Whether monozygotic (MZ) and dizygotic (DZ) twins differ from each other in a variety of phenotypes is important for genetic twin modeling and for inferences made from twin studies in general. We analyzed whether there were differences in individual, maternal and paternal education between MZ and DZ twins in a large pooled dataset. Information was gathered on individual education for 218,362 adult twins from 27 twin cohorts (53% females; 39% MZ twins), and on maternal and paternal education for 147,315 and 143,056 twins respectively, from 28 twin cohorts (52% females; 38% MZ twins). Together, we had information on individual or parental education from 42 twin cohorts representing 19 countries. The original education classifications were transformed to education years and analyzed using linear regression models. Overall, MZ males had 0.26 (95% CI [0.21, 0.31]) years and MZ females 0.17 (95% CI [0.12, 0.21]) years longer education than DZ twins. The zygosity difference became smaller in more recent birth cohorts for both males and females. Parental education was somewhat longer for fathers of DZ twins in cohorts born in 1990–1999 (0.16 years, 95% CI [0.08, 0.25]) and 2000 or later (0.11 years, 95% CI [0.00, 0.22]), compared with fathers of MZ twins. The results show that the years of both individual and parental education are largely similar in MZ and DZ twins. We suggest that the socio-economic differences between MZ and DZ twins are so small that inferences based upon genetic modeling of twin data are not affected.

Picloram (4-amino-3,5,6-trichloro-2-pyridinecarboxylic acid) and metsulfuron {2-[[[[(4-methoxy-6-methyl-1,3,5-triazin-2-yl)amino] carbonyl] amino] sulfonyl] benzoic acid} were applied to broom snakeweed (Gutierrezia sarothrae [Pursh.] Britt. and Rusby # GUESA) on two spring dates and three fall dates from October 1983 to 1985. Applications of picloram and metsulfuron in the fall more effectively controlled broom snakeweed than applications in the spring. Lower herbicide rates were necessary for 90% or greater control on a sandy loam than on a silty clay loam. Grass yield increased significantly the first, second, and third growing seasons when a majority of the broom snakeweed were killed by either herbicide, but was not different from untreated rangeland when less than 50% of the plants were killed. Reduction in broom snakeweed densities of 90% or greater following applications of picloram or metsulfuron resulted in 3- to 5-fold increases in the estimated carrying capacity of rangeland in east-central New Mexico.

During the 20th century, naturalized saltcedar has become common within major tributaries throughout the western United States. Often growing in nearly monocultural stands, saltcedar is suspected of lowering water tables, thus destroying wetlands and wildlife habitats. Management efforts have primarily relied on mechanical and cultural practices, but recent success in controlling saltcedar with imazapyr has led to wider herbicide use. Based on a number of research/extension field trials in New Mexico from 1987 to present, imazapyr applied alone or in combination with glyphosate was found to control saltcedar to levels of 90% or greater, especially when applied in August or September. For fixed-wing aircraft applications, we recommend applying imazapyr at 1.1 kg ai/ha or imazapyr plus glyphosate at 0.56 plus 0.56 kg/ha. For individual plant treatments, we recommend spraying the foliage to wet with imazapyr at 1% v/v in water, or imazapyr plus glyphosate at 0.5 plus 0.5% v/v. Herbicide activity may be reduced as saltcedar height and stem number increases.

In this study photo-identification data were used to better understand movements, population structure and abundance of common bottlenose dolphin (Tursiops truncatus) in south-west England and surrounding waters, to inform conservation efforts. A catalogue of 485 photographic sightings of 113 individuals was compiled from ~150 common bottlenose dolphin encounters made on 87 dates between March 2007 and January 2014. From these and other data, three likely sub-populations were identified in the western English Channel, demarcated by bathymetry and distance to land: (1) south-west England – inshore Cornwall to Devon, (2) offshore English/French waters and (3) inshore France from Brittany to Normandy. Maximum abundance estimates for south-west England coastal waters, using two methods, ranged between 102 and 113 (range 87–142, 95% CL) over the period 2008–2013, likely qualifying the region as nationally important, whilst the yearly maximum was 58 in 2013. The population was centred on Cornwall, where 19 well-marked animals were considered ‘probable’ residents. There were no ‘probable’ resident well-marked individuals found to be restricted to either Devon or Dorset, with animals moving freely within coastal areas across the three counties. Movements were also detected within offshore English waters and French waters (from other studies) of the western English Channel, but no interchange has as yet been detected between the three regions, highlighting the possible separation of the populations, though sample sizes are insufficient to confirm this. Given the findings, south-west England waters should be considered as a separate management unit requiring targeted conservation efforts.

A trend toward greater body size in dizygotic (DZ) than in monozygotic (MZ) twins has been suggested by some but not all studies, and this difference may also vary by age. We analyzed zygosity differences in mean values and variances of height and body mass index (BMI) among male and female twins from infancy to old age. Data were derived from an international database of 54 twin cohorts participating in the COllaborative project of Development of Anthropometrical measures in Twins (CODATwins), and included 842,951 height and BMI measurements from twins aged 1 to 102 years. The results showed that DZ twins were consistently taller than MZ twins, with differences of up to 2.0 cm in childhood and adolescence and up to 0.9 cm in adulthood. Similarly, a greater mean BMI of up to 0.3 kg/m2 in childhood and adolescence and up to 0.2 kg/m2 in adulthood was observed in DZ twins, although the pattern was less consistent. DZ twins presented up to 1.7% greater height and 1.9% greater BMI than MZ twins; these percentage differences were largest in middle and late childhood and decreased with age in both sexes. The variance of height was similar in MZ and DZ twins at most ages. In contrast, the variance of BMI was significantly higher in DZ than in MZ twins, particularly in childhood. In conclusion, DZ twins were generally taller and had greater BMI than MZ twins, but the differences decreased with age in both sexes.

For over 100 years, the genetics of human anthropometric traits has attracted scientific interest. In particular, height and body mass index (BMI, calculated as kg/m2) have been under intensive genetic research. However, it is still largely unknown whether and how heritability estimates vary between human populations. Opportunities to address this question have increased recently because of the establishment of many new twin cohorts and the increasing accumulation of data in established twin cohorts. We started a new research project to analyze systematically (1) the variation of heritability estimates of height, BMI and their trajectories over the life course between birth cohorts, ethnicities and countries, and (2) to study the effects of birth-related factors, education and smoking on these anthropometric traits and whether these effects vary between twin cohorts. We identified 67 twin projects, including both monozygotic (MZ) and dizygotic (DZ) twins, using various sources. We asked for individual level data on height and weight including repeated measurements, birth related traits, background variables, education and smoking. By the end of 2014, 48 projects participated. Together, we have 893,458 height and weight measures (52% females) from 434,723 twin individuals, including 201,192 complete twin pairs (40% monozygotic, 40% same-sex dizygotic and 20% opposite-sex dizygotic) representing 22 countries. This project demonstrates that large-scale international twin studies are feasible and can promote the use of existing data for novel research purposes.