Spatial scaling of allometry for terrestrial,mammalian carnivores

A regression slope of –0.75 between log₁₀ density and log₁₀ body mass is thought to express equivalence of energy conversion among species' populations of similar taxonomic and trophic status. Using larger sample sizes than the usual 1–3 density estimates per species, we estimated a regression slope of –0.71 for terrestrial mammalian carnivores. We investigated the sampling variation in this estimate, and those derived from smaller intra-specific subsets, using 1000-iteration bootstrap analyses to obtain 90% confidence intervals. As expected, these widened as random subsets were reduced in size, but always contained the postulated –0.75. However, log₁₀ density also declined as 3/4 of the log₁₀ spatial extent of study area, and study area accounted for virtually all of the variation in density that was previously thought due to body mass. We removed the effect of study area by using the species-specific regression models between density and study area to predict density at a common scale of 400 km². These common-scale densities regressed against body mass with a slope of –0.16, but separated into body mass classes less than and greater than 11 kg, they produced slopes that were not significantly different from zero. We show that the allometry of density could be a case of circular logic, whereby body mass has influenced the investigator's choice of study area, and the resulting scale-dependent densities are related back to body mass. To test the allometry hypothesis, the effect of study area on density estimates needs to be removed. This requires conducting larger-scale studies of the smaller-bodied species so that all species compared are represented by an average study area that is near the common scale. Furthermore, study sites need to be selected and designed to represent more than the local detail in species' density.     

Editor’s note

Purinergic Signalling -     

Effectiveness of Hospital-Wide Methicillin-Resistant Staphylococcus aureus (MRSA) Infection Control Policies Differs by Ward Specialty

Methicillin-resistant Staphylococcus aureus (MRSA) is a major cause of preventable nosocomial infections and is endemic in hospitals worldwide. The effectiveness of infection control policies varies significantly across hospital settings. The impact of the hospital context towards the rate of nosocomial MRSA infections and the success of infection control is understudied. We conducted a modelling study to evaluate several infection control policies in surgical, intensive care, and medical ward specialties, each with distinct ward conditions and policies, of a tertiary public hospital in Sydney, Australia. We reconfirm hand hygiene as the most successful policy and find it to be necessary for the success of other policies. Active screening for MRSA, patient isolation in single-bed rooms, and additional staffing were found to be less effective. Across these ward specialties, MRSA transmission risk varied by 13% and reductions in the prevalence and nosocomial incidence rate of MRSA due to infection control policies varied by up to 45%. Different levels of infection control were required to reduce and control nosocomial MRSA infections for each ward specialty. Infection control policies and policy targets should be specific for the ward and context of the hospital. The model we developed is generic and can be calibrated to represent different ward settings and pathogens transmitted between patients indirectly through health care workers. This can aid the timely and cost effective design of synergistic and context specific infection control policies.     

Why Do the Karo Batak Prefer Women with Big Feet?

Men may find women with small feet relative to body size more attractive because foot size reliably indexes nubility—i.e., age and parity. I collected judgments of attractiveness in response to drawings of women with varying foot sizes from a sample of 159 Karo Batak respondents from North Sumatra, Indonesia, as part of a collaborative project on foot size and attractiveness. The data revealed a contrarian preference among the Karo Batak for women with big feet. The judgments were compared with the results of an existing cross-cultural study that found a preference for women with small feet in aggregate, but a mix of small- and large-foot preferences in the societies taken individually. Using contingency table analysis, I found that ecology and less exposure to Western media were associated with a preference for women with big feet; patriarchal values were not. The findings suggest that human mating preferences may arise in response to local ecological conditions, and may persist and spread via cultural transmission. This has implications for the concept of universality espoused in some versions of evolutionary psychology.     

Microbe-mineral biogeography from multi-year incubations in oceanic crust at North Pond,Mid-Atlantic Ridge

Subseafloor oceanic crust is a vast yet poorly sampled habitat for life. Recent studies suggest that microbial composition in crustal habitats is variable in space and time, but biogeographic patterns are difficult to determine due to a paucity of data. To address this, we deployed hundreds of mineral colonization experiments at and below the seafloor for 4–6 years at North Pond, a borehole observatory network in cool (<10°C) and oxic oceanic crust on the western flank of the Mid-Atlantic Ridge. The overall community composition of mineral incubations reveals that colonization patterns are site dependent, with no correlation to mineral type. Only a few members of the Thioalkalispiraceae and Thioprofundaceae exhibited a mineral preference pattern, with generally higher abundance on metal sulphides compared to silicates, while taxa of the Gammaproteobacteria and Deltaproteobacteria were common in the colonization experiments. In comparison to datasets from other crustal habitats, broader biogeographic patterns of crustal communities emerge based on crustal habitat type (surface-attached communities versus fluid communities), redox environment and possibly crustal age. These comparisons suggest successional biogeography patterning that might be used as an indicator of how recently permeable pathways were established within oceanic crust.