genetic variability were compared between endemic species and their more widespread relatives. Six of seven narrowly distributed taxa of Saxifragaceae had significantly reduced genetic diversity relative to species of Saxifragaceae with broader distributions. Two endemic species of the fern Polystichum maintained significantly lower levels of genetic variation than did their more widespread congeners. The implications of these data and those reported for other endemic plant species for designing management strategies are also discussed

Healthcare Reform for Imagers Finding a Way Forward Now

The changing healthcare environment presents many challenges to cardiovascular imagers. This perspective paper uses current trends to propose strategies that cardiovascular imagers can follow to lead in managing change and developing the imaging laboratory of the future. In the area of quality, imagers are encouraged to follow guidelines and standards, implement structured reporting and laboratory databases, adopt ongoing quality improvement programs, and use benchmarks to confirm imaging quality. In the area of access, imagers are encouraged to enhance availability of testing, focus on patient and referring physician value and satisfaction, collaboratively implement new technologies and uses of imaging, integrate health information technology in the laboratory, and work toward the appropriate inclusion of imaging in new healthcare delivery models. In the area of cost, imagers are encouraged to minimize laboratory operating expenses without compromising quality, and to take an active role in care redesign initiatives to ensure that imaging is utilized appropriately and at proper time intervals. Imagers are also encouraged to learn leadership and management skills, undertake strategic planning exercises, and build strong, collaborative teams. Although it is difficult to predict the future of cardiovascular imaging delivery, a reasonable sense of the likely direction of many changes and careful attention to the fundamentals of good health care (quality, access, and cost) can help imagers to thrive now and in the future

Homeolog loss and expression changes in natural populations of the recently and repeatedly formed allotetraploid Tragopogon mirus (Asteraceae)

<p>Abstract</p> <p>Background</p> <p>Although polyploidy has long been recognized as a major force in the evolution of plants, most of what we know about the genetic consequences of polyploidy comes from the study of crops and model systems. Furthermore, although many polyploid species have formed repeatedly, patterns of genome evolution and gene expression are largely unknown for natural polyploid populations of independent origin. We therefore examined patterns of loss and expression in duplicate gene pairs (homeologs) in multiple individuals from seven natural populations of independent origin of <it>Tragopogon mirus </it>(Asteraceae), an allopolyploid that formed repeatedly within the last 80 years from the diploids <it>T. dubius </it>and <it>T. porrifolius</it>.</p> <p>Results</p> <p>Using cDNA-AFLPs, we found differential band patterns that could be attributable to gene silencing, novel expression, and/or maternal/paternal effects between <it>T. mirus </it>and its diploid parents. Subsequent cleaved amplified polymorphic sequence (CAPS) analyses of genomic DNA and cDNA revealed that 20 of the 30 genes identified through cDNA-AFLP analysis showed additivity, whereas nine of the 30 exhibited the loss of one parental homeolog in at least one individual. Homeolog loss (versus loss of a restriction site) was confirmed via sequencing. The remaining gene (<it>ADENINE-DNA GLYCOSYLASE</it>) showed ambiguous patterns in <it>T. mirus </it>because of polymorphism in the diploid parent <it>T. dubius</it>. Most (63.6%) of the homeolog loss events were of the <it>T. dubius </it>parental copy. Two genes, <it>NUCLEAR RIBOSOMAL DNA </it>and <it>GLYCERALDEHYDE-3-PHOSPHATE DEHYDROGENASE</it>, showed differential expression of the parental homeologs, with the <it>T. dubius </it>copy silenced in some individuals of <it>T. mirus</it>.</p> <p>Conclusions</p> <p>Genomic and cDNA CAPS analyses indicated that plants representing multiple populations of this young natural allopolyploid have experienced frequent and preferential elimination of homeologous loci. Comparable analyses of synthetic F₁hybrids showed only additivity. These results suggest that loss of homeologs and changes in gene expression are not the immediate result of hybridization, but are processes that occur following polyploidization, occurring during the early (<40) generations of the young polyploid. Both <it>T. mirus </it>and a second recently formed allopolyploid, <it>T. miscellus</it>, exhibit more homeolog losses than gene silencing events. Furthermore, both allotetraploids undergo biased loss of homeologs contributed by their shared diploid parent, <it>T. dubius</it>. Further studies are required to assess whether the results for the 30 genes so far examined are representative of the entire genome.</p