Landscape-scale benefits of protected areas for tropical biodiversity

The United Nations recently agreed to major expansions of global protected areas (PAs) to slow biodiversity declines1. However, although reserves often reduce habitat loss, their efficacy at preserving animal diversity and their influence on biodiversity in surrounding unprotected areas remain unclear2-5. Unregulated hunting can empty PAs of large animals6, illegal tree felling can degrade habitat quality7, and parks can simply displace disturbances such as logging and hunting to unprotected areas of the landscape8 (a phenomenon called leakage). Alternatively, well-functioning PAs could enhance animal diversity within reserves as well as in nearby unprotected sites9 (an effect called spillover). Here we test whether PAs across mega-diverse Southeast Asia contribute to vertebrate conservation inside and outside their boundaries. Reserves increased all facets of bird diversity. Large reserves were also associated with substantially enhanced mammal diversity in the adjacent unprotected landscape. Rather than PAs generating leakage that deteriorated ecological conditions elsewhere, our results are consistent with PAs inducing spillover that benefits biodiversity in surrounding areas. These findings support the United Nations goal of achieving 30% PA coverage by 2030 by demonstrating that PAs are associated with higher vertebrate diversity both inside their boundaries and in the broader landscape.

Tropical forest dung beetle-mammal dung interaction networks remain similar across an environmental disturbance gradient

Conservation outcomes could be greatly enhanced if strategies addressing anthropogenic land-use change considered the impacts of these changes on entire communities as well as on individual species. Examining how species interactions change across gradients of habitat disturbance allows us to predict the cascading consequences of species extinctions and the response of ecological networks to environmental change. We conducted the first detailed study of changes in a commensalist network of mammals and dung beetles across an environmental disturbance gradient, from primary tropical forest to plantations, which varied in above-ground carbon density (ACD) and mammal communities. Mammal diversity changed only slightly across the gradient, remaining high even in oil palm plantations and fragmented forest. Dung beetle species richness, however, declined in response to lower ACD and was particularly low in plantations and the most disturbed forest sites. Three of the five network metrics (nestedness, network specialization, and functionality) were significantly affected by changes in dung beetle species richness and ACD, but mammal diversity was not an important predictor of network structure. Overall, the interaction networks remained structurally and functionally similar across the gradient, only becoming simplified (i.e., with fewer dung beetle species and fewer interactions) in the most disturbed sites. We suggest that the high diversity of mammals, even in disturbed forests, combined with the generalist feeding patterns of dung beetles, confer resilience to the commensalist dung beetle-mammal networks. This study highlights the importance of protecting logged and fragmented forests to maintain interaction networks and potentially prevent extinction cascades in human-modified systems.

Pneumoperitoneum or Chilaiditi's sign

Chilaiditi's sign describes the incidental radiographic finding of the bowel positioned between the right diaphragm and the liver. This is often misdiagnosed as pneumoperitoneum or free air under the diaphragm, which may lead to unnecessary investigations or surgical procedures. Here, we report two incidental chest radiograph findings of air under the diaphragm in patients who were being screened for pulmonary tuberculosis. This case series highlights the importance of awareness of the diagnosis of Chilaiditi's sign to avoid unnecessary hospital referrals.

Measurements of middle-ear function in the Mongolian gerbil, a specialized mammalian ear

The middle ear of the Mongolian gerbil is thought to be specialized so that it can hear the 3,000-Hz and lower sounds produced by approaching predators. Evidence in the literature suggests several specializations: (1) an effect of the large middle-ear air spaces in the gerbil is to increase the sensitivity of this ear to sounds of 3, 000 Hz and lower in frequency; (2) the combined action of the middle-ear cavity and the significant pars flaccida of the tympanic membrane in the gerbil ear reduces the sensitivity to sounds of frequencies below 500 Hz. This paper describes anatomical and functional measurements of stapes motion and suggests that the stiffness of the gerbil ossicular system also acts to reduce sensitivity to low-frequency sounds. The primary conclusion is that the frequency dependence of the gerbil middle ear is the result of the interaction of multiple factors, thereby complicating the relationship between single structural specializations and overall function.

Effects of pars flaccida on sound conduction in ears of Mongolian gerbil: acoustic and anatomical measurements

This paper presents evidence on how the pars flaccida of the tympanic membrane affects the acoustic input to the middle and inner ear. Measurements of middle-ear acoustic input admittance and sound-pressure levels in both the ear canal and the middle-ear cavity were made in ears of eight gerbils before and after manipulations of the middle ear and tympanic membrane. The results are interpreted in terms of a model proposed by Kohllöffel [Hear, Res. 13(1984) 83-88]. The input-admittance measurements show that the pars flaccida of gerbil acts as a resonator with a resonance frequency of approx. 500 Hz. The admittance of this resonator appears in parallel with the input admittance of the pars tensa and its ossicular and cochlear load. At frequencies below the resonance, the pars flaccida admittance is compliance-like and its magnitude is comparable to that of the pars tensa and its load; consequently, the presence of pars flaccida increases the overall middle-ear input admittance and decreases the pressure difference across the tympanic membrane. At higher frequencies, the admittance of pars flaccida is mass-like and small in magnitude, and it has negligible influence on the overall middle-ear input admittance and the pressure difference across the tympanic membrane. These results suggest that the presence of pars flaccida reduces low-frequency acoustic input to the middle- and inner-ear and consequently decreases hearing sensitivity in this frequency range. Our measurements suggest that with a constant sound pressure stimulus, stiffening the gerbil pars flaccida would increase the motion of the pars tensa by 3-10 dB at frequencies below the normal flaccida resonance.