Mother–offspring distances reflect sex differences in fine‐scale genetic structure of eastern grey kangaroos

Natal dispersal affects life history and population biology and causes gene flow. In mammals, dispersal is usually male‐biased so that females tend to be philopatric and surrounded by matrilineal kin, which may lead to preferential associations among female kin. Here we combine genetic analyses and behavioral observations to investigate spatial genetic structure and sex‐biased dispersal patterns in a high‐density population of mammals showing fission–fusion group dynamics. We studied eastern grey kangaroos (Macropus giganteus) over 2 years at Wilsons Promontory National Park, Australia, and found weak fine‐scale genetic structure among adult females in both years but no structure among adult males. Immature male kangaroos moved away from their mothers at 18–25 months of age, while immature females remained near their mothers until older. A higher proportion of male (34%) than female (6%) subadults and young adults were observed to disperse, although median distances of detected dispersals were similar for both sexes. Adult females had overlapping ranges that were far wider than the maximum extent of spatial genetic structure found. Female kangaroos, although weakly philopatric, mostly encounter nonrelatives in fission–fusion groups at high density, and therefore kinship is unlikely to strongly affect sociality.     

Adipocyte lineage cells contribute to the skin stem cell niche to drive hair cycling

In mammalian skin, multiple types of resident cells are required to create a functional tissue and support tissue homeostasis and regeneration. The cells that compose the epithelial stem cell niche for skin homeostasis and regeneration are not well defined. Here, we identify adipose precursor cells within the skin and demonstrate that their dynamic regeneration parallels the activation of skin stem cells. Functional analysis of adipocyte lineage cells in mice with defects in adipogenesis and in transplantation experiments revealed that intradermal adipocyte lineage cells are necessary and sufficient to drive follicular stem cell activation. Furthermore, we implicate PDGF expression by immature adipocyte cells in the regulation of follicular stem cell activity. These data highlight adipogenic cells as skin niche cells that positively regulate skin stem cell activity, and suggest that adipocyte lineage cells may alter epithelial stem cell function clinically.     

Heterogeneity in male horn growth and longevity in a highly sexually dimorphic ungulate

In sexually dimorphic ungulates, sexual selection favoring rapid horn growth in males may be counterbalanced by a decrease in longevity if horns are costly to produce and maintain. Alternatively, if early horn growth varied with individual quality, it may be positively correlated with longevity. We studied Alpine ibex Capra ibex in the Gran Paradiso National Park, Italy, to test these alternatives by comparing early horn growth and longevity of 383 males that died from natural causes. After accounting for age at death, total horn length after age 5 was positively correlated with horn growth from two to four years. Individuals with the fastest horn growth as young adults also had the longest horns later in life. Annual horn growth increments between two and six years of age were independent of longevity for ibex whose age at death ranged from 8 to 16 years. Our results suggest that growing long horns does not constrain longevity. Of the variability in horn length, 22% could be explained by individual heterogeneity, suggesting persistent differences in phenotypic quality among males. Research on unhunted populations of sexually dimorphic ungulates documents how natural mortality varies according to horn or antler size, and can help reduce the impact of sport hunting on natural processes.     

Molecular biomonitoring of a population of nurses handling antineoplastic drugs

Many antineoplastic drugs have been found to have carcinogenic, mutagenic and teratogenic activity and so hospital personnel handling these substances are potentially exposed to health risk. Understanding this risk derived from protracted occupational exposure has great relevance even if the workers normally adopt individual and environmental protective measures. To address this question we have studied the presence of DNA and chromosome damage in a population of nurses employed in Italian oncology units and in matched controls. We used the comet assay to evidence the presence of DNA strand breaks, due to both acute and chronic exposure, and the micronucleus (MN) test, which is a measure of clastogenic and aneugenic events. Furthermore, since the individual response to the exogenous insults may be genetically determined, we studied the possible influence of single nucleotide polymorphism in XRCC1 and XRCC3 DNA repair genes on induced genetic damage. We also considered the effects of confounding factors like smoking, age and gender. The results indicated that the exposed subjects had significantly high levels of genetic damage. Age and gender were associated with increased values in MN, both in control and in exposed groups; the smoking habit affects MN frequency in controls, but not in workers. Furthermore we found that exposed subjects bearing at least one XRCC1 variant allele (399Gln) show higher values of MN. The present data provide the evidence to show that occupational exposure to antineoplastic drugs, even if in safety controlled conditions, represents a serious health risk. Furthermore we have shown that the presence of XRCC1 genetic polymorphism could contribute to increase the genetic damage in susceptible individuals who are occupationally exposed to dangerous substances.     

Don't forget to look down – collaborative approaches to predator conservation

Finding effective ways of conserving large carnivores is widely recognised as a priority in conservation. However, there is disagreement about the most effective way to do this, with some favouring top‐down ‘command and control’ approaches and others favouring collaboration. Arguments for coercive top‐down approaches have been presented elsewhere; here we present arguments for collaboration. In many parts of the developed world, flexibility of approach is built into the legislation, so that conservation objectives are balanced with other legitimate goals. In the developing world, limited resources, poverty and weak governance mean that collaborative approaches are likely to play a particularly important part in carnivore conservation. In general, coercive policies may lead to the deterioration of political legitimacy and potentially to non‐compliance issues such as illegal killing, whereas collaborative approaches may lead to psychological ownership, enhanced trust, learning, and better social outcomes. Sustainable hunting/trapping plays a crucial part in the conservation and management of many large carnivores. There are many different models for how to conserve carnivores effectively across the world, research is now required to reduce uncertainty and examine the effectiveness of these approaches in different contexts.     

Mass‐dependent reproductive strategies in wild bighorn ewes: a quantitative genetic approach

In the Ram Mountain bighorn sheep (Ovis canadensis) population, ewes differing by more than 30% in body mass weaned lambs with an average mass difference of only 3%. Variability in adult body mass was partly due to additive genetic effects, but inheritance of weaning mass was weak. Maternal effects could obscure genetic effects in the phenotypic expression of weaning mass, particularly if they reflected strategies of maternal expenditure that varied according to ewe mass. We performed a quantitative genetic analysis to assess genetic and environmental influences on ewe mass and on maternal expenditure. We used the mean daughters/mother regression method and Derivative Free Restricted Maximum Likelihood models to estimate heritability (h²) of ewe mass and indices of maternal expenditure. We found additive genetic effects on phenotypic variation in maternal mass, in lamb mass at weaning (absolute maternal expenditure) and in weaning mass relative to maternal mass at weaning (relative maternal expenditure). Heritability suggests that maternal expenditure has the potential to evolve. The genetic correlation of ewe mass and absolute maternal expenditure was weak, while ewe mass and relative maternal expenditure were strongly negatively correlated. These results suggest additive genetic effects on mass‐dependent reproductive strategies in bighorn ewes. Mass‐dependent reproductive strategies could affect lamb survival and phenotypic variation in adult mass. As population density increased and reproduction became costlier, small females reduced maternal expenditure more than large females. Constraints on reproductive strategy imposed by variations in resource availability are therefore likely to differ according to ewe mass. A general trend for a decrease in maternal expenditure relative to maternal size in mammals suggests that size‐dependent negative maternal effects may be common.