Asymmetrical Gene Flow in a Hybrid Zone of Hawaiian Schiedea (Caryophyllaceae) Species with Contrasting Mating Systems

Asymmetrical gene flow, which has frequently been documented in naturally occurring hybrid zones, can result from various genetic and demographic factors. Understanding these factors is important for determining the ecological conditions that permitted hybridization and the evolutionary potential inherent in hybrids. Here, we characterized morphological, nuclear, and chloroplast variation in a putative hybrid zone between Schiedea menziesii and S. salicaria, endemic Hawaiian species with contrasting breeding systems. Schiedea menziesii is hermaphroditic with moderate selfing; S. salicaria is gynodioecious and wind-pollinated, with partially selfing hermaphrodites and largely outcrossed females. We tested three hypotheses: 1) putative hybrids were derived from natural crosses between S. menziesii and S. salicaria, 2) gene flow via pollen is unidirectional from S. salicaria to S. menziesii and 3) in the hybrid zone, traits associated with wind pollination would be favored as a result of pollen-swamping by S. salicaria. Schiedea menziesii and S. salicaria have distinct morphologies and chloroplast genomes but are less differentiated at the nuclear loci. Hybrids are most similar to S. menziesii at chloroplast loci, exhibit nuclear allele frequencies in common with both parental species, and resemble S. salicaria in pollen production and pollen size, traits important to wind pollination. Additionally, unlike S. menziesii, the hybrid zone contains many females, suggesting that the nuclear gene responsible for male sterility in S. salicaria has been transferred to hybrid plants. Continued selection of nuclear genes in the hybrid zone may result in a population that resembles S. salicaria, but retains chloroplast lineage(s) of S. menziesii

The coming acceleration of global population ageing

The future paths of population ageing result from specific combinations of declining fertility and increasing life expectancies in different parts of the world. Here we measure the speed of population ageing by using conventional measures and new ones that take changes in longevity into account for the world as a whole and for 13 major regions. We report on future levels of indicators of ageing and the speed at which they change. We show how these depend on whether changes in life expectancy are taken into account. We also show that the speed of ageing is likely to increase over the coming decades and to decelerate in most regions by mid-century. All our measures indicate a continuous ageing of the world's population throughout the century. The median age of the world's population increases from 26.6 years in 2000 to 37.3 years in 2050 and then to 45.6 years in 2100, when it is not adjusted for longevity increase. When increases in life expectancy are taken into account, the adjusted median age rises from 26.6 in 2000 to 31.1 in 2050 and only to 32.9 in 2100, slightly less than what it was in the China region in 2005. There are large differences in the regional patterns of ageing. In North America, the median age adjusted for life expectancy change falls throughout almost the entire century, whereas the conventional median age increases significantly. Our assessment of trends in ageing is based on new probabilistic population forecasts. The probability that growth in the world's population will end during this century is 88%, somewhat higher than previously assessed After mid-century, lower rates of population growth are likely to coincide with slower rates of ageing

Symptomatic Glenoid Loosening Complicating Total Shoulder Arthroplasty

Glenoid component loosening is one of the most common causes of failed total shoulder arthroplasty. Previous reports indicate that it is desirable to reimplant the glenoid component during revision shoulder arthroplasty. The purpose of our study was to retrospectively evaluate the satisfaction of patients undergoing glenoid revision (reimplantation or resection) following total shoulder replacement specifically for symptomatic glenoid loosening. Twenty-eight shoulders that developed symptomatic glenoid loosening following primary total shoulder arthroplasty were included in the study. Patients were retrospectively evaluated at a minimum of 2 years postoperatively. Patients either underwent resection followed by reimplantation of the glenoid component (13) or resection of the component with or without bone grafting (15). Each patient was evaluated with the UCLA Shoulder Scale and the Constant–Murley Shoulder Assessment. There were seven excellent, 13 good, five fair and three poor results on the UCLA score. Functional outcome scores trended higher in the reimplantation group but were not statistically significant. Both groups reported equal pain relief and satisfaction. Five out of 15 patients underwent arthroscopic resection of the glenoid, and these patients scored as well on the UCLA and Constant scores as the reimplantation group. When symptomatic glenoid loosening is the indication for revision total shoulder replacement, patients tend to achieve good to excellent results. Though functional scores were slightly higher in the reimplantation group, satisfaction was equally high in both groups. Resection, when indicated, should be performed arthroscopically as this improved functional outcome in our series